|BLANCO, CARLOS - Animal And Plant Health Inspection Service (APHIS)|
Submitted to: Agricultural Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/21/2011
Publication Date: 1/26/2012
Citation: Scheffler, J.A., Romano, G.B., Blanco, C.A. 2012. Evaluating host plant resistance in cotton (Gossypium hirsutum L.) with varying gland densities to tobacco budworm (heliothis virescens F.) and bollworm (Heliocoverpa zea Boddie) in the field and laboratory. Acarology International Congress Proceedings. 3:14-23.
Interpretive Summary: Glands are found throughout the cotton plant and compounds contained in the glands protect the plant from pests and diseases. Cotton seed is a good source of high quality oil and protein, but one of these compounds, gossypol, decreases the value of cotton seeds and limits its use to feeding rations for ruminants such as dairy cows. There are breeding efforts in progress to decrease gossypol in the seed while maintaining or increasing the levels of protective compounds in other plant parts. In cotton, the ability of the plant to protect itself, termed host plant resistance, relies on these protective compounds. This study investigated possible methods to evaluate host plant resistance in cotton, since previous attempts to decrease seed gossypol failed because there were insufficient protective compounds in the selected plants and increased pest damage resulted in decreased yields. The methods developed in the study provide ways to evaluate host plant resistance not only in new low seed gossypol lines, but in any breeding lines under development.
Technical Abstract: Cotton (Gossypium hirsutum L.) produces a number of toxic terpenoid aldehyde (TA) compounds contained in epidermal glands that help protect the plant from pests and diseases. In the seed, one of these toxic compounds, gossypol, limits the use of the seed to ruminants such as dairy cows. There are breeding techniques and germplasm available to decrease gossypol in the seed, but the breeding process also needs to include methods to evaluate the plant’s ability to resist insect pests. Three approaches were used to assess resistance of cotton to herbivory from bollworm (Heliocoverpa zea Boddie) and tobacco budworm (Heliothis virescens F.) including field counts, controlled field antibiosis assays and laboratory feeding tests of young field grown leaves. Results indicated that both field and laboratory evaluation could provide an assessment of the cotton host’s resistance. Comparing the levels of terpenoid aldehydes in the seed and the leaves, confirmed that the levels and types of TAs in the seed were not always good estimators of leaf TAs and that other TAs such as hemigossypolone and heliocides contribute to host plant resistance.