Amit C. Kharkwal

Novel Symbiotrophic Endophytes

Endophytes are microorganisms that reside in the tissues of living plants without causing any immediate overt negative effect (Bacon and White 2000). Of the nearly 300,000 plants species that exist on the earth, each individual plant is host to one or more endophytes (Strobel and Daisy 2003). These endophytes are relatively unstudied and are potential sources of novel natural products for exploitation in medicine, agriculture, and industry. Very few of these endophytes have been studied to date, and this opens a new opportunity to find out novel endophytes in myriads of ecological niches. One of the important facets of these endophytes is their evolution with plants over a period of millennia that makes them live in a symbiotrophic relationship in such a way that both becomes indispensible to each other. While the symptomless nature of endophyte occupation in plant tissue has prompted the focusing on symbiotic or mutualistic relationships between endophytes and their hosts, the observed biodiversity of endophytes suggests they can also be aggressive saprophytes or opportunistic pathogens (Strobel and Daisy 2003). The most common endophytes of plants are bacteria and fungi, but evidence indicates that other life forms like viruses exist in plants as endophytes (Marquez et al. 2007). The most frequently isolated endophytes are the fungi (Hawksworth and Rossman 1987). Dreyfuss and Chapela (1994) estimated that there may be at least 1 million species of endophytic fungi alone. It can be readil concluded that majority of these endophytes are symbiotic and can have tremendous applications in the area of drug discovery, medicine and agriculture.

Promotion and Value Addition to Some Important Medicinal Plants Under Saline Condition by Intervention of a Novel Mycorrhizal Formulation

The use of plants in the remediation of saline and sodic soils is an emerging low cost approach in the reclamation of abandoned irrigated fields. The present study focuses on use of a novel AM-like-Fungus Piriformospora indica for phtyoremediation by early intervention with selected medicinal plants. Piriformospora indica, a root endophytic fungus, has been reported to promote growth of many plants under normal condition and allow the plants to survive under stress conditions. The fungus is able to associate with the roots of various plant species in a manner similar to mycorrhiza and promotes plant growth. P. indica has been reported to induce resistance in the monocotyledonous plant barley to fungal diseases, along with tolerance to salt stress without affecting the plant productivity. The prospects for improved agriculture, by the use of microbial inoculants as biofertilizers or biological control agents, are particularly good in less intensive, low-input agricultural systems. Hence, in developing countries microbial inoculation of plants could be of great importance. The advantages are: better yields, lower costs, reduced dependence on chemicals, and sustainable environment. The production of microbial inoculants is not very difficult; unsophisticated fermentors of modest volume can be used to produce significant quantities of bioinoculants. Present study was undertaken to investigate the effect of consortium of P. indica and Azotobacter chroococcum on salinity stress tolerance of important medicinal plants. Both inoculated and non-inoculated plantlets were subjected to four levels of salinity treatment—0, 100, 200, and 300 mM NaCl. The salinity stress decreased the ability of the consortium to colonize roots of plants, but the interaction resulted in an overall increase in plant biomass and greater shoot and root length as well as number of shoots and roots. The inoculated plantlets had significantly higher secondary metabolite contents as determined using HPLC. The higher secondary metabolite content may help the plants ameliorate oxidative stress resulting from high salinity. This was achieved by early interaction of the selected medicinal plants, namely, Glycyrrhiza glabra, Aloe vera, Bacopa monnieri, Asparagus racemosus, Coleus forskohlii, Withania somnifera, Vinca rosea, and Ocimum sp. with P. indica and A. chroococcum under in vitro (plant tissue culture), in vivo (greenhouse), and field conditions in Amity University and Issapur, respectively. For development of different formulations, P. indica was grown in large-scale fermentor. The formulated inoculum produced along with the culture filtrate was used for early intervention during the growth of plants. The plants were intervened both under in vitro (tissue culture) and ex vitro (greenhouse) conditions. The treated plants were then transferred to field for further evaluation at Issapur farm in Delhi. Plant growth was assessed on the basis of plant biomass and other morphological parameters. The rejuvenation of soil with the microbes also makes it suitable for organic cultivation of crops in the forthcoming years hence reducing the impact of chemical fertilizers.

Microbial Symbiosis and Bioactive Ingredients of Medicinal Plants

Medicinal plants have been used widely for their bioactive ingredients as they are highly potent and have least side effects. This has led to a surge in demand for medicinal plants for producing higher quantity and good quality bioactive compounds. Symbiotic association of microorganisms with plants has been shown to affect the production and quality of active ingredients. However, the effect is not consistent and is seen to vary under different microbial associations. This chapter elucidates the studies on microbial symbiosis with medicinal plants and the effect of this interaction on medicinally important bioactive ingredients. The role of both nutritional and non-nutritional pathways in this interaction has also been discussed.

Analytical Techniques to Assess Medicinal Plants Value Addition After Microbial Associations

In the high-throughput era of science, technologies like high-performance liquid chromatography (HPLC) are growing in importance for their accurate and precise analysis of chemicals and drugs of diverse nature. It is used widely in the pharmaceutical, medicinal, and aromatic plant industry for the isolation and purification of phytomolecules of therapeutic and commercial interest. Due to the gradual increase in the demand for phytochemicals in food and pharmaceutical industries, the importance of process-scale HPLC as a purification tool has been increasing. The most challenging and thrilling field of recent scientific research is the in vitro production of plant secondary metabolites. Therefore, in order to supply required phytochemicals, the in vitro protocol for the establishment of plant culture and production of phytochemicals has to be carefully monitored. In this chapter, the HPLC analysis of secondary metabolite content of an important medicinal plant Aloe vera L. has been performed under unstressed and salt-stressed environment. The secondary metabolite content has also been compared upon inoculation of A. vera with a symbiotic endophytic fungus Piriformospora indica.