Specific Isozyme Marker of a Virus Resistant Barley Derived from Interspecies Cross Between Hordeum vulgare and H. bulbosum THE RESISTANCE AND SUSCEPTIBILITY REACTIONS OF BARLEY VARIETIES OF JAPAN AND WEST-EUROPE TO CHINESE BARLEY YELLOW MOSAIC VIRUS (BaYMV) Ultrastructural Studies of Barley Mesophyll Cella lnfected with Barley Yellow Mosaic Viruses