| Cotton fiber is a primary raw material in the cotton industry.Upland cotton has made a great contribution to the fiber production of the cotton industry in the world.In recent ten years,cotton breeders have paid close attention to the fruit development physiology.Fiber quality and yield are important economic traits,depending on the interaction between plant genetic structure and environment.Photosynthesis is the source that affects cotton yield and fiber quality.In addition,the carbon assimilation of the subtending leaf accounted for a large proportion of the carbon source.Therefore,the purpose of this study was to investigate the relationship between the fiber yield and quality of the corresponding boll of Upland cotton.To track the effect of Subtending leaves on fiber quality and yield,a group of cotton germplasm with different types of Subtending leaves were removed at different stages.Genetic diversity of 355 upland cotton core germplasm was studied for two years to provide a basis for the selection of potential genotypes.The cotton bolls with35 days,40 days,50 days,and 60 days' bolls were divided into four treatments,and control was kept without subtending leaves removal.The cotton genotype traits investigated in this study included boll length(BL),boll width(BW),leaf area index(LA),boll weight(BW),seed weight(SW),fiber weight(FW)and lint percentage(LP)and other fiber quality parameters such as fiber length(FL),fiber uniformity(FU),fiber micronair value(MIC),fiber strength(FS),and fiber elongation(FE).The fiber quality data were measured by HVI-9000.The effects of the source on the fiber yield and quality were estimated by comparing different treatments(4 growth stages)with the control.Differences are considered to be the source-sink effect of corresponding traits.Different univariate(summary statistics,univariate analysis of variance,mixed linear model)and multivariate analysis(correlation,principal component analysis,cluster analysis)were performed on the obtained phenotypic data to determine genetic variability and diversity.Variance analysis showed significant differences in the source-sink relationship between different growth stages after removing subtending leaves.Further study by correlation analysis and principal component analysis(PCA)showed varying degrees of variation,i.e.,39.83% and 45.37% over two years,and revealed significant environmental effects on yield and fiber quality.When the cumulative eigenvalues were more than 80%,the genotypes were divided into six groups according to the variability of traits.According to PCA and cluster analysis,the germplasm resources were split into six groups with high diversity,which provided a basis for their potential application in breeding programs.This study showed that removal of subtending leaves after 50 and 60 days had little effect compared to control.subtending leaf removal after 35 days,had the greatest impact on yield traits and most fiber quality traits.Several germplasm resources had the least effect on subtending leaf removal at all developmental stages,indicating that boll development was the least dependent on subtending leaf.In addition,the results show that there is a significant positive correlation between different traits.Based on two years of data,PCA cluster analysis was divided into three groups.The results of this study will help breeders select materials with less impact of leaf damage on boll development and enrich the study of the cotton souring-sink relationship. |
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