Selecting a Potential Strain of Bioagent Against Alternaria porri and Increasing Vigour Index in Onion

Seventeen fungal isolates and six isolates of bacterial bioagents obtained from different sources were tested for their bio-efficacy against Alternaria porri, causing purple blotch of onion by dual culture method. Promising isolates (Th-3, Th-30, Tv-12, Tv-15, Pf-3 and Bs-2) were selected based on their ability to inhibit the radial growth of the pathogen. These selected isolates were further characterized for production of volatile and nonvolatile metabolites and their effect on seed germination and vigour induction of onion under in vitro. Among the bioagents tested, Trichoderma harzianum (Th-3) showed maximum growth inhibition of the pathogen by dual culture, non-volatile and volatile compound production. Strain Th-3 also increased the onion seed germination and vigour index.