Analysis Of Heterosis And Combining Ability Of Three-lines Of Japonica Rice Parents

In China, hybrid indica rice accounted for 80% of the total planting area of indica rice. However, hybrid japonica rice accounted for only 3% of the planting area of Japonica rice. The japonica rice cultivation in China covers a total land areas of about 82,800,000 hm2. This large land coverage has made it very important to improve yield level of japonica rice in our country therefore the need to increase the cultivation japonica hybrid rice. In order to understand basic actuality of three-line parents of japonica rice, we offer basic information to assist breeding of japonica rice hybrid. In this paper, we collected representative 16 varieties each for BT-type CMS lines, maintainers and restorers in each genus. Two hundred and twenty nine (229) cross combinations were made. In addition, we also systemically studied the heterosis, correlation between parents and progenies traits, as well as the correlation between characters in F1 combinations, and parents combining ability . The main results are as follow:1 According to the maintainers, restorers were higher, their stalks were thicker, spike types were bigger, which were favorable for pollination, seeding and thicker stalks production. Potential storage per plant of maintainers and restorers are close , about 30 gram in average, but tillers of restorers were ebber, seed setting rate and 1000-grain weight were lower, single plant yield of restorers were significantly lower than maintainers. The apparent quality of restorers was worse than maintainers.2 Hybrid Japonica rice had stronger mid-parent heterosis, but heterobeltosis of most characters were not strong. It was very clear that the growth force manifested competitive heterosis. It was evident that the panicle of hybrid japonica rice was bigger, but seed setting rate expressed as negative heterosis, which was the main limiting factor restricting yield heterosis of hybrid japonica rice.3 Mating the different parent types, most characters of F1 combinations were mid-way between their parents. Comparatively, crosses between many-panicle type CMS lines and large-panicle type restorers, yielded higher,which could be due to a better mating type of hybrid japonica rice. According to the apparent quality, chalky rice percentage and chalkiness score of F1 combinations mated by Late-ripeing restorers and erect panicles type restorers, were lower, which had good appearance quality.4 Analysis of the correlation between parents and progenies indicated that most characters of F1 combinations were codetermined by CMS lines and restorers, the correlation of F1 combinations and mid-parent heterosis were the best , the correlation of F1 combinations and high-parent heterosis were better than that of low-parent heterosis . Comparatively, the correlation of CMS lines and characters such as heading date, total spikelets per panicle were significant, while the correlation of restorers and characters such as plant height ,filled grains per panicle ,seed setting rate ,yield per plant, quality characters were significant. The correlation of parents and progenies in all yield characters were lower than 0.7, which indicated that yield characters of F1 combinations had close connection with SGA of parents .5 Analysis of the correlation among F1 characters indicated that correlation coefficient between agronomic traits and yield traits, agronomic traits and quality characters, yield traits and quality characters were small or not significant in general. So we could aggregate high yield, good rice quality and better agronomic traits to the same F1 combinations through selection..6 Combining ability variance analysis indicated that combining ability between CMS lines, restorers and CMS lines×restorers interaction were all highly significant, which indicated that most characters of hybrid japonica rice were codetermined by both parents GCA and F1 combinations SCA. The GCA of CMS lines were bigger at heading date, basic culm thickness, curvature of panicle neck, grain density, single plant panicles, total grains per panicle, while the traits of plant height and 1000-grain weight of restorers GCA were bigger, and F1 combinations SCA were bigger at seed setting rate, filled grains per panicle, yield per plant, spikelets per plant, potential storage. As regards to the appearance quality, GCA were more important than SCA, as well as the GCA of CMS lines were bigger , it was shown that good rice quality parents are extremely important to breed good quality japonica rice hybid. Also, with regards to cooking and edible quality, the effect of CMS lines on GCA was smaller, they were mostly determined by restorers GCA and F1 combinations SCA .7 As regards to CMS lines,GCA of nongken57A, LingfenA and LiqianxinA yield per plant were all good, while the GCA of appearance quality and cooking and edible quality in Shengdao301, LingfenA, Sidao9618A were all good. The 9522A, 863A, AizhixiangA and Nongken57A had merit of mated good appearance quality, while Sidao9618A, AizhixiangA and Shengdao301A had merit of mated prematurity, and Sidao9618A and 731A had merit of mated dwarf.8 With regards to the restorers, GCA of CR134 yield per plant, total grains per panicle, filled grains per panicle, 1000-grain weight, seed setting rate and appearance quality were all very good. Nonetheless, the SCA variations of these traits were not significant, and that could easily choosen and mated for good rice quality and high yield combinations, with good value in application. The GCA of Z12, Liaohui02, N138 and Ninghui8 yield per plant were also good. Xiangqing and HuiR254 had merit of mated good appearance quality, while 77302-1, Z12, N138 and Liaohui02 had merit of mated premature, and Wubaxiangqing and 77302-1 had merit of mated dwarf.9 Taking chalky rice percentage≤30% as choosing index, according to high and low of yield principle, ten good rice quality and high yield combinations were selected. Respectively they were LiuqianxinA×CR134, Yujing6A×CR134, ZaoyouA×Wubaxiangqing, Shengdao301A×HuR254, Yanjing93272A×Ninghui8, LingfenA×CR134, LiuqianxinA×Min120, Nongken57A×Liaohui02, Nongken57A×Ninghui8, Yanjing93272A×CR134. Therefore LiuqianxinA×CR134 and Yanjing93272A×CR134 were selected as part of the rice preparation test of Jiangsu and Anhui province respectively.