THE INHERITANCE OF GOSSYPOL LEVEL IN GOSSYPIUM II: INHERITANCE OF SEED GOSSYPOL IN TWO STRAINS OF CULTIVATED GOSSYPIUM BARBADENSE L

Joshua Lee ¹

¹ U.S. Department of Agriculture, Plant Sciences Division, North Carolina State University, N.C. 27607

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, Gl₂ and Gl₃, are "native" to G. barbadense, whereas the mutant alleles, gl₂ and gl₃, 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 Gl₂ and Gl₃ were associated with the production of similar amounts of gossypol, whereas previous trials with cultivated varieties of G. hirsutum showed that Gl₂ was more than twice as expressive as Gl₃. The greater average productivity of seed gossypol in cultivated G. barbadense, as compared with G. hirsutum, was attributed to greater activity at the Gl₃ locus in the former species.