Abstract: To isolate the Alternaria tenuis Nees from infected leaves of Dendrobium devonianum Paxt. and study the biological characteristics of this pathogenic fungus. Isolated the A. tenuis Nees from infected leaves of D. devonianum Paxt. according to the method of Fang ZD first and then used PSA as basic media to study the effects of pH value, different carbon and nitrogen sources, temperature and illumination on mycelial growth and sporulation of A. tenuis Nees. Results :The optimal temperatures for mycelial growth and sporulation of A. tenuis Nees isolated from D. devonianum Paxt. were 25℃ and 20℃ respectively. Media with pH values between 5.0 and 6.0 were beneficial for mycelial growth and sporulation of A. tenuis Nees. Illumination did not have significant effect on its mycelial growth while daily alternation of 12 hour's lighting and 12 hour's dark at 25℃ gave the highest spore yield. PSA media supplemented with starch or ammonium nitrate provided best results for mycelial growth. PSA medium with glucose was suitable for sporulation of this fungus. The fungus inoculated on PSA media with other carbon and nitrogen sources produced very few spores. A. tenuis Nees isolated from D. devonianum Paxt. could be cultured on PSA media with pH values between 5.0 and 6.0, glucose and ammonium nitrate at 25℃ and under the daily alteration of half lighting and half dark.

Key words: Dendrobium devonianum Paxt, Black spot, Alternaria tenuis Nees, Biological characteristics

CLC Number: 

• S435.672