SELECTION AND IN VITRO CHARACTERIZATION OF BIOCONTROL AGENTS WITH POTENTIAL TO PROTECT PEANUT PLANTS AGAINST FUNGAL PATHOGENS

摘要

Over 193 endophytic and epiphytic bacteria were isolated from different organs of peanut plants growing under field conditions. The diversity of the isolates was analyzed by ERIC/BOX-PCR and 16S ribosomal DNA sequencing. Their potential to protect peanut plants against the fungal pathogens Sclerotinia sclerotiorum, S. minor, Sclerotium rolfsii and Fusarium solani was evaluated by assaying important biocontrol traits. Of the isolates, 148 produced siderophores, 71 (most of them epiphytes) showed fungal growth inhibition in YEMA plates, while only 28 also exhibited this activity in PDA medium. The cell free-extract from 11 bacterial cultures showed antibiotic activity suggesting the secretion of soluble extracellular compounds, some being heat-labile compounds with mol. wt greater than 12 kDa. Fungal sensitivity to volatile compounds produced by isolates differed from those observed for soluble secreted compounds or bacterial cells.