Genetic Identification Of Early Maturing Mutant 8479 And 9184 In Rice

Heading date of rice is an important agronomic trait that determines regional and seasonal adaptability of rice varieties.Rice production areas are very extensive in China,so ecological conditions and tillage systems of rice are complex and diverse,and then different regions have different requirements on the growth period of rice varieties.Therefore,the cultivation of earliness and high-yield varieties is one of the important objectives of rice genetic breeding.In the preliminary work,two early maturing mutants8479 and 9184 were obtained in our laboratory.Here,we performed phenotypic observation,agronomic traits investigation,genetic analysis and gene mapping.Those studies lay a foundation for the identification and utilization of rice early maturing genes.1.Genetic identification of early maturing mutant 8479（1）Phenotype and main agronomic traits:The heading date of 8479 was earlier 10 to 14days than wild-type.Plant height,panicle length,number of primary branches,number of secondary branches,number of grains per panicle,1000-grain weight and seed setting rate of 8479 were significantly decreased,and its hull was brown.The iodine staining analysis of pollen grains showed that the 8479 pollen grains were significantly reduced,uneven staining,and partially incomplete,suggesting that pollen grains of 8479 were partially sterile.（2）Genetic analysis showed that the segregation ratio of early maturing and brown hull traits of 8479 in the F₂ population was 9:3:3:1,indicating that early maturing and brown hull traits were controlled by different recessive nuclear genes.（3）The individual phenotype of F₃ population was the same as that formed by self-fertilization of early maturing individuals in F₂ population,and early maturing was co-isolated with the decrease of plant height,panicle length,grain number per panicle,1000-grain weight and seed setting rate.These results indicated that these traits were affected by"multiple effects of one gene".（4）High-throughput sequencing and Mut Map analysis showed that the early maturing mutation site was located at the LOC＿Os10g41590 gene on the long arm of chromosome10.The 5294^th base of its genome was changed from G to A,resulting in the loss of 4 bp or10 bp of transcribed RNA.The gene encodes a ubiquitin ligase with C3HC4 type zinc finger domain protein.2.Genetic identification of early maturing mutant 9184（1）Phenotype and main agronomic traits:Compared with the wild type,9184 had 7 to12 days earlier heading,shorter plant height,fewer effective panicles,and longer leaves.The investigation of agronomic traits showed that 9184 had extremely significant increases in panicle length,number of primary branches,number of secondary branches,number of grains per panicle and leaf length.However,plant height,number of productive panicles per plant and seed setting rate significantly decreased.There was no difference in 1000-grain weight and leaf width.（2）Genetic analysis showed that the early maturing trait of mutant 9184 was controlled by a single dominant nuclear gene.（3）Allelic test:We constructed F₁ and F₂ populations using mutant 9184 and Ef-cd earliness 527（E527）as parents.Through the analysis of early maturing characteristics,we found that the dominant earliness of 9184 was controlled by Ef-cd gene.（4）The 9184 mutant derived from the Gn1a gene knockout mutation of restorer line Shuhui 527.Early maturing and large panicle characteristics which was controlled by Ef-cd/Gn1a gene pyramiding may have important application value in hybrid rice breeding.