Association Analysis Of Salt-alkali Tolerance At Budding Stage In Japonica Rice

In recent years,soil salinization has become a major factor for hindering crop yields and threatening food security.the seedling rate and final yield in saline-alkali soil are directly affected by the saline-alkaline tolerance of rice shoots.Therefore,it is of great significance to study the mechanisms of saline-alkaline tolerance in rice buds and explore the saline-alkaline tolerance genes,for the purpose of reducing salt-alkali damage and improving the productivity in saline-alkali soil.Association analysis is one of the hot topics in plant genomics research.The QTLs for saline-alkaline responsive traits in rice have been studied extensively at home and abroad.However,most studies utilized NaCl or Na₂CO₃ aqueous solution to simulate saline-alkaline environment while NaHCO₃,the main component in saline-alkaline soil was ignored.Hence,it is more practical to study the salinity tolerance of the japonica rice bud period under the stress of NaHCO₃ aqueous solution and soda alkaline soil.In this study,176 natural populations of japonica rice germplasm resources were used as test materials.The salt tolerance of japonica rice at the budding stage was identified under the stress of NaHCO₃ solution and soda saline soil.Meanwhile,association analysis were carried using 154pairs of SSR locus,and further excavate the excellent allelic variation and the corresponding carrier materials,in order to provide theoretical basis for saline/alkaline tolerance molecular marker-assisted breeding and innovation of s saline/alkaline tolerance germplasm in japonica rice.The main results of this paper are as follows:1.The three traits,relative seedling height,relative root number,and relative root length,measured at the 7th and 12th days under the stress of NaHCO₃ solution showed that the variation range of the three traits is quite large,and the variation range of relative root number at the 7th day was the largest.Then the Na⁺concentration,K⁺concentration,Na⁺/K⁺at the 13th and 18th days as well as the level of saline-alkaline damage at the 18th day were analyzed.The results explained that all traits basically conform to the normal distribution and consistent with typical quantitative genetic characteristics.2.Correlation analysis of three saline-alkaline tolerance relative traits,including relative seedling height,relative root number,and relative root length under NaHCO₃ stress solution at the7th days and the 12th days showed that the above traits were all extremely significant positive correlation;correlation analysis of three saline-alkaline tolerance relative traits under the 13th and the 18th days in Soda saline-alkaline soil showed the 18th days salt-tolerance level was significantly or extremely significantly positively correlated with the 13th days shoot Na⁺/K⁺concentration,the 18th days shoot Na⁺and K⁺concentration.And the shoot Na⁺concentrations at the 13th and the 18th days were significantly positively correlated with shoot K⁺and Na⁺/K⁺concentration.3.154 pairs of SSR locus were used to analyze the population structure and linkage disequilibrium of natural populations.Population structure analysis showed that the natural population was divided into three subgroups,of which 44 resources were from the P1subpopulation,71 resources were from the P2 subpopulation,14 resources were from the P3subpopulation,and the remaining 44 resources were mixed;LD analysis showed that there is a certain degree of linkage disequilibrium among SSR locus whether on the collinear?on the same chromosome?or non-collinear?between different chromosomes?.4.Using TASSEL 3.0 software GLM and MLM models analyze the correlations of saline/alkaline tolerance relative traits in rice buds.Under the NaHCO₃ aqueous solution stress,8SSR locus significantly associated with buds salt-tolerant-related traits were simultaneously detected in GLM and MLM models,with 18 times significant associations?P?0.01?.Among 8SSR locus,5 SSR locus were significantly associated with 2 or more traits.Under soda saline-alkali soil stress,there are 8 SSR locus simultaneously detected in GLM and MLM models which significantly associated with buds salt-tolerant-related traits,with a total of 14 significant associations?P?0.01?.4 SSR locus were significantly associated with 2 or more traits Among 8SSR locus.These results found that both RM286 and RM1219 were detected to be significantly associated with the salt-tolerant-related traits at the bud stage under both stress conditions.Compared with previous studies,13 of the 14 significantly correlated SSR sites were consistent,and one locus?RM1219?was the newly discovered site for this study.5.Excellent alleles and excavation of carrier materials were performed using the common significant association sites which simultaneously detected by GLM and MLM models.A total of28 and 24 excellent allelic variations were respectively excavated under NaHCO₃ solution stress and soda saline soil stress,and lists the five best varieties which carry this excellent allelic variation.The allelic variation and carrier materials excavated in this study can be used by molecular marker-assisted breeding methods,in the hope of playing an important role saline/alkaline tolerance breeding of japonica rice in Heilongjiang Province.