Evaluation of Trichoderma harzianum ITEM 3636 as a potential endophyte and biocontrol agent against late leaf spot in peanut

Abstract

Peanut late leaf spot, caused by Nothopassalora personata, is a disease that causes high yield losses in Argentina. Its management is mainly based on chemical fungicides, and there is frequently a low control efficiency with some of the active ingredients used. Trichoderma harzianum ITEM 3636 is efficient in the control of soil-borne pathogens. If this strain would have endophytic capacity and trigger plant systemic resistance, it could decrease the disease intensity on leaves. To confirm this hypothesis, peanut seeds were treated with T. harzianum ITEM 3636 and sown under sterile conditions. After seven days, seedlings were processed, and their roots were stained for observation under a confocal microscope. Additionally, a greenhouse assay was carried out with inoculated and no inoculated seeds. Plants were inoculated at 130 days after sowing with an N. personata and disease intensity was recorded. Images taken under the microscope showed that T. harzianum ITEM 3636 was able to grow inside peanut roots, and the seed application undercontrolled conditions caused a significant decrease in late leaf spot intensity (more than 20% reduction in the number of infected leaflets and disease incidence). These results suggest that strain ITEM 3636 could constitute a useful tool for biological control of peanut late leaf spot. Further studies are being carried out to elucidate the specific mechanisms involved in the capacity of the strain to induce plant resistance.