. For recording the head index (HBR index), the surface of the whole head was checked as follows: 0 = no symptom on the head surface; 1 = the symptoms only on the surface; 2 = symptoms on the surface and inside of leaf;3 = symptoms on the surface and inside of leaf, and form V-shape lesion; 4 = symptoms on the surface and inside of leaf, formV-shape lesion and veil discoloration.