Molecular tagging of biocontrol fungus Trichoderma asperellum and its colonization in soil.
To conduct molecular tagging of the biocontrol fungus Trichoderma asperellum strain T4 and elucidate its colonization patterns in soil. We constructed an expression vector harbouring a hygromycin B-resistant gene (hph) and an efficient green fluorescent protein (egfp) gene. By applying Agrobacterium AGL-1-mediated genetic transformation technology, we conducted molecular tagging of T. asperellum and monitored the colonization dynamics of T. asperellum in soil. The results of tracking five independent transformants of T. asperellum indicated that its expansion rates ranged from 4·7 to 6·8 cm week-1 . After inoculation in soil, the quantities of T. asperellum could be maintained at over 10 × 104 CFU per gram soil in the first year. In the third year after inoculation, the quantities of T. asperellum in soil were still higher than 1 × 103 CFU per gram soil. In addition, molecularly tagged T. asperellum in soil in the second year (i.e. 12 months) after inoculation could still reach the biocontrol effect on cucumber Rhizoctonia rot by more than 74%. Trichoderma asperellum strain T4 is capable of effectively colonizing in soil and surviving for more than 1 year. This study has provided the scientific basis for applying T. asperellum as the biocontrol fungus for prevention and control of plant diseases.