Fig. 1

Geographic distribution and population variation of upland cotton accessions. a The geographic distribution of upland cotton accessions. Each dot of a given color on the world map represents the geographic distribution of the corresponding cotton accession groups. b Principal component analysis (PCA) plots of the first two components for all accessions. c Variance analysis of six phenotype traits between two groups, with black points representing mild outliers. In box plots, center line indicates median; box limits indicate upper and lower quartiles; whiskers denote 1.5× interquartile range; points shows outliers. BW: boll weight; LP: lint percent; FL: fiber upper half mean length; FD: flowering date; BOD: boll opening date; LPA: leaf pubescence amount.  P values in this and all other figures were derived with in Duncan’s multiple comparison tests. d Percentages are shown in a stacked column chart for 3 breeding periods (early, medium, and modern). e Four traits are compared among three breeding periods. a, b, c above the bars show significant differents (P < 0.05)