Identification Of Saline-alkali Tolerant Soybean Varieties And Screening Of Marker Genes

Soybean(Glycine max)is the main food crop,and it is also an important oil and feed crop.However,China’s soybean planting area and output are relatively low,but the demand is large,which has caused China’s soybean to rely heavily on imports,and food security is subject to people’s "bottleneck" problem.In order to further expand soybean planting area and increase soybean yield,the No.1 document of the Ministry of Agriculture and Rural Affairs in 2023 pointed out that it is necessary to steadily develop saline-alkali land to grow soybeans.Saline-alkali land refers to a kind of land where there are too many salt and alkaline substances in the soil for various reasons,which increases the ion concentration and pH value in the soil and leads to the normal growth and development of plants.It has a great impact on agricultural production and ecological environment on a global scale.The damage caused by saline-alkali land to plants mainly includes oxidative stress,which leads to excessive accumulation of reactive oxygen species in plants,and then oxidative damage to cells;It disturbs the metabolic process of plants and affects photosynthesis and respiration.These damages ultimately affect the growth and development of plants and reduce the yield and quality of plants.Therefore,efficient identification,screening and cultivation of saline-alkali tolerant soybean varieties are of great significance to soybean planting in saline-alkali land.In recent years,molecular marker-assisted selection has become one of the important methods to predict and screen resistant crops,and molecular marker-assisted breeding has also become one of the important means of crop resistance breeding.At present,most of the research focuses on SSR and SNP markers at the base level,and it is a new research direction in recent years to directly use gene expression as candidate markers and predict their functions.Compared with molecular markers based on linkage relationship such as SNP,markers based on gene expression can directly provide information about gene functions and metabolic pathways,and theoretically,individuals with specific phenotypes can be selected more accurately.In this study,28 soybean varieties were used to simulate the saline-alkali soil environment in Northeast China,and the growth indexes and physiological indexes of soybean seedlings under mild saline-alkali stress and severe saline-alkali stress were collected.The membership values were calculated by the fuzzy membership function method to rank the salt-alkali tolerance.Some varieties were selected for transcriptome analysis,and combined with physiological index data,the prediction equation of soybean salt-alkali tolerance was constructed.The accuracy of the study was verified by qRT-PCR.The main conclusions are as follows:(1)The plant height,leaves and photosynthetic indexes of all soybean varieties decreased to different degrees due to different degrees of saline-alkali stress.According to the growth index data,28 soybean varieties were evaluated by fuzzy membership function method.Among them,Williams 82,Jiadou 3 and other varieties have strong salt and alkaline tolerance,Dengke 13,Zhonglong 608 and other varieties have medium salt and alkaline tolerance,while Beian and Kenbao varieties have weak salt and alkaline tolerance.(2)Different degrees of saline-alkali stress increased the physiological indexes such as superoxide dismutase in all soybean varieties,and based on these physiological indexes,the salt-alkali tolerance of 28 soybean varieties was evaluated.Among them,Shengdi 168 and other varieties have strong salt and alkaline tolerance,Dengke 13 and other varieties have medium salt and alkaline tolerance,and Beian varieties have weak salt and alkaline tolerance.(3)Through transcriptome analysis,it was found that the gene expression of phenylpropanoid biosynthesis,plant hormone transduction,starch and sucrose metabolism were important factors affecting the salt-alkali tolerance of soybean,and 18 genes significantly related to physiological indexes were selected as marker genes to construct the prediction equation of salt-alkali tolerance of soybean.The verification results of qRT-PCR were consistent with the prediction equation,physiological and growth indexes.In summary,in this study,28 soybean varieties were preliminarily evaluated by plant phenotype,growth index and physiological index,and 18 genes that could be used as markers of salt-tolerance and alkali-resistance of soybean were screened out according to transcriptome data.On this basis,the prediction equation of salt-tolerance and alkali-resistance of soybean was constructed and verified by quantitative PCR.At the same time,this study also provides an idea of using the expression of marker genes as molecular markers to preliminarily evaluate the stress tolerance of crops,which is a supplement to traditional molecular markers such as SSRs and SNPs,and provides new means and ideas for the breeding of salt-tolerant soybean varieties and guiding actual production in the future.