QTL Mapping For Stem Related Traits In Soyben

Intercropping was popularized in the south of China as supply-side structural reform of agriculture roll out.At present,the strip intercropping system of maize and soybean was widely applied in the south,northwest,Huanghuai area and so on.The platting pattern not only increases the land use capability,but also improves the crop yield and economic benefits.However,soybean was suffered from shade stress by maize,which increased pant height,reduced stem diameter,and limited seriously soybean production and mechanized harvesting.Up to now,the high and stable yield varieties are scarely in relay strip intercropping.It is urgent to breed soybean varieties suitable for intercropping.Therefore,understanding the heredity rule and effects of stem-related traits to shade,promotes intercropping soybean breeding.In this study,five stem-related traits?plant height,hypocotyl length,average internode length,number of main stem nodes and stem diameter?of 200 recombinant inbred lines(F_7-9)derived from Nandou 12?high shade tolerance?and Jiuyuehuang?low shade tolerance?were analyzed under monocropping and maize-soybean relay intercropping.The QTL mapping for stem related traits in soybean was carried out by the methods of complete interval mapping of software QTL IciMapping 4.1,with SNP high density genetic linkage containing 6366 SNPs.The main results were as follows:1.In 2015-2017,there were significant difference in five stem-related traits of two parents and RILs under monocropping and relay intercropping in four different times.Shade increased pant height,hypocotyl length,average internode length,and reduced number of main stem nodes and stem diameter.Difference of stem-related traits between monocropping and relay intercropping no changed with light recovery,after maize harvested.2.A total of 139 QTLs were detected four five stem-related traits on twenty chromosomes by QTL Icimapping 4.1.Under monocropping,ninty QTLs explained2.26%-32.12%of phenotypic variation were detected.Under relay intercropping,fourty-nine QTLs were identified with contribution from 1.27%-25.64%.The phenotypic variation of 34 and 49 QTLs was more than 10%under monocropping and relay intercropping,respectively.3.Four QTLs controlled the same traits were detected in different years and different growth periods.A total of 3 QTL gene clusters associated with different trats were identified in the same planting pattern.Several QTLs for plant height were located 3 similar regions as the QTLs for average internode length,explaining 18.23%of the total phenotypic variance.