Molecular genetic studies on the role of some soil bacteria strains in the induction of resistance to some pathogens

Six strains of Pseudomonas spp. and one strain of Serratia sp. were used in this study. Pseudomonas cells and their filtrate were tested for their effect in the induction of systemic resistance on cucumber plants against the pathogen (Pythium ultimum). All Pseudomonas cells showed indirect effect on the pathogen by systemic resistance. Some parameters were employed to evaluate Pseudomonas induction of systemic resistance. Four Pseudomonas putida strains; i.e. ps.3, ps.4, .ps.5, ps.6 proved to be good inducer for systemic resistance. Bacterial filtrate . showed no increase in all morphological parameters comparing with the control. Pseudomonas strains were improved as a biocontrol agent using intergeneric DNA transfer methods i. e. traditional transformation and protoplast fusion protocols using Serratia marcescens strain. Chitinase activity was selected via clear zone and was higher in the fusants than the traditional transformatant. Some enzymes and components, which related to induction of systemic resistance, i.e. Jasmonic acid, peroxidase production phenolic compounds, were measured in plants treated with Pseudomonas strains and their fusants. The maximum increase in JA levels of 1.5µg/g dry weight in plants treated with P. putida strain ps.3 and 1.7µg/g dry weight in plants treated with the same strain after fusion. Total proteins were separated from treated plants to study the effect of Pseudomonas strains and their fusants to induce a systemic resistance.Bands with M.W 215 and 50 KDa could be transferred from Serratia strain to fusants-l because there are not present in the other Pseudomonas parent strain (ps.3). Fusants proved to be better inducers for systemic resistance than the parental strains. These parental strains and the fused ones were characterized and showed variable protein banding pattern of the fused strains are apparently due to the Serratia genome. Data gained from rep and eric-PCR analysis revealed the presence of positive markers for different strains.