Rice allelopathy

Allelopathic effect of rice against lettuce was investigated with water soluble extracts from two rice (Oryza sativa L.) varieties, "PI312777" (highly inhibitory) and "Rexmont", (less inhibitory), which are suppressive and non-suppressive to weeds in the field. Water soluble extracts derived from rice seedlings at various stages were applied to lettuce seeds. Leaf extracts from the six-leaf stage rice seedlings were appropriate for the assessment of the difference of the two varieties. Quantitative trait loci (QTL) underlying allelopathic effect of rice were identified using RFLP markers and the water-soluble extracts method. QTL analysis was carried out using the F-2 population from the cross between PI312777 and Rexmont. Among the seven QTL detected, the QTL on chromosome 6 had the largest effect and explained 16.1% of phenotypic variation. The other six QTL explained from 9.4% to 15.1% of the variation. A multiple QTL model estimated that five QTL with LOD scores of higher than 3.0 explained 36.6% of the total phenotvpic variation. Digenic interactions in five pairs between the nearest RFLP markers to each of the seven QTL detected were significant at the 1% level. QTL on the chromosome 7 was also detected as the QTL for necrosis.