The genetics of ‘corky’. I. The new world alleles and their possible role as an interspecific isolating mechanism.

1. Interspecific hybrids between certain, strains of G. hirsutum var marie-galante and G. barbadense are abnormal. 2. The abnormal types have a characteristic bushy habit owing to their shortened internodes and excess production of lateral branches. Leaves are inrolled and exhibit a yellowish mottling; and stem, petiole, and leaf midribs tend to be covered with a thick layer of cork. Such ‘Corky’ types are more or less female sterile. 3. Corky symptoms depend on the interaction of complementary alleles, ck-x carried by the marie-galante, and ck-y carried by the barbadense parent. True breeding Corky types cannot therefore be isolated. 4. A geographic survey of the two species shows th.at the corky complementary alleles are most common in types occurring in, or originating from, areas where the geographical ranges of marie-galante and barbadense overlap and where the two species have been grown in mixed cultivation. 5. It is unlikely that this association is fortuitous and it is suggested that i6 is the result of seed selection by man in a partially out, crossed population.