Phvsiochemical Identification And Gene Mapping Of A Rice Early Senescence Mutant(es-32)

A new early senescence mutant(es-32)was obtained by induced-mutation breeding.In this study,the phenotype of the mutant were characterized,and the agronomic traits,physiological-biochemical and physicochemical traits of starch were investigated,also the mutant loci were premiliarly mapped.The main results are as follows:1.Mutant phenotype:es-32 showed normal phenotype before flowering while appeared sceneces after flowering till the whole filling stages,the leaves of es-32 lose green and appeared brown spots,especially on the tips of the leaf.Agronomic characters i.e.plant height?ear length?ear grains?setting rate and 1000-grain weight of mutant are significantly lower than WT,while the tiller number of mutant is more than WT.The germination rate of es-32 is lower than that of wild-type(WT)9311,showing poor seed vigor.2.Physiological and biochemical characteristics:After flowering,the content of chlorophyll?soluble protein?GSH and activity of SOD in es-32 decclined faster than that in WT,the content of hydrogen peroxide and MDA increased significantly than that in WT.At the same time,es-32 showed abnormal chloroplasts structure,losmiophilic particles increase,granum and thylakoid arrange chaotically,and the chloroplasts disassembled in advance.It indicates that change of bioactive products in plants influences its senescence,and it inversely affected biochemical parameters.3.Rice quality:the contents of amylose,gel consistency and alkali digestion value of mutant were lower than WT.Hot paste viscosity?cool paste viscosity?peak paste viscosity?breakdown and setback of es-32 were lower than WT.There were no significant differences between the starch granule structure of the mutant and WT,but the starch granule arranged more loosely in mutant than in the wild type,showed poor filling characters.4.Genetic analysis:es-32 mutation is controlled by a pair of recessive gene,which was prelimally mapped between RM5607 and RM166 on chromosome 2,the genetic distance are respectively 2.4cM and 10.2cM.These results laid foundation for later fine mapping and clone of early senescence gene.