| Wheat is one of major foodstuff crops in China, where drought stress has become an important environment factor limiting wheat yield. Wheat yield formation is not only associated with production of photosynthetic assimilates, but also attributed to the accumulation and remobilization of water soluble carbohydrates(WSC) temporarily stored in vegetative organs before anthesis to grain, especially under drought stress(DS). Based on the fast development of molecular quantitative genetics, QTL mapping and genetic dissection for related traits to WSC accumulation and remobilization regulated by the DS in different growth durations in wheat will provide critical theory for the genetic improvement in wheat drought tolerance at the molecular level.In present study, 160 wheat introgression lines(ILs) developed form repeat backcross between Jinmai 47 as recurrent parent and Xifeng 20 as donor parent(BC3F8) were used as plant materials. WSC and its component contents of different vegetative organs, and related traits to WSC accumulation and remobilization were employed to QTL mapping and further unraveled genetic bases of the complex quantitative traits and QTL-expression pattern. The results are as follows:1. The phenotypic variations in WSC-related traits in wheat ILs were significantly affected by water environment, organ and growth stage. All phenotypic values of ILs population were intermediated between those of two parents and showed wide variations and transgressive segregations with variation coefficients ranging from 9.23% to 63.72%. This indicated that favorable alleles from parents contributed to the target traits were widely separated in progenies and showed complex quantitative genetic attributes. Moreover, phenotypic values of ILs population were prone to recurrent parent Jinmai 47 in different water conditions and fully exhibited the characteristics of introgression lines. The broadsense heritabilities of all tested traits were rather low(0.30-0.65), whereas their genetic diversity index were higher(0.61-0.90).2. The genetic map for the ILs population was developed by SSR markers. The map spanned 2829.79 c M, in which average distance between adjacent makers was 20.81 c M.3. A total of 79 additive QTLs(A-QTLs) were detected for tested traits related to WSC accumulation and remobilization, mainly distributed on chromosome 2D, 5B, 5D, 6B and 7B. These loci showed positive or negative regulation to phenotypic variations in WSC and its component contents, as well as WSC accumulation and remobilization. Their additive effects differed from 0.01 to 15.24, individually explaining 0.01% to 32.99% of phenotypic variations. All detectable A-QTLs were interacted with water environments, of which interaction effects were performed to positively or negatively regulate the phenotypic variations and varied from 0.01 to 15.22, individually accounting for 0.01% to 16.32% of phenotypic variations.4. Detectable A-QTLs were clustered in some specific marker intervals or adjacent intervals, which formed QTL hotspot, such as maker intervals Xgwm539-Xgwm261, Xgwm261-Xwmc797 on chromosome 2D, Xbarc23- Xgdm11 on chromosome 5B, Xwmc104-Xwmc417 on chromosome 6B and Xgwm297-Xmag3166 on chromosome 7B, indicating that these regions carried a wealth of genes controlling WSC. Among them, Qfc.acs-2D.16 and Qfc.acs-5B.1 for fructan content and Qsc.acs-5D.7 for sucrose content had stronger positive regulation to phenotypic variations, of which additive effects were 12.34, 11.04 and 15.24, explaining 32.99%, 24.04% and 11.88% of phenotypic variations, respectively, suggestive of major QTLs. Some marker intervals, such as Xbarc159-Xcfd51 on chromosome 2D, Xgwm644- Xwmc417 on chromosome 6B, and so on, could have the pleiotropism. Furthermore, three new loci for sucrose content as Qsc.acs-6D.8, Qsc.acs-7B.3 and Qsc.acs-7B.6 were identified.5. A total of 112 epistatic QTLs(AA-QTLs) were identified for tested traits related to WSC accumulation and remobilization. These AA-QTLs showed positive or negative regulation to phenotypic variations in all tested traits. Their epistatic effects differed from 0.01 to 12.12, individually explaining 0.26% to 38.21% of phenotypic variations. Of these, 81 AA-QTLs were interacted with water environments, of which interaction effects varied from 0.01 to 1.90, individually explaining 0.02% to 6.53% of phenotypic variations. By contrast, some AA-QTLs on chromosomes 2B-3A, 1D-3B, 2A-3B, 2D-3A, 1D-6B and 2D-6B showed higher contribution rates to phenotypic variations(8.51-38.21%), indicating that epistatic effects in these intervals also played important roles in regulating the inheritance of WSC-related traits. |
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