Clones of `Blomidon' strawberry (Fragaria × ananassa Duch.) exhibiting a range of June yellows symptoms were grown in field plots to measure effects on productivity and fruit characteristics. Self-pollinated seedlings grown from these clones were evaluated for symptom expression as an additional measure of severity of June yellows. Large differences in yields were recorded among clones, ranging from 1.9 to 14.7 t·ha–1 in 1994 and 8.4 to 28.3 t·ha–1 in 1995. Clones with severe symptoms produced smaller fruit than clones with slight symptoms in 1994 but not in 1995. Small differences existed for the titratable acidity of the fruit but not for soluble solids concentration. The frequency of normal green seedlings among selfed progeny ranged from 48% to 98% and was negatively correlated with symptom severity ratings of the parent clones. Severity ratings and selfed seedling abnormality rates were good predictors of fruit yield. No clones of `Blomidon' were free of June yellows.
Andrew R. Jamieson and Katherine A. Sanford
Andrew R. Jamieson, Kevin R. Sanderson, and Roger J.A. Tremblay
P.G. Braun, P.D. Hildebrand, and A.R. Jamieson
Twenty-five cultivars of red raspberry (Rubus idaeus L.) and one purple raspberry (R. occidentalis L. × R. idaeus L.) were evaluated for their resistance to fire blight caused by Erwinia amylovora (Burr.) Winslow et al. Actively growing raspberry cane tips were wound inoculated with three isolates of the pathogen and disease development was assessed over 17 days. Three methods of evaluating resistance were used: area under the disease progress curve (AUDPC), a weighted AUDPC called the area under the disease severity curve (AUDSC), and lesion length. A wide range of resistance levels was observed, but no cultivars were symptomless. Primocane-fruiting cultivars tended to be more resistant than floricane-fruiting ones. Of the three E. amylovora isolates used in this study, one was significantly more virulent than the other two, but no cultivar × isolate interaction was detected.