Molecular Identification of Trichoderma spp. in Garlic and Onion Fields and In Vitro Antagonism Trials on Sclerotium cepivorum

Abstract

Trichoderma species are non-pathogenic microorganisms that protect against fungal diseases and contribute to increased crop yields. However, not all Trichoderma species have the same effects on crop or a pathogen, whereby the characterization and identification of strains at the species level is the first step in the use of a microorganism. The aim of this study was the identification -at species level -of five strains of Trichoderma isolated from soil samples obtained from garlic and onion fields located in Costa Rica, through the analysis of the ITS1, 5.8S, and ITS2 ribosomal RNA regions; as well as the determination of their individual antagonistic ability over S. cepivorum Berkeley. In order to distinguish the strains, the amplified products were analyzed using MEGA v6.0 software, calculating the genetic distances through the Tamura-Nei model and building the phylogenetic tree using the Maximum Likelihood method. We established that the evaluated strains belonged to the species T. harzianum and T. asperellum; however it was not possible to identify one of the analyzed strains based on the species criterion. To evaluate their antagonistic ability, the dual culture technique, Bell's scale, and the percentage inhibition of radial growth (PIRG) were used, evidencing that one of the T. asperellum isolates presented the best yields under standard, solid fermentation conditions.

Trichoderma from Brazilian garlic and onion crop soils and description of two new species: Trichoderma azevedoi and Trichoderma peberdyi

“…Trichoderma species are common in rhizospheric and non-rhizospheric soils and in endophytic relationships with many plants, displaying antifungal properties as well as promoting growth and inducing plant resistance against pathogenic fungi [10][11][12]. Three Trichoderma asperellum strains, one Trichoderma harzianum strain and a fifth unidentified Trichoderma strain from the rhizosphere of garlic and onion crops in Costa Rica have been tested for their in vitro antagonism against S. cepivorum, following their identification using ITS sequences [13]. The combination of different biocontrol agents to obtain synergistic or additive effects has also been tested in the field to control S. cepivorum, where simultaneous application of four selected species of Trichoderma (Trichoderma hamatum, T. harzianum, Trichoderma oblongisporum and Trichoderma viride), in association with fungicides, was shown to be effective for the management of white rot disease [14].…”