A differential interaction study of Bemisia tabaci Q-biotype on commercialtomato varieties with or without the Mi resistance gene, and comparative host responses with the B-biotype

Three tomato varieties (Motelle, Ronita, and VFN8) bearing the Mi-1.2 gene providing resistance to nematodes Meloidogyne spp. and to the potato aphid Macrosiphum euphorbiae Thomas, and three varieties not bearing this gene (M oneymaker, Roma, and Rio Fuego), were compared by choice assay for host pre ference using the Q-biotype of Bemisia tabaci (Gennadius). The most preferr ed hosts, determined by infestation levels and numbers of feeding adults we re Moneymaker, Rio Fuego and Roma, all of which were not carrying the Mi ge ne. Ronita and Motelle, both of which bore the Mi gene, were the least pref erred hosts. In a no-choice assay, B. tabaci females laid a significantly l ower number of eggs on the varieties that carried the Mi gene than on those lacking the gene. Differences were more dramatic when plants carrying the Mi gene were pooled together and compared with pooled plants without this g ene. Significantly greater values were obtained for the Mi-lacking group fo r all parameters tested. Comparing these results with those from a previous study on the B-biotype of B. tabaci, Q-biotypes were found to produce high er daily infestation rates on most of the tomato varieties. When results fr om plants carrying Mi were pooled, they showed lower infestation levels of Q-biotypes than B-biotypes. The Q-biotype infested less Mi-plants and more non-Mi plants than B-biotype. Q-biotype females produced significantly less pupae than the B-biotype females on both groups of plants. These results s uggest the existence of an antixenosis and antibiosis-based resistance to t he Q-biotype of B. tabaci in Mi-bearing commercial tomato varieties, which is greater than that previously reported for the B-biotype.