Biological Control of Fusarium Wilt of Cucumber by Chitinolytic Bacteria

Abstract

Two chitinolytic bacterial strains, Paenibacillus sp. 300 and Streptomyces sp. 385, suppressed Fusarium wilt of cucumber (Cucumis sativus) caused by Fusarium oxysporum f. sp. cucumerinum in nonsterile, soilless potting medium. A mixture of the two strains in a ratio of 1:1 or 4:1 gave significantly (P < 0.05) better control of the disease than each of the strains used individually or than mixtures in other ratios. Several formulations were tested, and a zeolite-based, chitosan-amended formulation (ZAC) provided the best protection against the disease. Dose-response studies indicated that the threshold dose of 6 g of formulation per kilogram of potting medium was required for significant (P < 0.001) suppression of the disease. This dose was optimum for maintaining high rhizosphere population densities of chitinolytic bacteria (log 8.1 to log 9.3 CFU/g dry weight of potting medium), which were required for the control of Fusarium wilt. The ZAC formulation was suppressive when added to pathogen-infested medium 15 days before planting cucumber seeds. The formulation also provided good control when stored for 6 months at room temperature or at 4 degrees C. Chitinase and beta-1,3-glucanase enzymes were produced when the strains were grown in the presence of colloidal chitin as the sole carbon source. Partial purification of the chitinases, followed by sodium dodecyl sulfate polyacrylamide gel electrophoresis and activity staining, revealed the presence of five bands with molecular masses of 65, 62, 59, 55, and 52 kDa in the case of Paenibacillus sp. 300; and three bands with molecular masses of 52, 38, and 33 kDa in the case of Streptomyces sp. 385. Incubation of cell walls of F. oxysporum f. sp. cucumerinum with partially purified enzyme fractions led to the release of N-acetyl-D-glucosamine (NAGA). NAGA content was considerably greater when pooled enzyme fractions (64 to 67) from Paenibacillus sp. were used, because they contained high beta-1,3-glucanase activity in addition to chitinase activity. Suppression of Fusarium wilt of cucumber by a combination of these two bacteria may involve the action of these hydrolytic enzymes.

Screening rhizobacteria for biological control of Fusarium root and crown rot of sorghum in Ethiopia

“…Because of their ability to degrade chitin, the major structural component of the cell walls of phytopathogenic fungi (Someya et al, 2004), chitinolytic enzymes are considered important in the biological control of soilborne pathogens (Singh et al, 1999). openUP In the current study, isolates KBE9-1 and KBE8-2 which were characterized by the production of a violet to reddish pigment on agar media were identified by the API as C. violaceum (Table 4).…”

Rapid detection of Ganoderma disease of coconut and assessment of inhibition effect of various control measures by immunoassay and PCR

“…In our study, the mixture of two antagonists (P. fluorescens + T. viride) suppressed Ganoderma disease development. Numerous modes of action have been postulated and demonstrated for the antagonistic effects of P. fluorescens in controlling diseases; they include synergistic effects observed on fungal pathogens with a combination of antifungal compounds (DOWLING & O'GARA 1994;DUNNE et al 1998), competition for nutrients (O'SULLIVAN &d O'GARA 1992), production of cell wall lytic enzymes (SINGH et al 1999) and induced systemic resistance (DALISAY & KUC 1995;NANDAKUMAR et al 2001). Several antibiotics have been reported to be produced by bacteria (RAAJIMAKERS & WELLER 2001).…”

Evaluation ofStreptomycesspp. for their plant-growth-promotion traits in rice

“…Cellulose and lipid present abundantly in the plant biomass can be degraded by enzymes such as cellulase and lipase (Lynd et al 2002). The cell wall of higher pathogenic fungi, such as Fusarium oxysporum, is composed of layers of β-1,3-glucan and lysis of this by β-1,3-glucanase-producing microbe leads to leakage of cell contents and collapse of the pathogenic fungi (Singh et al 1999;Macagnan et al 2008). Hence, microorganisms having these traits can be exploited for degradation of organic residues and/ or biological control of plant pathogens.…”

“…It was done as per the protocols of Singh et al (1999). Streptomyces strains were cultured individually in Tryptic soy broth, supplemented with 1% (weight/volume) colloidal chitin, at 28 o C for four days.…”