The Genetics of Flowering Response in Cotton. II. Inheritance of Flowering Response in a Gossypium Barbadense Cross.

N the first paper of this series, LEWIS and RICHMOND (1957) called attention I to the renewed scientific interest in the introduction of cotton stocks from tropical centers of variability and reviewed the collecting expeditions that have been made to Mexico and Central America in recent years. More than half of the collected stocks failed to set fruit in the temperate zone during the summer while all of them fruited readily in the greenhouse during the winter. The writers emphasized the fact that in the early development of the agricultural varieties of American Upland cotton, Gossypium hirsutum, in the Cotton Belt of the United States, only genotypes which were day-length neutral in fruiting habit persisted longer than the first growing season. The literature on the physiology of flowering in plants is extensive. It was adequately reviewed by MURNEEK et al. (1948) and by LEOPOLD (1951 ) and by others they cited. Purely genetic studies are less extensive, but the genetic basis of flowering has been recognized since the classic work of GARNER and ALLARD (1920)Although cultivated stocks of G. hirsutum account for almost all of the American cotton crop, cottons with staple lengths of over 1% inches come from varieties of G . barbadense. Formerly Sea Island types were important in the Southeastern United States and the West Indies. Currently most American extra-long staple cotton is grown in the irrigated valleys of Arizona, New Mexico and the TransPecos area of Texas. The primitive or semicultivated types of G. barbadense are of no less value in the improvement of commercial cottons than the primitive Uplands. Organized collecting expeditions have not been made to the center of variability of G. barbadense (the Andean valleys of Bolivia and Colombia) in recent years, but a few G. barbadense stocks from these regions have been obtained through colleagues in the United States and certain Latin American countries. so far, all the G. barbadense stocks collected in the tropics exhibit a short-day reaction when grown under the long-day conditions of summer in the American