Abstract
Biocontrol agents like Trichoderma play a vital role in controlling soil borne fungal pathogens either by killing or suppressing through antibiosis. The present study was designed to investigate the morphological, physiological and molecular characteristics of Trichoderma asperellum collected from different locations of Bangladesh. Rhizosphere soil samples of 49 crops (rice, spinach, brinjal, lentil, sundari, cane, mustard, marigold, tomato, bitter gourd, taro, red amaranth, banana, okra, jute, papaya, malta, tobacco, betel leaf, maize, nut grass, tea, asthma plant, litchi, bottle gourd, cotton, sissoo, onion, wheat, cabbage, hedge bean, broccoli, sweat gourd, german grass, napier grass, data shak, pointed gourd, pineapple, watermelon, sugarcane, jackfruit, sweat potato, dhaincha, til, garlic, chilli, mango, chickpea and natishak) were collected from 36 districts (Satkhira, Khulna, Bagerhat, Jhenaidah, Jessore, Kushtia, Barisal, Patuakhali, Jhalokati, Pirojpur, Comilla, Chittagong, Cox's Bazar, Khagrachari, Sylhet, Moulvibazar, Dhaka, Gazipur, Manikganj, Rajbari, Faridpur, Mymensingh, Tangail, Jamalpur, Rajshahi, Natore, Pabna, Sirajganj, Bogra, Chapainawabganj, Rangpur, Gaibandha, Kurigram, Lalmonirhat, Dinajpur and Thakurgaon) of Bangladesh. A total of 88 isolates of T. asperellum were collected from the 109 soil samples out of which 15 isolates (TR9, TR11, TR25, TR27, TR45, TR52, TR56, TR64, TR70, TR77, TR78, TR79, TR82, TR85 and TR87) were selected to characterize their morphological and physiological features as well as their potentiality against some important soil borne fungal pathogens. Out of 15 isolates of T. asperellum, 4 isolates viz. TR27, TR45, TR70 and TR85 were selected for molecular characterization using of ITS region and TEF nucleotide sequencing. Based on morphological, physiological and molecular featuring T. asperellum was identified. All the 15 Trichoderma isolates yielded the highest mycelia growth and spore density/ml at 30°C and pH 7.0. The isolates yielded better mycelial growth on sucrose, while the lowest growth was observed on lactose. Different types of salts and conventional fertilizers significantly increased the mycelial growth of the T. asperellum. From the Molecular based identification of four isolates of T. asperellum isolate TR27 showed the highest mycelial inhibition against Fusarium oxysporum (97.03%), Sclerotium rolfsii (87.61%) and Pythium aphanidermatum (89.33%) in dual culture followed by isolates TR45, TR70 and TRss. In pot experiment, all four T. asperellum isolates (TR27, TR45, TR70 and TR85) were identified as potential biocontrol agents against F. oxysporum, S. rolfsii and P. aphanidermatum. Moreover, T. asperellum isolates TR27, TR45, TR70 and TR85 resulted disease reduction by 72.04%, 72.96%, 68.74% and 74.97%, respectively against the above mentioned soil borne plant pathogens. Finally it may be concluded that these four isolates of T. asperellum viz. TR27, TR45, TR70 and TR85 can be successfully used as effective biocontrol agents against F. oxysporum, S. rolfsii and P. aphanidermatum. But further study at field levels need to be carried out for their confirmation.