QTL Mapping For Fiber Quality And Yield-related Traits In Upland Cotton (Gossypium Hirsutum.L) With Elite Fiber Quality

In order to establish theoretical basis on the molecular marker assisted selection for Upland cotton, two F₂ populations and their corresponding F_2:3 family lines were constructed, which included common male parent with high fiber quality, Xinluzao24, one female parent for populationâ… with commercial transgenic variety, Lumianyan28, and the another female parent for population II with high-yield traits, Jimian 516. The population of Lumiayan28×Xinluzao24 F₂ was used to construct the linkage map. Based on the map, the QTLs for fiber quality and yield traits were identified with Composite Interval Mapping (CIM) method. QTL mapping for fiber quality and yield traits could be very useful in the molecular marker assisted selection (MAS) breeding programs.The fiber yield and quality traits in F₂ and F_2:3 populations were investigated systematically.The results showed that there were extremely significant difference between male parent and two female parents for fiber strength, fiber length, Micronaire, lint percent and seed indexe, and significant difference for fiber uniformity and fiber elongation. Except for plant boll number of F_2:3 , plant seedcotton yield, plant lint yield in populationâ… and plant seedcotton yield, plant lint yield, plant boll number of F_2:3 in population II,the other fiber quality and yield traits were distributed in normal distribution with the absolute value of skewness below one for most traits, which match to the phenotypes conditioned by multiple micro-effect genes.The correlation analysis indicated that Micronaire was significant positive correlation with fiber uniformity, and significant negative correlation with the other fiber quality traits; Except for Micronaire, it indicated significant or very significant positive correlation between the other fiber quality traits; Lint percent was positive or significant positive correlation with plant seedcotton yield and plant lint yield; seed index was not correlation with Micronaire, but very significant positive correlation with the other fiber quality traits; There were significant negative correlation between the main yield traits including lint percent, plant seedcotton yield and plant lint yield, and fiber length and fiber strength, which indicated that it should be still difficult to improve fiber quality and fiber yield simultaneously.A total of 7638 pairs of SSR primers were used to screen the polymorphism between Lumianyan28 and Xinluzao24, 225 pairs of polymorphic primer were obtained for genotyping its F₂ population, which produced 238 polymorphic loci. A genetic linkage map with 185 loci were constructed, which comprised of 44 linkage groups covering 1509.38 cM with an average distance of 8.16 cM between the two neighbor markers, and approximately 33.91% of the cotton genome. 40 linkage groups were assigned to the corresponding chromosome.A total of 14 QTLs for fiber quality and 22 QTLs for yield traits were identified with Composite Interval Mapping (CIM) method in the population related to Lumianyan28 and Xinluzao24. A total of 4 QTLs for fiber strength, fiber elongation, micronaire, and seed index could be identified in population I and II. Especially, the main effect QTL for fiber strength(qFS-6-2) could be detected in different generations and two populations. There are six QTLs for fiber strength, fiber length, fiber uniformity, Micronaire, lint percent and seed index, which might be previously published in other genetic backgrounds. These stable QTLs should be useful in the molecular marker assisted selection (MAS) breeding programs.Integrated with other studies,it indicated some regions in chr.7 and chr.25 play an important role in QTLs clusters distribution for fiber quality, yield traits, seed physical traits and seed nutritional quality traits.So The related area on chr.7 and chr.25 is necessary for further research.