Development of New Rootstocks for Use in Napa Valley Fanleaf Sites
The bench grafted plants of a number of Vitis rupestris x Muscadinia rotundifolia rootstocks with Cabernet Sauvignon scions have been planted in BV#2 block C-2 to evaluate their resistance to fanleaf degeneration. This plot is designed to test a wide range of rupestris x rotundifolia hybrids, including some known to be very susceptible to X. index feeding. The inclusion of such selections will allow us to examine the effect that rotundifolia has on disease expression, when GFLV is present in the scion. 039-16 (yinifera Xrotundifolia) has this effect on scions – feeding damage does not occur, but X. index successfully transmits GFLV to the scion. However, fruit loss does not occur, and it may be that the rotundifolia parentage may induce tolerance to GFLV. The end of this plot will also house a separate experiment that Ed Weber and I are collaborating on – examining the potential of 039-16 to act as a resistant interstock, and limit GFLV expression and movement. I am attempting to make the nematode/GFLV pressure as uniform and intense as possible in this trial, by interplanting the highly susceptible St. George between all test vines. There are 5 single vine replicates of 36 rootstock selections, and 3309C, 039-16 and St. George as controls.