QTL Mapping And Physiological Function Analysis Of Salt And Alkali Tolerance In Rice At Bud And Seedling Stage

In order to analyze the quantitative trait loci(QTL)of rice at the bud and seedling stages under salt and alkali stress and to explore the physiological mechanisms of salt and alkali tolerance in rice,the recombinant inbred lines(RILs)with stable inheritance constructed from Luhui99(R99),an indica rice variety,and Shennong265(SN265),a japonica rice variety,was used as the test material.In this paper,the phenotypes of salt resistance and alkali resistance in rice at the bud and seedling stages were identified by the method of nutrient liquid water culture,genetic map was constructed and QTL analysis was carried out.According to the results of salt and alkali injury phenotype identification,salt resistant strains RS24 and RS77,salt resistant strains RS42 and RS138,alkali resistant strains RS8 and RS110,alkali resistant strains RS46 and RS116,and 2 parents were selected to determine the physiological and biochemical indexes such as electrolyte leakage,reactive oxygen metabolism,antioxidant enzyme activity,plant Na+ and K+ content under salt and alkali stress.The results show that:1.Salt and alkali stress reduced the germination potential and germination rate of the parents and RILs,resulting in the plant becoming shorter during the seedling stage and inhibiting the growth of the roots and the accumulation of dry matter.The inhibition effect under high salinity stress was stronger than that under low salinity stress.2.Under salt stress,nine QTL were located on chromosomes 5,6,7 and 9,which were related to germination rate,germination potential,and seedling height,root length,root number,and dry matter weight of rice sprouts.Under alkali stress,fifteen QTL were located on chromosomes 1,2,5,6,7,8 and 9,which were related to seedling height,root length,root number,and dry matter weight of rice germination,germination potential,and seedling stage.3.Under salt and alkali stress,the electrolyte leakage,MDA content,H2O2 content and superoxide anion production rate of the tested materials increased significantly.The parameters of salt-sensitive R99,RS42,RS138 and alkali-sensitive R99,RS46,RS116 increased more significantly.The salt-resistant(SN265,RS24 and RS77)and alkaline-resistant(SN265,RS8 and S110)varieties(lines)could reduce the damage of reactive oxygen species to cell membrane by increasing the activities of SOD,CAT,POD and APX.4.Under the stress of salt and alkali,the contents of Na+ in the aboveground parts and root of the tested rice increased significantly,while the contents of K+ in the aboveground and root decreased significantly.The Na+ contents of overground parts in the salt-tolerant and alkali-tolerant varieties(lines)were significantly lower than those in the salt-sensitive and alkali-sensitive varieties(lines)under stress,respectively.However,the Na+ contents of root,the K+ contents of aboveground parts and root in the salt-tolerant and alkali-tolerant varieties(lines)were significantly higher than those in saline-resistant varieties(lines),respectively.Although the ratio of aboveground parts to root Na+/K+ increased significantly under stress,salt-tolerant and alkali rice varieties(lines)hindered Na+ from transporting to stem and leaf,and enhanced the ability of K+ to transport to stem and leaf,which resulted that the Na+/K+ ratio of aboveground parts and root in the salt-tolerant and alkali-tolerant varieties(lines)were significantly lower.