Evaluation of allelopathic potential in rice germplasm

Abstract

Weeds in paddy are known to reduce rice yield severely. Use of herbicides for weed control has given rise to many problems related to environmental protection, herbicide-tolerant weeds and contamination of agricultural products, which endangered the sustainable development of agriculture. Since last decades, ecological methods for weed control have been developed. Research on rice allelopathy against weeds that started in late 1980's had been encouraging and developed fast. It is one of the first steps for research on rice allelopathy against weeds that involved the screening potential of rice germplasm (Oryza sativa L.). The objective of this research was to determine the allelopathic rice germplasm with both high allelopathic index (AI) and high activity against weeds. Seven rice germplasm (Oryza satica L.) were used as the test materials in this experiment which were primarily screened by bioassay methodology. The allelopathic indices (AIs) were determined with HPLC by the special secondary metabolite marking method, and then, the field experiments were conducted to confirm the weed control effects derived from rice varieties. High allelopathic activity against barnyardgrass (Echinochloa crusgalli L.) of the three rice germplasm (I-Kung-Pao, Parahainakoru from native Taiwan and HB-1 from Mainland China) was detected among the tested rice germplasm. The inhibitory ratios of barnyardgrass root length were 57, 64 and 55%, respectively. The AIs were 0.61, 0.56 and 0.59, respectively, similar to the allelopathic rice PI312777 from the United States considered as control in the experiment. Satisfactory weed control effects in field were obtained as reductions of both the plant density and the fresh weight of barnyardgrass. On short, the rice varieties of I-Kung-Pao, Parahainakoru and HB-1 were regarded as valuable rice germplasm with high allelopathic potential in China.