Species diversity of indigenous Trichoderma from alkaline pistachio soils in Iran

Abstract

The diversity of <em>Trichoderma</em> spp. was investigated in alkaline soils of pistachio orchards at different geographic areas in Kerman province, Iran. A total of 161 <em>Trichoderma</em> isolates were obtained and identified at the species level by their morphological characters and sequence analysis of their internal transcribed spacer (ITS) and tef1-α genomic regions. Totally, five species of <em>Trichoderma</em> were identified, including <em>T. harzianum</em>, <em>Trichoderma</em> sp., <em>T. virens</em>, <em>T. brevicompactum</em> and <em>T. longibrachiatum</em>. ITS nucleotide sequences could not find molecular differences between <em>T. harzianum</em> and <em>Trichoderma</em> sp. To identify and differentiate these two species, the sequences of the translation-elongation factor 1-α (tef1-int 4 (large)) were determined for five representative isolates of <em>T. harzianum</em> and <em>Trichoderma</em> sp. The TrichoBLAST similarity search using the tef1-α sequences of the <em>T. harzianum</em> and <em>Trichoderma</em> sp. isolates determined in this study, revealed as <em>T. harzianum</em>. However, there was 34 nucleotides difference in tef1-α sequences, between the two groups of isolates. According to the results, more than 80% of the isolates belonged to two species <em>T. harzianum</em> and <em>Trichoderma</em> sp. <em>T. harzianum</em> was introduced as the dominant species in soil of pistachio orchards. Logistic regression analysis showed no relationship between the soil properties (pH, EC) and presence of <em>Trichoderma</em> spp. (R2 = 0.26, Pr = 0.74, 0.26 > 0.05).