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Plant growth promoting fluorescent Pseudomonas aeruginosa strains An-E and An- F were used for the suppression of replant disease organisms which were isolated from replant site of apple in Shimla district of Himachal Pradesh. Full and half concentration of individual and consortial strains were used for the experiment. Among all the treatments, full concentration of compatible consortial strains were quite effective in decreasing the deleterious rhizobacterial (197-99 cfu/g) and fungal population (7-0 cfu/g). Total rhizobacterial count starts decreasing after each cyclic application of fluorescent P. aeruginosa strains An-E and An-F due to root colonization property of these plant growth promoting strains in the replant site of apple. Establishment of Pseudomonas aeruginosa strains at replant site was inversely correlated with decreasing deleterious bacterial and fungal population in the replant site. 70 per cent survival of apple rootstocks was recorded in full concentration of consortial treatment (An-E and An- F) as compared to control after three years of plantation. Four major fungal pathogens viz. Dematophor anecatrix, Phytophthora cactorum, Pythium ultimum and Fusarium oxysporum were isolated and identified from National centre for fungal taxonomy, New Delhi. These strains can be further exploited and recommended for the management of replant problem of apple. [ABSTRACT FROM AUTHOR]

Strain An-F was isolated from the rhizosphere soil of replant site of apple orchard at Shimla district H.P. and identiûed as Pseudomonas aeruginosa on the basis of biochemical tests and by 16S rRNA sequences. This bacterium exhibits a broad-spectrum antifungal activity towards phytopathogenic fungi. The antifungal metabolite by An-F was extracted and characterized using TLC and HPLC (High pressure liquid chromatography). Production of siderophores, phosphatase, HCN, ammonia, indole-3-acetic acid (IAA), gibberellins and cytokinins in An-F were determined. The antifungal metabolite produced by An-F has been identiûed as 2, 4-diacetylphloroglucinol on the basis of TLC and HPLC data. Present study reports the production of 2,4-diacetylphloroglucinol as well as IAA, gibberellins and cytokinins for the ûrst time by a saprophytic P. aeruginosa strain An-F isolated from the replant site of apple. Because of the production of siderophore, growth hormone, protease and phosphatase and its innate fungicidal potential, this strain can be used as biofertilizer and antagonist against a range of phytopathogenic fungi. [ABSTRACT FROM AUTHOR]