Antagonistic Evaluation of Bioactive Metabolite from Endophytic Fungus, Aspergillus flavipes KF671231

Of the total 40 endophytic fungi isolated from foliar tissues of medicinal plant Stevia rebaudiana Bertoni, a fungal isolate, Aspergillus flavipes, was subjected to bioassay guided fractionation. The fractionation was found active against medicinal plant pathogen Sclerotinia sclerotiorum with an inhibition zone of 29？mm in size. Further the metabolite was extracted which shows 20% growth inhibition in 24？h and 46% after 48？h, respectively. Bioassay guided chemical compound was identified as 1,2-benzenedicarboxylic acid, mono(2-ethylhexyl) ester. On the basis of morphological characters and rDNA sequencing of ITS region the endophyte was identified as Aspergillus flavipes which showed promising plant growth promotory properties. 1. Introduction Bioprospecting refers to the search for novel products of economic importance from animal, plant, and microbial sources [1]. Traditionally we always relied on natural remedies for treating and healing our ailments. Natural products have been exploited for human use for thousands of years and plants have been a major source of compounds of medicinal use. Plants are found to be associated with microorganisms which are capable of producing molecules possessing remarkable biological activities. Microorganisms that live in the intercellular spaces of different parts of plants showed no evident expression of their presence and are called endophytes [2]. The relationship between plant and endophyte is considered to be mutualistic, the former being protector and feeder for the latter which in return produces bioactive substances that provide protection to plant and also enhance the growth and competitiveness of the host in nature [3]. Sclerotinia sclerotiorum, a phytopathogenic fungus, occurs worldwide and infects a wide array of plants, resulting in considerable losses. Although a significant number of natural bioactive compounds have been reported to antagonize this fungus [4], Stevia (Stevia rebaudiana Bertoni; Asteraceae), an exotic annual plant originating from Paraguay, contains glucosides of a diterpenoid nature, which are used as a low-caloric sweetener in some South American and South East Asian countries [5]. The main active ingredient of Stevia is a stevioside, which is 100 to 300 times sweeter than sucrose. Traditionally, farmers use agrochemicals to protect plants from diseases and to optimise the crop yields. Prolonged and persistence use of pesticides including fungicides and herbicides made several organisms resistant to such chemicals besides causing the environmental pollution. This present study