Screening And Evaluation Of Salt Tolerant Germplasm In Rice

With the rapid development of science and technology as well as industry and agriculture,great convenience is brought to the life of people,series of environmental problems are also leading to the increase of soil salinity and the decrease of cultivable land,which causes a shortage of food resources.Rice(Oryza Sativa),a kind of moderate salt-tolerant crop,is one of the most important food crops in the world and has been used as a pioneer plant for salt and alkali development.Developing salt tolerant rice germplasm resources and breeding the wide adaptative salt tolerant rice varieties is of great significance for restoring the salinized soil and development of saline-alkali soil.In this study,229 rice germplasm resources were collected from Professor Susan R.McCouch in Cornell University and the International Rice Research Institute,which were from many countries in the world.Especially,every germplasm has a higher density of the SNP marker genotype data.The rice plants were treated with 0.8%NaCl and 0.5%NaCl respectively during the forth leaf stage and booting stage.Different physiological characters were then determined to screen and evaluate of the salt tolerance varieties.The main results were as Follows:1.After salt treatment during seedling stage,the chlorophyll content,plant height,fresh weight and death rate in many varieties increased with salt stress continued,which showed different degrees of salt resistance.According to the death rate 4 d and 6 d after seedling treatment,13 rice varieties with strong salt tolerance were screened out by comparing with the other indexes,which were belong to 4 different subpopulations.2.After salt treatment during reproductive stage,there were significant differences in leaf chlorophyll content and chlorophyll fluorescence parameters(Fv/Fm,Fv/Fo),Na+ contents and Na/K values,ear length and seed setting rates among the rice cultivars.The rice ear length and seed setting rate were used as the criteria to divide the salt tolerance level,and finally 10 varieties with strong salt tolerance were screened out.Compared with the rice control cultivars with known salt tolerance,no difference were found between the ear length and seed setting rate under salt treatment,showed strong salt tolerance,while nearly 50%of the rice cultivars did not complete their whole growth period.3.Subpopulation classification were carried out for the total of 229 rice germplasm resources,and the salt tolerance of different supopulation during seedling stage and reproductive stage were compared.During seedling stage,there were 8 varieties in TRJ(tropical japonica rice)group and 6 varieties in IND(early rice)group were belong to grade 1 salt tolerance,and AUS(Oswald rice)group had the weakest salt resistance.When the seed setting rate was used as salt tolerance indicator during reproductive stage,the TEJ(temperate japonica)group has the strongest salt tolerance,and the AUS group was the weakest.Based on the above results,it was found that only two rice varieties had strong salt tolerance in both seedling stage and reproductive stage,that is,the variety named Kiang-Chou-Chiu in IND(early rice)group from Taiwanand Dourado Agulha in TRJ(tropical japonica rice)group from Brazil.The TRJ and TEJ groups have relatively strong salt tolerance in both seedling stage and reproductive stage,while the AUS group has the weakest salt tolerance.Based on the identification of salt tolerance during seedling and reproductive stage,as well as the SNP genotype inFormation and relevant physiological characters,the genome-wide association study(GWAS)can be carried out to rapidly explore salt tolerant genes/QTLs,and to improve the salt tolerace of rice or create new cultivars with salt tolerance.