INDUCED RESISTANCE TO ANTHRACNOSE AND CHANGES IN FREE AMINO ACID CONTENT IN MYCORRHIZAL STRAWBERRY PLANTS

Tolerance to anthracnose and the influence of symbiosis with arbuscular mycorrhizal fungi (Glomus mosseae) on free amino acid content were investigated in strawberry (Fragaria × ananassa Duch., cvs. Nohime, Nyoho, Sachinoka, Toyonoka, Hogyoku and Hokowase) plants. Ten weeks after AMF inoculation, mycorrhizal plants showed higher dry weights of both shoots and roots than did non-mycorrhizal ones in most of the cultivars. AMF colonization level was highest in ‘Nohime’, and no major difference appeared among the other cultivars. Four weeks after Colletotrichum gloeosporioides inoculation (14 weeks after AMF inoculation), the incidence, severity and disease index of anthracnose became lower in mycorrhizal plants than in non-mycorrhizal ones, regardless of the cultivars; the effects differed among the cultivars. As for free amino acid content, GABA, aspartic acid, threonine, serine, glycine and citrulline increased in mycorrhizal plants before Colletotrichum inoculation; the effect differed among plant portions. These findings suggest that induced resistance to anthracnose occurred through symbiosis with AMF in strawberry plants. In this case, the increase in free amino acid content in mycorrhizal plants might be associated with the disease resistance as a direct or indirect factor.