Study On Genetic Basis Of Heterosis Of Upland/Sea-island Inter-specific Hybird Cotton

Cotton, being the leading fiber crop of the world and an important source of edible oil, isone of the most important economic crops. Among the four cultivated Gossypium species,upland cotton (Gossypium barbadense L.) and sea-island cotton (Gossypium hirsutum L.)play extremely important roles in cotton fiber production. Upland cotton has a high yieldwhile sea-island cotton has excellent fiber quality and disease resistance. An interspecifichybrid is expected to be the best way to extract all their advantages. But to date, a successfulexample of cotton interspecific hybrid breeding has only rarely been seen as the genetic basisof heterosis. To stride over this obstacle, exploration on heterotic mechanism seems animportant and necessary work.In this paper，a set of CSILs using Gossypium hirsutum TM-1as the recipient parent andGossypium barbadense Hai7124as the donor parent were used to map QTL for agronomic,yield and fiber quality traits of cotton. Two sets of F1populations individually derived fromCSILs crossing with both parents were configured to investigate heterotic loci (HL) andsubstitution effect loci (SL). A diallel cross was designed using26selected introgression linesto analyze the interaction between two different introgression chromosome segment. Themain results were listed as follow:1. Using a method of RSTEP-LRT,70QTLs were identified in CSILs population.Among all QTLs,14QTL were identified for agronomic traits,38QTLs for yield traits and18QTLs for fiber quality traits.11QTLs could be detected stably in two years,5QTLs(qLP-A8-1, qLP-A10-1, qLP-D6-1, qSI-D13-1, qFS-D5-1) could be detected in all three years.2. A total of82HL were identified, including16HL for agronomic traits,42HL foryield traits and24HL for fiber quality traits.58SL were identified,9SL for agronomic traits,30SL for yield traits,19SL for fiber quality traits. Some important loci were listed as follow:a stable HL (hLP-A4-3) could be detected in all3years; hBS-A9-1and hFBP-A1-1couldexplain34.31%and25.30%of the phenotypic variation respectively.3. All loci tended to be distributed in some hot chromosome segments with closepositions. Compared with QTL detected result, HL showed little overlap with QTL, indicating that trait phenotype and heterosis might be controlled by different sets of loci. All three formsof genetic effects (partial-, full-, over-dominant) were identified, while the over-dominanteffect made the main contribution to heterosis.4. In the diallel cross population,909significant interactions were detected among alltrial design, which certified that the interactions was widespread in all introgression segment.All three manners (the interaction between HL and HL, HL and non-HL, non-HL and non-HL)were existed in our analysis, but interaction between HL and non-HL had a main contribution,which took a ratio of52.81%of all interactions.In summary, we got an conclusion that the over-dominance in single loci level and thewidespread interaction in double-loci level was the heterotic basis of inter-specific hybrid“TM-1×Hai7124”.