Diversity of biocontrol agents,isolated fromseveral sources,inhibitory to several fungal plant pathogens

Diversity of biocontrol agents, isolated from several sources, inhibitory to several fungal plant pathogens.Biodiversitas 22:298-303.This study investigatedtheinhibitorypotentialof diversity of antagonist bacteria residing in the rhizosphere zone and mature compostto counterfungal plant pathogens. Soils collected from rhizosphere of lettuce farms in Bali-Indonesia and Tasmania-Australia, mature compost, commercial biocontrol (Dipel®), and laboratory contaminants with significant inhibition against tested fungal pathogens were used as sources of antagonist bacteria. These antagonists were isolated by applying dilution and spread method on trypticase soya agar (TSA) or potato dextrose agar (PDA), and their ability to inhibit Sclerotinia minor, Sclerotinia sclerotiorum, Fusariumspp., and Rhizoctonia solaniwas assessed in dual culture assays. The results showed that 67 out of more than 100 isolates hadantagonistic activity in vitroagainst at least one of tested fungal pathogens. In the preliminary identification, Bacillusspp. or Pseudomonasspp. were found to be pre-dominant isolates. Following screening studiesin a non-replicated glasshouse experiment against S. minorand S. sclerotiorum, 8 of the most promisingisolates were further identifiedusing molecular methodsbased on their 16s rDNA sequences aligned with those deposited at the GeneBank.These 8 isolates were identified as Pseudomonas corrugata, Bacillus megaterium, Bacillus polymyxa, Bacillus mojavensis, Bacillus pumilus, Bacillus thuringiensis, Exiguobacterium acetylicum, and Chryseobacterium indologenes.Keywords: Antagonist, biological control, compost, diversity, plant pathogens, rhizosphere