Effect of PGPR on population growth parameters of cotton aphid

Plant-growth-promoting rhizobacteria (PGPR) help plants by increasing plant growth and defending them against pathogens and pests. There is considerable research supporting the use of these bacteria in plant pathogens management, but the number of research papers that have focused on their effect on insect pests control is quite few. In this research, we examined the ability of four native strains of Pseudomonas fluorescens to manage the cotton aphid, Aphis gossypii, on greenhouse-grown cucumbers in Iran. The strains UTPF (University of Tehran Pseudomonas fluorescens) 68, UTPF1, UTPF6 and PF169 of P. fluorescens were used as seed treatment to evaluate their impact on both cucumber growth and cotton aphid population growth parameters. The strains UTPF68 and PF169 of this bacterium influenced phenology of cucumber by decreasing the Growing Degree Days of flowering period. Also, the plants treated with these bacterial strains had a significant increase in yield weight of approximately 58%. In the other part of the study, various effects on developmental parameters of aphid were recorded among bacterial strains, but only PF169 caused significant decreasing effect on r_m value of aphid, which is the most important factor in aphid's life table. We conclude that the PF169 treatment had significant negative effects on population growth rate of A. gossypii. The PF169 could be reliable in a control programme for A. gossypii on cucumber plants in greenhouses.