EVALUATING RESISTANCE TO GRAPE PHYLLOXERA IN VITIS SPECIES WITH AN IN-VITRO DUAL CULTURE ASSAY

Forty-one accessions of 12 Vitis L. and Muscadinia Small species were evaluated for resistance to grape phylloxera (Daktulosphaira vitifolia e Fitch) using an in vitro dual culture system. The performance of the species tested in this study was consistent with previously published studies with whole plants and helps confirm the utility of in vitro d ual culture for the study of grape/phylloxera interactions. This in vi tro system provides rapid results (8 wk) and the ability to observe th e phylloxera/grape interaction without interference from other factors . This system also provides an evaluation that overemphasizes suscepti bility, thus providing more confidence in the resistance responses of a given species or accession. Among the unusual responses were the sus ceptibility of V. riparia Michx. DVIT 1411; susceptibility within V. b erlandieri Planch.; relatively wide ranging responses in V. rupestris Scheele; and the lack of feeding on the roots of V. californica Benth. , in contrast to the severe foliar feeding damage that occurred on thi s species. Vitis californica #11 and V. girdiana Munson DVIT 1379 were unusual because phylloxera on them had the shortest generation times. Such accessions might be used to examine how grape hosts influence ph ylloxera behavior. Very strong resistance was found within V. aestival is Michx. DVIT 7109 and 7110; V. berlandieri c9031; V. cinerea Engelm; V. riparia (excluding DVIT 1411); V. rupestris DVIT 1418 and 1419; an d M. rotundifolia Small. These species and accessions seem to possess enough resistance to enable their use in breeding with minimal concern about phylloxera susceptibility.