Detection and characterisation of bean yellow mosaic virus in corms of Gladiolus grandiflorus

Bean yellow mosaic virus (BYMV) could not be detected in corms of infected gladioli unless they were cut 6–60 days before testing. Detection after cutting was time- and temperature-dependent, was restricted to the cut area, and varied among cultivars. Virus could be recovered from uncut corms after storage for over 2 yr at 6 ^oC. BYMV in corms could be detected by enzyme-linked immunosorbent assay and by immunosorbent electron microscopy with antisera against a gladiolus isolate purified from gladiolus leaves or corms. It could not be detected in corms with antiserum against a lupin isolate which readily detected BYMV in gladiolus leaves. Protein subunits of corm-BYMV banded in SDS-PAGE as a single 31 000 dalton polypeptide, while leaf-BYMV produced a major 34 000 and several smaller polypeptides. Both major polypeptides retained the different serological properties of their source virions but their peptide maps indicated a common origin. It is suggested that the smaller polypeptide from corm-BYMV is a stable cleavage product of the intact leaf-BYMV coat subunits. Corm-BYMV, although lacking some of the antigenic properties of leaf-BYMV, was still infective.