ROMERO Fernando Matias
congresos y reuniones científicas
Characterization of bacterial endophytes from tomato leaves showing antagonism to Botrytis cinerea and Pseudomonas syringae in vitro and in planta
ROMERO FM; MARINA M; PIECKENSTAIN FL
Workshop; II Latin American PGPR Workshop; 2014
Introduction Many endophytic bacteria colonize host tissues internally without causing damage or eliciting disease symptoms and in some cases promote plant growth and protect them against pathogens. This work aimed to characterize bacterial members of the leaf-endophytic community of tomato plants grown under conditions of commercial production, and to analyze their antagonistic properties against Botrytis cinerea and Pseudomonas syringae. Materials and Methods Eleven bacterial isolates from the endophytic community of tomato leaves were co-cultured with B. cinerea and P. syringae, in order to evaluate their antagonistic properties in vitro. Production of antimicrobial compounds was tested as the ability of cell-free supernatants to inhibit germination of B. cinerea conidia and growth of P. syringae. Bioassays were performed by inoculating each antagonist either on roots or leaves, and further pathogen inoculation of leaves. Expression of defense genes was analyzed in plants inoculated with the antagonists. Results Isolates NT2 (Pseudomonas veronii), BT2 (Pseudomonas rhodesiae), BT4 (P.veronii), NT6 (Pantoea eucalypti) and MT3 (Bacillus methylotrophicus) inhibited mycelial growth of B. cinerea in vitro. NT2, BT4 and MT3 also inhibited growth of P. syringae in vitro. Cell-free supernatants of BT4, BT2 and NT2 reduced the germination of B. cinerea conidia. Supernatant of isolate BT4 inhibited growth of P. syringae. Leaf infiltration with NT2, BT2 and NT6 reduced the foliar damage caused by B. cinerea. When the antagonists were inoculated on roots, isolates NT2 and BT4 also reduced foliar damage caused by B.cinerea. Leaf infiltration with NT2 and BT4 reduced P.syringae propagation. Finally, we analyzed the expression of PR1, PINII and GLUB, three genes regulated by salicylic acid, jasmonates and ethylene, respectively. PR1 expression was down regulated in plants inoculated with BT2 and BT4, while PINII expression was up regulated in plants inoculated with BT4. Inoculation with NT6 increased PINII and GLUB expression, but had no effect on PR1 expression. Inoculation with MT3 increased GLUB expression, while none of the three genes was affected by NT2 inoculation. Conclusion This work allowed the identification of bacteria from endophytic communities of tomato leaves able to reduce disease symptoms caused by B. cinerea and P.syringae when inoculated on tomato plants. For some isolates, inhibition of pathogen growth could be attributed, at least in part, to the production of antimicrobial compounds. Finally, even though some isolates were found to activate jasmonate/ethylene-dependent defense genes, a clear relation between the induction of a particular signaling pathway and protection against pathogens was not evident. Besides the hereby reported features of isolates corresponding to P. veronii (BT4, NT2), P. rhodesiae (BT2) and P. eucalypti (NT6), these bacteria were previously shown to be capable of plant growth promotion, phosphate solubilization, siderophore and phytohormone production. These features, along with their potential for disease control, render the above-mentioned isolates interesting candidates for the development of biological formulations for growth promotion and the control of tomato diseases caused by B. cinerea and P. syringae.