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Submitted to: American Journal of Plant Sciences
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 5/15/2016 Publication Date: 5/18/2016 Citation: Scheffler, J.A. 2016. Evaluating protective terpenoid aldehyde compounds in cotton (Gossypium hirsutum L.) roots. American Journal of Plant Sciences. 7:1086-1097. Interpretive Summary: Cotton (Gossypium hirsutum L.) has epidermal glands containing special compounds that help protect the cotton plant from pests and diseases. One compound called gossypol, is found predominantly in seed and roots and has two forms, plus (+) and minus (-) present in varying amounts. The (+) form is less toxic to animals and humans, but is reported to be as effective as the (-) form in protecting the plant from insects and disease. If the cotton root’s self protection mechanisms, referred to as host plant resistance (HPR), could be enhanced by selecting for increased levels of gossypol in the root or the ability of the root to produce more gossypol in response to pest attack, it would be possible to maintain yield potential without increased use of expensive pesticide treatments. This study found that there is selectable variation in cotton for root gossypol content, which varies in response to biotic or abiotic stresses. One line had large quantities of gossypol in the roots with 90% in the less toxic plus form. Crossing experiments showed that these traits could be transferred to other cotton lines. Technical Abstract: Cotton (Gossypium hirsutum L.) has epidermal glands containing terpenoid aldehyde (TA) compounds that help protect the cotton plant from pests and diseases. One terpenoid aldehyde called gossypol, is found predominantly in seed and roots and has two forms, plus (+) and minus (-) present in varying amounts. The (+) form is less toxic to animals and humans, but is reported to be as effective as the (-) form in protecting the plant from insects and disease. If the cotton root’s host plant resistance mechanisms could be enhanced by selecting for increased level of TAs in the root or the ability to increase TA quantity in response to pest attack, it would be possible to maintain yield potential without increased use of expensive pesticide treatments. Results reported here found that as in seed, gossypol was the predominant TA in roots with no heliocides detected and only trace amounts of other TAs, such as hemigossypolone or hemigossypol. Among normally glanded lines, there were significant differences in gossypol quantity between lines. Percent (+) gossypol was consistently 4-10% higher in roots than seed. One line ‘Mac7’ had 12-14 ug/mg gossypol in roots and 18 ug/mg in seed as well as 90% plus (+) gossypol in both roots and seed. The large quantity of root gossypol and the high percent in the (+) form was successfully transferred from Mac7 to other cotton lines demonstrating that it was heritable. The roots of glandless lines consistently produced gossypol with 77% to 82% in the plus (+) form, indicating that unlike other parts of a glandless plant, the roots have a functioning biochemical pathway for gossypol production. Multi-year field tests to measure the effect of insect pressure on TAs in roots and seed indicated that root gossypol levels were more responsive to environmental influences than were seed. Results indicate there is selectable variation in upland cotton for root gossypol content, which varies in response to biotic or abiotic stresses. |
