 Good morning. Welcome to this webinar on advancing agricultural herbicides through chemistry. My name is Jessica Wolfman and I'm a research associate with the Chemical Sciences Roundtable at the National Academies of Sciences, Engineering and Medicine. The Chemical Sciences Roundtable provides a neutral forum to advance the understanding of issues important to the chemical sciences and engineering and promotes the exchange of information among government industry and academic sectors. This year we are continuing our series of webinars on pressing topics affecting the chemical sciences. This webinar series is entering its third year, and all of the presentations and recordings from 2020 and 2021 are available on the CSR website. If we can go to the next slide. Thank you. Today we will discuss the nature and magnitude of herbicide resistance and explore opportunities through chemistry and needs to better control weeds and agriculture. The format will consist of three presentations, followed by a question and answer discussion session with the virtual audience. Note that there will be that there will be time for one or two clarification questions following each presentation, but all other questions will be addressed in the discussion time after the presentations. Dr. Mark Jones will be our moderator for this webinar. Dr. Jones is a member of the Chemical Sciences Roundtable, and is a retired industrial chemist now works as an independent consultant. He will be asking all questions on behalf of the audience. Questions can be submitted through the Q&A button on Zoom, which is located on the bottom control panel of your screen. The chat feature has been disabled on Zoom for audience members, so please use the Q&A feature to submit your feedback. With that, I would like to introduce our first speaker, Dr. Mithila Jogolam. Dr. Jogolam is a professor of weed physiology in the Department of Agronomy at Kansas State University. Her work is recognized for increasing our understanding of the evolution and fundamental mechanisms of herbicide resistance and needs. Her research also focuses on the effect of climate change factors on herbicide efficacy, as well as weed management and identification of herbicide resistant traits in crops. And with that I will turn it over to you Dr. Jogolam. Thank you Jessica for the kind introduction. Greetings everyone. First I would like to thank National Academies for giving me the opportunity to speak on this important topic, evolution of herbicide resistance in weeds. I'm really excited about the opportunity. I also would like to thank all those folks that are joining or participating in this webinar. Here is an outline of my presentation. I'm going to give an overview on global food production needs, and also touch base on crop production constraints specifically related to weed issues. And give me an overview on herbicide resistant crops and how introduction of these technology help the way growers manage the weeds. And spend a little bit more time on evolution of herbicide resistance in weeds and some mechanisms of resistance that confer herbicide resistance. And glance at glyphosate or roundup most commonly known as roundup resistance in crops as well as weeds. And also touch base on some of the management strategies that we can use for herbicide resistance resistant weed control. Finally wrap up with summary and conclusions. So the global population is projected to be at 9 billion by 2050. So there is tremendous pressure on our farmers to increase food production by 60% to feed the increasing population. By 2050, scientists have been helping growers to meet the food production needs. However, we must work even more diligently than ever before and introduce technology so that we can feed the growing population across the globe. However, the farmers are facing a number of crop production constraints. Among those infestation with the pest crop pass can can be a significant one crop losses because of infestation of the spread pass could be tremendous, especially as you can see from this chart, weed infestations can cause significant losses. So chemical weed control or use of herbicides to manage the meat has been extremely successful ever since herbicides were released for commercial use after the Second World War. Several different chemistries have been developed by industry and released for weed control. Additionally, upon development and commercialization of herbicide resistant crops, the way the weeds were managed has changed significantly in growers fields. So the field started to look more like this weed free upon adoption to herbicide resistant crop technology. This was almost like a silver bullet for growers. However, that didn't last long because of use of herbicide as a sole means of weed control strategy and also rapid and immediate or extensive adoption to herbicide resistant crop technology resulted in evolution of herbicide resistance in weeds. So you can see the field started to look more like this infested with weeds in some parts of the Midwestern US and also in other countries as well. So the evolution of herbicide resistance in which is one of the major constraints that growers are facing currently. In herbicide resistance, you may come across different definitions for herbicide resistance, but I'm using one that was suggested by Dr. Pat Trannell at University of Illinois, which suggests it's a loss of effectiveness of a herbicide on weed population. Again, herbicide resistance is a naturally occurring phenomenon and herbicide resistance evolves due to selection, meaning if we use same herbicide chemistry or same site of action of herbicide over and over again, you will see the evolution of resistance in weeds. As it's shown in this cartoon, the plan shown here in black or resistant plants that are generally present in any weed population, but because of selection, the number of resistant individuals increase in the population over period of time, eventually getting dominated in the population. This is when it becomes really challenging for controlling these weeks. So then how do these weeks evolve resistance? What are the mechanisms that confer herbicide resistance in weeds? So the mechanisms can be grouped into two types. One is target site resistance. Here the herbicide target. Again, each herbicide has a specific target which could be a protein in the plant. So any alterations to herbicide target can make that plant insensitive to herbicide. So this can be possible because of mutations in the gene that is coding for the herbicide target, thereby there will be modification in the herbicide target protein resulting in inability of the herbicide to work in the plant. Also, it could be because of amplification or duplication of herbicide target gene resulting in increased gene expression, thereby enough herbicide protein is available for the plant to function normally. The second mechanism is non-target site resistance. In this mechanism, herbicide target is still sensitive to herbicides, but other mechanisms such as reduced herbicide absorption or translocation are in many cases because of herbicide metabolism or degradation of herbicide. In other words, the herbicide becomes inactive due to activity of certain enzymes in the plant, thereby the plant that can survive herbicide application. It's also important to remember if weeds have target site resistance, then it does not confer resistant to other herbicide target. It is very specific to your particular site of action of herbicide. Whereas the metabolic resistance is a very challenging phenomenon. Here the weeds, if they have metabolic resistance, they can confer resistance to other herbicide targets as well. I'm going to spend a little more time on metabolic resistance later in my presentation. So this chart shows the global number of cases in terms of herbicide resistance in weeds. As you can see, the number of weeds that are resistant to herbicides have increased steadily and steeply in the last two and a half decades or so. Here, the scenario in the US is not any different from a global scenario. Again, we have seen steady increase in number of cases of herbicide resistance in weeds. But even more important or more challenging is that currently we see a lot of weed species evolving resistance to more than one site of action of herbicide. So if we have a number of weeds with such multiple resistance, then it gives very few options for us to manage these weeds. Therefore, there is a need for new herbicide chemistries to discover and make available to combat herbicide resistance. So the two other talks following mine would be focusing on the new herbicide chemistries and I'm also really excited about those talks. So as I mentioned, I want to also give you an overview of glyphosate are roundup resistant crops as well as roundup resistance in weed species. As you can see here in this graph upon introduction of roundup ready trade technology, majority of corn, cotton or soybean grown here in the US on also many other developed countries. They grow roundup ready trade consisted crops of these. So as you can see more than 90% of acreage of these crops grown here in the US contained roundup ready trade. Because of this obviously there is extensive use of glyphosate in these cropping systems. Consequently we have seen evolution of herbicide resistance in glyphosate resistance in weed population. Globally there are 55 weeds that are known to be resistant to glyphosate 17 of those are present here in the US. Another unique aspect of this herbicide glyphosate is that you remember all the mechanisms of target site and non target site resistant that I alluded earlier. All those have been documented for the herbicide glyphosate, of course in different weed species. One such mechanism is gene amplification or gene duplication based resistance to glyphosate. This mechanism was first documented for this herbicide glyphosate. Here, what happens is the herbicide target gene which is in all pyruvel, chikimic, phosphate synthase, in short, APSPS. This target gene or the gene coding for this enzyme duplicated several folds, thereby the glyphosate resistant plan showing this mechanism can survive glyphosate application and function normally. In this regard, one of the most fascinating findings that came out of our lab recently was the APSPS gene amplification has been seen in an extra circular chromosomal DNA here. So this extra chromosomal circular DNA consisting the APSPS gene amplified several folds. And as you can see in this picture, all those pink dots refer to amplified copies of APSPS gene. So because of this massive amplification, there is sufficient enzyme available for the plant to function normally even after application of glyphosate. So I did mention that if we have metabolic resistance in weeds, then it could be really a challenge for the management. So why is it so? In that sense, all plants including weeds have certain enzymes known as cytochrome P450s or glutathione as transferases. These enzymes are there for plant to protect them from the biotic and abiotic stresses. So if we have increased activity of these enzymes, then while protecting the plant from the stresses, they can also act upon the herbicide molecules and degrade them while making them inactive in the plant. So when you have increased activity of these enzymes, they not only work on one particular chemistry or one site of action of herbicide and degrade them, they also work on multiple herbicide with different chemistry. So the reason if we have stacking and accumulation of these enzymes, this will be a challenge because the plant would be predisposed to have evolved resistant to other herbicide molecules as well. So how do we manage resistance? This is the really key thing for growers in terms of controlling the weeds that are resistant to herbicide. So again, there is no simple answer for this. It has to be a systems approach. I borrowed this cartoon from CropLife where they clearly show multiple tactics need to be followed for managing weed resistance. So farmers should be looking at crop rotations or using cover crops as weed suppression strategy or use multiple herbicides with different modes of action. Essentially, the mantra here is that you need to follow integrated weed management involving multiple tactics. Again, if weed has a target site resistance, then mixing or rotating different herbicide chemistries can be very effective to manage such resistance. However, if weeds have metabolic resistance, then that strategy will not be effective and we need to look at multiple strategies. And more importantly, we should look at reducing the weed feedback. So to conclude, I am an optimist. I believe the opportunity still exists. Stewardship is extremely important in this case and also we have to emphasize on transdisciplinary research, bringing multiple expertise to come up with strategies to manage herbicide resistance and also increase public-private partnerships and more importantly, effective communication. We need to get the extension scientists as well as field days to be conducted on a regular basis and also through social media convey the message of importance of herbicide resistance, how growers can tackle that to manage resistance. So with that, I thank you all for your patience listening and also thank my asked and present group members and I can take any questions you may have inside. Thank you very much for that interesting presentation. I don't see any questions currently in the question window. So for participants, if you would like to ask a question, please type it in and we will pass it on. So I guess without further ado then since I don't, I do have a question coming in. So the question coming in is what detection of herbicide resistance would be most effective so how could you find new ways to look at herbicide resistance. Oh, what would be the most perfect way of detecting herbicide resistant. Yeah, so there are multiple methods that we use to detect herbicide resistance. I, in my opinion, most reliable one is we need to test them at a whole plant level under greenhouse conditions. To suspect a population of weed that has resistance, we need to ask the grower or we, we can go ourselves and get the seed and grow them in controlled environment and treat those plants with the herbicide that is potentially the weed is resistant to. And then also in my opinion, we need to make sure that trade is transferred to next generation basically let those plants that survive herbicide application and generate treat from those survivors and test the next generation if the trade is transferred inherited in the next generation then that would be the confirmation best confirmation that we have resistance in the population. Thank you. Once we prompted we got a lot of questions I'll save those till till the end, I think moving right along we'll move on to our next speaker. This is Jens Lukerl. Jens is head of herbicide and early biology at BAS F corporations agricultural research station located in Limburg Hof Germany. He supervises research on modes of action, herbicide resistance and uptake and the transport and metabolism of herbicides. Jens take it away. Guys, thank you very much for the kind introduction, the great organization and things to other organizers for inviting me to give this 100 to 100 feet overview like you see here on the farmers field on how to get new herbicides. So let's see. I think it works well here with a moving the slides and I would like to connect to what my fellow said. Yeah, in your state you can't harvest seeds without killing weeds weeds are your drivers number one. And in line with global a track the herbicide resistance action committee and crop life international. Indeed, it's important to use integrate past management to keep our sharp weapons sharp. The efficacy will be rolled. Actually, we're living in a period of time. And this is an example from the EU where two of three pesticides will be banned due to new regulatory hurdles. And where out of the 1000 compounds that were available only two to 300 will remain. There are four actives leaving the market, only one new will enter the market. And that means for the different segments we will have much less solutions and the future. And that also puts a special pressure on resistance management because the options getting fewer so we need new sharp weapons. And that in the context of societal demand, where the society takes a critical look at metabolites residues. And when you get the registrations Reese Taylor say okay we don't accept the maximum residual levels that are defined we just accept 20%. So it goes beyond the mere regulatory scheme but the regulatory authorities, of course, are driven by the public opinion and policy makers. There are some region specific study requirements, and the lately released and they just be she's act in the US is one of it, but we'll also have a lot discussion in Europe about what a preservation, and within Green Deal of the EU, the cutting of the herbicides or the pesticides by half also pressure on the use rate so the new compounds that we were looking at have a higher attrition rate due to the higher thresholds. And there are more hurdles to overcome. And that is a special requirement and challenge for us because we have to foresee within the long time to develop these compounds, the new requirements in advance. And where the easy answer to what does it take to make a new herbicide as well. Imagine, it takes $50 every minute for 11 years. That is roughly the effort and around 250 million euros. You have to screen a lot, you have to fail early because it's so expensive to fail late so we really need good indicator assays in early research looking for new chemistry is to really develop and advance the right compounds. And very often the knockout is the regulatory framework. So we have to look for the compounds that can be registered, and it's not necessarily always the ones that show highest efficacy. So we have to look for new solutions to get the products into through the pipeline into the market. So one key message here is if you fail, fail early in order to save the resource because it's already quite costly to bring products to market. So there are not that many companies driven by innovation and new actives consolidation of the market has led to basically now six major companies doing active research. And these companies and relative terms lose market share. So it's the time of the gender compound companies with less new actors being found so they market share voted by about 18% and only six years. That's remarkable and the company's of course, try to get more more productive in order to get new products to market. When you take a look at a press release last month, what has shown up as new products in the first quarter, you'll realize and also taking a look back that lifecycle management products dominate the new products going to market so you have new combinations of chemistries combined in a new way maybe within tank mix option or with different use rates over the new formulation in order to combat the key weeds, be it dicots or monocut weeds. When we take a look at chemistry that came to market the last five years there actually only eight actives at largely known mode of action so new variations of chemistries that are known for quite some time. In the Netherlands here in green is an old mode of action but it has found a new market segment and their side of action was newly discovered. When you take a look at the near future 2022 and 24 and beyond, there are a few compounds to come into our truly new modes of action. One is a pyramid in biosynthesis inhibitor dihydro or TTI drudgenase and the other one is basically following HPVD. These are two products that go into petty rice or rice that way it's selective. A number of companies of course are working in this field and a few new patterns have been published. There are compounds there's a shift to some Asian companies that especially King agro is a new emerging player since last decade basically they're looking into food security in China then bring products mainly to China. When you then take a look at where can we actually get chemistries from what are the main sources, you can do mass screening, you can use natural compounds. You can do patent watch so what are the others doing like I just showed you on the chemistry the new modes of action, you can work on old targets with new chemical modifications. You can do my database mining, you might have had some interesting compounds which you did not follow it you to a different strategy so cinematic in such a case. You can use antibacterials, the plastic is a very interesting target for herbicides, and then according to the end is on beyond theory. This is an organ that comes from bacteria so they share a lot of targets so you can screen 100 thousands of antibacterials known in literature you can use open innovation. You can exchange with your compounds with farmer companies if you don't have the same arena and don't work on the same areas. With these herbicide discovery companies, you can acquire license or a co develop products, and then new technologies, addressing the finding new herbicides which I will show you in a few minutes. The old way to address it is okay we need new chemistry let's buy a few hundred thousand compounds and there are a number of suppliers on the market. And we have to apply a filtering system, which for a certain criteria like the Lepinsk rules molecular weight, the publicity chemical structure hydrogen bonding and other criteria. You don't want to have anything among the that's highly reactive explosive or other things. And you need very experienced people. I balling up feeling paired with new approaches like machine learning algorithms to select compounds. And here is an example in 2010 we bought 100,000 compounds it compound was nine to 15 euros it costs you point nine to 1.5 million. When you take a look at this today. The molecules are not tremendously. And this is most probably not the future way to screen millions of molecules anymore therefore companies are looking for new ways to access chemistry. One is open innovation. So, you can basically join several of the companies by just sending your molecules, you never might have never intended to test it for effects on weeds funger and sector. So insects, you just go to the websites of the companies, and take a look at their contacts on open innovation. And also my colleague Anna Mikrosko will be happy to receive any input there but there was other companies out doing with the same way. There are numerous new players in the era of hope site discovery. And here you see a list of a few companies. It's not complete, but you see companies like more technology having some certain new technologies and margin is available you see the King mainly focusing on China, and you could of course think of moving with those compounds global 40 fast and Israel ankle chem in the US work on bioinformatics approaches you have more on bioscience working on natural compounds, harpy by her beside a cleanest that just worked on in silicon models, and they advertise for the APH one compound. You see other companies from other university or industry, the latest company going into the arena's mankind agro tech from India it's basically Danuka a pharmaceutical company that wants to capitalize on their expertise in in with their chemical libraries, and there are other so you can basically look and see get in contact and test and potentially invest if there's something interesting, because not all the companies are able to bring products to the market and spend the 240 million at the end. When you take a look at our current situation how many herbicides that we have on the post you'll find 25 known, known modes of action, and 264 herbicides that are listed. 16 compounds have an unknown mode of action and six months basically represent the great value of the market so one question could be why so few targets and how many herbicide targets exist. We've tried to answer at least one part of the question and did the literature pattern research or search, and we found at least 203 31 targets, of which 62 are chemically validated 191 or genetically validated by antisense army and knockouts other other means. And you can see the distribution here around that different many different function what's interesting is many of the steps or components here are located in the plastic like lipid metabolism chlorophyll biosynthesis, but also fatty acid biosynthesis photosynthesis photo respiration sugar metabolism so obviously the antimicrobials and the plastic is a very good target very often it has targets that have no homology to humans mammals. And very often the protein function is limiting plant growth and catastrophic downstream effects. So what you need as a good target is screening system and you need drug ability. So, why are there so many theoretical targets, but only a relatively no numbers targets is is addressed by chemistries. And I think the reason is that not all targets are druggable a study in the past, try to better understand what are the mainstream characteristics of the binding pocket. And what makes it good herbicide for a good herbicide 60 drug targets were compared that have crystal structures. And what was compared with the subset of alligant proteins in the public domain. A algorithm was applied or developed and applied to isolate basically the relevant binding pocket parameters, and the beta finding is that the size of the pocket, the depth of the hydrophobicity range in the binding pocket and the subset channel the charges in the pocket and the closure are key parameters for protein drug ability. This is the mainstream rule. So the majority of compounds most probably has to fit this rule but they're exceptions for example, and enzymes with small binding types like HPB D, the EPS PSM phase or, or also the glutamine synthase HPB D requires an iron collating motive, meaning nitrogen oxygen containing groups and glyphosate and clophacinate one hit wonders so obviously there's a reason why this product is not druggable and there are only a few exceptions, escaping this mainstream rule. So if we take a look at other ways to access chemistries can we model new herbicides in silicone in principle. Yes, we can. There are several companies claiming to have new early in silicone leads on the pipeline. And it goes into this area in my note atom wise that's got a 45 million fund by a consortium of different investors working on your neural networks for by activity prediction and structure based design. So I think it's just lately Bayer invested in progeny ACAM and Israel based company that's working on in silicone prediction, especially on protein protein interaction and the claim is made there. Well the crop protection market like the farmer market was slowly but surely adopt novel artificial intelligence discovered small molecules so clear with time going by diversity of approaches tried and the resources poured into it. There is an increase of probability of success with a claim of several companies having you in silicone it's still too early to see the candidates at the front of the pipeline, but it looks like they will come very soon. And you do not always need big company money can also use academic sources for pocket to drug ability prediction like the university with a tool of that of University of Paris. Furthermore, the real strength of modeling is the refinement of the lead structure, the optimization. There are already half large data sets, you can use those to learn from them, and basically with the structure biology data, rationally optimize the molecule. One example is drifted in oxazine tyrexor, which binds in the binding pocket of PPO, and that has a beta wall. In the binding pocket, and this was used this information was used to find specific binders to the beach to a wall, they were found and introduced to the molecule, and we have now additional anchors on the molecule so resistance that might be caused by one amino acid to other molecules does not affect drifted in oxazine the same way because you have more binding in the pocket and single mutations on the PPO2 enzyme do not do not harm the binding of the inhibitor. We see in greenhouse and field trials that it still inhibits the target site resistance in the field so that's one new sharp weapon that will go to market in the future. In order to find new draggable targets, you can basically hijack a principle that's called protag, it's hijack ubiquitination, tagging the protein for degradation. So you combine a binder, you do not need an inhibitor binder binder is that's less complex to find that's a hit on binding a protein. Nice screening systems available for it. Then you combine it with a linker and with a molecule that binds to the E3 ligase. So if you bring the product of interest in contact with the E3 ligase, the protein of interest gets tagged with ubiquitin and degraded. And that is great because you can now use undraggable targets that are important for growth so one of the 191 targets that have been shown before and hopefully get new herbicides. The challenge is you have to of course optimize several components, the molecule gets bigger, sometimes also cost of goods. Another concern is you need real metabolic stability because a bigger molecule offers more attack groups and uptake is very important because with a molecule weight above 500 will have less efficient solutions to bring the compound into the plant to basically get it over the plant and the cell wall. And finally, RNAi technology is around. It was, yeah, promoted 10 years ago and started. We see quite some significant successes, especially in B health, and the user has insecticides, it works very well on larvae system of bean beetle or flea beetle beetle beetle. We also see some successes on fungicides. We will see very little reports on herbicides, because there again, the delivery, how to get a large polar and charged molecule through the leaf surface is an unsolved challenge. And of course at the end of the matter of the use rate and the cost of goods, whether such a solution could be brought to market so far, we require abrasive methods, mechanical wounding or stomata flooding through spreaders to get some of the material into the system, but it's not yet a robust system to combat weeds but would be a great tool if we can overcome this challenge with new innovation because it could really resharpen our herbicide tools. And finally, there is one more technology that's the DNA encoded libraries, you can synthesize DNA barcodes and do chemistry on the backbone of the DNA. The DNA barcode is used really as a flag to identify the molecule that gets screened in target by chemistry. And this is done together with different companies either in vitro or even in vivo, you can deconvolute the results sequence and then know which chemistry is basically on the backbone of the DNA that was synthesized of course you can only use chemistry that does not damage the DNA, but it gives you billions of molecules, a great chemical space to look for a new target chemistry that could be further tested and optimized for the lead structure. And I would like to conclude with this slide. There are many nice new technologies out there. And all these in vitro assets lead to many hits. And the question is, are these chemistry active on whole plant level, and therefore you need systems to test it in a higher throughput. This is an example. You see soil of trace 96 well trace with two monocards and a die card and a pre emergence in post emergent setting in order to indicate whether there's an initial effect on the plant. And of course, we realize that these good uptake parameters are basically an intrinsic characteristic of the hit lead, and it's very hard to, to define that the novel. So, you really need some good chemical hits that have an activity on the plant for further optimally to optimization. And I think this is one of the key hurdles in finding new chemistry. I would very much like to thank you for your attention and just remember at the end it's really finding the right balance for success to have a regulatory okay product, but one which really solves the problems and has a key unique value for the parma. Thank you very much. Thank you so much and thank all of you for typing in your questions. We have many for the, for the end period question answer period, but I do have one I think a couple people touched on on regulatory you mentioned it just there at the end yens can can you circle back and talk about what the, what the regulatory burden is and whether there are new advances that may help to bring materials to market and what are the advantages and disadvantages of getting things faster to market. Well, I think the disadvantage of getting things faster to market is that you increase uncertainty and risk, because you have to basically live with limited information. And, as you go in parallel with all the different studies, you might be catch on a ways on the rank foot and a, a parameter might not fit to really meet the hurdle so that's why it's so important to have early indicator essays that allow us to really throw throughout the bad aspects from the good ones, but we still need more than one candidate but a few backups for the further phase and the optimization to learn about our chemistry is and to see whether there's a pitfall. And sometimes it's just one group on the whole molecule that makes the big difference, either in the kinetics and the animal that you see in effect, or you don't see in effect at all because maybe it's not taken up. So the risk really is higher because we have to go in parallel, we have to make early decisions and we have to speed up the process. And yeah, risk, hopefully versus payout and we have to really focus on the ones that are regular to wise okay. And that can lead to a good solution, not necessarily one molecule that really has the highest efficacy. Really read registration and the requirements and toxicology ecotoxicology and the e fight drive it for Europe the highest attrition rate is the leaching potential. So if you find something in ground water, it's a not out for herbicide in in Europe, and these this can be tested early on. And toxicology ecotoxicology have made quite some advancements in the early prediction tools, and this is very important and also building up artificial intelligence and gathering data sets in order to increase predictivity on on our new lead molecules. Thank you so much for that. And I think now we'll segue to our next feature. Thank you again yens. Our next speech speaker is Dr Stephen o Duke. Many of you have asked questions about biologicals I think you're going to be in for some interesting learning here. Steve is a principal scientist at the University of Mississippi School of Pharmacy is an authority of the modes on the modes of action and resistance to herbicides. He's highly focused on glyphosate natural phytotoxins that may form the basis of future herbicides is now an area where he is very active. That's the focus of his presentation today. So without further ado Steve the floor is yours. Thanks Mark, and thanks to the organizers for inviting me to to speak today in this very interesting webinar. Okay. This part of the webinar will deal with natural products as a source of new herbicide targets. And it's again events and animation here. And the percentage of percent of commercial pesticides are either natural products or clearly derived from natural products. However, only 7% next click. Yes, only 7% of commercial herbicides are derived from natural products and then the hatch bars represent pesticides that could have been inspired by natural compounds. The gray bars are those that are really synthetic. That's the value of natural product and natural product drive pesticides herbicides. Next click again. That's sure why I can't control it but next click. You can see the actual value of these natural product drive pesticides and herbicides is higher than the actual number of commercial compounds next slide. And click through these as I speak about them. There are several advantages of natural product based herbicides. They're likely to have a shorter environmental half life than many synthetic compounds. And nature is green countless compounds for biological activity and very often the biological activity might be utilized as a as a pesticide. They can be produced by biosynthesis which has become more important as new technologies have been elaborated next slide or next click. They can have resistance genes associated with the genes for synthesis and these genes can be imparted into crops to make the crop resistant to the natural product that can be used as a herbicide. They're more likely to have multiple target sites there are no commercial herbicides that have more than one target sites, but there are some compounds in nature that are fighter toxic via more than one target site. Next slide. And often but not not always they have novel modes of action which is the focus of most of what I'm going to talk about next slide. There's some caveats though. They have the wrong physical chemical properties to be a bit pesticide. Yins mentioned, well Pinsky's rules for pharmaceuticals and types is Helen Tyson's rules for pesticides very often these natural products don't fit those rules. And for the, for those reasons they don't have the right chemical properties to be good pesticides. Complexity is often very challenging, which means the cost is very high even for pharmaceuticals. Some of these natural products are exorbitantly complex and therefore very expensive next and generating simpler cheaper and more effective analogues may not work evolution may have maximized activity next. And toxicity is an issue with some of these natural is not always safe. Some of the most toxic compounds non natural products. Next, and the environmental half life may be too short to be effective to be effective as a pesticide the compound has to stick around long enough to kill the target organism. Several commercial herbicides as I mentioned that are from natural sources that you can see here. I've listed them, those from plants are in green, those from microbes are purple. There's one from an insect that's in red, and they have some interesting target sites. Next slide. So the phosphate is one of the more successful compounds for natural source is from a soil like streptomyces, which produces L-phosphonethrysin, which is an irreversible binder of glutamine synthetase. And the synthesized version of this resemic mixture of the DNL forms of phosphonethrysin are sold under several trade names as a very successful herbicide. The streptomyces also has a gene for resistance to L-phosphonethrysin. And this is used to make sun crops resistant to it, which makes the product even more valuable. So it's been a very successful herbicide. Next slide please. Next. A good example of a herbicide inspired by a natural compound is from the bottle brush plant. Keep clicking through. And it produces a very fighter-taxic compound called leptospherbone trichetone. Imperial chemical industries developed this into Mesa trial, which was one of the first HPPD inhibitors that Jens mentioned. And several trichetone herbicides are on the market now that were all derived from a natural plant compound. There is a category of HPPD inhibitors that were purely synthetic though. Next. A herbicide that Jens mentioned may have originated from 1,4-Cinneole, which is a natural monotropine. It's simply 1,4-Cinneole with some other molecular baggage. It was discovered by next shell. And after several consolidations, just keep clicking through it, it ended up with BASF. Next. And it's been sold under several trade names. It's been introduced as being sold in Australia now. And next. And BASF found the actual molecular target site, which was unique at the time that inhibits ACP thioesterase or a fatty acid thioesterase that is involved in synthesis of mid-chain link fatty acids. There are other herbicides that inhibit other stages of fatty acid synthesis. There is a purely synthetic compound, the thiozolin, which was recently found to also inhibit fatty acid thioesterase. Next slide, please. Cantheredin is an old pharmaceutical compound produced by blister beetles, which to be active has to be converted to cantheredic acid. As you can see, it's very structurally similar to endothol, which is a pretty old herbicide. The only differences are two methyl groups. And we recently found that it has a unique target site that inhibits serine 3-anine protein phosphatase, and it's the only herbicide known to have this particular target site. Next slide, please. Next. Many natural phyto toxins have natural, novel modes of action that are not shared by commercial herbicides. And I'm going to go through a few of these, but these are only a few. An example is high dantacidin, which was discovered by Sankyo in Japan. Over 30 years ago is produced by a streptomyces species. It has similar activity to glyphosate on seven monocot and 10 dichot species, but it has a different, very different mode of action on glyphosate. Next, click, please. It's a pro herbicide that must be phosphorylated in planta to inhibit adenylose succinate synthetase, which is a unique target site, not sure by any commercial herbicides. And quite a bit of effort has been put into trying to develop dantacidin at the rivers of dantacidin as a herbicide by several different companies, but so far no commercial product. Next, please. A similar situation is with corn existing another Sankyo compound from a, from a fungus, I think growing on dung in Canada, if I remember right. It inhibits the transketolase involved in plant carbon metabolism. Partial knockouts of that gene give a phenotype very similar to treating a plant with corn existing that BASF has a patent for a altered transketolase that makes crops resistant to it if it were a successful commercial herbicide. Next, please. Currently, a drum and lab discovered this exotic sugar from a cyanobacterium. You can see that its activity is at least as good as glyphosate in this particular bio assay. As most of you know, and as was mentioned by a mental a glyphosate inhibits EPSPS, one of the last enzymes that chemic acid pathway, this particular toxin inhibits dehydroquinate synthase you can click the next one and you'll see that enzyme. The inhibiting the chemic pathway at a different target site. So far that has not developed into a commercial product yet. Next. Another recent discovery was an asterisk acid which is produced by soil fungus aspergillus terrius. This compound was known to be a fighter toxin but the motive action was not known. The motive action was discovered by this group by finding that with the genes for synthesis of this particular compound and aspergillus was a gene for dihydroxy acid dehydratease were the last enzymes the branch chain amino acid sent a pathway click and you'll see that there we go. And this, this is a target site that's not found in any commercial herbicide. The other oval there is over a pseudo lactate synthase, which is a target site of a very large number of commercial herbicide so that pathways been very productive in the herbicide but only centered on one enzyme this particular compound as good at inhibiting a later enzyme in the pathway. So this indicates that it is drugable, and you can kill plants by inhibiting that. But again, no commercial product yet with this target site. Next. The five innovations is a small company in California involved in microbial by herbicides. And one of those particular compounds in the I014 is a Berkholdi or rhinogenesis which is a soil microbe that they have found has to active fighter toxins and their product will be killed Berkholdi or rhinogenesis. It contains these two compounds sprayed on the crops to kill them. So they determine these two compounds are in their product. Next slide please. And that the Romadepsin inhibits histone deacetylase and that the reduced form of the compound is much more active than the oxidized form. Next slide please. I think that a few years earlier a German lab found that the benzoxinoids, which are allelochemicals produced by some grass crops like wheat are converted to a compound click one more click please. They are called Ampo, which is much more toxic to plants than the benzoxinoids. And these are actually what are causing most of the damage to competing weeds in these crops. They found that Ampo is also a histone deacetylase inhibitor, indicating that there's a, there are several different chemistries from natural products that are phytotoxic via this mode of action. Next slide please. Here you see the royalty potes, you splice your statin, see the other phytotoxin produced in the NBIO 14. And you can see on pigweed, which is one of the most virulent weeds in North America now. It's much more active on the grass per hectare level than several commercial herbicides, very active at a half a gram per hectare. Next slide please. We worked on the mode of action of splice of statin C, and I show herbidine, herboxidine also, which is a Monsanto compound from several decades ago, both produced by microbes, both selective herbicides, herboxidine, lower cholesterol, and it's a non-splicing inhibitor, splice of statin C is an analogue of splice of statin A, an anti-cancer agent and splicing inhibitor, and a selective herbicide. Next slide. And since those splicing inhibitors, they interfere with the spliceosome, causing intron retention, and we found looking at a number of genes that you do get intron retention. The mRNA is not processed properly, so you get a number of different if you have several introns, you get a number of different mispliced versions of mRNA. Here you see tubulin and the subunit of the spliceosome is also affected. Next slide please. As a result, you get improper proteins, here you see all the proteins that are affected by splice of statin C and herbidineopsis. These are the ones that are statistically significantly affected by a very low dose of splice of statin C. Next slide please. And we did molecular docking studies and found that splice of statin C there that you see in purple does bind between a couple of the subunits of the spliceosome. Next slide please. So to summarize in this cartoon you see that you get retention of introns and resulting in incorrect translation inactive proteins and proteins that are translated and folded wrong. Next slide please. And there are advantages of a product like this. Bethela mentioned that one of the strategies for resistance management is to use more than one mode of action. Here in one product you have two target sites in the same product that can be used for resistance management. And you have two different, totally two different chemistries for herbicide non-target site resistance management. It's possible that enzymes that metabolize one of these will not metabolize the other one. So there's a chance that it could also be used to fight non-target site resistance management that's based on metabolic resistance. Next slide please. So in summary, only a small fraction of commercial herbicides are derived from natural compounds. However, the commercial herbicides derived from natural compounds have very unique modes of action. So fighter toxins have many molecular targets not utilized by commercial herbicides. And some of these are very effective targets indicating that these targets are drugable, at least by the natural products that are very effective on them. So this suggests that there are several more target sites that can be enlisted in the exploration for new herbicides. So with that next slide, I think the people that did the work that came from our lab and thanks for listening. Thank you very much, Steve. I guess I one somewhat clarifying question here. Seems like there's a lot of interest in the question the questioners around purely biological herbicides. I did a non-scientific study I went to my local garden supply place walked in and the only thing that was labeled an all natural herbicide was a bottle of 30% acetic acid, which they were basically saying apply, you know, directly to plants at 30%. That wasn't really what I was seeking are there, if I wanted, and let's not talk about the reasons I might want them but or whether they're valid if I wanted a purely natural herbicide I could walk in a store today and buy is there such a thing. I mentioned Pelergenic acid. That's a natural compound. I'm not sure whether what's sold is synthesized or derived from a natural source, but it is a natural compound. And it's a good deal more active than acetic acid. It's a non carbon fatty acid. And there are there are other products that are mixtures of organic acids, etc. that that are approved by by the, the are recommended by the organic gardening organizations, but they, in terms of using them for broad scale agriculture to control weeds with those products as much more expensive and much less efficacious. Okay, there's, there's a lot of work out there on using microbial bio pesticides. This NBI 014 is an example of one and that that those products have really not gone. There have been a number of commercial products that have been on the market. We haven't really done very well we're having an OECD symposium in Italy. This fall that is trying to get out the reasons why these the technical reasons why these products have not worked very well. I think with new technologies. There is some hope that some of these microbial bio herbicides can be efficacious and economical in the future. And maybe I'm incorrect so please correct me. It seems like there's a big difference between the pesticides where plants seem to have developed things that we can more or less pull from the plant in its natural native form and be effective against insect pests and other things. Is there a reason, is there an underlying reason that that isn't so easy and herbicides. Well, auto toxicity is an issue. Plants that make herbicidal compounds can poison themselves. Okay, from an evolutionary standpoint. It's much easier for the plant to make compounds that kill fungi and insects without poisoning themselves than to make highly efficacious herbicidal compounds. And that's a whole nother issue that the most potent natural compounds in terms of fighter toxicity are produced by microbes, especially plant pathogens that kill weeds. They tend to make very highly potent fighter toxins that kill the food before they eat it. And as you know there's a great deal of information on these compounds. They tend to be very complicated compounds. Some of them are fairly toxic to humans also. But they are examples. They do prove that certain new targets are very effective for could be very effective for herbicides. So why don't we now formally start our question and answer period so if we can bring back in our other speakers, please. And so, again, please keep your questions coming. I'll start with a question that relates to something that someone pointed or another question, and this is. You had a plot of unique resistance cases, and it maxed out in the US at 160. What defines a case is that an individual weed species or is that a weed species in a particular spot or what does that mean. Okay, we, those individuals we call biotypes in wheat science, it could be within the same species there could be different biotypes from different populations. That's what I meant individual cases would be a same species in US or Canada, evolving resistance to same herbicide that would be an unique case here in the US or in multiple places in the US as well. It could be within the same species different biotypes as well. Okay, and the 160 should sound like a lot to us or it should sound like a little to us. Okay, it's an interesting question. If that 160 contains several of those agricultural really important weeds like you know sometimes you have each on the roadside which may not be very specific to agriculture fields, then we should be worrying in terms of crop production issues. So it all depends on the what are the prominent weed species we see in our cropping systems it could be different for different crops as well. See the weeds different weeds emerge at different period of times right, the weeds that are specific to corn may not be the same for sorghum or Milo so. Okay. But that opens up kind of an interesting lead in which is a question is open to all. If we frequently talk about the crops that are grown here in the US and in the industrialized world if we if we talk for a moment about potential for developing agricultural or, or new crops, and I knew I guess I'll put in parentheses and things like cassava other, but I see sorghum my you know, these other things that people are saying we should be eating more of. What should we be doing relative to to commercial herbicides around those types of crops and I'll open it to anyone who wants to answer. So in even in the new crops that you are referring even in US there is a lot of emphasis on growing for millet production we do have a research program on small grains and millet. So in that situation also again we have to look at the period or time during the year at which these crops are grown on what are the weeds that are going to emerge. And also depending on the region sometimes those weeks already have documented to be resistant to herbicide that can work in these crops so it has to be looked into more detail about where these crops are grown and what type of weeds and in that situation we already have resistant. Otherwise, yeah if there is, I mean, giving an example of other countries where herbicide resistance is not such a big issue then chemical weed control may still work but again, they should learn the lessons from us like you know, just do that multiple strategies and make sure they won't use the same herbicide mode of action over and over again. Jens or Steve, any comments? Yeah, I'm happy to get comments. I think sorghum will gain importance because it's yeah it doesn't need that much water. And chemistry is the work in corn very often also work well in sorghum. So with less water available, sorghum will gain importance. Globally, I think the highest calorie rate per hectare would come from potatoes. So that's something for development countries to adopt more. But I don't think that will change the main habits of the people so I think wheat and rice corn and soybean. Yeah, the big crops they will remain and we need this new traits in order to make those crops more resilient therefore all the new breeding technologies are very important and hopefully all the politicians and the countries of the world will realize that. Yeah, there are more countries now to allow genome editing like China, like India, and I hope you will follow, because that has the potential to speed up breeding and to allow new traits. And I am convinced there will be some some advances with respect to drought resistance and even yield can be increased. I didn't hear on your list rice is was that purposely split rice. I was included I'm sorry if I forgot that rice is definitely there. Steve, any comments. Yeah, well, when it costs $300 million to get a new product to market. The emphasis has to be on new pet herbicides and pesticides that fit those crops. And then some of these crops like millet is fine if you have a herbicide or pesticide that works with that particular crop but the companies that are putting $300 million out to bring a product to market have to emphasize its utilization on the major crops. Yeah, I guess I'll ask a very sweeping question to all of you. All of the presentations took a point of of assuming that herbicides were necessary for agriculture as we know it. And I guess a couple of people have questioned whether that really is true so can we put a little more meat on that bone if you will can can you come back and explain to me why we really need herbicides. Yeah, we had a great could listen a great presentation by an economic professor for agronomy at the units of getting he made up the calculation what it would mean to not to use pesticides. Basically, we would cut yield by 40 to 50% of course depending on the crop. And what would that mean for the world for the development work that people cannot afford the food prices will go up. We will foster geopolitical issues. We already today have an issues with 24% of the grain is produced in Ukraine and Russia, and some countries are highly dependent on it, we really need to make sure that we produce enough. We also allocated the right way that people have access to it. But if we basically want to go organic, basically mean you double water consumption, you reduce yield, and unfortunately also quality. That's just one part of it. Many people ignore that if you don't do anything you got fun guy you'll have the mic higher microtoxin level in there. And that can lead to severe issues in health, and also not just in food, also in feed. So feeding the animals. So, of course, if we cut our meat consumption, that would help the world a lot. Any comments from other other panels. And I think one of the things that we do with regard to herbicides is that, at least modern herbicides have greatly reduced the amount of tillage that's required in agriculture and tillage can cause long term damage to soil, and and sometimes almost irreversible damage to soil. Also tillage requires a lot of fossil fuel. And post emergence herbicides reduce tillage by quite a bit and which which in terms of fossil fuel use and soil retention are very beneficial. Okay, any other comments from you. I was going to say no till no till is really critical in many parts of the US, especially where I am like cancers we we because the wind issues and soil erosion this no till to preserve no till use of herbicide is indispensable. And also, like John said it is economical so far farmers have that chemical based weed control seem to be economical for them in terms of crop productivity. And also the principle of selectivity help them like you know crops are not affected by herbicides and we can manage we so with all those features I think chemical weed control will continue to be important in our strategy to manage weeds. One add on our nice blue planet has its name because 70% of the surface is water. And when you then further look into deserts and Arctic Arctic areas, mountains, seas, etc. And then a half percent of the of the surface of the world available for food production and agriculture. And this is limited with urbanization we cannot reactivate huge amounts of of areas without basically destroying the rainforest in Brazil and other countries. I'll start this one at the end, but other please for chime in. Suppose your dream of a new mode of action comes true and today you come up with one that's just great. Is it really possible to manage that in a way that resistance will forever be preserved. And if not, if it if resistance is inevitable. What does the timeline look like how long before we start seeing things that are resistant. Well a second glyphosate would help a lot, but not forever, and you need to have integrated past management because whenever you select, you will enrich certain populations that cope better with the selection pressure. So you really need to integrate all your measures and also go away from just growing corn and soy. Certainly when you take a look at certain regions in the US and will not be able to buy machinery or find suppliers for other crops. For wheat for example, you don't even find the find the harvester anymore in those regions and most probably it's important to really come down to a rotation. Some will have to lose some commercial value. So rotation is another word for reserve what you need to do is reserve. Okay, rotation is one part of the CC MB it's the chemistry cultural manual and biological control and you have to use all those weapons in order to keep the weapon sharp as long as long as possible. I think no more of action will last forever, because there are so many ways how the organism can become resistant. Already in the lab you have RNA I resisted insects, yeah. So even that mode of action will not last forever, because there are certain mutations that basically make the diversity that makes the organism cope with this selection pressure better. And entropy is a real real pain. Yeah, so anybody else got any comments on that. Any, any, that's a little gloomy outlook any any brighter way to interpret that. I think we have to be realistic. Okay, all right. So, again, I'm reading some of the questions here I think that they're now, you know, full disclosure, it's been a while but for many years my my butt was in a tractor seat, and then a combine seat every year. So I have played in the fields. Modes of that modes of action different is not what I'm looking for. But, but you have pre emergent you have post emergent you have spot type herbicide applications you kind of go through what the challenges of each of the different types of herbicide are as far as whether it's pre emergent or something that you spray to kill a plant once it's already emerged. I think, go on please. I mean, you want me to the challenges that you asked in terms of use of pre versus post emergent herbicide or spot herbicide spot application. Emergence is very, very critical and important mark but the challenge here is you need activation like moisture as soon as you apply pre emergent herbicide. They should be some rain in be this should be there in the forecast or some way we have to get these herbicides activated otherwise they're not going to be effective. Why the post emergent herbicides work best is like you know, most of these post emergent herbicide applied after the crop but we both emerge, and it gets, you know easy in terms of application they can go on combine and do, and not much activation needed in that and most of especially as I mentioned you know glyphosate is applied as a post emergent herbicide foliar herbicide. So growers once they have their own the pretty crops growing it was pretty easy for them to go and apply a post emergent. I think it's really good even some of the resistant ways that for post herbicide, they could be susceptible to pre herbicide application, but again, the challenge is the activation. Any comments from our other speakers. But it's really important to also have a pre emergence application scheme in order to reduce the pressure and perfect will be to have a few herbicide in the future that just does not kill just at the early stage of plant growth, but which will also kill a bit later. So any of the heavy sites how the problem that amaranth for example grows too fast, and then you have slippage or doesn't work anymore to kill the plant the plant because it just out grows and out competes the herbicide activity. So the spring window the timing is very important for the farmer, and to have the combination of the different modes of action and rotation of the modes of action from year to year, not just use the same product every year. And that should help to control control the weeds better. And then it's also all the companies are monitoring and they have the sales wrap and they're looking at the situation and making the recommendation on which products to use in order to can bet local resistant with populations that the problem doesn't spread further into the next county or your state during the season. I think that Steve are you good. Also, the site specific application more and more advanced technologies are being developed so that you know we can have site specific application that way reduce the amount of herbicide used and also reduce the pressure on. That research is, I would say, still not very advanced but a lot of progress has been made in wheat science so that is going to be, I think in the future, people would look into the robotics or site specific based week. We've touched on it a couple of times but nobody really highlighted it the the interaction now between genetics, as in modified genetics and herbicides is very strong. Is that likely to continue in the future is the luster gone off of that and will, will it be the actual question was will it be replaced with some of the technologies that were just mentioned like AI and robotics. There is a clear advancement but I think not doing the next few years. Jones applied already in many countries that helps a lot. The farmer, but think about these millions and millions of actors, and you have to do the screening you have to go maybe over the future several times. So you need multiple robots or very smart systems that really are able to combat at the time of that at the time of emergence that different flushes. So, I think it will first gain importance in the specialty crops. But in the big field crops, it takes longer time, or we need different solutions so pre emergence plus post cleanup with the more. If you know really your key areas your key problems on your fields where the population so digital information, helping you, then it can be solution for quite some promise, but I doubt that it will be the 100 million acre solution that will take more time. Again, this might be a little bit farther out but but there's one question concerning perennial crops that several have pointed. I mean I know literature is out there, and there are perennial crops they're grown worldwide are perennial crops a solution or more of a problem. Nobody wants to bite on that one. I think sugar beet has a similar issue. So it's also prone to herbicide resistant weeds. And that's a, yeah, two year crop basically. You have to put it into soil then and harvest the next season. It's, I think, But things like sugar cane sugar cane bananas things like that that are more perennial is weed control so big issue there and does it does the perennial crop make it easier or harder. Okay, and what is totally different, because you have to have a lot of strong coverage and your herbicides really need to come down to the to the wheat. That's a special challenge. So it's a very special market and also a low price market. I think that's one of the key reason why power quite is still used there. And we're getting close to the end. I think this will be the final question before our final comments. I guess I'll direct this one first to Steven. I guess people looked at a lot of your structures and we're thinking they were relatively large in in microbial in nature and I guess our chemist among us is a chemical sciences round table we're asking whether it's the end of small molecule actives. Do you have any comments. That is an issue as I pointed out and theoretically some of these compounds might be reduced to smaller molecules that still get the same target site, these large molecules prove the target site is a viable target site. There may be other compounds that are related that could be economical. That's the hope at least. Of course they're not all small glue phosphate or phosphonethrion is a relatively small molecule that's very a very effective herbicide. We, there are some very highly fire toxic compounds that are not so complicated that I didn't go over so. The molecular size is an issue. If you're using a bio a bio pesticide like a microbial bio herbicide that's producing its own compounds. Molecular size is not an issue or complexity is not an issue because you're not synthesizing it in a factory that the microbes producing it. So let's go around the table here. So you have any final comments with the online. My comments again as I mentioned the herbicide resistance is an issue of read management would be challenging but we have to emphasize on integrated read management that that's the thing. I have like a take home message from this. And industry will go on to look for new chemistry. There's a clear need for innovation and drives industry, but it's sad we need to keep our new weapons sharp. See, a lot of new technologies many that ends mentioned in his presentation and there are even some others that if if half of these pan out I think we will have new products in the future that that we don't have resistance to yet, but nature will find a way if we use something over and over. There's no doubt about that. Well, I certainly want to thank our three speakers, Phillip, Jens and Steve, and thank you all for attending. The three presentations and recording of the webinar will be posted on the chemical sciences roundtable website next week, the URL is on the screen as you as you see now. If anyone has additional questions or comment comments or concerns please email see SR at nas.edu, which is also on the screen. The webinar closes attendees will automatically be directed to a survey to provide the feedback on the webinar please do that upcoming CSR events include two fully virtual events two webinars, one on bio polymers occurring on July 19. The other is on hydrogen occurring on October 7. Exciting to me because we'll be face to face a bit one and a half day in person workshop which will also be aired virtually on innovations and catalysis to address modern challenges will take place in Washington DC on October 24 and 25. For more information about these events and and more you can subscribe for updates on the CSR website. I'd like to thank you all for attending and for all the great questions. And with that, I think we will close.