Pythium Damping-off Of Cucumber Research Articles

Endophytic Enterobacter cloacae exhibits antagonistic activity against Pythium damping-off of cucumber

ABSTRACT: The study was performed to examine the potential presence of biological control agents against Pythium damping-off disease of cucumber.Examining eleven bacterial strains isolated from acid lime roots and rhizosphere soil showed that the bacterial strain RB1 was the most efficient in suppressing mycelial growth of P. aphanidermatum, producing an inhibition zone of 5mm. Scanning electron microscopy study of the mycelia at the interaction zone showed that the pathogen hyphae were deformed and shriveled by the bacterial strain.In pot experiments, pretreatment with the RB1 bacterial strain reduced disease incidence significantly by 63%.The bacterial strain did not exhibit any negative significant effects on cucumber growth (plant height and root dry weight) in comparison with untreated control under growth chamber conditions. Molecular identification of strain RB1 based on the 16S rRNA gene revealed that it is Enterobacter cloacae. Findings from this study suggested that E. cloacae has a potential to be used as a biocontrol agent for suppressingcucumber damping-off disease caused by P. aphanidermatum. This is the first report of the antagonistic activity of E. cloacae against P. aphanidermatum-induced damping-off of cucumber.

Lack of Evidence for a Role of Antifungal Metabolite Production byPseudomonas fluorescensPf-5 in Biological Control of Pythium Damping-Off of Cucumber

Pseudomonas fluorescens Pf-5 protected cucumber from preemergence damping-off caused by Pythium ultimum and produced a number of antifungal metabolites in culture, including a fluorescent siderophore (pyoverdine), pyoluteorin, pyrrolnitrin, cyanide, and an uncharacterized compound termed antibiotic 3. Of these, the roles of pyoluteorin and pyoverdine in the biocontrol activity of Pf-5 against Pythium damping-off of cucumber were investigated. Tn5 insertion mutants of Pf-5 were screened for loss of pyoluteorin production (Plt - ) or pyoverdine production (Pvd - ) (...)

Biological control of rhizoctonia and pythium damping-off of cucumber: An integrated approach

Abstract Binucleate Rhizoctonia spp. were evaluated singly and in combination with seed treated with selected biocontrol bacteria, fungicides, or osmopriming agents in the greenhouse and field for control of Rhizoctonia and Pythium damping-off of cucumber. In the greenhouse, in a pasteurized soil mix, treatments with 8 of 19 isolates of binucleate Rhizoctonia spp. yielded decreased (P = 0.05) levels of preemergence damping-off caused by R. solani. Osmopriming cucumber seed with KNO3, NaCl, or polyethylene glycol (PEG 8000) did not protect cucumber from Rhizoctonia and Pythium damping-off in naturally infested soil in the greenhouse. Treating cucumber seed with strain E6, ECH, and ECT of Enterobacter cloacae and sowing in soil alone or in soil amended with isolate 232-CG of binucleate Rhizoctonia sp. resulted in decreased (P = 0.05) levels of Rhizoctonia and Pythium preemergence damping-off in naturally infested soil in the greenhouse but not in the field. Amendment of isolate 232-CG to soil and combining it with seed treatment or soil application of metalaxyl produced decreased (P = 0.05) levels of Rhizoctonia and Pythium preemergence damping-off in 12 naturally infested fields at three geographic locations when compared with nontreated seed sown in soil alone or in soil amended with isolate 232-CG alone. Seed treated with metalaxyl and sown in soil amended with isolate 232-CG developed decreased (P = 0.05) levels of Rhizoctonia and Pythium preemergence damping-off at 20 and 30% of the field sites compared to seed treated with captan and metalaxyl, respectively. However, seed treated with metalaxyl or captan had higher (P = 0.05) disease incidence of Rhizoctonia at 20 and 60% of the field sites, respectively, when compared to seed treated with metalaxyl and sown in soil amended with isolate 232-CG. Control of cucumber damping-off caused by R. solani and Pythium spp. requires an integrated approach and can be achieved using the binucleate Rhizoctonia sp. isolate 232-CG combined with the fungicide metalaxyl. This treatment protected cucumber from Rhizoctonia and Pythium damping-off as effectively as the recommended fungicide captan.