Gossypol content of C X (AD)1 and G X (AD)1 hexaploids and parents

Abstract

Gossypol, found in pigment glands, serves as a resistance mechanism against insects in the foliage of cotton, however, is toxic to non-runiinant animals when found in the seed. The ideal genotype would have glanded foliage and glandless seed (GPGS). This trait has been observed in C and G genome diploids. Three hexaploids, developed from crosses of C and G genome diploids with upland-type cottons (G. hirsutum L.), were used for this study: two C genome hexaploids, G. australe x Hancock and G. sturtianum x Acala 44; and one G genome hexaploid, G. bickii x Acala G8160. The purpose of this study was to evaluate these hexaploids and their diploid and tetraploid parents for glanding pattern and gossypol content in the seed, foliage, and flower buds. Glanding pattern was determined by counting the glands in cross-sectioned seeds, in the veinal and interveinal regions of the leaves and within the calyx crown of third-grown flower buds, while gossypol content was determined by high performance liquid chromatography (BPLC). Flower bud gossypol was not determined. The C genome hexaploids were intermediate to the parents for seed glanding pattern and gossypol content, both having fewer glands and less gossypol than the tetraploid parent. The G genome hexaploid, derived from glandless parents, had glands as well as gossypol in the seed. The C genome hexaploids were mostly intermediate to the parents for leaf glanding, having fewer glands than the tetraploid parent, with one being more similar to the diploid parent. The G genome hexaploid was intermediate to the parents for glands in the interveinal regions but had more glands than both parents at the veinal regions. All of the hexaploids were mostly intermediate to the parents for terpenoid content. Compared to their respective tetraploid parent, the C genome hexaploids had smaller terpenoid concentrations, whereas the G genome hexaploid had higher concentrations. The C genome hexaploids had significantly more flower bud glands than their tetraploid parent, while conversely, the G genome hexaploid had very few glands. These findings suggest different mechanisms for glanding in the seed, foliage, and flower buds between the C and G genomes.