Barley yellow dwarf virus (BYDV) distributed widely in barley, wheat, rye, oat, maize, teosinte and foxtail millet showing a yellowing, redding or dwarfing in Kanto area. Wheat, rye, maize, teosinte and foxtail millet were newly recorded natural host plants of BYDV in Japan. New diseases named yellow dwarf or yellows for them. Two BYDV isolates from maize and oat were characterized by the aphid transmission, host range, physicochemical properties, serology and intracellular appearance. These two isolates were regularly transmitted by Rhopalosiphum padi and R. maidis, respectively, indicating that the isolates may be differ from other known isolates of BYDV.
A selective medium for isolation of Pseudomonas syringae (SPS), the causal agent of bacterial blossom blight of Kiwifruit was developed. The composition of the medium was as follows: NH4H2PO4 1.0g, KCl 0.2g, MgSO4⋅7H2O 0.2g, adonitol 2.0g, phenol red 20mg, methyl violet 1mg, pheneticillin potassium 50mg, cetrimide 10mg, agar 15g, pH 6.8 per 1.000ml of distilled water. Thirty two P. syringae strains pathogenic to Kiwifruit were grown on the medium and 31 strains showed convex colonies with entire margin. Color of the colonies was purple at the center and opalescent white at margin. One strain formed small opalescent white colonies. Colony forming efficiency of the medium was less than those of King's medium B. Twenty one isolates of Pseudomonas from Kiwifruit except P. syringae and 21 strains of phytopathogenic bacteria belonging to 5 genera were grown on the medium and they didn't grow with few exceptions which showed distinctive colonies from that of P. syringae. SPS was used for isolation of P. syringae from field-grown Kiwifruit. One hundred candidates were isolated and tentative characterization showed that all of them were identical with the P. syringae. Those results indicated that the possible application of the medium was useful for ecological studies of the bacterium in fields.