Dissection Of Seed Dormancy QTL Qsd-1and Physiological Character In N22Cultivar(Oryza Sativa L.)

Rice is an important grain crop in the world. Seed dormancy in rice is an important agronomic trait as it relates to food quality, seed quality and yield. In the post-mature stage, if the seeds have very stong dormancy, they’ll be resistant to PHS. But when long periods of hot, humid weather occur during harvesting seasons, On the contrary, high level dormancy of seeds whose dormancy dosen’t release will lead to lower emergence rate and uneven seedling establishment during planting season, and it can lead to weed problems for the follow crop. Therefore, it is necesssary to raise an intermediate level of dormancy in rice. The indica cultivar ’N22’ have one of the most strongest level of dormancy in our previously works. Here, we have described several near isogenic lines(NILs) bred from crosses between cv.’N22’ and the non dormancy cvs.’Nanjing35’, identify and genetic analyse the seed dormancy QTL qSd-1. Our study could provide convenience and theory reference for the breed selection of appropriate dormancy by marker assisted selection, and elucidated the functions of the seed dormancy genes in cv.’N22’ from genetic and physiological aspects.1. Xie Kun et al.have used an advanced back-cross (BC6F2) population which has been developed from the Nanjing35/N22//N22BC1F1by successive backcrossing and MAS to detect qSd-1in the chromosome1. We developed a trio of near-isogenic lines, one containing only qSd-1-1, one only qSd-1-2, and the last both qSd-1-1and qSd-1-2. Here, we found their96%of genetic background are homozygous for the N22allele by MAS and SNP genotyping analysis and detected the QTL qSd-1. Then the qSd-1can be detect into a pair of distinct, linked loci qSd-1-1and qSd-1-2, which act additively to promote dormancy. Here,we found a major QTL to control dormancy in cv.’N22’ and provided genetic theory to elucidate its couse of strong dormancy. 2. As saving at room temprature (37℃) longer, the level of dormancy in N22was weaker or even eliminated, so the germination was higher. To determ the concentration of endogenous ABA and GA in N22during germination process, we put the seeds at4℃for7days,50℃dry heat treatment for7days and removal the seed coat after saveing at4℃for7days, respectively. So we detected the pattern of concentration of endogenous GA was basically identical. But the concentration of endogenous ABA was higher than GA. Because ABA is antagonize to GA, so limiting the role of GA lead to remain dorancy and the seeds losing the ability of germinate. The after-riping seed of N22, Nanjing35and NIL(qSd-1-1)、 NIL(qSd-1-2)、NIL(qSd-1) incubated in ABA delayed germination, but it does not appreciably affect the kinetics of embryo protruding. These denoted that ABA mainly inhibits germination, but not embryo protruding. Moreover, N22is hypersensitive to ABA; Then testa permeability test suggest that the permeability of N22is worse than Nanjing35. In addition, the a-amylase activity of N22seed is also poor in contrast to Nanjing35in the germination process. From above, we can see the partial physiological cause leading to the stronger dormancy than Nanjing35. So these can provide physiological and structural basis for exploring the dormancy of N22.