C-T LO and C-Y LIN

Taiwan Agricultural Research Institute, Wufeng, Taichung, Taiwan

Background and objectives
Trichoderma spp. are known antagonists of several soilborne and airborne plant pathogenic fungi under both greenhouse and field conditions [1]. In some cases, the increased growth response induced by Trichoderma species has been reported for various crops including bean, cucumber, pepper, carnation [2]. The objectives of this study were to determine how many isolates of Trichoderma species in Taiwan could promote plant growth, and to determine the biocontrol efficacy of Trichoderma spp. to control Rhizoctonia solani and other soilborne pathogens.

Material andmethods
Trichodermaharzianum, T. aureoviride and T. virens were separately mixed with peat sandy loam soil (sand : loamy soil : peat moss = 1:1:1). The soil mixtures were then filled in soil boxes. Cucumber, luffah and bitter gourd seeds were separately sown in soil boxes (one seed per box). Seedling height, leaf area, root exploration and root dry weight were investigated to determine if the increased growth response could be attributed to the isolates of Trichoderma spp. on the plants. Sixty isolates of Trichoderma spp. from rhizosphere soils of several crops were tested for linear growth rates and dual culture with R. solani. The ability of these isolates of Trichoderma spp. to inhibit the Rhizoctonia root rot of carnation was then tested in greenhouse.

Results and conclusions
In greenhouse tests, these isolates of Trichoderma species significantly increased from 9-59% in seedling height, 58-159% in root exploration, 27-38% in leaf area, and 15-42% in root dry weight for 15 days after sowing seeds of bitter gourd. Similarly, these Trichoderma isolates also increased seedling growth of luffah and cucumber. Twelve isolates among the isolates tested overgrew and parasitized to the pathogen.

The ability of 12 isolates to inhibit Rhizoctonia root rot of carnation was tested in the greenhouse. A bran/peat preparation of various Trichoderma species, applied to either loamy soil or sandy soil with peat (1:2), efficiently suppressed root/stem rot induced by R. solani AG-4 in carnation. Disease reduction of up to 80, 66.7 and 66.7% was obtained in carnation after adding T. harzianum , T. aureoviride and T. virens, respectively. Consequently, the results indicate that various species of Trichoderma from Taiwan may not only promote plant growth, but also reduce Rhizoctonia diseases of crops.

1. Adams PB, 1990. Annual Review of Phytopathology 28, 59-72.
2. Chang Y-C, Baker R, 1986. Plant Disease 70, 145-148.