Study on the non aromatic rice (Oryza sativa L.) varietals resistance to rice stem borers (Lepidoptera: Pyralidae) and yield factors

This research mainly aims at improving the profitability of rice production through increased productivity and better crop prtection. A total of 26 non aromatic rice genotypes were field examined for their resistance at natural infestation of insect pests to manage rice yellow stem borer Scirpophaga incertulas (Lepidoptera: Pyralidae). Observations on the incidence of pests were recorded by counting the total leaves/ damaged leaves and total tillers/ whiteheads for stem borer from randomly selected hills and calculated as percent damage. The results showed that all genotypes had variable reactions toward incidence of pest intensity as the percent deadhearts and the percent whiteheads recorded after transplanting were significantly different. In field conditions, genotypes IR6-20-2B, IR6-15E and IR6-15A exhibited high levels of resistance against natural infestation of stem borer and the damaged plants based on deadhearts or whiteheads were less than 1%. Moreover, grain yield was higher in theses genotypes inspite of pest infestation. Nevertheless, the genotypes IR6-300, IR6-30-2 and IR8-2.5-4 were highly susceptible to borers incidence with a corresponding reduction of paddy yield. These results demonstrate that the expression of resistance gene in tolerant genotypes can provide season-long protection from the natural infestation of lepidopteran insect pests.