This report presents results of Walker lab efforts to optimize the breeding of fanleaf degeneration (fanleaf) resistant rootstocks through molecular genetic methods. These efforts are two-fold: 1) to understand and utilize O39-16?s (a Muscadinia rotundifolia based rootstock) ability to induce tolerance to fanleaf virus infection in scions; and 2) to understand and utilize resistance (XiR1) from Vitis arizonica to the dagger nematode, Xiphinema index, which vectors grapevine fanleaf virus (GFLV) from vine-to-vine by root feeding. We made minor adjustments to a genetic map of a small population of vinifera x rotundifolia (VR) hybrids. Dr. Hwang took a new position at Missouri State University and is currently completing a manuscript detailing this map. To better map rotundifolia-based characters in a rootstock background we are turning mapping attention to an expanding population of 101-14Mgt x rotundifolia Trayshed. This population now has about 100 individuals and over 600 viable seed from 2010 crosses are now being germinated to expand the population. Nematode testing has found that the progeny segregate for rooting ability and resistance to dagger and root-knot nematodes, but all are resistant to ring nematode. Once metabolites associated with tolerance to fanleaf are discovered we will examine this population and develop markers to this tolerance. We have completed two years of xylem sap tests from fanleaf infected O39-16 and the highly susceptible St. George compared to uninfected O39-16 and St. George. This analysis was done at the UCD Metabolomics Center and yielded data on thousands of metabolites in grape sap at bud break and bloom. We used the four saps to identify compounds that were at very similar levels in infected O39-16 and uninfected O39-16 and St. George, but different from infected St. George. Dr. Doug Adams helped us identify precursors to phytohormones involved in flowering and other compounds that may play a role in inducing virus tolerance. The final decisions on which of these compounds to pursue this year is waiting for equipment repair at the Metabolomics Center. We do have eight metabolites that appear to be highly associated with rootstock-induced fanleaf tolerance and we will be testing for them in saps from our campus and industry plots this year. The genetic and physical mapping of dagger nematode resistance gene, XiR1, was published after several revisions and submissions (Theoretical and Applied Genetics 121:780-799 (2010)) and we have started testing the first candidate genes (XiR1.1 and XiR1.2) to determine which is responsible for resistance. This process involves engineering the genes into cells from the highly susceptible St. George and testing to see if the resulting transformed plants resist dagger nematodes. The first transformations were recently completed. These tests will not only identify the resistance. We are also working on ways to rapidly evaluate fanleaf resistance and tolerance through in vitro grafting.
/wp-content/uploads/2017/09/AFV-Header-Logo.png 0 0 AVF /wp-content/uploads/2017/09/AFV-Header-Logo.png AVF2010-10-16 06:22:042017-10-16 06:23:06Molecular Genetic Support to Optimize the Breeding of Fanleaf Resistant Rootstocks