Rhizobacterially induced protection of watermelon against Didymella bryoniae

Abstract

Aims: 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. Methods and 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 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. Conclusions: The endophytic bacterium Ps. aeruginosa 231‐1 can control D. bryoniae in watermelon by antibiosis and induced resistance under greenhouse and field conditions. Significance and Impact of the Study: 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.

From Native Plants in Central Europe to Cultivated Crops Worldwide: The Emergence of Didymella bryoniae as a Cucurbit Pathogen

“…Thus, it is ideally suited to continue to plague cucurbits grown in humid environments. (2010); Kagiwata (1970); Lee et al (1984); Nga et al (2010); and Punithalingam and Holliday (1972). Gray = approximate centers of origin of cucurbit hosts according to Pickersgill (2007), and Robinson and Decker-Walters (1997).…”

Engineering Pathogen Resistance in Crop Plants: Current Trends and Future Prospects

“…Even worse, bacteria pathogenic to humans could eventually develop new traits of resistance derived from the microcosmos of bacteria surrounding GM plants either in the field or during the processing and digestion of the crop. This problem is familiar from biological control studies in which bacteria closely related to human pathogens have regularly been found to be effective biological control agents (75,87). Such concerns cannot be rejected as based purely on unscientific speculation.…”

Biocontrol of verticillium wilt and colonization of cotton plants by an endophytic bacterial isolate

“…The populations of HA02‐ gfp in roots were about 100 times higher than those in stems, and the different colonization populations of antagonistic bacteria between organ have also been reported by Nga et al . (), who discovered that a Pseudomonas aeruginosa 231‐1 systemically protect watermelon against gummy stem blight, mainly colonized in the hypocotyls of watermelon but not found in the true leaf after seed soaking and subsequently soil drenching to 7‐day‐old seedlings. Seven days after HA02‐ gfp inoculation, HA02‐ gfp was mainly distributed in the maturation zone of cotton roots, which had similar root‐colonizing patterns of Pseudomonas fluorescens A6RI in tomato (Gamalero et al .…”