Heterosis for photosynthesis, dry matter production and grain yield in F1 hybrid rice (Oryza sativa L.) from thermo-sensitive genic male sterile line cultivated at different soil nitrogen levels
2003
Pham, C.V. (Kagoshima Univ. (Japan)) | Murayama, S. | Kawamitsu, Y.
This study was conducted to determine the effects of soil nitrogen levels (0.22, 0.44 and 0.88 g N pot sup (-1)) on the heterosis for photosynthetic characters, dry matter production and grain yield in F sub 1 hybrid rice obtained from thermo-sensitive genic male sterile line. Net C02 exchange rate (CER) and other related characters viz., SPAD reading, leaf N content, soluble protein content and ribulose-1, 5-bisphosphate carboxylase/oxygenase (Rubisco) activity increased significantly with increasing N level in all the F sub l hybrid and parental cultivars. With increasing N level, the number of tillers, leaf area, root weight, whole-plant dry weight and grain yield also increased. Under the low N I\level, the F sub 1 hybrid did not show heterosis for most photosynthetic characters. However, at high N level, heterosis for CER over both the male parent and the mean of parents was ascribed to high leaf N content and several characters related to CER. The F sub l hybrid exhibited substantial heterosis over the male parent for whole-plant dry weight, number of panicles per plant, number of spikelets per panicle and grain yield in all N levels. Among the yield components, the strengthening of heterosis for number of filled grains per panicle was the major cause of greater heterosis for grain yield in the F sub l hybrid at high N level.
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