Effects of soil pH on isoxaflutole injury to tolerant and sensitive chickpea genotypes

The relative susceptibilities of two desi chickpea genotypes, 97039-1275 (tolerant line) and 91025-3021 (sensitive line), to isoxaflutole were studied under a range of soil pH levels in a pot trial under glasshouse conditions. Isoxaflutole was applied pre-emergence at 0, 100 (recommended rate) and 400 g ha⁻¹. The soil pH was adjusted to approximately 5.0, 6.8, 7.9 and 8.8. The results demonstrated the existence of differential tolerances among chickpea genotypes to isoxaflutole at different rates and soil pH. Isoxaflutole applied pre-emergence resulted in increased phytotoxicity with increases in soil pH and herbicide rate. Even the most tolerant chickpea genotype was damaged when exposed to higher pH and herbicide rates, as indicated by increased leaf chlorosis (22-43%) and significant reductions in plant height (22-50%), shoot dry weight (32-67%) and root dry weight. The effects were more severe with the sensitive genotype. The susceptibility of chickpea to this key herbicide needs to be taken into account in breeding of new lines and in the agronomy of chickpea production.