natural-products-in-plant-pest-management

Fungal Endophytes 22111.2 Diversity in EndophytesOf the myriad of ecosystems on Planet Earth, those having the greatest generalbiodiversity of life seem to be the ones that also have the greatest numberand most diverse endophytes. Tropical and temperate rainforests are themost biologically diverse terrestrial ecosystems. The most threatened of thesespots cover only 1.44% of the land’s surface, yet they harbour over 60% of theworld’s terrestrial biodiversity. In addition, each of the 20–25 areas identifiedas supporting the world’s greatest biodiversity also support unusually highlevels of plant endemism (Mittermeier, 1999). As such, one would expect,that with high plant endemism, there should also exist specific endophytesthat may have evolved with the endemic plant species. Biological diversityimplies chemical diversity because of the constant chemical innovation thatis required to survive in ecosystems where the evolutionary race to surviveis most active. Tropical rainforests are a remarkable example of this type ofenvironment. Competition is great, resources are limited and selection pressureis at its peak. This gives rise to a high probability that rainforests are asource of novel molecular structures and biologically active compounds(Redell and Gordon, 2000).Bills et al. (2002) describe a metabolic distinction between tropical andtemperate endophytes through statistical data which compares the numberof bioactive natural products isolated from endophytes of tropical regions tothe number of those isolated from endophytes of temperate origin. Not onlydid they find that tropical endophytes provide more active natural productsthan temperate endophytes, but they also noted that a significantly highernumber of tropical endophytes produced a larger number of active secondarymetabolites than did fungi from other substrata. This observation suggeststhe importance of the host plant as well as the ecosystem in influencingthe general metabolism of endophytic microbes.11.3 Techniques for Isolation, Preservation and Storage ofEndophytesCultures for product isolationDetailed techniques for the isolation of microbial endophytes are outlined ina number of reviews and technical articles (Strobel et al., 1993; Strobel, 2002;Strobel and Daisy, 2003; Strobel et al., 2004; Castillo et al., 2005). If endophytesare being obtained from plants growing in polar regions, the dry tropics, orsome temperate areas of the world, one can expect to acquire from none toonly one or two endophytic cultures per plant sample (0.5–10.0 cm limbpiece). However, from the wet tropics this number may rise to 20–30 or evenmore microbes per plant piece. Given limited fermentation capabilities, it iscritical to label and store cultures of freshly isolated microbes for work in thefuture and for patent and publication purposes.