Effects of some Iranian Trichoderma isolates on maize seed germination and seedling vigor

Trichoderma species are commonly used as biological control agents against phytopathogenic fungi and some of their isolates are able to improve plant growth. In the current study, we evaluated some Iranian Trichoderma isolate cultural filtrates as well as their direct effect on seed germination and seedling vigor of maize (Zea mays L. cultivar B73); they are Trichoderma harzianum T 969, T. harzianum T 447, Trichoderma hamatum T 614, Trichoderma roseum T678, Gliocladium virens G525 and the unknown Trichoderma species isolate (Trichoderma sp. T) obtained from the soil of Moghan Area, Ardabil Province of Iran. The culture filtrates reduced the speed of seed germination, but no influence (p >= 0.05) was recorded at the final rate of the seed germination. When maize seeds were exposed to the Trichoderma spore suspension, all the Trichoderma isolates colonized the seed surface and inhibited the seed germination. The maize seed potted in inoculated soil did not emerge from the soil among all tested Trichoderma isolates, except for non-inoculated soil 30 days after potting. When Trichoderma conidia were added on the surface of soil near the emerged seed, significant (p <= 0.01) decrease of seedling treated separately with T. hamatum T614 isolate was observed on the leaves area, fresh root and shoot weight, compared to the non-inoculated seedling. Whereas T. hamatum T447 and T. harzianum T969 reduced markedly (p <= 0.01), seedling fresh root weight and fresh shoot weight were respectively increased as compared to the control. Trichoderma isolates had no influence on chlorophyll content in leaves and root length as well as stomata conductivity, except for Trichoderma spp. isolate T that increased stomata conductivity of seedling significantly (p <= 0.01).