Antifungal activity of chitinases produced by some fluorescent pseudomonads against Colletotrichum falcatum Went causing red rot disease in sugarcane

Chitinase production and growth of certain fluorescent pseudomonads isolated from sugarcane rhizosphere on different subtrates were studied. When chitin was substituted for glycerol in King's B medium, 3 of the 4 strains showed enhanced bacterial multiplication. Bacterial cells grown on chitin-containing medium showed enhanced antifungal activity against Colletotrichum falcatum Went causing red rot disease in sugarcane. Chitinase production was significantly higher when chitin was amended to King's B medium. Higher chitinase production was also recorded when fluorescent pseudomonad strains were grown in the medium containing crab-shell chitin. Cell-free bacterial culture filtrate from chitin-containing medium significantly inhibited mycelial growth of the pathogen. These cell-free conditioned media contained 3 to 7 polypeptides. Western blot analysis revealed five isoforms of chitinase with molecular masses of 47, 36, 32, 20 and 18.5 kDa. A possible role of chitinases in red rot disease management is discussed.