In vitro and in vivo AHAS activity response to imazamox herbicide in wheat cultivars

BRECCIA, G.; NESTARES, G.; PICARDI, L.

Foz de Iguazú

Congreso; International Congress of Genetics; 2018

International Genetics Federation & Brazilian Society of Genetics

Imidazolinone (IMI) herbicides control weeds by inhibiting the acetohydroxyacid synthase (AHAS). Three genes ahasl-A, ahasl-B and ahasl-D coding for the AHAS catalytic subunit were identified in wheat. Mutations at the ahasl-D and ahasl-B genes confer resistance to IMI. The objective of this work were to evaluate the in vitro and in vivo AHAS activity in response to imazamox of nine wheat cultivars differing in IMI resistance. The three susceptible cultivars showed the lowest ED50 values (herbicide concentration causing 50% enzymatic activity) for in vitro and in vivo AHAS activity. In vitro dose-response curves for the IMI-resistant cultivars were fitted to a two-phase dose-response model. ED50 value for the resistant phase was 200-fold higher than the susceptible one. The upper limit for the resistance phase significantly differed (p100-fold that of the susceptible cultivars and near 10-fold higher than cultivars with a single resistant gene. In vivo ED25 also differed among cultivars with the same number of resistance genes. It wasconcluded that in vitro and in vivo AHAS activity in response to imazamox allowed distinguishing cultivars with different number of resistant genes. The response in the in vivo assay was also affected by other biological factors that could be explained by the different genetic backgrounds of cultivars.