Resistance to transmission of grapevine fanleaf virus by <i>Xiphinema index</i> in some <i>Vitis</i> species and hybrids

Abstract

Many vineyards in Germany are infested by nematodes which can transmit virus diseases. Breeding of rootstocks resistant to nematode feeding and virus transmission is an important way to control these virus diseases.
A method has been developed for testing breeding stocks for these characteristics with regard to grapevine fanleaf virus (GFV) and its vector Xiphinema index.
The plants to be tested were first grown together in a single pot with both GFV-infected plants of Vitis cv. Siegfried and plants of the same cultivar which were virus negative according to an ELISA test: 2 months after planting, the pots were inoculated with about 50 nematodes. In a second experiment, single healthy plants of different hybrids and species were potted and inoculated with about 200 nematodes carrying GFV. After 3-10 months, roots were inspected visually for swellings and galls and tested for the presence of GFV by ELISA.
In all cases, the previously healthy cv. Siegfried showed symptoms of feeding on the roots and these roots showed a positive reaction to the ELISA test. After 6 months, GFV could also be detected by ELISA in the basal parts of the stems.
The reaction of the test plants was dependent on their genotype. A high susceptibility to feeding by the nematodes and high percentage of transmission to GFV was displayed by American species and interspecific hybrid rootstocks. One of the V. vinifera x V. rotundifolia hybrids showed no visual symptoms of nematode feeding and no virus transmission 9 months after inoculation.