Abstract
Experiments were carried out to develop suitable techniques for testing the resistance of cocksfoot varieties to Typhula ishikariensis and T. incarnata and to study the relationship between winter hardiness and the resistance to the disease. Experimental methods are as follows ; Seedlings were grown in a glasshouse for 10 weeks, followed by artificial hardening for 2 weeks at 3℃ with 8-h photoperiod. Then each plant received 0.37-0.72g of inoculum, and was incubated under a snow cover more than 50cm thick for 65 days to test the resistance to T. ishikariensis and 80 days in the case of T. incarnata. Plants were transferred into a glasshouse after incubation, and tops were clipped. Then the plants were allowed to recover for a month, and plant survival was recorded. The varieties from colder regions were more cold tolerant and were generally resistant to T. ishikariensis except for a few cases. The resistance to T. ishikariensis was closely related to the winter hardiness in Sapporo. On the other hand, the varietal response to T. incarnata did not always coincide with that to T. ishikariensis. Two south European varieties, Dora and Montpellier, were as resistant as the north European ones to T. incarnata. This contributed to a decrease in the overall correlation coefficient with winter hardiness. The highly positive correlation between the resistance to Typhula spp. and winter hardiness suggests that the primary factor for the wintering of cocksfoot in Sapporo is the resistance to Typhula spp.
