| The development of early maturity cotton varieties could release the contradiction between foodsupplies and cotton fiber production caused by limited plowland in China. With the improvement of earliness, yield and fiber quality should be improved together for such varieties. The fast development of modern breeding techniques accelerate the combination of conventional breeding and molecular breeding in early cotton variety breeding programes to improvement yield and fiber quality simultaneiously. The genetics anlaysis and QTL mapping for earliness, yield and fiber quality traits in cotton were performed in this study,the result show that:1. Genetic analysis of cotton earliness, yield and fiber quality traitsFor earliness traits, the broad heritability rate of growth duriation was the highest (88%) and the first fruit branch position had the highes narrow-sense heritability (49%). Both the broad and narrow sense heritability rate of length from flowering to first boll opening were the lowest. For yield related traits, lint percentage showed the highest broad sense heritability rate (74%) and narrow-sense heritability rate (65%). Lint yied had higher broad sense heritability rate (73%) while low narrow heritability rate (23%). Boll size and seed index also showed lower narrow-sense heritability. For fiber quality traits, fiber elongation (73%) and fiber length (49%) showed the highest broad- sense and narrow-sense heritability respectively. Both the broad heritability of strength (21%) and the narrow heritability (16 %) of fiber strength were very low.In the early maturity traits, the growth period showed significant positive correlation with all the other four earliness traits and had both higher phenotypic and genetic correlation with the length from flowering to first boll opening with the value of 0.827 and 0.895 respectively. In yield traits, the lint yield showed significant positive correlation with lint percentage and boll size at phenotypic and genetic level. The lint yield and seed index is negatively correlated. Micronaire value showed significant genetic and phenotypic correlation with, and the correlation coefficient was 0.730 and 0.646 respectively. Significant positive correlation at phenotypic and genetic level was also detected between fiber uniformity and fiber strength. Fiber strength and elongation showed significantly negative correlation. Lint yield was negatively correlated with most earliness traits, while duriation of squaring to flowering showed positive correlation with seed index and boll size. Significant correlation between earliness traits and fiber quality traits were not detected indicating the possibility to improve them together.in breeding programes.Path analysis indicated that, in earlinesn traits, the length from flowering to first boll opening showed the highest path coefficient (0.690) for growth period, then was the length from meraging to first bud (0.449).For yield traits, boll size and lint percentage showed negative path coefficients for growth period. Most of the fiber quality traits (micronaire, fiber maturity, fiber length) showed negative path index on the growth period and of which micronaire path coefficient was the largest.2. QTL mapping of earliness, yield and fiber quality traitsBased on a F2:3 mapping population of 216 lines from the cross of Lu19×Xinfeng66, 80 loci from 76 pairs of SSR primers and four SRAP combination were used for map construction and 50 marker were mapped and covering 398cM A total of 13 QTL were detected for three kinds of traits, including there QTL for early maturity traits explaing 5.2% ~ 15.3% phenotypic variation, four QTL for yield traits explaining 1.8% ~ 36.5% of the phenotypic variation and, six QTL for fiber quality traits explaining 1.9% ~ 9.6% phenotypic variation, repectively . |
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