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

Luis Alvarado-Marchena And,William Rivera-Méndez

doi:10.1590/18069657rbcs20150454

Luis Alvarado-Marchena And, William Rivera-Méndez

Open Access

https://doi.org/10.1590/18069657rbcs20150454

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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.

Highlights

Species from the genus Trichoderma include a vast number of strains with economic importance based on their biological control potential, being commercialized as biopesticides, biofertilizers, and soil enhancers
The objective of this study was the identification, at a species level, of five different strains of Trichoderma isolated from soil samples gathered at garlic (Allium sativum) and onion (Allium cepa) production fields from the region of Llano Grande in Cartago, where microorganisms had not been implemented, through the study of the ribosomal RNA regions ITS1, 5.8S and ITS2; as well as the in vitro determination of the antagonistic effect of each strain on Sclerotium cepivorum Berkeley
The amplified sequences from each strain were compared to the GenBank database through the “Nucleotide Blast” search, where the A, B and C strains (GenBank: KM456214, KM456216 and KM456217, respectively) evidenced a 99 % similarity with the KF723005.1 T. asperellum accession number

Summary

Introduction

Species from the genus Trichoderma include a vast number of strains with economic importance based on their biological control potential, being commercialized as biopesticides, biofertilizers, and soil enhancers. They are non-pathogenic microorganisms that provide protection against fungal diseases caused by Phytophthora, Rhizoctonia, Sclerotium, Pythium, and Fusarium genera (Peteira et al, 2001); they promote high yields in crops (Ezziyyani et al, 2004a). The strain characterization and identification at a species level is the first step required to select the correct microorganism, since it determines which isolate presents a higher antagonistic effect over another particular organism (Rubio et al, 2005)

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