Response of maize (Zea mays L.) inbred lines and hybrids to chlorsulfuron

Summary Twenty inbred maize lines, raised in a growth chamber, were treated with 0 or 1 ng g−1 of chlorsulfuron which caused a variable reduction in root‐length. In a second experiment, all crosses (reciprocals included) among two tolerant lines (T: Va85 and Mes44) and two susceptible lines (S: B73 and B79) were raised in a growth chamber together with the parental lines and exposed to 0,0×5 or 1 ng g−1, The interaction of reciprocal effects x rates was not significant for all traits, The T × S hybrids showed an intermediate response between the T × T and S × S responses for root‐length and dry weight. Interaction (hybrids vs. parental lines) × rates was not significant for all traits. These results indicate that susceptibility to chlorsulfuron is not controlled by extra‐nuclear factors and that additive gene actions prevail. Four crosses (one T × T, two T × S and one S × S) were further investigated at nine rates from 0 to 1 ng g−1. The responses confirmed the intermediate behaviour of T×S hybrids, resulting in a GR20 of 0×07, 0×55 and 0×94 ng g−1 for S × S, T × S and T × T, respectively. In a third experiment, the four crosses previously considered were grown in the field with parental lines and treated at five rates from 0 to 1·12 g a.i. ha−1. Effects on shoot height and dry weight were consistent with root effects found in growth chamber experiments.