Analysis Of Genetic Stability For Milling Quality By Two Sets Of Reciprocal Introgression Lines In Rice

Rice is one of the most important crops in the world,and is the staple food of more than half of the world's populations.With the increase of living standard,rice quality has been paid more attention by both consumers and producers than ever before.There is large conflict between high consumer's demand and low quality of rice.Milling quality is a very important quality.Head milled rice with unbridged endosperm is the direct food of people.The price of head milled rice is typically twice or even some times more than that of broken grain rice,so the percentage of milled rice is affects milling industry and farmers' incomes.Thus,it's very important and urgent for us to dissect the genetic basis of rice milling quality,identify the its responsible genes,mine novel alleles of these genes,develope tightly linkage molecular markers and finally improve milling quality by molecular breeding technology.In the present study,a set of reciprocal introgression lines(ILs)derived from Minghui 63,an elite indica restorer for three-line hybrid,and 0428,a wide compatible temperate japonica variety,were developed,and all lines were genotyped by resequencing.They were planted at five environments,Shenzhen,Nanjing,Xuzhou,Jingzhou and Sanya,and measures their brown rice rate,milled rice rate and head milled rice rate.Combined with genotypes,main effect QTL and digenic epistatic QTL were identified for rice milling quality.Besides,the genotype and environment interactions were analysis,and important main-effect QTL stably expressing at multiple environments and different genetic backgrounds were mined.The main results are as follows:(1)The reciprocal ILs contained 424 lines,with 226 and 198 lines in Minghui 63 and 02428 background respectively.A high through-put Bin map which consisted of 4568 Bins was constructed.It covered 97.66% of Nipponbare genome,and the average length of each bin was 807.09 kb,ranging from 30.01 kb and1809.76 kb.The average recovery rates of ILs at Minghui 63 and 02428 background were 91.19% and 76.60%.(2)There was no significantly difference for brown rice rate between two parents,Minghui 63 and 02428.The milled rice rate of Minghui 63 was significantly higher than that of 02428 at Xuzhou and Jingzhou,while there was no significantly difference between them at the rest three environments.Minghui 63 had higher head milled rice rite than 02428 at Xuzhou and Sanya,while it had lower head milled rice rate than 02428 at the rest three environments.The IL progenies showed continuous and transgressive segregations,suggesting that all three milling quality traits were controlled by multiple genes.Correlation analysis indicated that the three milling quality traits had significant positive correlations with each other.However,the correlations among different environment within one trait were very different among different traits,and only about half correlations were significant.ANOVA analysis showed genotypes,environments and interaction between them were all highly significant,and the heredity was low,indicated that they were largely affected by environments.(3)Combines with genotypes and phenotypes across five environments,a total of 31 and 18 main-effect QTL were identified in Minghui 63 and 02428 background,respectively.Among them,6 QTL were genetic background independent,and 12 and 2 QTL stably expressed at multiple environments at two backgrounds respectively.Besides,46 and 17 digenic epistatic QTL were detected in the two backgrounds,respectively.Among them,three epistatic QTL were identified in both two environments,while no epistatic QTL was detected genetic background independent.(4)6 QTL regions stably expressed at multiple environments and controlling two or more traits were identified at Minghui 63 background.Moreover,1 QTL region independent from genetic background was detected for more than two traits.(5)About half of detected 49 main-effect QTL were detected to interact with environment.Among them,two QTL significantly interacted with two environments,and two QTL were identified to significantly detected with environment at both genetic backgrounds.