Bioligical control options of Verticillium wilt (Verticillium dahliae kleb.) of cotton by endophytic bacteria

In 2004-2005 growing season, the study was carried out in cotton growing areas of Aydin province and towns with the aim of isolating endophytic bacteria from cotton and weed plants and using the bacteria in-vitro and in-vivo activity against Verticillium wilt and growth promotion of cotton radicle. Eight fungal isolates (7 from cotton plants and 1 Amaranthus sp.) were collected from cotton growing fields in Aydin and identified as Verticillium dahliae according to the morphological characteristics and pathogenicity tests. Twelve bacterial strains out of 280 isolates were isolated from weeds and cotton plants showed in-vitro antagonistic effect against V. dahliae. None of the twelve-endophytic bacterial strains reacted as non-pathogenic in tobacco hypersensitivity test. The most effective isolates against V. dahliae were and F2 (% 66,8), F5 (% 61,8) and B8 (% 48,7) in -vitro tests while the isolates E21, C5 and F5 were significantly reduced Verticillium wilt symptoms in vivo tests. The rifampicin resistant strains of E21, C5 and F5 were also tested for colonization in cotton seedlings and disease reduction ability comparing non-mutant ones. Endophytic strains were further evaluated for the inhibition capacity of mycelial growth of V. dahliae and growth promotion effect of cotton seedlings by means of volatile compounds in divided plastic petri dishes. The volatile compounds of F5 (% 31,43), F2 (% 31,43) and C5 (% 11,43) significantly inhibited mycelial growth of V. dahliae and E22 (% 20,75), I3 (% 11,32) and E21 (% 9,43) significantly induced radicle growth of cotton. The antagonistic strains were determined for the ability of phosphate solubilization and E22, E21, B5, F8, I3 and H9 were found to solubilize phosphate in-vitro. Two endophytic strains were identified as Bacillus sp. and eight was fluorescent Pseudomonas according to gram staining and biochemical tests.