Identification And Mapping Of An Around Seed Gene And A Narrow Leaf Gene In Rice(Oryza Sativa L.)

The shape of rice seed is not only one of the important appearance characters,but also plays an important role in increasing yield.Therefore,it has been a high spot of breeders that clones the gene which regulates the shape of seed.The shape of seed is a complex character controlled by multiple genes.We characterized a semi-dwarf mutant T135 with the round shape.The wild type is the japonica variety Kita-ake.Agronomic traits were investigated between Kita-ake and T135 by paraffin section,scanning electron icroscope,and hormone treatment;On the other hand,in order to clone the gene that regulated the shape of seed,the F2 segregation population was constructed by crossing japonica T135 with Indica IR36.Then we selected the individuals of round shape as the recessive gene pool from the population for linkage analysis using 174 polymorphic molecular markers on 12 chromosomes of the rice genome.The height of T135 decreased by 17%as compared to Kita-ake,thus it showed a semi-dwarf mutation.The number of culm node of T135 wasthe same as Kita-ake,and the dwarf character of T135 was caused by alteration of the length of nodes.The type of dwarf character preferred d6 due to the decrease ratio of every node,although every node of T135 was shorrter than that of Kita-ake.The morphology of vascular bundle was different obviously between Kita-ake and T135,and the number of elementary tissue ply in Tl35 is a bit more than Kita-ake with observation of cross section of culm,supposing the change be the reason of the stronger culm of T135.From the cell of endepidermis in leaf sheath,we found thatthere was no obvious difference in length of cell,suggesting that the shorter culm of T135 was not caused by the length of cell.Mostly,the growth and development of rice culm is affected by plant hormones’including gibberellin.We showed that the second leaf sheath increased duo to the increase of concentration of GA3.The lengthes of second leaf sheath of Kita-ake and T135 were the same at the concentration up to 0.1mM.Because T135 responded to exogenous GA3 and recovered some characters under the low concentration of GA3,the pathway of gibberellin was not defective in T135.The seed shape of T135 was shorter and more round compared with Kita-ake.The result showed that the seed length of T135 decreased by 15%,and the seed width and thickness were 14%and 13%,repectively.Similarly,the hulled seed length of T135 decreased by 22%,and the hulled seed width and thickness were 13%and 10%,repectively.Moreover,the 1000-grain weight decreased about 7%.In order to investigate the shape of T135,we surveyed the glume in cytological level.The results from scanning electron microscope showed that the shape of T135 was due to the change of the cell type and cell width in some means.The leaf angle,shape of panicle and fertility of T135 also differented from wild type except for plant height and shape of seed.We supposed that the three phenotypes of plant height,shape of seed and the leaf angle were controlled by different genes through a survey of the F2 separated population from T135/IR36.To clone the gene that regulated the shape of rice,we selected the extreme round individuals from the F2 separated population from T135/IR36 toconduct linkage analysis and map-based cloning.Finally,the gene was mapped between molecular maker Dly-3 and T135-10-13 on chr.10 with physical distance of two molecular makers 1.15M.On the other hand,leaf morphology is one of the important factors of rice plant type,leaf area also impacts yield by influence the Photosynthetic efficiency.A semi-dwarf mutant T88 with the narrow leaf was analysed.Agronomic traits were investigated between Kita-ake and T88.To clone the gene that regulated the width of leaf,an F2 separated population was constructed by crossing japonica T88 with Indica IR36.Then we selected the individuals of narrow leaf as the recessive gene pool from the separated population,and map the gene using 225 polymorphis molecular markers on the 12 chromosomes of rice.Identification of agronomic trait between the wild type Kita-ake and the mutant T88 showed that the height of T88 decreased significantly compared Kita-ake.The number of culm node of T135 was as same as Kita-ake,so the dwarf character of T135 was caused by the change of node lengthes.The type of dwarf character preferred dm due to the decrease ratio of every node,although every node of T88 was shorter compared with that of Kita-ake.When comparing the cross-sections of flag leaf between Kita-ake and T88,we found that small vascular bundle number of T88 was decreased,suggesting that that the narrow leaf phenotype of T88 is associated with the number of small vascular bundles.Through Kita-ake and T88 reciprocal cross progeny genetic analysis,we showed that the stem phenotype is controlled by one recessive nuclear gene.To clone the gene that regulated the leaf width of rice,we selected the extreme narrow leaf individuals from the F2 separated population from T88/IR36 to conduct lingage analysis and map-based cloning.Finally,the gene was mapped between molecular maker T88-1-13 and T88-1-21 on chr.1,with the physical distance 1.5M.