Start Date: Jan 01, 2012
End Date: Dec 31, 2012
Phytoalexins are compounds produced by plants in response to microbial infection and exhibit antibiotic properties. We have identified, cloned, and sequenced the dHG-OMT gene from Gossypium barbadense. This gene converts the cotton phytoalexin esoxyhemigossypol (dHG) into desoxyhemigossypol-6-methyl ether (dMHG). This gene is expressed in glands throughout G. barbadense. The gene is also present in G. hirsutum, but it is not expressed in glands or is expressed only at extremely low levels. However, when attacked by fungal pathogens, the gene is expressed in G. hirsutum juvenile tissues such as the root tip and the hypocotyl; these are common points of attack of fungal pathogens. dHG, HG, dMHG and MHG are fungitoxic, but dMHG and MHG are significantly less toxic to fungal pathogen compared to dHG and HG, respectively. Thus, the methylation step reduces the effectiveness of the phytoalexins at juvenile tissue sites. Our objective is to down regulate dHG-OMT expression using an RNAi construct. In related proposed research, we have identified a new sesquiterpenoid in wild species of cotton. The structure of this compound indicates it will exhibit effective fungicidal activity as well as insecticidal activity. The structure of this terpenoid is under potential intellectual property consideration. Thus, its exact structure is not provided herein. However, the structure has been provided to individuals at Cotton Inc. who have signed a Confidentiality Agreement with ARS. The fungicidal and insecticidal properties of this and other newly identified compounds will be investigated as part of this proposal. Appropriate plants, plant parts, or extracts of the plant will be assayed for resistance to fungal pathogens and insects that affect cotton yield and fiber quality.