Identification Of Cytoplasmic Yellow-leaf Mutant 1048-3 And Gene Mapping Of Rolled Leaf Mutant 8354 In Rice

1.Identification of cytoplasmic yellow-leaf mutant 1048-3 in riceLeaf is the main organ for photosynthesis in rice and is closely related to rice yield.Leaf color mutant is a very obvious mutant,which has important significance in the research of chlorophyll biosynthetic pathway,chloroplast differentiation and development,gene expression regulation,and so on.The material studied in this experiment is a mutant 1048-3 from japonica rice variety ZH11 during tissue culture,and its main phenotype is yellow leaf.Investigation of leaf color and marker genes of F₁ and F₂ plants from different combinations of reciprocal crosses suggested that the mutant can be used for inheritance segregation and is a leaf color mutant controlled by cytoplasmic genes.Investigation of agronomic traits of wild type and mutant found that the mutant in terms of plant height,panicle length,number of productive panicles,grain number per panicle,seed setting rate,kernel length,length-width ratio,number of branches per stem and the number of secondary branches was lower than those of wild type,but its grain width and 1000-grain weight were higher than those of wild type.Comparing the pigment content of the wild type and the mutant at different growth stages,it was found that the pigment contents of the mutant was lower than those of the wild type at different periods,indicating that the cause of the leaf yellowing of the 1048-3 mutant was related to its pigment content.Observation of chloroplasts by transmission electron microscopy revealed that no significant difference was observed in the morphological structure between the wild-type and mutant chloroplasts,but the mutants were thinner in the stack thickness of the basal particles.Experiments showed that yellowing of the mutant 1048-3 leaves may be caused by a decrease in photosynthetic pigment content and abnormal development of chloroplasts.2.Gene mapping of rolled leaf mutant 8354 in riceThe ideal plant type has always been a part of breeders’attention to improve yield in rice.Rice leaf curl can keep the plant upright.Moderate leaf rolling can reduce the transpiration of the leaves,prevent water loss in the plant,and effectively increase the photosynthetic efficiency per unit area,thereby increasing the accumulation of photosynthetic products to increase yield.This experimental material is a leaf curl mutant derived from 188R by EMS mutagenesis,tentatively named 8354.The investigation of agronomic traits of wild type and mutant showed that the mutants were significantly lower than wild type in plant height,panicle length,grain number per panicle,seed setting rate,thousand kernel weight,number of primary branches and secondary branches,decreasing by 6.68%,6.18%,9.98%,5.97%,18.41%,9.65%and 15.16%,respectively.But the number of its number of productive panicles and the length-width ratio ratio of grains did not change significantly.When mutant 8354was crossed with 188R,F₁ showed a normal phenotype.The F₂ segregation population obtained by selfing showed two types of leaf-rolling mutant phenotype and normal phenotype,and the separation ratio was 1:3.It was shown that the leaf-rolling traits of the 8354 mutant were controlled by a pair of recessive nuclear genes.Based on the results of In Del marker mapping and high-throughput sequencing,the gene was located in the 4710 kb region of the short arm of chromosome 2,and there were three sense mutations,temporarily named gene1,gene2,and gene3.There are no reported leaf rolling genes in this interval,so we speculate that 8354 may be a new rolled-leaf gene.