 Hello everyone. My name is Elina Koneva and I'm a fruit crop extension specialist with the Alabama Cooperative Extension System and a faculty at the Department of Horticulture at Auburn University. Today I'm going to present information about size controlling fire blight resistant apple rootstocks mainly their performance in Alabama. Well worldwide USA is the second largest world producer of apples in the 2021 season and red delicious and golden delicious have dominated apple production in Alabama and the southeast for some time. Fuji has adapted well to southeastern conditions and continues to be planted by commercial growers around but the production is facing some challenges and the most significant of them is the fire blight disease that is called that is caused by the bacterium hervinia milivora. This is a disease that affects apples and pears. So another emerging problem is the warming climate that causes in some winters low or insufficient chilling hour accumulation and apples are known to have relatively high chilling requirements. So this is a real challenge for apple production. Also the conventional orchards being in use right now they provide relatively low production efficiency and there are currently some systems developed for their high production efficiency and we wanted to see how they will perform. So on this picture you can see the typical shepherd's group symptom of fire blight on newly formed apple shoot but in addition to blighted shoots fire blight can cause symptoms on blossoms or fruit on trunk and even on the rootstock of the tree. The annual national losses that are caused by fire blight to apple production exceed 100 million dollars. There are chemical control options available such as some copper compounds could be used or antibiotics like streptomycin but the most reliable management option is considered to be the cultural control through the use of fire blight resistant rootstocks. The current advances in apple production led to development of fire blight resistant rootstocks from different rootstock breeding programs around the world and also the size controlling rootstocks for high density orchards have been developed. In addition the new training systems for high density orchards have been also developed and the release of this relatively low chill Aztec Fuji cultivar is very beneficial for locations like us in alabama with lower chilling winters. The idea of using dwarf or size controlling rootstocks to reduce the size of an apple tree is not new. It has been around since 1920s when a series of mulling rootstocks have been developed at the east mulling in England. More recently Russia released the budugovsky series of rootstocks and in Canada we had a violent series of rootstocks and Cornell University has developed and released a series of Geneva rootstocks with different size control levels. Recent development of various training systems also led to the establishment of high density highly efficient orchard systems where the maximum blight interception was provided and a better blight distribution within the canopy occurs. Typical for these systems is also reduced need for pruning and reduced labor costs for maintenance of those orchards. Also earlier returns to the growers are due to the precocity and improved fruit quality are very typical especially for the tall spindle training system which is considered to be the best. Aztec Fuji cultivar was developed in New Zealand and it was released as the most colored strain of Fuji. The texture of the fruit is crispy and the flesh is very juicy and very sweet. Chilling requirements of Aztec Fuji are between 400 and 500 hours and of course since this is a new release very little is still known about the performance of Aztec Fuji in North America. In order to establish if the recent advancements and innovations in apple production would provide benefits to our growers, apple growers in Alabama we established an apple rootstock study in 2014 with the objectives to evaluate the effect of 14 newly developed size controlling fire blight resistant root stocks on yield fruit quality and crop efficiency of Aztec Fuji apple grown under Alabama environment using innovative tall spindle orchard system. The experiment was established at the Chilton Research and Extension Center and the planting density was 672 trees per acre. The tall spindle system consisted of three row wire support and a height of three meters. During the eight years of this study we collected sets of data to determine the effect of the rootstock on tree vigor, productivity and also on fruit quality and this chart represents our 2021 data based on the trunk cross sectional area and you can see that our green bars here represent our most vigorous vigorously growing rootstocks and they are mainly from the Van Land series and the growth represented by the white bars reflects mostly semi-dwarf rootstocks while the orange bars here represents six rootstocks mainly from Geneva series that had dwarf type of vigor or grew slowly and were the smallest anywhere between 50 percent or smaller trees in comparison to our Vineland series of rootstocks. During the years of our study we have recorded significant rootstock effect on number of root per tree. Here the chart represents our 2021 data where our most dwarfing rootstocks from Geneva series are colored in orange and you can see that Geneva 202, Geneva 935, Geneva 214, Geneva 11 and Geneva 41 had a very similar number of root per tree in comparison to trees that were on the most vigorous Vineland series of rootstocks namely v7, v1, v5. This light represents the rootstock effect on cumulative youth in kilograms per tree for the eight years of our study. So in 2021 we established that trees on Geneva 969 produced the highest cumulative yield throughout the years and trees that were grafted on v10 had the least cumulative yield. But also we noticed that trees that were grafted on Geneva 935 performed very similarly to G30 and two of the Vineland series trees on v5 and v6. Also Geneva 11 cumulative yield was the same like the cumulative yield of trees that were grafted on Vineland 1. When the yield efficiency was calculated and expressed as kilograms per square centimeter of trunk cross sectional area we found out that trees that were grafted on four Geneva series like Geneva 214, Geneva 41, Geneva 935 and Geneva 202 provided the highest efficiency. All of them were dwarf dwarfing trees. So we also evaluated the rootstock effect on the mean fruit weight during the years and in some years we saw significant differences and in some seasons there were not significant differences. So this table represents our 2021 data when the mean fruit weight varied between 239.7 grams and 276.1 grams but the fruit weight was not significantly different between different rootstocks and the fruit weight on trees that are considered dwarf trees are highlighted in green here. Throughout the years of this study we have seen some significant rootstock effect on Nazi Fuji fruit quality attributes but usually the sugars were within the normal typical rate of 13 to 15 percent bricks throughout the years. When evaluating the rootstock effect on tree survival I should mention that trees on M9-337 were completely lost two years ago but also this is a rootstock from the Moring series and it does not have any fire blight resistance. It was included as one of the standard cultivars of rootstocks in our study. Looking at the suckers formation we can see that two Geneva series of rootstocks namely G969 and G11 did not produce any suckers and that is a good news for the nurseries while Geneva 30 produced the highest number of suckers per tree and this was 3.9 suckers on average. But to summarize our 80 results from this study I'd like to mention that G41, B10, G935, G202, G214 and G11 are promising size controlling rootstocks providing 30 to 50 percent smaller tree. Also these smaller trees produced between 71 and 85 percent of the total yield of the most diverse trees. Trees grafted on dwarf rootstocks G41, B10, G935, G202, G214 and G11 had the highest yield efficiency. Also trees on the fire blights acceptable M9 rootstock did not survive after the seventh season. Violent series of rootstocks may not be a proper choice for Alabama and the Southeast due to their high vigor. With that I would like to thank for your attention and please email me if you have any questions about this information presented today.