Rhizobacterially induced protection of watermelon against Didymella bryoniae

• Published in: Journal of applied microbiology Vol. 109; no. 2; pp. 567 - 582
• Main Authors: Nga, N.T.T, Giau, N.T, Long, N.T, Lübeck, M, Shetty, N.P, de Neergaard, E, Thuy, T.T.T, Kim, P.V, Jørgensen, H.J.L
• Format: Journal Article
• Language: English
• Published: Oxford, UK Oxford, UK : Blackwell Publishing Ltd 01.08.2010; Blackwell Publishing Ltd; Blackwell; Oxford University Press
• Subjects: Antibiosis; Antibiotics; Ascomycota - physiology; Bacillus; Bacillus spp; Bacteria; Bacteria - isolation & purification; Biological and medical sciences; Blight; Citrullus - microbiology; Citrullus lanatus; Didymella bryoniae; Disease control; Endophytes; Fruits; Fundamental and applied biological sciences. Psychology; Hydrogen peroxide; induced resistance; Infections; Isoforms; Microbiology; Pathogens; Peroxidase; Pest Control, Biological; Plant bacterial diseases; Plant Diseases - microbiology; Plant Diseases - prevention & control; Planting; Pseudomonas aeruginosa; Pseudomonas aeruginosa - growth & development; Pseudomonas aeruginosa - isolation & purification; Pseudomonas aeruginosa - physiology; Pseudomonas aeruginosa 23; Pseudomonas aeruginosa 231‐1; Seeds; Stability; Stem blight; Strains (organisms); Vietnam; Water melons; watermelon; watermelons; Vietnam; Ascomycota; Pseudomonadales; Applied microbiology; Pseudomonas aeruginosa 23; Bacillaceae; Induced resistance; Antibiosis; Bacillus spp; endophytes; Fungi; Bacillales; Bacillus; Bacteria; Pseudomonadaceae; Didymella bryoniae; Endophyte; Pseudomonas aeruginosa; watermelon; Protection
• ISSN: 1364-5072; 1365-2672
• DOI: 10.1111/j.1365-2672.2010.04685.x

To identify rhizobacteria from the Mekong Delta of Vietnam, which can systemically protect watermelon against Didymella bryoniae and elucidate the mechanisms involved in the protection conferred by isolate Pseudomonas aeruginosa 23₁₋₁. Bacteria were isolated from watermelon roots and their antagonistic ability tested in vitro. Of 190 strains, 68 were able to inhibit D. bryoniae by production of antibiotics. Four strains were able to reduce foliar infection by D. bryoniae when applied to watermelon seeds before sowing. Strain Ps. aeruginosa 23₁₋₁ was chosen for investigations of the mechanisms involved in protection and ability to control disease under field conditions. In the field, the bacterium was able to significantly reduce disease in two consecutive seasons and increase yield. Furthermore, it colonized watermelon plants endophytically, with higher numbers in plants infected by D. bryoniae than in noninoculated plants. To elucidate the mechanisms involved in protection, the infection biology of the pathogen was studied in bacterially treated and control plants. Pseudomonas aeruginosa 23₁₋₁ treatment inhibited pathogen penetration and this was associated with hydrogen peroxide accumulation, increased peroxidase activity and occurrence of new peroxidase isoforms, thus indicating that resistance was induced. The endophytic bacterium Ps. aeruginosa 23₁₋₁ can control D. bryoniae in watermelon by antibiosis and induced resistance under greenhouse and field conditions. These findings suggest that rhizobacteria from native soils in Vietnam can be used to control gummy stem blight of watermelon through various mechanisms including induction of resistance.