Abstract
The most bothersome weed in rice fields in the Indonesian province of West Java is Monochoria vaginalis (Burm. F.) C. Presl, an aquatic herbaceous plant. Metsulfuron-methyl has long been used in wetland rice in West Java with a high enough intensity. However, the case of Monochoria vaginalis resistance to metsulfuron-methyl herbicides in Indonesia has not been widely reported and investigated. The study aims to (1) classify the resistance level of M. vaginalis toward metsulfuron-methyl, (2) identify Target Site Resistance (TSR) mechanism mutations in the MvALS1 gene of the resistant biotype of M. vaginalis. The Whole Plant Pot Test method was utilized to assess the resistance level of Monochoria vaginalis. Following that, all samples were subjected to DNA sequencing using the PCR method to identify mutations in the MvALS1 gene from the resistant biotype. After then, this study used DUET, a server with an integrated computational methodology, to anticipate the effect of mutations on protein stability. The result showed that Monochoria vaginalis from Rawamerta, Karawang showed a moderate level of resistance to metsulfuron-methyl with a resistance ratio of 6.00, Patokbeusi, Subang showed a low level of resistance to metsulfuron-methyl with a resistance ratio of 3.89, compared to susceptible Monochoria vaginalis. Nucleotide base alignment in the MvALS1 gene revealed that base substitutions occurred in the Monochoria vaginalis biotype from Rawamerta and Patokbeusi, resulting in 5 amino acid substitutions: Ser-64-Ala, Asp-66-Glu, Asn-240-Asp, Glu-426-Asn, and Ser-469-Asn and Sukra: Ser-64-Ala, Asp-66-Glu, and Asn-240-Asp. The analysis showed that S64A, D66E, and N240D stabilize the protein, whereas E426N and S469N destabilize it. This study confirms for the first time that Ser-64-Ala, Asn-240-Asp, and Glu-426-Asn amino acid mutations were found in cases of M. vaginalis resistance to metsulfuron-methyl (ALS inhibitor).