The variability of yield characters associated to Thrips tabaci (Thysanoptera: Thripidae) resistance was estimated in 62 half-sib progenies of onion cv. ValeOuro IPA-11. The controls were the cvs. ValeOuro IPA-11 and the parentals Roxa IPA-3 and Belém IPA-9. The experiment was conducted in field conditions, in Juazeiro, Bahia State, Brazil, following a complete randomized block design, with three replications. The estimates of the parameters from the population of ValeOuro IPA-11 demonstrated high enviromental influence for all characters. The highest estimates of herdability and expected gain with 20% of selection pressure were, respectively, 35.74% and 10.39% for the production of commercial bulbs (PBC), 31.33% and -24.48% for percentage of unproductive plants (%I), 33.92% and -16.80% for production of non commercial bulbs (PBNC) and 30.31% and 13.18% for percentage of non commercial bulbs (%BNC). These characters seem to indicate better possibility of genetic progress with the selection. The characters mean infestation of immature T. tabaci on the two completely developed inner leaves (NINFA) present herdability of 18.24 and 21.34% and expected gain with 20% of selection pressure of 18.24 and -11.22% at 48 and 69 days after transplanting (DAT), respectively, indicating superior gains in selections at 69 DAT. Although NINFA were 31.96 insects, 45.16% of ValeOuro IPA-11 progenies demonstrated PBC values above the average, suggesting that tolerance may be the resistance mechanism.
Allium cepa; Thrips tabaci; herdability; genetic parameters; tolerance; plant resistance
