natural-products-in-plant-pest-management

234 R.N. Kharwar and G. Strobelantioxidant compounds from natural resources has increased, so that theshelf life of stored crop produce and plant health could be enhanced to caterfor a hungry population, and endophytes may be one of the novel naturalresources to achieve this goal (Tejesvi et al., 2008).Immunosuppressive compounds from fungal endophytesImmunosuppressive drugs are used today to prevent allograft rejection intransplant patients and in the future they could be used to treat autoimmunediseases such as rheumatoid arthritis and insulin-dependent diabetes. Theendophytic fungus, Fusarium subglutinans, isolated from Tripterygium wilfordii,produces the immunosuppressive, but non-cytotoxic diterpene pyrones,subglutinols A and B (Lee et al., 1995). Subglutinols A and B are equipotent inthe mixed lymphocyte reaction (MLR) assay and thymocyte proliferation(TP) assay with an IC 50of 0.1 μM. The famed immunosuppressant drugcyclosporin A, also a fungal metabolite, was roughly as potent in the MLRassay and 10 4 more potent in the TP assay. However, the lack of toxicity associatedwith subglutinols A and B suggests that they should be explored ingreater detail as potential immunosuppressants (Lee et al., 1995).11.5 ConclusionGeographical, floristic and significant seasonal variations that exist in differentparts of globe provide conducive/or adverse conditions for the luxuriantgrowth of microbes in a wide range of different habitats, including livingtissues of higher plants where they grow as endophytes. Due to great variationin plant biodiversity and seasonal changes in tropical and subtropicalregions, there is a need to collect/isolate various types of promising endophyticfungi, especially from rainforests and mangrove swamps, which maybe able to produce an enormous variety of potential bioactive natural compounds.The fungi, as a group, hold enormous potential as sources of antimicrobials.The observations prove that this group of organisms resides insidethe healthy plants tissue, as endophytes, without causing any detectablesymptoms. Therefore, we strongly feel that there is a need to accelerate andfocus the research to exploit the maximum potential of the promising endophytesfor natural-product discovery, which could at least facilitate someexisting problems of the huge population.The past history of endophytic research in India especially with fungi isnot so encouraging. It seems that workers who have started this research inIndia are still actively involved in advancing their research manifesto withthis ‘under-studied’ group of microbes, and have not advanced to the fieldsand forests of the countryside looking for novel microbe–plant associations.Prof. T.S. Suryanarayanan and his group (Chennai) have initiated biodiversityand distribution patterns of fungal endophytes with some medicinal plantsin India and have published several papers along this line. They have also