Genetic Analysis Of Vascular Bundle-related Traits Of Neck-panicle And Yield Traits In Rice

Food is the paramount necessity of the people and food security has always been a concern for the whole world,especially for China.With population growth,climate warming and soil environment deterioration,it is critical to ensure food supply.Rice is one of the main food in the world,high and stable yiled is the primary goal of rice breeding."Source-sink-flow" is an important part of rice yield formation,and the impact of "flow" on yield has been paid more and more attention.Neck-panicle is the most important “flow” organ,due to its role in connecting “source” and “sink”.Therefore,excavating the genetic factors regulating vascular bundle-related traits of neck-panicle is of great significance and is a crucial aspect for the improvement of rice yield.In this study,a set of 122 chromosome segment substitution lines(CSSLs)population,which was derived from the cross between indica rice variaty 93-11 and japonica rice variaty Nipponbare,was used to investigate vascular bundle-related traits of neck-panicle and yield traits.The main results are as follows:1.Parents Nipponbare and 93-11 had significant differences in vascular bundle-related traits and yield-related traits.The observation of vascular bundle cross-sections showed that 93-11 had better performances than Nipponbare.For example,compared with Nipponbare,93-11 had thicker neck-panicle,more numbers of vascular bundles,larger vascular bundle area and so on.The performance of yield-related traits such as number of primary branches,number of spikelets,number of filled grain,ratio of seed setting,thousand-seed weight,and weight of panicle in 93-11 were also significantly higher than those of Nipponbare.2.The correlation analysis showed that most of the vascular bundle-related traits were significantly correlated with each other.Meanwhile,most of the vascular bundle-related traits were also significantly correlated with yield traits.Notably,each of vascular bundlerelated traits were significantly positively correlated with the weight of panicle,the correlation coefficient between the number of small vascular bundles and the weight of panicle was 0.47 and was the highest among them.3.The QTL analysis using ridge regression method detected a total of 126 QTLs.A total of 42 QTLs were detected for 7 vascular bundle-related traits,and 16 alleles derived from Nipponbare had positive effects.A total of 76 QTLs were detected for 9 yield-related traits,of which 28 alleles derived from Nipponbare acted synergistically.And 8 QTLs were detected for the ratio between the number of large vascular bundles and primary branches,and 4 alleles derived from Nipponbare had positive effects.This result indicated that the chromosome segment substitution lines also can be used to dig up superior genes hidden in inferior parents.4.QTL co-localization analysis revealed 9 QTL clusters that simultaneously regulate vascular bundle-related traits and yield traits,distributing on chromosomes 1,4,5,7 and 8.Among them,6 QTL clusters had the same direction of additive effect,and 3 QTL clusters had the opposite direction of additive effec.Based on previous studies and candidate gene analysis,pleiotropic genes Ghd7 and IPA1 may be candidate genes on chromosome 7 around 9Mb and on chromosome 8 around 25 Mb respectively.