Reduction of latent infection of strawberry anthracnose by long-term cold seedling storage below freezing.

OKAYAMA K., HIRAYAMA Y.

doi:10.3186/jjphytopath.79.269

The incidence of strawberry anthracnose, caused by Glomerella cingulata (Colletotrichum gloeosporioides), is increasing nationwide in Japan. The fungus, which overwinters in latently infected strawberry plants can act as an inoculum source in nursery beds next year. We monitored isolation frequency of the fungus on semiselective medium from latently infected plants in December, February and April and studied the effect of cold conditions on mycelial growth and the influence of long-term cold storage on infected strawberry plants. The isolation frequency of G. cingulata from plants latently infected with strawberry anthracnose was remarkably decreased after overwinter. The isolation frequency from infected strawberry plants placed in open field was lower than those placed in a plastic house. To further study this reduction, we pre-incubated colonies of G. cingulata on PSA and stored them at −2°C, then transferred a 6-mm mycelial disk from each colony to PSA at 25°C; after 21 days, the fungus had died. The isolation frequency of G. cingulata from pre-inoculated petioles and from pre-inoculated plants remarkably decreased after cold storage at −2°C for over 90 days. And after cold storage for 180 days, the fungus of G. cingulata was not isolated from any part of the plant (leaves, petioles, base of petioles or crowns). These results show that the infection frequency of strawberry anthracnose is significantly reduced by long-term cold storage and indicate that latently infected strawberry plants can become pathogen-free by this treatment.<br>

Reduction of latent infection of strawberry anthracnose by long-term cold seedling storage below freezing.

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