Rhizobacteria-mediated Induced Systemic Resistance in Cucumber Plants against Anthracnose Disease Caused by Colletotrichum orbiculare

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Efficacy of resistance induction by the bacterial isolates Pseudomonas putida (TRL2-3), Micrococcus luteus (TRK2-2) and Flexibacteraceae bacterium (MRL412), which were isolated from the rhizosphere of plants growing in Jeju Mountain, were tested in a greenhouse. The disease severity caused by Phytophthora infestans was effectively reduced in the potato plants pre-inoculated with bacterial isolates compared with those of the untreated control plants growing in a greenhouse. In order to estimate the level of protection by the bacterial isolates, Mancozeb WP (Diesen M®, Kyong nong) and DL-3-amino butyric acid (BABA) were pre-treated, whereas Dimethomorph WP (Forum®, Kyong nong) and phosphonic acid (H3PO3) were post-treated the challenge inoculation with the pathogen. Disease severities of chemical pre-treated as well as post-treated plants were reduced compare to those of the untreated. The disease reduction in the plants pre-treated with Mancozeb WP was the highest, whereas that of post-treated with Dimethomorph WP was the lowest. The yields of plants pre-inoculated with three bacterial isolates were greatly increased than those of control plants. These results suggest that biological control by bacterial isolates might be an alternative strategy against late blight disease in potato plants growing in greenhouse.

Section: Discussionmentioning

confidence: 85%

Resistance Induction and Enhanced Tuber Production by Pre-inoculation with Bacterial Strains in Potato Plants againstPhytophthora infestans

Kim¹,

Jeun²

2006

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“…In most cases, the levels of resistance triggered by chemical inducers were higher than those triggered by biotic inducers such as PGPR or mycorrhizal fungi in cucumber or potato plants (Jeun et al, 2004; Kim and Jeun, 2007; Lee et al, 2005; Potlakayala et al, 2007). On the leaf surfaces of cucumber plants pre-inoculated with PGPR strains Serratia marcescens (90-166) and Pseudomonas fluorescens (89B61), no decrease in germination rate or suppression of appressorium formation of C. orbiculare was observed unlike the leaves of untreated plants.…”

Section: Discussionmentioning

confidence: 99%

“…Therefore, it is likely that BABA causes a defense reaction in the apoplast rather than in the symplast (Jeun et al, 2007). In fact, there were decreases of appressorium formation and germination of fungus C. orbiculare on the surface of cucumber plants when pretreated with BABA (Jeun et al, 2004; Lee et al, 2005). …”

Section: Discussionmentioning

confidence: 99%

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Ultrastructures ofColletotrichum orbicularein the Leaves of Cucumber Plants Expressing Induced Systemic Resistance Mediated byGlomus intraradicesBEG110

Jeun¹,

Lee

Kim

et al. 2008

The colonization of an arbuscular mycorrhizal fungus Glomus intraradices BEG110 in the soil caused a decrease in disease severity in cucumber plants after fungal inoculation with Colletotrichum orbiculare. In order to illustrate the resistance mechanism mediated by G. intraradices BEG110, infection patterns caused by C. orbiculare in the leaves of cucumber plants and the host cellular responses were characterized. These properties were characterized using transmission electron microscopy on the leaves of cucumber plants grown in soil colonized with G. intraradices BEG110. In the untreated plants, inter- and intra-cellular fungal hyphae were observed throughout the leaf tissues during both the biotrophic and necrotrophic phases of infection. The cytoplasm of fungal hyphae appeared intact during the biotrophic phase, suggesting no defense response against the fungus. However, several typical resistance responses were observed in the plants when treated with G. intraradices BEG110 including the formation of sheaths around the intracellular hyphae or a thickening of host cell walls. These observations suggest that the resistance mediated by G. intraradices BEG110 most often occurs in the symplast of the host cells rather than in the apoplast. In addition, this resistance is similar to those mediated by biotic inducers such as plant growth promoting rhizobacteria.

“…In our previous study the disease severity in the cucumber plants pre-inoculated with both bacterial strains P. putida and M. luteus were suppressed after challenge inoculation with C. orbiculare (Jeun et al, 2004a). In the present study, infection structures of the pathogen and defense responses of its host plants were cytologically examined on the leaf surfaces of the cucumber plants pre-inoculated with P. putida or M. luteus .…”

mentioning

confidence: 93%

Observations of Infection Structures after Inoculation withColletotrichum orbiculareon the Leaves of Cucumber Plants Pre-inoculated with Two Bacterial StrainsPseudomonas putidaorMicrococcus luteus

Jeun

Lee

2005

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Infection structures were observed at the penetration sites on the leaves of cucumber plants inoculated with Colletotrichum orbiculare using a fluorescence microscope. The cucumber plants were previously drenched with suspension of bacterial strains Pseudomonas putida or Micrococcus luteus. The plants pre-inoculated with both bacterial strains were resistant against anthracnose after inoculation with C. orbiculare. To investigate the resistance mechanism by both bacterial strains, the surface of infected leaves was observed at the different time after challenge inoculation. At 3 days after inoculation there were no differences in the germination and appressorium formation of conidia of C. orbiculare as well as in the callose formation of the plants between both bacteria pre-inoculated and non-treated. At 5 days, the germination and appressorium formation of the fungal conidia were, however, significantly decreased on the leaves of plants pre-inoculated with M. luteus at the concentration with 1.0 × 107 cfu/ml. Furthermore, callose formation of plants cells at the penetration sites was apparently increased. In contrast, there were no defense reactions of the plants at the concentration with 1.0 × 106 cfu/ml of M. luteus. Similarly, inoculation P. putida caused no plant resistance at the low concentration, whereas increase of callose formation was observed at the higher concentration. The results of this study suggest that the resistant mechanisms might be differently expressed by the concentration of pre-treatment with bacterial suspension.