Evaluation of some Plant Growth Promoting Rhizobacteria (PGPR) to Control Pythium aphanidermatum in Cucumber Plants

Twenty isolates of bacteria were successfully isolated from rhizosphere soil samples collected from different plant species growing at various locations in North Jeddah, Saudi Arabia to investigate their effects on Cucumis sativus L. cv. Marketmore growth and damping-off disease caused by Pythium aphanidermatum. The results of dual culture method showed that only three isolates out of twenty, which have a great antagonistic effect on the growth of P. aphanidermatum referring to inhibition index. The selected isolates were identified in two genera with three species as Bacillus subtilis, B. amyloliquefaciens and Pseudomonas aeruginosa, that causing inhibition in fungal growth by rate 38.1±3.8, 66±5.0 and 78.1±6.8%, respectively. Under greenhouse condition, the efficacy of different treatments with bacterial isolates and their possible combination were recorded a varied significant effect to suppress damping off symptoms caused by P. aphanidermatum. All treatments with the isolates of PGPR were recorded growth promoting effect in the absence of pathogenic fungus comparing with untreated plant. The best result in plant height, stem length, plant fresh and dry weight were recorded in treatment with B. subtilis (23.7±1.04 cm, 13.5±0.87 cm 0.62±0.02 g and 0.033±0.007 g), flowed by P. aeruginosa (19.3±1.15 cm, 9.00±1.0 cm, 0.61±0.07 g, 0.029±0.002 g) then B. amyloliquefaciens (17.0±1.30 cm, 8.97±0.90 cm, 0.53±0.01 g, 0.031±0.004 g). On contrast, all seeds were completely dead, when treated with P. aphanidermatum individually or in combination with PGPR isolates except two treatments, which used B. amyloliquefaciens and P. aeruginosa for coating seeds. Consequently, these two isolates have the potential not only to protect cucumber seedling against P. aphanidermatum infection but also to improve the plant growth parameters. [Ahmed M. Elazzazy, Omar A. Almaghrabi, Tarek A. A. Moussa, Tamer S. Abdelmoneim. Evaluation of some Plant Growth Promoting Rhizobacteria (PGPR) to Control Pythium aphanidermatum in Cucumber Plants. Life Sci J 2012;9(4):31473153] (ISSN:1097-8135). http://www.lifesciencesite.com. 461