Effects of plant age and late-season hardening on development of resistance to winter crown rot in first-year sainfoin (Onobrychis viciifolia)

The effect of plant age and autumn growth on development of resistance in f irst-year sainfoin seedlings to winter crown rot caused by the low-temperat ure basidiomycete (LTB) was evaluated under field and controlled environmen t conditions during 1991 and 1992. Early-seeded sainfoin exhibited greater survival and had greater dry shoot weight than lace-seeded treatments. Sain foin plants, seeded in May of 1991 and 1992, were sampled from the Geld on three dates. between September and November, which represented three differ ent levels of cold hardiness in the first-year sainfoin. Plants exposed to the longest hardening conditions prior to:inoculation exhibited the highest percentage survival and shoot dry weight, and the lowest crown rot rating. These results demonstrated that early planting and exposure of plants to p rolonged hardening conditions in the autumn reduce injury due to winter cro wn rot in first-year sainfoin.