Streptomyces bio-products against apple and pear diseases in organic orchards

Erwinia amylovora as a fire blight pathogen and Venturia inaequalis as a scab pathogen were isolated from the blossoms, exudates, infected fruits, leaves and bent branches of diseased apple, pear and hawthorn trees, selected in the Chy, Osh and Jalal Abad regions. Biochemical and pathogenicity tests, alongside PCR analyses were conducted to identify the local isolates of Erwinia amylovora and Venturia inaequalis. The alternative antagonistic microorganisms which combat bacterium E. amylovora and fungus Venturia inaequalis were tested within in vitro and in vivo conditions. The results revealed the ability of Streptomyces antagonistic bacteria to decrease fire blight severity on pear and apple trees during the first stage of the fire blight disease in leaf tissues. Streptomyces strain C1-4 suppressed E. amylovora disease symptoms in the leaf tissues and excised apple and pear shoots. The incidence of fire blight on leaves was reduced by about 70 with two applications of bacterial antagonists. Streptomyces sp strains were tested for apple scab control in vitro and field conditions. Two applications of Streptomyces strain C1-4 within 35 days completely stopped the scab disease in seedling leaves. Within 40 days, the seedlings were recovered; the new leaves have blossomed on branches. Seedlings grew new shoots and leaves around 50 days after the second treatment. Orchard experiment results provide great hope that a biological product based on Streptomyces could work as an effective agent to suppress the development of the pathogen in the early spring, when leaves start to show scab disease symptoms. Further studies at different locations in Kyrgyzstan, using large scale application, would allow for stronger recommendations to be made, including studies and recommendations on their ability to prevent diseases and to use them as main components in an integrated pest management program.