Resistance to onion thrips (Thysanoptera: Thripidae) in onion cultivars does not prevent infection by Iris yellow spot virus following vector-mediated transmission

Abstract

Onion thrips, Thrips tabaci Lindeman (Thysanoptera: Thripidae), is a global pest of onion, Allium cepa L., and the principal vector of Iris yellow spot virus (IYSV) that can cause 100% crop losses. The purpose of this study was to evaluate onion cultivars resistant to T. tabaci feeding damage for their reaction to IYSV following exposure to viruliferous T. tabaci in both laboratory and field experiments. In the laboratory experiment, virus-free onion cultivars grown in pots were infested with 32 T. tabaci second instars collected from onions in an IYSV-infected field. In the complementary field experiment, virus-free onion plants in pots were moved to an onion field where IYSV was present. In both laboratory and field trials, plants were tested for IYSV by DAS-ELISA after 2 and 3 wk, respectively. Although plants were exposed to T. tabaci for a short period, IYSV was detected in all onion cultivars with the percentage of infected plants varying from 3 to 25% and 37 to 70% in the laboratory and field experiments, respectively. IYSV infection levels did not differ statistically between thrips-susceptible and thrips-resistant onion cultivars in laboratory and field experiments.