QTL Mapping For Saline-alkali Tolerance In Maize Seedling And Development Of SSR Markers Associated With Salt Tolerance In Maize Inbred Lines

Maize is one of the main food crops in China and played an important role in ensuring national food security.Due to the influence of factors such as unreasonable irrigation,fertilization,and environmental degradation,The losses was next only to drought for soil salinization brought to the agricultural production.Soil salinization has become one of the main factors affecting the current maize production.Maize is moderately sensitive to salt,especially in seedling.Saline-alkaline tolerance is a quantitative trait controlled by micro-polygenes.It is very difficult to breed varieties solely by conventional breeding techniques.In recent years,with the rapid development of molecular biology,the construction of genetic linkage maps based on various molecular markers and related molecular genetics studies,it provided new opportunities for improving salt tolerance of crops.QTL mapping and development of functional markers combined with accurate phenotypic identification can more accurately detect and trace dominant alleles and ultimately promote the implementation of marker-assisted selection in breeding practice.It would provide guidance for the cultivation of maize inbred lines tolerant to saline-alkaline and greatly shorten the age of relying solely on conventional breeding.In the study,The F2 populations were derived from an inter-cross between two inbred lines(Zheng 58 and Chang 7-2)and genetic linkage map was constructed by SSR markers.Five traits of the F2:3 populations and their parents were analyzed,which included germination rate,relative conductivity,pro content,single plant weight and seedling tolerance rating.Based on this,QTL analysis for the above five traits were performed using Windows QTL Cartographer Version 2.5 software.Composite Interval Mapping(CIM)was used to map the QTLs.At last,the markers associated with salt tolerance were screened by the combination of QTL mapping and 20 inbred lines with known salt tolerance.The results were as follows:1.Five traits of the F2:3 populations and their parents were analyzed respectively in 200mmol/L Na Cl and 100 mmol/L Na2CO3 solutions,which included germination rate,relative conductivity,pro content,single plant weight and seedling tolerance rating.The correlation between five traits was analyzed.The results showed that there were significantly correlated among salt tolerance rating and other traits besides germination rate under the salt stress condition.The salt tolerance rating was positively correlated to relative conductivity and pro content.The salt tolerance rating was negatively correlated to single plant weight.The procontent was positively correlated to relative conductivity.There was pairwise-correlated between traits besides relative conductivity.2.The F2 populations consisting of 142 individuals were genotyped by 276 SSR markers.The genetics linkage map was constructed by Join Map4.0 software,with the whole length of4507.798 c M,an average marker interval of 19.35 c M based on 233 SSR markers.3.QTL analysis for the above five traits were performed using Windows QTL Cartographer Version 2.5 software.Composite Interval Mapping(CIM)was used to map the QTLs.Under salt stress condition,3 QTLs were respectively detected for germination rate and pro content,1 QTL was detected for relative conductivity and salt tolerance rating.Under alkali stress condition,2QTLs were respectively detected for germination rate and alkali tolerance rating,1 QTL was detected for relative conductivity and pro content,4 QTLs were detected for single plant weight.4.This study was carried out by the analysis tolerant to salt of 69 maize inbred lines and the evaluation based on the principal component analysis(PCA),and 10 salt tolerant and 10 sensitive lines were collected.With the above 20 inbred lines as test materials,ANOVA(analysis of variance,ANOVA)was used to statistically evaluate salt tolerance of each allele of24 SSR loci selected from the fifth linkage group within Zheng 58/Chang 7-2 linkage map constructed by this laboratory,resulting in four SSRmarkers related to salt tolerance(umc1416,umc1349,umc2295 and umc1686).