Genetic variability for resistance to trifluralin in Zea mays

Soil carryover of the herbicide trifluralin can injure Zea mays. Therefore, the development of resistant hybrids can be an important breeding objectiv e. This research was conducted to study the genetic variability for triflur alin resistance in Z. mays, the effects of genes controlling resistance, an d the seed lipid content of resistant (R) and susceptible (S) inbreds. Twen ty inbreds were tested under greenhouse conditions at three trifluralin rat es (0, 12.5, and 125 g ai ha(-1)). Lo1067 was the most resistant, and A632 was the most susceptible inbred. Hybrids among R and S inbreds were tested, along with their parents, under greenhouse conditions (using the same thre e rates) and in the field (at 0, 0.4, and 0.8 kg ai ha(-1)). Under both gre enhouse and held conditions, inbreds R were more resistant than S. Hybrids R x R were more resistant than S x S, indicating that additive effects were important. Hybrids R x S and S x R did not significantly differ, indicatin g that reciprocal effects were not important. On average, hybrids R x S and S x R were intermediate between R x R and S x S, suggesting that nonadditi ve effects were negligible. The difference between the mean across hybrids and the mean across parents (further estimating the importance of nonadditi ve effects) was significant only for parameters investigated in the greenho use. Greenhouse data were correlated with field data, but the coefficients of determination were < 50%. The ability to predict hybrid resistance on th e basis of parental mean was higher in the greenhouse (r(2) = 0.78) than in the field (r(2) = 0.47). R and S inbreds also differed in seed lipid conte nt, but correlations were negligible with greenhouse and field data. Data i ndicated the presence of genetic variability for trifluralin resistance, th at additive effects were prevailing, and that the resistance level was not related to seed lipid content.