Genetical and Cytological Study of Species Hybrids of Asiatic and American Cottons

Abstract

1. One thousand seven hundred and eight crosses were made between Asiatic and American cotton species and six hybrid plants were obtained. 2. Out of 1017 crosses in which Asiatic cottons were used as the female parent, one hybrid plant was produced, while in 691 crosses using American cotton as the female, five hybrid plants were obtained. This would indicate that when crosses are made between Asiatic and American cotton species better success is obtained when American cotton is used as the female parent than when Asiatic cotton is so used. Since American cotton has 52 somatic chromosomes while Asiatic cotton has 26, this agrees with the general observation that crosses using the species with the higher chromosome number as the female are more successful. 3. Studies of pollen tube growth suggest that the low percentage of success in Asiatic-American species crosses is due not to the slowness of foreign pollen tube growth, but probably to an actual incompatibility of gametes. 4. The F1 hybrid plants obtain...