| Wheat is one of the most important cereal crops in the world, and it is the main food for one thirdpeople in the world. It is essential to meet the demands of increasing wheat yield to ensure globalfood safety. Chlorophyll-deficient mutation is a kind of mutations with significant phenotypes. For itsadvantages, chlorophyll-deficient mutant has been used in the research of chlorophyll metabolism,chloroplast differentiation and development, plant physiology and gene function, it also has thepotential to be used in application.In this study, two yellow green leaf mutants were studied, one of the yellow green leaf mutantygld was derived from Triticum durum var. Cappelli treated by gamma radiation, the other yellowgreen leaf mutant ygla identified from population of Triticum aestivum var. YZ4110treated by EMS.The agronomic traits, chloroplast ultrastructure, environment-sensitivity and genetic characteristics ofthe mutants were studied. And the genes controlled yellow green leaf trait from Triticum durum var.Cappelli were mapped. The results are as follows:1. Phenotype characteristics of two mutants: All mutant leaves displayed yellow green leaf color,which is obviously different from the leaves on wild type, and expressed in the whole growthstage. Plant height, number of spikes per plant, number of grains of spike, grain yield per plant,1000-grain weight in the two mutants were significantly decreased than those in their wild types.Moreover, the phenotype of ygld is influenced by environment stresses.2. Chloroplast ultrastructure observation: The TEM analysis showed that there were no differencesin the size or the number of the chloroplasts between the mutants and their wild types. However,the shape and structure of the chloroplast were different between the ygld mutant and its wildtype. The wild-type plant had ellipsoidal chloroplast, while in the ygld mutant, the shape ofchloroplast changed from ellipsoidal to circular and the grana stacks in the stroma were highlyvariable in size and exhibited a disorganized appearance. In ygla mutant, compared with the wildtype, the envelop of chloroplast was ruptrued, but thylakoid and grana remain intact, nosignificant change in number were observed.3. Pigment content analysis: Compared with the wild types, the pigment content of the mutants,including chlorophyll a, chlorophyll b, total chlorophyll, and carotene, was decreased in themutants. In contrast, the chla/chlb ratio of the mutant was increased in comparison with thenormal green leaves.4. Photosynthetic efficiency analysis: Chl fluorescence kinetic parameters indicated that there waslittle different from maximal quantum yield of PS Ⅱ (Fv/Fm) between ygld and wild-type.However, the minimal fluorescence (Fo), maximal fluorescence (Fm), photochemical quenching(qP), non-photochemical quenching (NPQ) and the electron transport (ETR) were largelydecreased in the mutant. These results indicated that the PS in ygld mutant were severelyinhibited, and photosynthetic capacity was reduced. In ygla mutant, the same decreases in all the above index were observed. These results indicated that photosynthesis efficiency was decreased inthe mutant.5. Genetic analysis and mapping of the mutants: The phenotype of yellow green leaf in the ygldmutant was controlled by two recessive nuclear loci. The genes were designated ygld1and ygld2.Two molecular markers co-segregated with these genes. ygld1co-segregated with the SSRmarker wmc110on chromosome5AL, and ygld2co-segregated with the SSR marker wmc28onchromosome5BL. These results will contribute to the field of gene cloning and theunderstanding of the mechanisms underlying chlorophyll metabolism and chloroplastdevelopment in wheat. |
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