Progress in rootstock breeding was made in a variety of areas in 1993. The best of the 1989 seedlings, crosses of rupestris x rotundifolia, and one solonis x rotundifolia, have almost completed testing at the UC Kearney Ag. Center in Mike McKenry’s nematode tanks with 3 of his most aggressive Meloidogyne races. Several of the 1989 seedlings have good resistance. Dormant cuttings of some of these seedling selections have been grafted with Chardonnay and are destined for planting in a nematode/phylloxera trial in Ripon. These were also grafted to Flame Seedless for establishment in a root knot trial in Fowler. 926 1992 seedlings of an original 1,888 were recently planted in the new breeding block. 1,671 1993 seedlings have also been planted in this block. Ninety three new crosses designed for the production of nematode (both dagger and root knot) resistant rootstocks were produced in 1993. These utilized selections that L.A. Lider produced utilizing arizonica, candicans, champinii, and longii. We crossed these Lider selections with species selected to improve rooting, nematode resistance and drought tolerance. We also made 55 crosses designed to allow study of the taxonomic relationships among the North American Vitis species. Some of these may also prove very valuable as potential rootstocks. The 1994 pollinations emphasized the same objectives as the 1993. Thus far, forty-four crosses have been made. We completed the second round of a screening of Vitis and Muscadinia for resistance to Meloidogyne incognita. Resistance was common in aestivalis, champinii, and rotundifolia, it was also found in cinerea and rufotomentosa. Evaluation of an embryo-rescued population of Thompson Seedless seedlings for resistance to fanleaf virus continues, thus far all seedlings allow virus replication. This was expected since resistance to fanleaf appeared to be a rare recessive trait in earlier studies. We have made significant progress in developing an in vitro co-culture system for phylloxera using only root cultures. This system is now being tested to confirm that resistant and susceptible species act as expected in tissue culture. We have had trouble finishing our studies of DNA diversity in phylloxera, but procedures are now working and the data ready for final analysis. Preliminary examinations of the data show that phylloxera are variable within and among biotypes. There are no consistent A or B genetic markers. This suggests that B type phylloxera are not spreading, but that they are selected for at different AXR#1 sites.
/wp-content/uploads/2017/09/AFV-Header-Logo.png 0 0 AVF /wp-content/uploads/2017/09/AFV-Header-Logo.png AVF1993-11-22 15:06:242017-11-22 15:07:01Breeding grapevine rootstocks for resistance to soil-borne pests and diseases