Evaluation of onion accessions for resistance to thrips in Brazilian semi-arid regions

This study aimed to evaluate onion accessions regarding their resistance to Thrips tabaci Lindeman, in order to enable the development of cultivars that are resistant to this pest. The experiments were carried out without chemical control, in a randomized block design with three replications, in Petrolina, PE and Juazeiro, BA. Six evaluations of thrips populations were carried out starting 15 days after transplanting, each one after 7 days. Simple correlations were estimated among all variables. Statistical differences were observed for the number of adults in different evaluations, while the number of nymphs showed no statistical differences. The largest average yields of commercial bulbs were observed for ‘Vale Ouro IPA 11?, ‘BRS Alfa São Francisco’, ‘Franciscana IPA 10? and ‘Sirius F1? while ‘Red Creole’, ‘Creole Mercosul’ and ‘Conquista’ had the lowest yield. The bulb commercial yield had simple negative correlations with nymph degree of infestation (DI) in the four evaluation phases and adult DIs at 22 days. Negative correlations between commercial bulb yield and central angle of the plant were observed, indicating that plants with higher bulb yield have a lower angle of the central leaves. The results of the study suggest that the resistance mechanism is due mainly to tolerance to the pest.