Competitive ability of imidazolinone-tolerant rice (cv. Luna) with different weedy rice (Oryza sativa f. spontanea) biotypes

Weedy rice (Oryza sativa f. spontanea) is becoming a significant concern in rice (O. sativa L.) cultivation in Turkey, despite its recent introduction. These studies determined the competitive ability of different weedy rice biotypes and yield responses of imidazolinone (IMI)-tolerant variety "Luna" when grown in competition with variable population densities of weedy rice. The field experiments were conducted at a farmer's field, Trachea Region Edirne Turkey in 2017 and 2018. A split plot design was used in which three different straw hull weedy rice biotypes (i) awnless (WRB-1), (ii) short-awned (WRB-2), and (iii) long-awned (WRB-3) were kept in the main-plots and three weedy rice densities (i) being free of weeds, (ii) being low in weed density (< 10 plants m-2), and (iii) having a high weed density (> 30 plants m-2) were in the subplots. Weedy rice biotypes significantly decreased the biomass, the tiller production, the leaf area, the plant height, and grain yield of Luna rice variety; however, the biotypes differed in their effect on Luna rice. The weedy rice genotype WRB-1 decreased the growth parameters of rice to the largest extent. All weedy rice biotypes (both at low and high densities of weedy rice) decreased the grain yield of Luna rice while the weed-free plots produced the highest grain yield. WRB-1 exposed to environments with a high density of weeds could decrease rice yield by 17.8%. In conclusion, weedy rice biotypes varied for their competitive ability against the cultivated rice and WRB-1 was the most competitive biotype.