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

Abstract

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.

Bio-Sulfur Pre-Treatment Suppresses Anthracnose on Cucumber Leaves Inoculated withColletotrichum orbiculare

“…Generally, callose formed in host cells indicates a defense response against fungal invasion [28]. Callose, also known as “papillae” forming on host secondary cell wall, may play a role as barriers during early infection stages of the pathogen [29].…”

Improved species level bacterial characterization from rhizosphere soil of wilt infected Punica granatum

“…On the other hand, an abundance of Micrococcus luteus has been reported in the ISI sample. Micrococcus luteus is a gram-positive bacterium that has been reported to exhibit antifungal activity 42 , 43 and its growth promoting properties, biocontrol properties 44 , biotic and abiotic stress tolerance 43 . Another study has reported the growth promoting properties of Micrococcus luteus against F.oxysporum in chickpea 45 .…”

Characterization of the defence response to Venturia inaequalis in ‘Honeycrisp’ apple, its ancestors, and progeny

“…Fluorescent compounds often have rigid structures common to phenolic compounds involved in defence responses (Nicholson and Hammerschmidt, 1992;Davidson, 1996). Auto-fluorescence has been observed in other pathosystems and has been attributed to phytoalexin, amino acids, flavonoids, callose, and phenolic acids (Nicholson, 1977;Nicholson and Hammerschmidt, 1992;Dai et al, 1996;Jeun and Lee, 2005). In lettuce leaves infected with downy mildew, auto-fluorescence was attributed to the accumulation of ester-linked syringaldehyde and caffeic acid on plant cell walls, as well as the release of preformed phenolics from the vacuole in the HR (Bennett et al, 1996).…”