Evaluating Resistance to Grape Phylloxera in<i>Vitis</i>Species with an<i>in vitro</i>Dual Culture Assay

Abstract

Forty-one accessions of 12 <i>Vitis</i> L. and <i>Muscadinia</i> Small species were evaluated for resistance to grape phylloxera (<i>Daktulosphaira vitifoliae</i> Fitch) using an <i>in vitro</i> 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 <i>in vitro</i> dual culture for the study of grape/phylloxera interactions. This <i>in vitro</i> system provides rapid results (8 wk) and the ability to observe the phylloxera/grape interaction without interference from other factors. This system also provides an evaluation that overemphasizes susceptibility, thus providing more confidence in the resistance responses of a given species or accession. Among the unusual responses were the susceptibility of <i>V. riparia</i> Michx. DVIT 1411; susceptibility within <i>V. berlandieri</i> Planch.; relatively wide ranging responses in <i>V. rupestris</i> Scheele; and the lack of feeding on the roots of <i>V. californica</i> Benth., in contrast to the severe foliar feeding damage that occurred on this species. <i>Vitis californica</i> #11 and <i>V. girdiana</i> 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 phylloxera behavior. Very strong resistance was found within <i>V. aestivalis</i> Michx. DVIT 7109 and 7110; <i>V. berlandieri</i> c9031; <i>V. cinerea</i> Engelm; <i>V. riparia</i> (excluding DVIT 1411); <i>V. rupestris</i> DVIT 1418 and 1419; and <i>M. rotundifolia</i> Small. These species and accessions seem to possess enough resistance to enable their use in breeding with minimal concern about phylloxera susceptibility.