Rhizobacterially induced protection of watermelon against Didymella bryoniae.
OBJECTIVE
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 23(1-1).


RESULTS
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 23(1-1) 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 23(1-1) 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.


CONCLUSIONS
The endophytic bacterium Ps. aeruginosa 23(1-1) can control D. bryoniae in watermelon by antibiosis and induced resistance under greenhouse and field conditions.


CONCLUSIONS
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.
Nga
N T T
NTT
 Department of Plant Biology and Biotechnology, Faculty of Life Sciences, University of Copenhagen, Thorvaldsensvej 40, Frederiksberg C, Denmark.| Department of Plant Protection, College of Agriculture and Applied Biology, Can Tho University, Can Tho City, Vietnam.
Giau
N T
NT
 Department of Plant Protection, College of Agriculture and Applied Biology, Can Tho University, Can Tho City, Vietnam.
Long
N T
NT
 Department of Plant Protection, College of Agriculture and Applied Biology, Can Tho University, Can Tho City, Vietnam.
Lübeck
M
M
 Department of Plant Biology and Biotechnology, Faculty of Life Sciences, University of Copenhagen, Thorvaldsensvej 40, Frederiksberg C, Denmark.| Section for Sustainable Biotechnology, Copenhagen Institute of Technology, Aalborg University, Lautrupvang 15, Ballerup, Denmark.
Shetty
N P
NP
 Department of Plant Biology and Biotechnology, Faculty of Life Sciences, University of Copenhagen, Thorvaldsensvej 40, Frederiksberg C, Denmark.
De Neergaard
E
E
 Department of Plant Biology and Biotechnology, Faculty of Life Sciences, University of Copenhagen, Thorvaldsensvej 40, Frederiksberg C, Denmark.
Thuy
T T T
TTT
 Department of Plant Protection, College of Agriculture and Applied Biology, Can Tho University, Can Tho City, Vietnam.
Kim
P V
PV
 Department of Plant Protection, College of Agriculture and Applied Biology, Can Tho University, Can Tho City, Vietnam.
Jørgensen
H J L
HJL
 Department of Plant Biology and Biotechnology, Faculty of Life Sciences, University of Copenhagen, Thorvaldsensvej 40, Frederiksberg C, Denmark.
D001203:Ascomycota / Q000502:physiology*; D001419:Bacteria / Q000302:isolation & purification; D029773:Citrullus / Q000382:microbiology*; D010572:Pest Control, Biological; D010935:Plant Diseases / Q000382:microbiology / Q000517:prevention & control*; D011550:Pseudomonas aeruginosa / Q000254:growth & development / Q000302:isolation & purification / Q000502:physiology*; D014744:Vietnam