A Second Locus for Pollen Color in Pima Cotton, Gossypium barbadense L.1

Pollen color in the amphidiploid species of Gossypium varies from deep golden yellow to cream and is conditioned by one pair of alleles, P and p , with yellow dominant to cream. A mutation causing orange pollen was found in ‘Pima S‐I’, a normally yellow pollen commercial variety of Pima cotton (Gossypium barbadense L.) . The mutant, when selfed, showed pleiotropic effects which gave ranker plants that flowered later and fruited higher. Also, the flower buds were not conical and the stigma extruded beyond the scalloped tips of the corolla. The inheritance of orange pollen was determined from crosses of yellow with mutant orange, yellow with cream, and cream with mutant orange pollen strains. Single gene differences conditioned pollen color in the first two crosses; yellow was dominant. Pollen color in the cross of cream with mutant orange was conditioned by two complementary genes, giving an F 2 segregation of 9 yellow: 3 orange: 4 cream. One of the cream phenotypes in F 2 was found to be conditioned by the homozygous double recessive — a new genotype for cream pollen. The symbols P 1 or p 1 and P 2 or p 2 are proposed for the genes conditioning pollen color in G. barbadense . True breeding yellow and cream pollen strains would have the genotypes P 1 P 1 P 2 P 2 and p 1 p 1 P 2 P 2 , respectively. The orange pollen mutant would have the genotype P 1 P 1 p 2 p 2 .