Targeted selection of Trichoderma antagonists for control of pepper Phytophthora blight in China

Abstract

Pepper Phytophthora blight, caused by Phytophthora capsici is the most destructive soilborne pathogen, can lead to serious economic losses in pepper. Some strains Trichoderma isolates can act as potential biocontrol agents and are able to control many plant diseases in crops. The present study was carried out to screen valid Trichoderma isolates against P. capsici and to study potential modes of action of involved. In vitro, the most successful isolate, Trichoderma HNA12, was able to inhibit P. capsici development and significantly reduce sporulation, inhibition effect for 62.3 % compared to the control treatment. Trichoderma HNA12 was further evaluated under field condition and, over a 2-year period, was able to significantly suppress P. capsici on root and stem parts giving a similar level of disease control as the fungicide thiram, and Trichoderma HNA12 showed the lowest disease index and significantly increases the plant stem heights and the fresh and dry weights. The mechanisms of action of Trichoderma HNA12 were postulated to be a combination of competition for space, production of antifungal metabolites and possible mycoparasitism. Mycoparasitism appeared to contribute to the aggressive nature of Trichoderma HNA12 against P. capsici when observed under scanning electron microscope. Trichoderma HNA12 was identified as T. Harzianum by molecular identification technology. The strategic approach described in this paper demonstrates an efficient way of screening microorganisms for biocontrol activity and validates the notion that certain microorganisms can be antagonistic to a variety of plant pathogens.