Submitted to: Physiologia Plantarum
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 13, 1997
Publication Date: N/A
Interpretive Summary: Mycoherbicides are being considered as an alternative to standard control measures for coca production. Leaves of Erythroxylum coca var. coca (coca) are the primary source of the drug cocaine. Very little is published on the response of coca leaves to stress, especially considering the social and economic impact of coca cultivation and cocaine production on the producing and consuming nations. We report here some of the responses of coca leaves to stress induced by the plant hormone ethylene and fungal proteins. The fungal proteins induce ethylene production by coca leaves and also kill plant cells. The insight gained into the physiology of the responses of coca leaves to stress factors could be useful to scientists in developing better control strategies. This would include the development of strains with enhanced pathogenicity using molecular genetic manipulations involving fungal proteins.
Technical Abstract: Leaves of Erythroxylum coca var. coca (coca) are the primary source of cocaine, and there is interest in using Fusarium oxysporum as a mycoherbicide to control coca production. Deleafing coca plants stimulates rapid production of new leaves, and the young expanding leaves readily abscise in response to ethylene. Commercial enzyme preparations as well as a 24 kDa protein from Fusarium oxysporum induced significant levels of ethylene production by coca leaves. None of the proteins in the commercial enzyme preparations were cross-reactive with the antiserum to the 24 kDa denatured protein. Ethylene pretreatment of coca leaves enhanced the ethylene response of the leaves to the commercial enzyme preparations, Driselase and the 24 kDa protein. However, ethylene pretreatment did not enhance the rate of necrosis induced in response to either Driselase or purified 24 kDa protein. Driselase failed to elicit levels of necrosis comparable to the 24 kDa protein even at 30 fold higher protein concentrations. The response of coca leaves to the 24 kDa protein saturated at 6.7 micrograms/mL. The age of coca leaves influenced both the level of resulting necrosis and the amount of ethylene produced in response to protein. The very young leaves produced the highest levels of ethylene and necrosis in response to Driselase and the 24 kDa protein. The insight gained into the physiology of the response of coca to stress factors should be useful in designing better control strategies.