Abstract:

Late-maturing japonica rice (Oryza sativa L.) is planted 10×10⁴ hectares annually in Suzhou region, Jiangsu Province. Average yield is about 9t/ha, which is the highest yield in Jiangsu province. At the beginning of 1990’s, the hybrid rice was popularized, and the planting area was enlarged gradually, increasing by 10%. However, as the continuous improvement of pure line variety, superiority of the hybrid has not been conspicuous. If this question cannot be solved well, the planting area of hybrid rice will be reduced. This study was conducted to evaluate parents of combinations used currently in the south of Jiangsu Province and the heterosis of late-mature japonica rice and combining ability of their parents. Seven CMS lines with BT cytoplasm and seven restorers were used as parents. CMS lines were newly bred in Wuzhong Institute of Agricultural Sciences. Restorers were introduced from other provinces or newly bred in Suzhou. With NCⅡ genetic design, 49 combinations (7×7) were made by paper bag isolation in Hainan. The plots of F1s and parents were arranged in the field in a randomized complete block design with 3 replications in Suzhou. Ten agronomic characters were investigated. Research results were as follows: ⑴ Both positive and negative heterosis existed in all the 10 characters. Among them, heterosis of spikelets per panicle was the highest，showing the average heterosis over 22.6% of the control and over 8.6% of high parents. The average value of the heterosis over high parent in yield per plant was 9.5%, the highest among ten characters, ranging from －38.0% to 43.9%. The competitive heterosis of yield per plant ranged from －54.8% to 10.3%(Table 3). ⑵For character of yield, 852-77A, Hou 36A and 9522A were elite CMS lines(table 5); 161-10, 3402, HP121 were excellent restorers(Table 6); 9522A/161-10, 9522A/C166、852-77A/3402 were superior combinations.

Key words: Late-mature hybrid japonica rice(Oryza sativa L.), Heterosis, Combining ability