INTERRELATIONSHIPS BETWEEN PLANT AGE, ROOT-ROT INFECTION, AND COLD HARDINESS IN WINTER WHEAT

Abstract

The effect of plant age and root rot caused by Bipolaris sorokiniana and Fusarium culmorum on the cold hardiness of winter wheat and the effect of cold injury on root-rot infection were studied during 3 years at Lethbridge, Alberta. The oldest and youngest plants were less cold hardy than those of an intermediate age. Root-rot damage predisposed plants to cold injury and, in turn, cold injury predisposed plants to root-rot damage. Winter wheat inoculated with B. sorokiniana and F. culmorum and seeded at the earliest dates had recovered from infection before exposure to the freezing treatment and, apparently because of delayed development, was more cold hardy than uninoculated wheat seeded on the same date. Results from cold-chamber and field studies indicated that the severe root-rot damage often observed in nearly mature winter wheat seeded early the previous year is not a direct result of heavy infection at or near the time of seeding but is secondary to winter injury that often occurs in early-seeded winter wheat.