Frequency and Distribution of Trichoderma spp. in the Rice (Paddy) Fields of Mazandaran Province, Iran

Samples were collected from soil and as well from phyllosphere of rice plant and subjected to dilution plate technique on RBSF Trichoderma selective medium. A total of 202 Trichoderma isolates were obtained from rice fields at different geographical locations distributed all over Mazandaran Province. Single spore isolates were obtained and genomic DNA extracted from all the isolates using DNA extraction kit. For an identification of isolates, morphological as well as molecular characteristics were studied. Morphological identifications were accomplished through morphological keys and subsequent descriptions. For molecular identification, the Internal Transcribed Spacer (ITS) region of the rDNA gene complex, including ITS1, the 5. 8S rRNA gene and ITS2 was amplified using primers ITS1 and ITS4. To identify the isolates at the species level, ITS sequence analysis was carried out for all isolates with the aid of the program TrichOKEY 2. The identified isolates belonged to six species of: Trichoderma harzianum, T. virens, T. atroviride, T. hamatum, T. brevicompactum and T. asperellum. More than 90 percent of the isolates belonged to species T. harzianum and T. virens. Therefore, these two important biocontrol agent species of plant diseases, are the most common ones occurring in the rice (paddy) fields. T. harzianum is the most dominant Trichoderma species observed in rice phyllosphere while T. virens being more abundant in soil. None of the isolates of the four remaining species were isolated from phyllosphere. In addition, all T. atroviride isolates, except for one, originate from the eastern part of the Mazandaran province.