| Four introgression line populations derived from Minghui86as a recurrent parent and the four donor parents (Gayabyeo, Shennong265, Zaoxianl4and Y134) was screened and evaluated for salt tolerance (ST) under salinization of0.5%salt concentration over the whole growth stage in Sanmen county of Zhejiang province. In this study, the ST-restorer lines and their test-cross hybrids with the two cytoplastic male sterile lines, Ⅱ32A and Chuan345A were investigated for grain yield and its related agronomic traits under normal irrigated condition. Meanwhile, we identified QTL affecting salt tolerance (ST), high yield (HY) and heterosis (HE), and dissected their genetic overlap. The main results were summarized as follows:1. Total of69,121,103,64ST-plants were selected from the four populations of Gayabyeo, Shennong265, Zaoxianl4, Y134as donors were obtained with selection percentage of salt-tolerance of3.69%,4.89%,3.49%,4.44%, respectively, after progeny test, indicating there was high reproducibility and durability for ST screening across the two years.2. Segregations presented in yield and its related traits among those lines, having varied types of segregation depending the populations and traits. Thirty promising restorer lines with significant higher yield and ST were selected. Most of the promising restorer lines showed shorten panicle length (PL), lower plant height (PH) and thousand grain weight (TGW), but significantly increased panicle numbers per plant (PNP) and seed setting rate (SSR), thus resulting in significant increase in grain yield.3. As compared with hybrid between Minghui86and the two sterile lines, test-crossing populations derived from the crosses between the ST-restorer lines and the two sterile lines showed shorten PL and PH, similar PNP, but significant increaseed TGW when tested with Ⅱ32A, indicating there were partial differences in trait performance between ST-restorer lines themselves and their hybrids. Twenty-two and23hybrid combinations showed stronger heterosis as compared with the hybrids derived from Minghui86and the two corresponding sterile lines. Among them,7(fromⅡ32A) and4(from Chuan345A) hybrids significantly surpassed the yield of Shanyou10as the commercial check combination.4. The Chi-square statistical analysis showed that QTL affecting ST related-traits detected in the four backcross introgression line (BIL) populations were19,19,10and12, respectively. Almost ST-QTL were donor excessive introgression. And ST-QTL detected in BILs derived from Japonica donor (Gayabyeo, Shennong265) are more than those from indica donor (Zaoxianl4, Y134). There are five ST-QTL were detected in3or above population, locating in Binl.1, Bin2.2, Bin2.6, Bin5.2and Bin6.1, respectively.5. Eight yield-related traits were investigated. Total of20,14,12and18QTL related to high yield (Qhy) were detected in the four BILs by single-marker analysis method. Many Qhy cluster on chromosome with pleiotropy. Total of193QTL associated with F1and heterosis (Qhe) advantaging over mid-parents was identified in test crosses with the two male sterile lines. Among them,121(62.7%) QTL showed over-dominant effect while10(5.18%) showed dominant effect, suggesting that over-dominance is mainly responsible for heterosis in rice. 6. In the four BIL populations, two Bin, the Bin1.3from Minghui86/Gayabyeo and the other Bin2.2from Minghui86/Zaoxianl4, were detected for rice ST, HY and HE; other11Bins affected ST and HE. Among them, the Bin2.2was detected in the four populations, and it could have important significane of marker-assisted breeding.7. Eight pyramiding populations of ST were implemented to screen ST using nutrition solution method at the seedling stage. We found that two crosses, ZY20/ZY94and ZY58/ZY131had better pyramiding effect, from them11and four ST plants were selected, which had stronger than pyramiding parents and the recurrent parent with average score on salt toxicity symptoms on leaves of4.0and4.4, higher1.5grade than that of the parents. |
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