The inheritance of gossypol level in Gossypium. II. Inheritance of seed gosypol in two trains of cultivated Gossypoium barbadense L.

Two strains of cultivated Gossypium barbadense L., Sea Island AS-2 and Pima S-4, were used to study the effects of alleles at two loci on the production and/or storage of gossypol in mature embryos. The normal alleles, Gl(2) and Gl(3), are "native" to G. barbadense, whereas the mutant alleles, gl(2) and gl(3), were introduced from Gossypium hirsutum L. through backcrossing. Each strain was grown in three replications per trial, and one, Sea Island AS-2, was grown in three environments. Each experiment consisted of all possible crosses, including reciprocals, of the four true-breeding genotypes, plus parents. Additive effects accounted for more than 90% of the total genetic variance for seed gossypol level in all trials. Epistatic effects, though small, were frequently significant. In G. barbadense Gl(2) and Gl(3) were associated with the production of similar amounts of gossypol, whereas previous trials with cultivated varieties of G. hirsutum showed that Gl(2) was more than twice as expressive as Gl(3). The greater average productivity of seed gossypol in cultivated G. barbadense, as compared with G. hirsutum, was attributed to greater activity at the Gl(3) locus in the former species.