Yield and yield components in autotetraploid and diploid rice genotypes ('Indica and Japonica') sown in early and late seasons

要旨

Asian cultivated rice (Oryza sativa L.) can be divided into two sub-species indica and japonica. The present study was conducted to investigate the effect of inter-seasonal variations in meteorological parameters e.g., temperature, solar radiation and rainfall on morphological and yield traits of autotetraploid and diploid rice including indica and japonica genotypes. The contribution of dry matter production and harvest index in improving yield were also investigated. Mean daily solar radiation (MJ m-2 day-1) was higher during late seasons (14.5) than early seasons (11.8). Daily maximum temperature (>= 35degreesC) was observed for more than three consecutive days at flowering during early seasons. Photothermal quotient (MJ m-2 d-1 degreesC-1) showed more close relationship with yield (0.905 and 0.807) and seed set (0.965 and 0.834) compared to temperature or solar radiation alone in autotetraploid and diploid rice. Inter-seasonal variations showed a strong influence on diploid cultivars compared to autotetraploid cultivars. Late seasons produced significantly higher yield, number of panicles per plant, filled grains, flag leaf area and dry matter production than early seasons. Autotetraploid cultivars produced significantly (P 10 g) and flag leaf area (2.6 9.6 cm2) than diploid cultivars, but yielded very low due to low seed set (<= 38.1%). The results suggest that greater amount of solar radiation, photothermal quotient (0.905 MJ m-2 d-1 degreesC-1) and suitable temperature (25.6degreesC) during late seasons contributed to higher amount of sink and biomass accumulation, which increased the grain yield of diploid and autotetraploid cultivars during these seasons.

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