The antagonism of Pseudomonas putida biotype A (C1-1B), P. putida biotype B (Santa Bárbara), P. fluorescens (C2-8C and RA2), Bacillus subtilis (OG and RC2) and Flavobacterium sp. (CIS/NA) against Phytophthora parasitica and P. citrophthora, rhizobacteria, agent of root rot of Citrus sp., was evaluated by mycelial growth inhibition (paired culture) and reduction of disease percentage in seedlins (seeds treatment). In a preliminary screening, 33 bacteria isolates were tested. The citrus seeds were immersed in the bacteria suspensions (10(9) ufc/ml) and then sown in plastic tubes containing natural soil, previously infested with the pathogen at a concentration of 50 ml of suspension/kg of soil. The evaluation of the disease percentage was carried out after 15 days. In vitro, the isolates of bacteria RC2, OG, CIS/NA and C1-1B were the most effective inhibitors of the mycelial growh of Phytophthora. In greenhouse conditions all the isolates reduced the disease percentage. Beneficial effects were obtained with the isolates OG, RC2, CiS/Na and C1-1B in relation to plant growth.
Biological control; PGPR; root rot; Citrus
