natural-products-in-plant-pest-management

Fungal Endophytes 225of a given fungus will produce a highly biologically active compound inculture. A great deal of uncertainty also exists about what an endophyte producesin culture and what it may produce in nature. It does seem possiblethat the production of certain bioactive compounds by the endophyte in situmay facilitate the domination of its biological niche within the plant or evenprovide protection to the plant from harmful invading pathogens, insectsand environmental stresses (Omacini, et al., 2001; Rodriguez, et al., 2008). Furthermore,little information exists on the biochemistry and physiology of theinteractions of the endophyte with its host plant. It would seem that manyfactors changing in the host depending on the season, and other factorsincluding age, environment, and location, may influence the biology of theendophyte. Indeed, further research at the molecular level must be conductedin the field to study endophyte interactions and ecology. All of these interactionsare probably chemically mediated for some purpose in nature. An ecologicalawareness of the role these organisms play in nature will provide thebest clues for targeting particular types of endophytic bioactivity with thegreatest potential for bioprospecting.There is a general call for new antibacterial, antifungal, antiviral and chemotherapeuticagents that are highly effective and possess low toxicity. Thisnew approach of search is driven by the development of resistance in infectiousmicroorganisms (e.g. Staphylococcus, Mycobacterium, Streptococcus, Bacillus,Aspergillus spp.) to existing drugs and by the menacing increase ofnaturally resistant organisms. The ingress to the human population of disease-causingagents such as AIDS, Ebola and SARS requires the discoveryand development of new drugs to combat them. Not only diseases such asAIDS require drugs that target them specifically, but new therapies areneeded for treating ancillary infections that are a consequence of a weakenedimmune system. Furthermore, others who are immunocompromised (e.g.cancer and organ-transplant patients) are at high risk of infection by opportunisticpathogens, such as Aspergillus, Cryptococcus and Candida sp., that arenot normally major problems in the human population. In addition, moredrugs are needed to treat efficiently parasitic protozoan and nematodal infectionssuch as malaria, leishmaniasis, trypanomiasis, incephalitis and filariasis.Malaria alone is more dangerous in causing human death each year thanany other single infectious agent with the exception of AIDS and tuberculosis(NIAID, 2001). However, the enteric diseases as a group claim the most liveseach year of any other disease complex and, unfortunately, the victims aremostly children (NIAID, 2001).Endophytic fungi are now attracting great interest from researchers as analternative source in controlling plant pathogens. The control of late blight,caused by Phytophthora infestans, is very difficult by chemical means, becauseof the high virulence of the pathogen and increasing resistance to availablefungicides (Griffith et al., 1992). The fermentation broths of 52.3% of endophyticfungi displayed growth inhibition of at least one pathogenic fungus,such as Neurospora sp., Trichoderma sp. and Fusarium sp. (Huang et al., 2001).In a similar study, fermentation broths of nine (4.8%) out of the 187 endophyticfungi isolated from mainly woody plants were highly active against