Evaluation of Rice Genotypes for Tolerance to Imazethapyr Herbicide in Direct-Seeded Rice Systems

Aims: The aim of this study was to evaluate the resistance of different rice genotypes to the herbicide imazethapyr.

Study Design: Pot culture experiment.

Place and Duration of Study: The experiment was conducted in pot culture at the Department of Agronomy, Tamil Nadu Agricultural University, Coimbatore, Kharif 2024.

Methodology: Pot culture experiment was conducted with three replications by using fourteen rice genotypes (G1, G2, G3, G4, G5, G6, G7, G8, G9, G10, G11, G12, G13, and G14) to assess the phyto-toxicity tolerance. A herbicide spray was applied at the 2-3 leaf stage of weeds in the pot culture. Imazethapyr 10% SL was used at a concentration of 2.5 ml/L, applied at 23 days after sowing (DAS). The herbicide solution was prepared by adding 5 ml of Imazethapyr to 2 L of water. The spray was applied using a 500 ml capacity hand sprayer. The experiment was carried out under controlled (Field) environmental conditions to assess the response of rice genotypes in terms of phytotoxicity, including any visual damage or growth reduction caused by the herbicide treatment. The data collected were used to identify tolerant and susceptible rice genotypes to imazethapuyr herbicide.

Results: The results revealed significant variation in tolerance among the rice genotypes. Genotype G14 exhibited the highest tolerance, displaying minimal phytotoxicity symptoms such as chlorosis and necrosis, and showed no adverse effects on growth. Moderate tolerance was observed in genotypes G1, G2, G3, G4, G5, G6, G7, and G8, which exhibited some injury but were able to recover and maintain growth potential. In contrast, the susceptible genotypes G9, G10, G11, G12, and G13 showed severe phytotoxicity symptoms and completely dried out.

Conclusion: The tolerant genotypes G1, G2, G3, G4, G5, G6, G7, G8 and G14, can be utilized for further rice breeding programme for the development of herbicide tolerant rice varieties.