INTERSPECIFIC INCOMPATIBILITY IN GOSSYPIUM. III. THE GENETICS OF TUMORIGENESIS IN HYBRIDS OF G. GOSSYPIOIDES

Abstract

Stem tumorigenesis in interspecific hybrids of G. gossypioides is governed by a three-allele genetic system — Go, Gx, and Gy. In this system GxGy is the only tumorigenetic genotype. Among the 30-odd diploid and tetraploid species of Gossypium, G. gossypioides is the only diploid to carry Gy and G. raimondii is the only diploid that carries Go. Three of the four tetraploid species, G. hirsutum, G. tomentosum, and G. caicoense, have the Go allele in one genome and the Gx allele in the other; tetraploid G. barbadense has the Go allele in both genomes. Hybrids between G. gossypioides and Gx diploids (GxGy) develop tumors early in ontogeny and die as seedlings. Hybrids between G. gossypioides and GoGx tetraploids (GoGxGy) do not develop tumors until the 10-14 leaf stage and can survive several years. Hybrids with the GoGoGxGy and GoGoGoGxGy tumor genotypes (synthesized with polyploid stocks) have few and no tumors, respectively.