Resistance of potato genotypes (Solanum spp.) to Bemisia tabaci biotype B

The resistance of 24 potato genotypes to B. tabaci (Genn.) biotype 13 (Hemiptera: Aleyrodidae) was evaluated in five greenhouse experiments. The first experiment we evaluated the attractiveness and preference for oviposition in a free-choice test (randomized blocks, 24 treatments, and eight replications). In two other experiments we evaluated no-choice preference for oviposition (randomized blocks, six treatments, and tell replications). The whitefly egg-adult cycle was monitored using a statistical design in randomized blocks with five replications. Trichome density was evaluated in all experiment with 24 treatments and six replications, in a completely randomized design. In the free-choice test, potato genotypes NYL 235-4 and IAC-1966 were the most attractive to adults, while Cultivars Achat, Aracy Ruiva, and Monte Bonito presented the lowest number of adults. Also in this assay, cultivars Achat, Ibituacu, Panda, IAC-1966, and Agata presented the lowest number of eggs, while in the no-Choice test, only Cultivar Achat and lAC-1 966 remained resistant. Consequently, for these two genotypes non-preference is the oviposition resistance mechanism. The eg adult cycle varied from 2 1 days (cultivar Panda) to 22.5 days (clones IAC-1966 and NYL 235-4). The adult emergence varied from 91.2% (clone IAC-1966) to 99.3% (cultivar Ibituacu). Clone NYL 235-4 had the greatest number of simple (ST)and glandular(GT)trichomes while clone IAC-1966 had the lowest number of Stand, clone IAC-6290, of GT. There were significant correlations between adult attractiveness and oviposition preference; between oviposition preference and ST density; all between oviposition preference and GT density. Considering all characteristics, cultivar Achat was tile most resistant to B. tabaci biotype B among all potato genotypes studied, while clone NYL235-4 proved (past tense) to be susceptible.