CHARACTERIZATION OF ACTINOMYCETES AND RHIZOTOXINS INVOLVED IN REPLANT PROBLEM OF APPLE AND THEIR INTERACTION WITH PLANT GROWTH PROMOTING FLUORESCENT PSEUDOMONAS SPECIES
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Date
2015
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ABSTRACT Replant disease is a major problem of apple orchard, which is a main cash crop in TransHimalayan region. Among different approaches, application of Plant Growth Promoting Rhizobaceria (PGPR) at replant site is one of the promising methods. Fluorescent Pseudomonas, a major component of rhizobacteria, promotes the plant growth through their multifarious activities. In the present study, fluorescent Pseudomonas and actinomycetes were isolated from the rhizosphere of apple plants of their normal and replant sites and found that the count of fluorescent Pseudomonas species were more in normal site as compare to replant site. The fourteen Pseudomonas isolates were screened out for various plant growth promoting activities like siderophores, phosphate solubilization, production of HCN and ammonia, lytic enzymes, plant growth regulators (auxins, gibberellins and cytokinins) and antifungal activity. The seven actinomycetes isolates were screened out for various plant growth promoting activities like siderophores, phosphate solubilization, production of HCN and ammonia, lytic enzymes and antifungal activity. One isolate of Pseudomonas sp. (Ar-4-De) and two isolates of actinomycetes (Act-1-Mgr and Act-1-Sir) were genotypically characterized by 16S rRNA gene sequencing. Ar-4-De showed 95% homology with Pseudomonas aeruginosa with accession number (KU139389). In replant site of Maggota and Siao, three strains of Pseudomonas aeruginosa I, J and K were used individually and their consortia for treatment of apple rootstocks before planting. Estimation of total phenols, sugars and amino acids were done from the root exudates collected from the roots of treated apple plants. Root exudates were found to be helpful in colonization of beneficial microorganisms. The performance of apple plants was much better in terms of root colonization capacity, plant establishment and increase in plant growth in terms of plant height, number of nodes, chlorophyll content of leaves and NPK of rhizosphere soil over their respective control after nine months of treatment. These strains can be further exploited for management of replant problem of apple after conducting few more field trials in replant sites and can have great importance in the field of horticulture.