The Genetic Bases For Excellent Traits Of Rice Elite Parent Huanghuazhan

Rice is one of most important staple food on the world that feed billion of people.In order to ensure food security,developing high yield,good quality and high resistant rice varieties is the major objective of rice breeding.Elite parents are the important foundation of rice breeding.The selection,application and development of a series rice elite parents greatly accelerate the process of rice breeding in China.As a new generation of indica elite parent with excellent comprehensive characters,Huanghuazhan have already planted on a large scale in southern part of China and have spawned several elite varieties.Recently,emerging evidence suggests that the rice elite parent integrate multiple excellent characters,which stem from a series of elegant combinations of varieties with distinct genetic components.In recent years,tens of genetic loci controlling key agronomic traits of rice have been identified from several elite parents.However the source and transitive relation of excellent characters and genes regulating these traits in Huanghuazhang are still poorly understood.To systematically study the genetic bases for elite traits of Huanghuazhan,Huanghuazhan and its parents in breeding pedigree were used to analyze the source of high-yield,good quality and other important agronomic traits in Huanghuazhan and genetic basis contributing to these traits by means of traditional genetic methods and advanced molecular biology techniques.The results of our study indicate that: 1.Signicant differences in yield traits and quality traits have been observed in Huanghuazhan pedigreed cultivars: Guichao 2 has the highest production,Zhaoyangzao 18 is the lowest,the production of Huanghuazhan is lower than Guichao 2 but much higher than that of Zhaoyangzao 18;in terms of the grain quality,Huanghuazhan has the optimal comprehensive quality and the early stage parents,especially Guichao 2,have very poor quality.In general,Huanghuazhan had undergone a breeding process of "high yield but poor gain quality—low yield but good quality—higher yield and good quality".2.The number of secondary branches and the thousand grain weight are determining factors affecting grain yield in Huanghuazhan pedigreed cultivars.The early stage parents,like Guichao 2,have a very high number of secondary branches,and the new Ghd8^ZYZ allele may contribute to the grain number per panicle.The introduction of 28 Zhan genome produced severe negative effect on the number of secondary branches,leading to the decreased yield in the later stage cultivars.Thousand grain weight is related to grain shape,the gs3 and gs5 allele derived from Changsizhan caused the transition of grain shape from round grain to long grain inlater cultivars.In addition,the reducing 1000-grain weight has negative effects on the grain yield.3.Chalkiness and amylose content are the key traits affecting rice grain quality in Huanghuazhan pedigree cultivars.From Guiyangai 49 to Teqing,the grain quality is poor because of the high degree of white belly and amylose content in the endosperm.Changsizhan offered the Chalk5-H94 allele which contributes to low degree of Chalkiness belly.The low amylose content genotype is mainly controlled by Wx^b gene,which comes from 28 Zhan.The two genetic factors provide important genetic basis for a high grain quality of Huanghuazhan.4.Huanghuazhan pedigreed cultivars could be clustered into two groups with unweighted pair-group method with arithmetic means（UPGMA）cluster analysis based on SNP and indel information.The genetic similarity is consistent with their pedigrees relationships and phenotypic similarity.In summary,we reveal the source and contribution of several key genetic components to the polygenic characters and excellent comprehensive traits in Huanghuazhan and provide the basis for further understanding the genetic composition of this elite parent.