Genetic Analysis And Gene Mapping Of A Yellow-Green Leaf Mutant Ygl82in Rice

The leaf color mutants are important materials for rice functional genomics research, and the leaf color as a specific marker character has a certain value in the actual production application. In this study, with ethyl methane sulphonate (EMS) mutagenesis of the late maturing mutant10079of the japonica variety Nipponbare, we found a yellow green leaf mutant in the progeny of the mutant and named it temporarily as ygl82. We carried out morphological analysis, genetic analysis, determination of chlorophyll and the electron microscope of leaves and so on, and finished gene mapping of target gene of the mutant by map-based cloning. All we have done lay a solid foundation of cloning the target gene and elucidating the molecular mechanism of this yellow green leaf mutant. The main results are as follows:Phenotype characteristics and agronomic traits of the ygl82mutant:The mutant stays yellow-green throughout the entire growth period, and can fruit. Compared with wild type, growth period of the ygl82mutant prolonged a little and its growth potential was weaker. All measured agronomic traits of the mutant decreased, except flag leaf width increased3.5per cent. Plant height, number of productive panicles per plant, panicle length, number of spikelets per panicle, flag leaf length, seed setting rate and1000-grain weight, reduced17.4per cent,14.4per cent,5.5per cent,5.8per cent,22.7per cent,5.9per cent,4.3per cent, respectively.The chlorophyll and carotenoid content of the ygl82mutant leaf:The content of photosynthetic pigments in the ygl82mutant leaves at jointing stage was significantly lower than wild type leaves. Compared with wild type, the total chlorophyll, chlorophyll a, chlorophyll b and β-carotene content decreased77.7per cent,69.1per cent,77.5per cent and52.3per cent, respectively, but chlorophyll alb increased37.3per cent. It indicated that the photosynthetic pigment synthesis of the mutant has suffered serious suppression.The electron microscopy structure of the ygl82mutant leaf: The transmission electron microscopy analysis showed:Compared with wild type, the thylakoid lamellae in the chloroplast of the ygl82mutant reduced significantly, and many mitochondria showed abnormal structure with the ridge becoming less or even disappearing. The result suggested that the chloroplast and mitochondrial development of the mutant leaves was severely inhibited.Genetic Analysis of the ygl82mutation:By reciprocal crossing the ygl82mutant with Nipponbare and ZheFu802, and by analysing the F1and F2, we got the result that the yellow-green mutation phenotype of the ygl82mutant was controlled by a pair of recessive nuclear genes.The gene mapping of the mutant ygl82:By taking the F2population of the mutant ygl82/Zhefu802as the mapping population, and using SSR markers and InDel markers, we finally map the mutant gene on the short arm of chromosome6in a116kb region between the two InDel markers ST-1and ST-2, with a genetic distance of0.44cM and0.55cM, respectively. So we infer that the mutant gene is a new leaf color mutation gene, and designate it as ygl82(t).