Abstract
In order to confirm the resistance of 'M16-AR 1, 2 and 3' to isolates of Alternaria alternata strawberry pathotype occurring in Tohoku and Hokkaido, 'M16-AR' lines were inoculated with 8 isolates of the pathogen collected from 8 municipalities in both districts.
Conidia of these 8 isolates were morphologically undifferentiable. However, the isolates differed slightly in their cultural characters.
As a result of inoculating each of 8 isolates into leaf blades of various test plants, black spot, a typical symptom of this disease was formed only on strawberry cvs. Morioka-16 and Robinson and the Japanese pear cvs. Nijisseiki and Shinsui. Thus, it was confirmed Ithat the host range of the isolates was not different from that of Alternaria alternata strawberry pathotype reported previously in Japan.
'M16-AR' lines inoculated with the 8 isolates were found to be resistant. Furthermore, these lines cultured for three years (1989 to 1991) under field conditions were not affected by Alternaria black spot of strawberry. Consequently, it seems that selections of 'M16-AR' lines may be the preferred cultivars to plant instead of 'Morioka-16' for Tohoku and Hokkaido in Japan.
