Influence of crop species and edaphic factors on the distribution and abundance of Trichoderma in Alfisol soils of southern India

The effect of crop species and edaphic factors on the distribution of Trichoderma species in Alfisol soil under different agrosystems was evaluated. Each soil sample was assayed for nine abiotic factors and culturable microfungal populations. Fungal abundance was determined by dilution plate technique, and the identification of fungi was based on morphological characteristics. Pearson’s correlation coefficient was used to determine the relationship of association between these factors and the presence and abundance of Trichoderma species in each soil type. The abundance of soil fungi ranged between 7.0 × 103 and 13.6 × 103 colony forming units (cfus) per gram of dry soil. The population densities of the two Trichoderma species (T. koningii and T. viride) isolated in the present study varied significantly with crop species and their abundance (varied from 0.6 to 3.6 × 103 cfus g–1 dry soil). Twenty-two other colony-forming fungal types with an abundance ranging between 7.0 × 103 and 13.6 × 103 cfus g–1 dry soil were also isolated in the present study. As soil pH negatively influenced relative abundance of T. koningii, soil P and relative abundance of T. viride were significantly and positively correlated to each other. Further, relative abundance of T. koningiiwas significantly and positively correlated to relative abundance of Aspergillus fumigatus but negatively correlated to relative abundance of Stachybotrys atra. Likewise, a significant negative correlation existed between relative abundance of T. viride and Absidia glauca.