Trichoderma harzianum ITEM 3636: a fungal biological control agent for sustainable management of peanut diseases

PASTOR, N; GANUZA M.; ERAZO, J; PALACIOS, S; GIORDANO, F; REYNOSO M.M.; ROVERA, M; TORRES, A.M.

Salamanca

Workshop; TG2018 15th International Trichoderma & Gliocladium Workshop; 2018

In Argentina, brown root rot and peanut smut are diseases that cause severe economic losses. Both causal agents, Fusarium solani and Thecaphora frezii, may be present in the soil and, depending on environmental factors, cause disease. T. harzianun ITEM 3636 is a microbial agent with high potential for controlling both diseases (Ganuza et al., 2018). In this work, we report the impact of sowing seeds inoculated with ITEM 3636 on bacterial and fungal communities of agricultural soils. Knowledge of the effects of fungal or bacterial strains inoculated in agricultural fields on native microbial communities is of great interest. The study of the possible changes caused is relevant with respect to the safety of introducing microorganisms into the environment. Soil samples were obtained from two commercial fields located in the south of the province of Córdoba, Argentina, at two different times, before peanut sowing and at 120 days post sowing (harvest). Fields included plots with inoculated seeds and plots without inoculation with ITEM 3636. We extracted total DNA from soil samples using PowerSoil® DNA Isolation Kit (Mo Bio). Samples were lyophilized and sent to CD Genomics (USA) for the metagenomic study. To analyze the diversity of bacteria and fungi, the primers 338F/806R and ITS1f/ITS2 were used, respectively. The sequencing was performed with HiSeq2500 (Illumina). UCLUST was used in QIIME (V 1.8.0) to group the labels with 97% similarity and generate Operational Taxonomic Units (OTUs). The number of OTUs obtained was similar among all the analyzed samples (before sowing and post-harvest). Results of alpha and beta diversity showed that there were no significant variations between bacterial and fungal communities. We also tested ITEM 3636 for initial estimation of biocontrol traits. We detected the presence of the operon for the biosynthesis of ß-1,3-glucanase by PCR and observed that the enzymatic activity increased over time to reach a maximum of 0.0598 U ml-1 after 264 h of cultivation. Also, ITEM 3636 was proven to produce proteases and a maximum of 65.9% of siderophore units after 3 days of cultivation in minimal medium without Fe. In conclusion, these results highlight the potential of T. harzianum ITEM 3636 as a fungal biocontrol agent for sustainable management of peanut diseases, since it decreases the incidence and severity of agriculturally relevant diseases without causing significant changes in the microbial communities of agricultural soils.