EVALUATION OF THE BIOLOGICAL CONTROL ACTIVITY OF NATIVE PGPR FROM MENDOZA AGAINST TOMATO SEEDLING PHYTOPATHOGENS

PÉREZ-RODRIGUEZ M.M; LOBATO-URECHE MA; LUCERO G; AGARAS B; COHEN A.C.

Chapadmalal, Buenos Aires

Congreso; XVIII Congreso de la Sociedad Aregentina de Microbiología General; 2023

Sociedad Argentina de Microbiología General

Agriculture aims to meet food demands of a growing population. However, this goal has been pursued through indiscriminate use of chemical fertilizers and pesticides, resulting in environmental pollution. Consequently, there is a requirement for agricultural strategies that can sustainably support crop growth without causing harm to natural ecosystems. In response to this, the integration of Plant Growth-Promoting Rhizobacteria (PGPR) into agricultural practices has emerged as a biocontrol approach. PGPR can promote plant growth by producing pathogen-antagonistic substances and by inducing systemic resistance. The aim of the work was to evaluate the in vitro antagonistic activity of native PGPR strains of Mendoza against pathogenic fungi of tomato seedlings; and then, to evaluate the effect of the most effective PGPR by inoculation of tomato seedlings infected with Rhizoctonia solani under greenhouse conditions. The test to determine antagonism activity was carried out by fourfold and repeated two times. One disc of a 5 mm plug carrying mycelia fungi (R. solani, Sclerotinia Sclerotiorum, Phytophthora capsici and Phytium sp.) previously grown for 5 days in PDA media, was placed at the end of a petri dish. Each individual bacterium (Cellulosimicrobium 60I1, Ochrobactrum 53F, Enterobacter 64S1 and Pseudomonas 42P4), grown on LB medium for 24 h at 28 °C with orbital shaking, was streaked as line at the opposite edge. The assay was performed incubating the plates at 28 °C for 7 days. The mycelium growth was digitally determined. A control plate (fungi without bacteria) was included. The percentage of inhibition was calculated comparing to the control. In the greenhouse assay, the following treatments were applied to tomato seedlings: 1) Control, 2) Pseudomonas 42P4, 3) Carbendazim (chemical fungicide) 4) R. solani, 5) R. solani + Pseudomonas 42P4, 6) R. solani + Carbendazim. Physiological parameters were evaluated two month after seeds sown. In the in vitro assay, Enterobacter 64S1 and Pseudomonas 42P4 inhibited R. solani, P. capsici and Phytium sp. mycelium growth, meanwhile Ochrobactrum 53F and Pseudomonas 42P4 inhibited S. Sclerotiorum mycelium growth. In the greenhouse assay, R. solani reduced Root and Shoot Dry Weight (RDW and SDW) compared to control seedlings. Pseudomonas 42P4 inoculation reduced the disease incidence in a similar percentage to carbendazim treatment and increased RDW and SDW of infected R. solani seedlings by more than 10 % respect to R. solani seedlings treated with carbendazim. Furthermore, Pseudomonas 42P4 inoculation increased RDW and SDW of non-infected R. solani seedlings. The results suggest that Pseudomonas 42P4 was the most effective PGPR in the antagonistic assay, and was capable of lowering the negative effects of R. solani on tomato seedlings, acting as a biocontrol agent. It is a promising candidate for developing a bioinput to reduce the chemical pesticides in the context of sustainable agriculture.