natural-products-in-plant-pest-management

232 R.N. Kharwar and G. Strobelin treating seeds, fruits and plant parts in storage and while being transported.In addition, M. albus is already in a limited market for the treatmentof human wastes. Its gases have both inhibitory and lethal effects on suchfaecal-inhabiting organisms as Escherichia coli and Vibrio cholera. It will beused for this purpose in coming years. Studies are underway that show itspromise to fumigate buildings, thus removing the potential for fungi tocontaminate building surfaces and cause health risks.Using M. albus as a screening tool, it has now been possible to isolate otherendophytic fungi producing volatile antibiotics. The newly described M. roseuswas twice obtained from tree species found in the Northern Territory ofAustralia. This fungus is just as effective in causing inhibition and death oftest microbes in the laboratory as M. albus (Worapong et al., 2002). Other interestingM. albus isolates have been obtained from several plant species growingin the Northern Territory of Australia and the jungles of the Tesso Nilo area ofSumatra, Indonesia (Ezra et al., 2004; Atmosukarto et al., 2005).A non-muscodor species (Gliocladium sp.) has also been discovered toproduce volatile antibiotics. The volatile components of this organism aretotally different from those of either M. albus or M. roseus. In fact, the mostabundant volatile inhibitor is [8]-annulene, formerly used as a rocket fueland discovered here for the first time as a natural product. However, thebioactivity of the volatiles of this Gliocladium sp. is not as good or as comprehensiveas that of the Muscodor spp. (Stinson et al., 2003). Due to the volatileantibiotic producing properties of these fungi, they could be used againstseveral soil plant pathogens to reduce their inoculum. The latter, G. roseum,has already shown its potential through the production of a series of hydrocarbonsand hydrocarbon derivatives as mycodiesel (Strobel et al., 2008).Interestingly, another novel species of Muscodor sp., M. crispans, has beenreported to produce a mixture of strong volatile compounds (VOCs) thatwere effective against a wide range of plant pathogens, including the fungiPythium ultimum, Phytophthora cinnamomi, S. sclerotiorum and Mycosphaerellafijiensis (the black sigatoka pathogen of bananas), and the serious bacterialpathogen of citrus, Xanthomonas axonopodis pv. citri (Mitchell et al., 2010).Antiviral compounds from endophytic fungiAnother fascinating use of products from endophytic fungi is the inhibitionof viruses. Two novel human cytomegalovirus (hCMV) protease inhibitors,cytonic acids A and B, have been isolated from solid-state fermentation of theendophytic fungus Cytonaema sp. Their structures were elucidated asp-tridepside isomers using MS and NMR methods (Guo et al., 2000). It isapparent that the potential for the discovery of compounds having antiviralactivity from endophytes is in its infancy. The fact, however, that some compoundshave been found already is promising. The main limitation to compounddiscovery to date is probably related to the absence of commonantiviral screening systems in most compound discovery programs. Since noantiviral compound isolated from endophytes has been tested against