Isolation and characterization of Pseudomonas spp. from the rhizosphere of soybean plants and induction of the plant defense response against corynespora cassiicola

MICHAVILA G; ADLER CONRADO; CORBALÁN NATALIA SOLEDAD; POMARES MARÍA FERNANDA; DE CRISTÓBAL RE; PAULA A VINCENT

La Falda Córdoba

Workshop; pgpr Latinoamérica 2014; 2014

Universidad Nacional de Río Cuarto

Introduction The ring spot disease of soya (Glycine max (L.) Merr.) caused by Corynespora cassiicola, is found in most Argentinean soybean-growing zones, although is more common in the north provinces. Symptoms consist in roughly circular, necrotic leaf lesions; affect also petioles, stems, pods and seeds causing a decreasing in yield. Currently chemical controls for the management of this disease, usually in the reproductive phenological stages of the crop R3 and R5, are made. The most common fungicides used are of three chemical groups: Benzimidazols, triazols and strobilurins. The inadequate use of these agrochemical products could be dangerous for the environment, so it is of interest to search management alternatives that are effective, that do not select resistance in the pathogen and that can be produced without petrochemical industry energy use. One alternative is the use of natural origin agents, non-synthetic, used as biocontrol strategies. Our laboratory addressed a screening for rhizospheric bacteria that promote plant growth and antibiotic action against plant pathogens. The bacteria that inhabit the rhizosphere and have ability to cause a positive effect on plants are called plant growth promoting Rhizobacteria (PGPR). In general, biological control mechanisms and plant growth promotion by rhizospheric bacteria are based on microbial metabolites produced that adversely affect the pathogen or induce systemic resistance in the plant. Objectives Isolation and characterization of soya plants rhizospheric bacteria. Study of biochemical markers associated with growth promotion and pathogen defense induction. Evaluation of protective effect of the Pseudomonas strain against the causal agent of ringspot disease in soy (Corynespora casiicola). Materials and methods Some bcteria were isolated from soybean plants rizosphere on different cultures. They were characterized by amplifying the DNA and sequencing of 16srRNA gene. Then the study of biochemical markers associated with growth promotion (siderophore production, synthesis of indole acetic acid, phosphate solubilization) was performed. Finally protection assay in soybean plants infected with the fungi Coryrespora cassiicola was carried out using the isolated bacteria. Resultados Pseudomonas bacterial genera were isolated from soy rhizosphere. We studied biochemical markers associated with growth promotion; it was positive for synthesis of siderophore and phosphate solubilization and negative for indole acetic acid production. Preliminary in vivo assays using soy plants treated with the bacteria 3 and 7 days before infection, showed the protective effect of the Pseudomonas strain against the causal agent of rings pot disease (Corynespora casiicola). However, no antibiotic activity was observed in vitro against the fungi. Conclusion These results indicate a promising role of this Pseudomonas strain as a biocontrol agent for plant diseases through the induction of the plant defense response. Areas temáticas propuestas: Biotecnología [4] y Aplicaciones agronómicas [5]