| 1. Lesion mimic mutant refers to the plants which spontaneously produced lesions that resemble disease symptoms in the absence of pathogen attack and other damage or suppressed conditions. Lesion mimic mutant is important for understanding of the defense-single system of disease resistance, it also is focused on the fields of plant physiology, molecular biology and molecular genetics.A lesion mimic mutant, obtained by radiation mutagenesis on the seeds of a japonica rice variety Zhejing 22, exhibited a lesion mimic phenotype during the whole growth stage under different environments. Blue dyed trypan analyses showed that cells death in the leaves of spl(t), and H2O2 were accumulating in leaves showed by DAB. It could be presumed that spl(t) was caused by the programmed cell death, and had relationship with oxidative burst. By inoculation of rice bacterial leaf blight and rice blast strains, the resistances of the mutant were similar to the wild variety Zhejing 22. Genetic analysis indicated that the mutant trait was controlled by a single recessive gene named spl(t). Relying on simple sequence repeats (SSR) and recessive class analysis method to map the spl(t) gene with a F2 population was constructed by crossing the mutant spl(t) (japonica) with Zhenshan 97B (indica). spl(t) was mapped in the interval of 0.8cM between RM7195 and RM27929 near the centromere region on the short arm of chromosome 12. So, this gene can be used as mark genes in transgenic breeding.2. Rice panicle type has relationship with rice quality and yield. For example, the quality of curved panicle type varieties is superior to erect panicle type varieties, but its output is lower than erect panicle type varieties relatively, erect panicle type varieties with high yields, but also high the chalky grain rate, poor appearance quality. Some studies showed that changing the ear could improve the chalky rate of the dense panicle varieties at the same panicle length and grain density of the circumstances. A spreading panicle mutant, obtained by radiation mutagenesis on the seeds of a japonica rice variety Zhejing 22, and named spr8. The base primary branches of the mutant extend outward, and there was a enlargement organization on the inside of the extended primary branches, through the resin slice analysis show that the fundamental tissue hyperplasia formed a inflated structure which made the primary branches outgrowth of the panicle relative to the rachis, and giving the panicle spreading appearance.Mutant has slightly shorter panicle length and higher grain density comparing with the wild type Zhejing 22. The results of quality analysis and cross-sectional scanning through electron microscope showed that the mutant had lower chalky grain rate and amylose contents, starch grain arrangement was more uniform than Zhejing22. The study of amylose contents at the different positions showed that the upper of panicle had highest amylose contents, the middle of panicle took the second place and the basal of panicle had lowest amylose contents both in the mutant and Zhejing22, but there was less difference between middle and basal of a panicle for the mutant which may cause by the primary branch outward at basal of panicle. Spreading panicle could improve the internal environment of the panicle and increase the pool competition of the basal of panicle. Therefore, rice quality could be improved through the panicle type changed. To map the spr8 gene, an F2 population was constructed by crossing the mutant(japonica) with Zhenshan 97B (indica). spr8 was mapped in the interval of 3.4cM between RM257 and 9-69-2 on the chromosome 9. |
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