Abstract
The use of Trichoderma isolates with efficient antagonistic activity represents a potentially effective and alternative disease management strategy to replace health hazardous chemical control. In this context, twenty isolates were obtained from tomato rhizosphere and evaluated by their antagonistic activity against four fungal pathogens (Fusarium oxysporum f. sp. lycopersici, Alternaria alternata, Colletotrichum gloeosporoides and Rhizoctonia solani). The production of extracellular cell wall degrading enzymes of tested isolates was also measured. All the isolates significantly reduced the mycelial growth of tested pathogens but the amount of growth reduction varied significantly as well. There was a positive correlation between the antagonistic capacity of Trichoderma isolates towards fungal pathogens and their lytic enzyme production. The Trichoderma isolates were initially sorted according to morphology and based on the translation elongation factor 1-α gene sequence similarity, the isolates were designated as Trichoderma harzianum, T. koningii, T. asperellum, T. virens and T. viride. PCA analysis explained 31.53, 61.95, 62.22 and 60.25% genetic variation among Trichoderma isolates based on RAPD, REP-, ERIC- and BOX element analysis, respectively. ERG-1 gene, encoding a squalene epoxidase has been used for the first time for diversity analysis of antagonistic Trichoderma from tomato rhizosphere. Phylogenetic analysis of ERG-1 gene sequences revealed close relatedness of ERG-1sequences with earlier reported sequences of Hypocrea lixii, T. arundinaceum and T. reesei. However, ERG-1 gene also showed heterogeneity among some antagonistic isolates and indicated the possibility of occurrence of squalene epoxidase driven triterpene biosynthesis as an alternative biocontrol mechanism in Trichoderma species.
Highlights
The genus Trichoderma has gained immense importance in past several decades due to its antagonistic ability against wide range of plant pathogens and growth promotion in crop plants
Antagonistic activity of Trichoderma isolates Antagonistic capabilities of the Trichoderma isolates were assessed by the growth inhibition of four fungal pathogens (FOL, AA, Colletotrichum gloeosporoides (CG) and Rhizoctonia solani (RS)) through the dual culture assay
Twenty isolates of Trichoderma collected from rhizosphere soil of tomato were phenotypically, biochemically and genetically characterized to identify and screen the most efficient antagonistic against four tomato fungal pathogens (FOL, AA, CG and RS)
Summary
The genus Trichoderma has gained immense importance in past several decades due to its antagonistic ability against wide range of plant pathogens and growth promotion in crop plants. These sequences appear to be located in distinct, intergenic positions around the genome elements (Mohapatra et al 2007) Methods based on such repetitive elements have been used for studying the diversity in the ecosystem, presenting the phylogenetic relationship between strains and discriminating between microorganisms those are genetically close to each other (Rai et al 2015; Kashyap et al 2016). These methods have not been extensively used for the differentiation of Trichoderma spp. The confirmation of the differences will help in revealing the biodiversity, origin, and evolutionary processes of Trichoderma under different biological niches
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