Dreisigacker, Susanne
(Ed.)
The cotton genus Gossypium shows wide variation for pollen color. Pima cotton (G. barbadense), which is known for premium fiber quality, is characterized by yellow/orange pollen, while the widely cultivated upland cotton (G. hirsutum) usually has cream-colored pollen. We conducted a genome-wide association study using a diversity panel of 136 accessions of upland cotton genotyped with the cottonSNP63K array and identified three significant marker–trait associations for pollen color within a 226 kb region on chromosome A05. Phenotyping of two recombinant inbred line (RIL) populations derived from the parental accessions DES 56 (white pollen), and Sealand #2 and Southland M1 (yellow pollen) at the F1 and F5 generations showed that the yellow pollen color was controlled by a single dominant gene at a locus designated as GH-PA1. Molecular mapping using two RIL populations genotyped with SNP markers further localized GH-PA1 locus to a 5.36 cM region on chromosome A05. The flanking markers (i12529Gh and i12525Gh) of the GH-PA1 locus in the linkage map identified a 112.83 kb region in the sequence-based physical map. This genomic region consisted of four putative genes, with one predicted to encode phytoene synthase of the carotenoid biosynthetic pathway was identified as a probable candidate gene controlling the yellow pollen color. Analysis of phytochemicals confirmed higher carotenoid content in yellow- than in white-colored pollen grains, while no significant differences in flavonoids were found. Deciphering the molecular-genetic architecture of GH-PA1 could aid in the understanding of the role of phytochemicals in cotton pollen physiology and adaptation.
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