Genetic Identification And Candidate Gene Analysis Of Dwarf Small Grain Mutant D502(t) And Drooping Leaf Mutant Dl8636(t) In Rice

Rice(Oryza sativa L.)is one of the world's major food crops,more than half of the world population feed on rice.The height and the grain size are two of the important agronomic characters,which have significant effects on both grain yield and quality in rice.On the other hand,leaf is the main organ of photosynthesis,which takes an important part in plant architecture and production.Vein is one of important components in leaf morphosis,which plays a key role in transporting nutrients and water and providing mechanical support for leaf.At the same time,the plant leaf vein is also the important marker trait for high-yield rice breeding.Therefore,studies on height and grain size and vein mutants by exploring and applying the related genes could provide theoretical significance and application value for wide genetic diversity and high-yield rice breeding.In this study,we isolated semidwarf small grain mutant d502(t)and drooping leaf mutant dl8636(t)from rice varieties Nipponbare and Lehui 188 by ethylmethane sulfonate(EMS)treatment,respectively.Then we investigated phenotypes of the d502(t)and dl8636(t)mutants and their wild-types.At the same time,we conducted genetic identification and candidate gene analysis of the two mutants.We expect to explore novel genes for semidwarf and vein development,which could lay foundation for further study.The main results were described as follows.(1)Semidwarf small grain mutant d502(t):Compared with the wild-type parent,d502(t)exhibited characters of semidwarf and small grain.Comparison of the length of each internode between d502(t)and its wild-type showed that the dwarf phenotype of d502(t)was caused by average decrease of each internode,and the fourth internode of d502(t)becomes short most seriously.Genetic analysis showed the mutant character was controlled by a recessive gene.MutMap cloning and sequence analysis showed that the target gene was finally mapped on chromosome 6.No dwarf gene was reported on this chromosome,so it was considered that the mutant gene of d502(t)could be a novel dwarf small grain gene in rice.(2)Drooping leaf mutant d18636(t):This mutant exhibited character of drooping leaf.Genetic analysis showed the mutant character was controlled by a recessive gene.Through map-based cloning,gene dl8636(t)was mapped a region between primer RM6038 and RM7576 on the rice chromosome 3,with 1.25 cM physical distance.By analysis of the candidate gene,it was suggested that LOC_Os03g11600 might be the candidate gene of dl8636(t),in other words,dl8636(t)might be allelic to the DL gene that was previously reported.