Growth and Morphological Characteristics of Asp376Glu Mutation in AHAS-Resistant and-Susceptible Yellow Burrhead (Limnocharis flava (L.) Buchenau) Populations

Herbicides are considered the most effective weed management approach in the world. Acetohydroxyacid synthase (AHAS, EC 2.2.1.6) is widely used due to its advantages in crop selectivity, effectiveness to control broad-spectrum weeds and low mammalian toxicity has become one of the most popular herbicides used by farmers. The overreliance on the same herbicides over the years to control the weeds led to the evolution of herbicide resistance by several weed species, including Limnocharis flava (L.) Buchenau is among the resistant weed species in the rice fields of Southeast Asia. This species has been reported to develop resistance to bensulfuron-methyl (AHAS inhibitor). This study aims to determine the morphological characteristics of susceptible and resistant L. flava populations by comparing the growth and development of the plants. Results showed that the Asp-376-Glu mutation in the AHAS gene of the L. Flava-resistant population has exhibited significantly stronger (dry weight) or no significantly different impacts as compared to the susceptible population in the fresh weight, height, epicuticular weight, and leaf area. The insignificant differences were observed in the leaf structure and morphology of R and S plants which appears to have no possible fitness cost in the R population. This is the confirmation of the differences between the AHAS-resistant and susceptible populations that emphasizes the morphological characteristics that is crucial for herbicide application for controlling L. Flava populations.