the number of shoot tips (young flushes with at least five opened leaves) was counted and disease severity was rated for each of the tips: class 1=no symptom; class 2=mild chlorotic patterns and slight distortion of only the base of leaves; class 3=mosaic patterns on all leaves, leaf distortion; class 4=mosaic patterns on all leaves, leaf distortion, and general reduction in leaf size; class 5=leaves twisted/misshapen and stunting of whole plant. Means of shoot tip severities per plant were used in the analysis.