| The anoxia germinability of rice seeds is an important trait for direct-seeded rice,and it is also the key factor to solve the problem of seedlings emergence which affects the grain yield of direct-seeded rice.Therefore,the high vigor seeds of hypoxia germinability play an important role in direct seeding rice and improvement of grain yield.In this study,the seeds of 229 rice chromosome single segment substitution lines(SSSLs)germinated under hypoxic condition at the height of 5.1 cm flooding for seven days in a chamber at 30? with a 16 h photoperiod.The coleoptile lengths were analyzed to identify quantitative trait loci(QTLs)controlling hypoxia germinability.The main results are as follows:1.The length of coleoptile was used as the phenotypic index of anaerobic germination,and the materials were evaluated in five cropping seasons.The coleoptile lengths ranged from 1.59 to 3.24 cm,1.49 to 2.87 cm,1.06 to 2.87 cm,1.61 to 3.45 cm and 1.05 to 2.65 cm in early and late seasons of 2015,early and late seasons of 2016 and early season of2017.The average coleoptile length was 2.56 cm,2.31 cm,2.30 cm,2.32 cm and 2.05 cm,respectively.In comparison,the average coleoptile length of HJX74 in the corresponding five seasons was 2.54 cm,2.20 cm,2.28 cm,2.38 cm and 2.28 cm,respectively.the coleoptile lengths of HJX74 ranged from 2.16 to 2.56 cm.As a control,the phenotypic value of HJX74 was in an appropriate position which is suitable for the analysis of the positive and negative effects of anaerobic germination(AG)QTLs.2.Nineteen SSSLs exhibited significant difference to recipient parent HJX74 on coleoptile length index in at least two seasons.Nine SSSLs showed positive effects and ten SSSLs showed negative effects in this study.The positive additive effect contributions ranged from 4.3 to 11.2%.The negative additive effect contributions ranged from 7.2 to18.5%.3.The substituted segments of the 229 SSSLs come from 24 donors.The substitutedsegments of the 19 SSSLs with putative AG QTLs come from seven donors,including Zhong 4188,Zihui 100,Katy,Suyunuo,IR64,Basmati 370 and IRAT 261.It should be noted that the substituted segments of SSSLs coming from Zihui 100 were detected the largest number of QTLs,indicating its significant role in the study of rice seed anaerobic germination.Among the 19 SSSLs with QTLs,the donor parents of 13 SSSLs were indica varities and six were japonica varieties.4.Based on substitution mapping,11 AG QTLs were identified,including six positive QTLs with additive effect contribution from 6.8% to 11.2% and five negative QTLs with additive effect contribution from 12.8 to 18.8%.Eight QTLs,qAG1,qAG2-1,qAG2-2,qAG5,qAG7-1,qAG7-2,qAG8 and qAG9 showed overlapped regions with previously reported QTLs.Noticeably,qAG9,has been fine mapped and cloned.However,qAG4,qAG6 and qAG11,may represent novel ones.5.Here,11 AG QTLs were mapped on nine chromosomes.Two QTLs were detected on chromosome 2 and 7 and one QTL was detected on chromosome 1?4?5?6?8?9 and11,respectively.Nevertheless,no QTL were detected on chromosome 3,10 and 12.Taken together,229 SSSLs were used for genetic analysis of seed anaerobic germination in this work and 11 AG QTLs were identified.It will provide more selections for breeding elite direct-seeded rice varieties and have great significance for the security of food. |
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