Inheritance of maize weevil resistance in maize hybrids among lines from southern Africa, Mexico and CIMMYT-Zimbabwe
1999
Derera, J. | Pixley, K.V. (Centro Internacional de Mejoramiento de Maiz y Trigo (CIMMYT), Harare (Zimbabwe)) | Giga, D.P. (University of Zimbabwe, Harare (Zimbabwe). Department of Crop Science)
Maize weevils cause considerable losses to stored maize grain worldwide. Maize inbred lines, six each from southern Africa, Mexico (resistant) and CIMMYT-Zimbabwe were mated in sets according to the North Carolina Design II. Fifty-two experimental F2 hybrids, three commercial hybrids and popcorn were screened in no-choice tests, with four replications, at 28+2.C and 70+5% relative humidity. The number of weevils emerged (F1 ), grain weight loss and susceptibility indices were calculated after all weevils had emerged. Maternal effects were significant for susceptibility index and weevils emerged. GCA and SCA effects were of similar importance for susceptibility index, weevils emerged and grain weight loss. Susceptibility indices ranged from 6.08 (for a hybrid of lines from Muneng8128 and Pool23QPM) to 15.73 (popcorn), grain weight loss was 0.13 to 12.75%, and number of weevils emerged was 18 to 188. Very few hybrids showed resistance to weevils. The best regional hybrid was NAW5867 x M37W (relative index = 8.7) and the best CIMMYT hybrid was CML216 x M37W/ZM607 (relative index = 7.6), but both of these hybrids were classified 'susceptible'. Commercial hybrid checks were susceptible, with indices between 9.3 and 10. Our results suggest that development of weevil resistant varieties is a challenging task, as additive (GCA), non-additive (SCA) and maternal effects were important in determining maize weevil resistance for these maize hybrids.
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