Chitin-supplemented formulations improve biocontrol and plant growth promoting efficiency of Bacillus subtilis AF 1

Formulations of a chitinolytic biocontrol and a plant growth promoting Baci llus subtilis AF 1 were prepared in peat, in peat supplemented with either 0.5% chitin or Aspergillus niger mycelium, or in spent compost obtained fro m Agaricus bisporus cultivation and were evaluated for biocontrol of two fu ngal pathogens and plant growth promoting activities on pigeon pea and grou ndnut. A steady increase in cell numbers of introduced B. subtilis AF 1 was observed in all the formulations at 30 degreesC. The increase in cell numb ers was about 5.0 log units. Peat or spent compost inoculated with physiolo gically active and dormant states of B. subtilis AF 1 showed different time period requirements to attain maximum cell numbers. The presence of chitin or A. niger (in peat) or A. bisporus (in spent compost) as supplement in t he carrier material improved the multiplication of B. subtilis AF 1. When u sed as seed treatments, formulations of AF 1 in peat supplemented with chit in or chitin-containing materials showed better control of A. niger (causin g crown rot of groundnut) and Fusarium udum (causing wilt of pigeon pea) th an AF 1 culture alone, in both groundnut and pigeon pea. Bacillus subtilis AF 1 formulations promoted seed germination and biomass of both groundnut a nd pigeon pea even under pathogen pressure. Survival of AF 1 on fresh cultu re-treated and formulation product-treated plants was similar in pathogen-i nfested soil.