ENDOPHYTES: A STORE HOUSE OF PLANT GROWTH PROMOTERS AND BIOACTIVE COMPOUNDS

A diverse variety of plants establish relationship with microorganisms. Endophytic microbes whether bacteria or fungi are ubiquitous in most of the plants and colonize inside the plant tissues either localized or systemic way without causing harm on their hosts. Endophytes are most potent phytohormone producers. We have found nitrogen fixing endophytic bacteria, along with phosphate solubilizers and different types of siderophore producers. They even have ACC deaminase activity which actually helps in plant growth promotion by lowering the ethylene level in plants. The endophytes gain entrance in plants by various mechanisms. In ancient period, they were regarded as virulent plant pathogens but after exploring its antagonistic potential against several bacterial and fungal phytopathogens and various plant growth promoting activities, they are used as bioinoculants for the development of plants. As chemical fertilizers, synthetic fungicides are hazardous to plants as well as to human and animals, natural bioactive compounds from endophytes especially from fungi gained attractions of scientists. Several alkaloid, terpeniod, peptide, polyketide derivatives that have antimicrobial properties against plant pathogens have been explored. As in this review, properties of some secondary bioactive metabolites like collectotric acid, phomenone, trichodermin, helvolic acid, pestalachloride A, cryptocin, pyrrocidines A, loline alkaloid, leucinostatin A have been discussed. There are more bioactive compounds from endophytes have been studied in various researches which have antagonistic effects against human pathogens, but not enlisted in this study. We tried to enlist the beneficial roles of endophytes on their host and non-host plants in this review.