Genetic variability for resistance to trifluralin inZea mays

Abstract

Soil carryover of the herbicide trifluralin can injureZea mays.Therefore, the development of resistant hybrids can be an important breeding objective. This research was conducted to study the genetic variability for trifluralin resistance inZ. mays, the effects of genes controlling resistance, and the seed lipid content of resistant (R) and susceptible (S) inbreds. Twenty inbreds were tested under greenhouse conditions at three trifluralin rates (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 three rates) and in the field (at 0, 0.4, and 0.8 kg ai ha−1). Under both greenhouse and field conditions, inbreds R were more resistant than S. Hybrids R × R were more resistant than S × S, indicating that additive effects were important. Hybrids R × S and S × R did not significantly differ, indicating that reciprocal effects were not important. On average, hybrids R × S and S × R were intermediate between R × R and S × S, suggesting that nonadditive effects were negligible. The difference between the mean across hybrids and the mean across parents (further estimating the importance of nonadditive effects) was significant only for parameters investigated in the greenhouse. Greenhouse data were correlated with field data, but the coefficients of determination were < 50%. The ability to predict hybrid resistance on the basis of parental mean was higher in the greenhouse (r2= 0.78) than in the field (r2= 0.47). R and S inbreds also differed in seed lipid content, but correlations were negligible with greenhouse and field data. Data indicated the presence of genetic variability for trifluralin resistance, that additive effects were prevailing, and that the resistance level was not related to seed lipid content.