ISOLATION OF ACTINOBACTERIA AS POTENTIAL BIOLOGICAL CONTROL AGENTS AGAINST SOYBEAN FUNGAL PATHOGENS

VILLAFAÑE DL, ; BERCOVICH BA, ; GRAMAJO H; CHIESA MA, ; RODRÍGUEZ EJ

Congreso; SAIB 2020; 2020

By the year 2050 agricultural production will have to increase by 60% to satisfy the growing food demand. Argentina is one of the countries with the potential to supply this demand with the production of extensive crops such as soybean [Glycine max (L.) Merr.]. However, there are numerous phytopathogens that threaten this crop causing an approximate decrease of 11 % in annual yield. Currently, protection against fungal diseases is carried out through the use of chemical fungicides, but they have a negative impact on the environment (soil, air and water) and human health. The biological control of pests, generated by beneficial soil microorganisms, has been proven to be an ecological alternative for phytosanitary protection. In addition, it offers another advantage as promoters of plant growth, improving yield. In the present work, it was proposed to initiate the development of new technology based on autochthonous strains of actinobacteria for soybean crop protection, taking advantage of the ability of these soil bacteria to produce a wide range of natural compounds with multiple applications. Seventy-eight actinobacteria, mainly belonging to the genus Streptomyces, were isolated from the root, stem, nodules, and rhizosphere of soybean plants cultivated in the core productive area of Argentina (Zavalla, Santa Fe). Half of them showed a good antagonistic effect in vitro against two phytopathogenic fungi with great impact on this crop, while they were compatible with Bradyrhizobium japonicum. Moreover, the ability to stimulate plant growth at different stages by the isolated actinobacteria was assayed as follows. According to the Standard Germination Test, it was demonstrated that none of them negatively affected the germination of pretreated seeds while few showed an enhanced germination rate. In greenhouse assays, it was found that nodulation and vegetative growth were not affected by the inoculation with the bacteria, and some of the growth parameters were promoted, suggesting that they could improve the crop yield. Then, the biocontroller effect of the isolated actinobacteria against Diaporthe aspalathi, the causal agent of Stem Canker in soybean, was tested under greenhouse conditions. Some strains showed that seed treatment resulted in 0 % of Dead Plants (DP) in comparison to the untreated control