Bio-control and plant growth promotion potential of siderophore producing endophytic Streptomyces from Azadirachta indica A. Juss.

Three endophytic actinomycetes strains recovered from surface sterilized root tissues of Azadirachta indica A. Juss. (Meliaceae), plants were selected through tests for their potential as bio-control and plant growth promoting agents. It was also observed that the seed treated with the spore suspension of three selected strains of Streptomyces, significantly promoted plant growth and antagonized the growth of Alternaria alternata, causal agent of early blight disease in tomato plant. It was observed that the three selected strains prolifically produce IAA and siderophores that play vital role in promotion of plant growth and in suppression of Alternaria alternata. Interestingly, Streptomyces strain AzR-051 produced the highest amount of IAA at 13.73 μmol ml(-1) , compared to strains AzR-049 and AzR-010 9.22 μmol ml(-1) and 10.43 μmol ml(-1) respectively. It also produces siderophores higher than the other two strains. Thus these endophytic isolates have the potential as plant growth promoters as well as a bio-control agent, which is a useful trait for crop production in nutrient deficient soils.