Settling and feeding behavior of sharpshooter vectors of Xylella fastidiosa on plum genotypes resistant to leaf scald disease

Plum leaf scald (PLS) is a serious disease caused by Xylella fastidiosa subsp. multiplex , a pathogenic bacterium transmitted by xylem-sap feeding leafhoppers, commonly named sharpshooters (Hemiptera: Cicadellidae: Cicadellinae). In Brazil, the development of plum genotypes that apparently are not infected under field conditions has opened new perspectives for disease control based on host plant resistance. For example, PLS incidence on ‘SC13’ and ‘SC7’ genotypes is almost null under field conditions, although ‘SC13’ is infected by graft inoculation. Thus, we hypothesized that the performance of these genotypes in the field may be related to vector behavior. To verify this hypothesis, we investigated the settling preference and probing and feeding behavior of the sharpshooters Bucephalogonia xanthophis (Berg) and Sibovia sagata (Signoret) on the PLS-resistant plum genotypes, ‘SC7’ and ‘SC13’, and on the naturally infected cultivar, ‘Laetitia’. In the settling experiments, ‘SC7’ was less preferred by both vector species. For S. sagata held on ‘SC13’, reduced sap ingestion rates were observed. For B. xanthophis, probing and feeding activities differed between individuals held on ‘SC13’ and ‘Laetitia’. Specifically, duration of the stylet pathway phase, duration of xylem sap ingestion events, and number of interruptions of the xylem phase differed for B. xanthophis held on ‘SC13’ and ‘Laetitia’. The results show that the resistant genotypes affected host plant selection by the sharpshooters and highlight the importance of incorporating vector behavior into studies aimed at identifying or developing X. fastidiosa -resistant genotypes.