Physiological Characteristics And Gene Mapping Analysis Of A Spotted Leaf Mutant Spl167 In Rice

Plants have developed complex defense mechanisms against pathogen attack,the most common of which is hypersensitive response（HR）,It inhibits further invasion or proliferation of pathogens in host plant tissues by triggering rapid programmed cell death（PCD）.Rice speckled leaf mutants are ideal materials for studying hypersensitive response in plants.In this study,japonica rice SN9816 was mutagenized into mutant spl167 by EMS,the agronomic characters and chloroplast ultrastructure of the mutant were observed,and the chlorophyll content,photosynthetic fluorescence parameters,and histochemical detection and analysis were carried out,the results of the study are as follows:The mutant spl167 appeared spots from the top of the leaves at heading stage.With the increase of time,the spots became more and more and began to spread downward.The spots were affected by light.Compared with the wild type,the mutant spl167 had shorter plant height and fewer tiller number.Stoma is the main channel for gas exchange between rice leaves and the outside world.Ci and gs are two important parameters to judge whether the net photosynthetic rate is limited by stomata.When the internal CO₂（Ci）,stomatal conductance（gs）and assimilation rate（A）both decrease,the decrease in assimilation rate is due to stomatal confinement.By observing the ultrastructure of wild type and mutant spl167,it was found that the chloroplasts of the mutant spl167 non-spotted mesophyll cells were arranged at the edge of the cell wall like the wild type,and the lamellar structure was not as clear as that of the wild type.The chloroplast arrangement of some mesophyll cells near the mutant spots was loose and irregular,the chloroplast membrane dissolved,the lamellar structure was destroyed,and the number of starch grain and Osmiophilic granules increased obviously.The results of diaminobenzidine（DAB）and nitro blue tetrazolium（NBT）staining experiments showed that hydrogen peroxide（H₂O₂）and superoxide anion(O_2-)were accumulated in mutant spl167,and the results of trypan blue staining experiments showed that Mutant cells die.The contents of peroxidase（POD）and superoxide dismutase（SOD）in mutant spl167 increased,but ascorbate peroxidase（APX）had no significant change,and catalase（CAT）decreased significantly,which further indicated that the plant The body produces a lot of hydrogen peroxide..Compared with the wild type,the 1000-grain weight of the mutant increased,but the number of tillers decreased,the ear length decreased,and the number of full grains decreased,so the yield of the mutant decreased.Compared with the wild type,the quality of the mutant rice was also reduced..The spl167 mutant was located between markers A11 and A12 on chromosome 1 with a physical distance of 289 kb.