2017 ASHS Annual Conference

Grape phylloxera (Daktulosphaira vitifoliae Fitch) can decimate crops due to its ability to infest roots of European grapevine (V. vinifera) leading to secondary infections and vine decline. This insect pest can also infect the leaves of North American native species and hybrid cultivars, with some reports of crop reduction in serious infestations. We identfied a major quantitative trait locus (QTL) for resistance in to the foliar form of phylloxera in a hybrid breeding family (n = 125) on chromosome 14 using field observations and a replicated greenhouse study. We quantified multiple traits in order to identify a phenotyping method that was most efficient to capture the variation observed in the population. Visual rating (1-7 scale) identified the same QTL as counts of galls per plant, count of infected leaves per plant, or the area under disease progress curve over three weeks. Additionally, two novel QTL for root resistance were identified on chromosomes 5 and 10.