). Isolation of actinobacteria as potential biological control agents against soybean fungal pathogens

GRAMAJO, H.; VILLAFAÑES, D; CHIESA M.A; BERCOVICH, B; RODRIGUEZ, E

Mendoza

Congreso; XV Congreso Argentino de Microbiología General (SAMIGE).; 2020

Sociedad Argentina de Microbiología General ? SAMIGE

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 developing of a 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 of phytopathogenic fungi with great impact on this crop, while they were compatibile 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 affect negatively the germination of pretreated seeds while few showed an enhance germination rates. In greenhouse assays it was found that nodulation and vegetative growth was 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, causal agent of Stem Canker in soybean, was tested under greenhouse conditions. Some strains showed that their seed treatment results in 0 % of Dead Plants (DP) in comparison to the untreated control with 100 % DP, at the end of the assay. Besides, a temporary delay of four weeks on the onset of typical symptoms were visualized for these treatments and at least one week of delay for all the remaining isolates tested simultaneously, and slower rates of disease progression. In this way, we can conclude that the isolated actinobacteria have the ability to protect soybean plants from the tested fungal phytopathogen, achieving in some cases improvements in plant growth. To confirm the ability to improve crop yield, further work in field trials will be required.