| Soybean?Glycine max L.?is an important crop with high protein content.In South China,maize-soybean strip intercropping not only increased the planting area of soybean,but also improved the benefit.However,it was not clear whether or how soybean protein content changed under relay intercropping.To clarify the genetic mechanism of protein content in soybean,we measured the seed protein content?SPC?and the 11S and 7S globulin relative content from storage protein of the RILs(F6:9–10)derived from the cross of?Nandou 12‘?ND12?and?Jiuyuehuang‘?JYH?under monoculture and relay intercropping.Based on a genetic linkage map with 6,366 SNP markers,QTLs associated to protein content related traits were detected in three environments?E1,E2,and E3?.According to bioinformatics analysis,the candidate genes involved in protein biothesis and accumulation were annotated in these QTLs.The expression level of candidate genes during seed development stage was determined by the real-time quantitative PCR to explore the correlation between candidate genes and protein content in soybean.The main results were as follows:1.Soybean protein content related traits were sensitive to different environments and planting patterns.The seed protein content and 11S/7S ratio of JYH were almost significantly or extremely significantly higher than ND12 in E1 and E2,and the differences of the 11S/7S ratio between ND12 and JYH were extremely significant in E3,but the differences of the seed protein content between ND12 and JYH were not significant.Under different planting patterns,the differences of some protein content related traits between parents were significant or extremely significant.There were significant or extremely significant differences in the phenotypes of the protein content related traits in RILs under the factors of environment,planting pattern,family,and their interaction,but there was no significant difference in the sum content of 7S and 11S in different environments2.37 QTLs related to protein content were detected by ICIM method under monoculture and relay intercropping in E1,E2,and E3.19 QTLs for seed protein content were distributed in 11 linkage groups with the phenotypic variation of 3.62%–19.22%,and seven QTLs were identified under monoculture while 12 QTLs were under relay intercropping.18 QTLs for 11S and 7S fractions relative content were distributed in 14linkage groups with the phenotypic variation of 5.63%–9.68%,eight QTLs were detected under monoculture while 10 QTLs were under relay intercropping.3.According to the soybean genomic information,2,534 genes were annotated in the QTLs associated with protein content.A total of 1,995 genes were annotated in the QTLs for seed protein content,and there were 1,222 genes and 773 genes being annotated under monoculture and relay intercropping,respectively.A total of 539 genes were annotated in the QTLs for the relative content of 11S and 7S globulin,165 genes of them were found under monoculture while 374 genes were under relay intercropping.Glyma.14G086300,Glyma.16G066600,Glyma.16G109200,and Glyma.06G243800 were discovered as the candidate genes related to protein content according to the annotation descriptions.4.From 30 to 60 days every 10 days after flowering?DAF?,the accumulation of seed protein content of RIL80,RIL104,RIL180,and RIL199 increased first and then gradually levelled off.The seed protein content of four families under shade net was significantly or extremely significantly higher than that under normal light.The results of RT-qPCR showed that the expression levels of SF14 declined after 30DAF and approached zero gradually,and the expression trends of LASP were approximately opposite to that of SF14.The expression levels of AP4E1 roughly declined from 30DAF to 40DAF and increased from 40DAF to 60DAF,and the expression trends of TYR were generally contrary to that of AP4E1.The expression levels of SF14 and LASP were approximately higher under normal light than those under shade net. |
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