Heritability of thrips resistance in the 'IPA-3' onion cultivar in South Texas

A two season study was conducted to compare the onion cultivars TG1015Y and IPA-3 for resistance to thrips in South Texas. Narrow and broad sense heri tabilities were estimated from populations developed from the cross, 'IPA-3 ' x 'TG1015Y'. Parents, F1, F2, and the respective backcross populations we re evaluated for thrips numbers at the Texas Agricultural Experiment Statio n, Weslaco, TX. 'IPA-3' had significantly fewer thrips than 'TG1015Y' in bo th seasons. Yield was significantly different only in the 1996-97 season. T he heritability of thrips resistance in this study was very low. Depending on the methods of estimation h(2) was 5.3% and 4.0%, and H-2 was 4.1% and 8 .0%. These results suggest that greater genetic gains for thrips resistance in onion can be achieved by selection on a family basis rather than using single plant selection.