A selective medium for improving quantitative isolation of Trichoderma spp. from soil

A Trichoderma-selective agar medium (TSM) was developed for quantitative isolation of Trichoderma spp. from soil. Selectivity was obtained by using chloramphenicol as a bacterial inhibitor, and pentachloronitrobenzene, p-dimethylaminobenzenediazo sodium sulfonate and rose-bengal as selective fungal inhibitors. The TSM also contains a low concentration of glucose which still allows relatively rapid growth and sporulation of Trichoderma, enabling convenient and rapid identification of Trichoderma colonies. All the 15 Trichoderma isolates tested formed colonies and grew well on this medium. Recovery of Trichoderma from artificially inoculated soils was high and was not affected by soil type or by other microorganisms. A positive correlation was observed between Trichoderma added to soil and counts of Trichoderma colonies on TSM plates. When combined with a soil pellet sampler, the selective medium was also used successfully for recovery of the indigenous Trichoderma population of natural soils.