Characterization of Acetyl CoA carboxylase resistance in Phalaris minor populations of North-Western states of India

Adoption of rice-wheat monoculture in North-Western states of India ushers the major weed flora shift. Phalaris minor is an important grass weed of wheat and it has developed resistance towards most of the prevailing herbicide groups due to many reasons. To understand the mechanism of the resistance in different populations of P. Minor from Punjab, molecular studies were carried out. Phalaris minor populations which escaped the herbicide spray, samples from them were collected from the fields of 66 farmers from fourteen different districts of Punjab alongwith known susceptible and resistant check populations grown in pots and sprayed with all the recommended herbicides for the control of P. minor at the rates of 0.5 to 4X of the recommended dose of herbicide. Screening of P. minor populations was done for resistance studies. The common T to A nucleotide transversion in the region of the ACCase (Acetyl CoA carboxylase) gene is primarily involved in resistance and this region has been used in the current study using PCR-restriction digestion and sequencing of ACCase gene. The PCR amplification and restriction digestion assay yielded 3 types of alleles viz. 13 accessions with homozygous resistant allele (404 bp band), 41 accessions had homozygous sensitive alleles (169 and 235 bp band) whereas 12 accessions possessed heterozygous resistant alleles (169, 235 and 404 bp band). Sequencing and data analysis revealed the presence of homozygous sensitive alleles in more than 50% of P. minor populations. So, to prevent or delay of resistance development, site-specific and ecological-based agronomic inventions are needed.