Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/28/2000
Publication Date: N/A
Interpretive Summary: Opium poppy is the source of the illegal narcotic drug heroin. Cultivation of opium poppy occurs around the world. We are seeking to develop alternative control measures to traditional chemical weed control for the illegal cultivation of opium poppy. Pleospora papaveracea is a fungal pathogen of opium poppy but at present biocontrol strategies using this pathogen have shown only limited promise. Nep1 is a protein produced by Fusarium oxysporum that induces a hypersensitive response in many dicot plant species including opium poppy. By combining Pleospora papaveracea with Nep1 in foliar sprays, we were able to enhance the damage caused to opium poppy in greenhouse studies and in limited field tests. The combination greatly accelerated the damage to opium causing extensive foliar necrosis within two weeks after treatment. The combination of a protein that induces a hypersensitive response in plants with a plant pathogen to achieve enhanced weed control is a new and novel strategy and offers a new tool in the control of weeds in general and the narcotic plant opium poppy specifically. The control of opium poppy production, and thereby the reduction in the production of heroin, is of national and world wide importance and is of benefit to drug control agencies and citizens of the United States and the world.
Technical Abstract: The fungus Pleospora papaveracea, a pathogen of opium poppy (Papaver somniferum L.), and Nep1, an extracellular phytotoxic fungal protein, were evaluated in combination for their biocontrol potential on opium poppy. Modifications of four formulations, control, P. papaveracea conidia, Nep1 (5 micrograms/mL), and P. papaveracea conidia plus Nep1 (5 micrograms/mL), were used in detached leaf, greenhouse and field studies involving whole plants. The formulations contained 0.001% polyoxyethylene-sorbitan monolaurate (detached leaf studies), 0.5% Tactic (greenhouse studies) or 0.2% 1,1,1,3,5,5,5-heptamethyltrisiloxanyl propyl-methoxy-poly[ethylene oxide](field studies)as wetting agents. Conidia of P. papaveracea in 0.001% Tween 20 remained viable for at least 38 days when stored at both 20 and 4 C. The presence of elicitor had no effect on conidia germination or appressoria formation by P. papaveracea. Nep1 was stable in the presence of P. papaveracea for at least 38 days when stored at 4 C and 28 days at 20 C. Nep1 could be recovered from formulation drops applied to opium poppy leaves in both detached leaf and field experiments 24 h after treatment. In greenhouse and field studies, opium poppy treated with the combination of Nep1 and P. papaveracea had an increase in necrosis ratings and a reduction in the number of leaves with less than 50% necrosis compared to the other formulations. There were major changes in the intercellular protein profiles as determined by SDS-gel electrophoresis after treatment with Nep1, P. papaveracea, or the combination of Nep1 and P. papaveracea. Nep1 and P. papaveracea combined in formulations can enhance damage caused to opium poppy compared to either component alone.