Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 22, 2005
Publication Date: January 26, 2006
Citation: Stipanovic, R.D., Puckhaber, L.S., Bell, A.A. 2006. Ratios of (+)- and (-)-gossypol in leaf, stems and roots of selected accessions of Gossypium hirsutum var. Marie Galante (Watt) Hutchinson. Journal of Agricultural and Food Chemistry. 54(5):1633-1637. Interpretive Summary: Cottonseed could be a plentiful and nutritious protein source for animal feed. However, the natural occurrence of a toxic compound called gossypol in the seed prevents it from being used a feed source for non-ruminant animals. Gossypol occurs as a mixture of so called (+)- and (-)-forms. Only the (-)-form is toxic to non-ruminants. Commercial cottons usually have a (+)- to (-)- ratio of 3 to 2. The wild cotton referred to as moco cotton in Brazil is unique in that produces almost exclusively the (+)-form in the seed. This unique trait can be introduced into commercial cotton cultivars through traditional breeding techniques. However, gossypol and related compounds also help protect the plant from diseases and insects. The ratio of the (+)- to (-)- forms and the concentration of gossypol and related compounds had not been measured in other moco plant tissues. We studied several different moco type cottons that had (+)- to (-)- ratios that were as high as 95 to 5 and as low as 66 to 34. We found that the moco cotton #2452 with the highest (+)- to (-)- ratio in the seed, had equivalent or higher levels of gossypol and related compounds in the roots, leaves and stems as compared to a commercial cotton, but the concentration in the seed was not different than the commercial cotton. Thus, cotton plants derived from moco #2452 should not be unusually susceptible to attack by diseases or insects. Furthermore, their seed should not be more difficult to process than commercial cottons.
Technical Abstract: Gossypol is a sesquiterpene that occurs naturally throughout the cotton plant as an enantiomeric mixture. Gossypol and related terpenoids protects the plant from insect herbivores. Cottonseed has a high protein content, but it is underutilized because gossypol occurs in the seed. Its (-)-enantiomer is toxic to non-ruminants. Commercial Upland cottons usually have an approximate 3:2 (+)- to (-)-gossypol ratio in the seed, but plants can be bred with <8% (-)-gossypol using accessions of Gossypium hirsutum var. marie galante as parents. We report the (+)- and (-)-gossypol ratios and the concentration of related terpenoids in the stems, leaves and roots of four accessions of marie galante that show high, moderate and near normal levels of (+) gossypol in the seed; we compare these values to the commercial cultivar Stoneville 474, which has 62% (+)-gossypol in the seed. Compared to Stoneville 474, the percent (+)-gossypol and the concentration of the related terpenoids were significantly higher (P=0.05) in the stems and leaves of the two marie galante accessions that have the highest level of (+)-gossypol in the seed. We hypothesize that progeny from these parents should not be overly susceptible to herbivorous insects.