Necrotic Ring Disease of Japanese Iris (Iris kaempferi Sieb.), A New Disease Caused by Japanese Iris Necrotic Ring Virus.

A previously undescribed virus, named Japanese iris necrotic ring virus (JINRV), was detected in 27 out of 52 cultivars of Japanese iris (Iris kaempferi Sieb.). The virus was transmitted mechanically but not by the aphids Myzus persicae and Rhopalosiphum padi or through soil. It caused necrotic spindle-shaped streaks or rings in the leaves of Japanese irises and latent local infection in I. sanquinea and I. laevigata, but did not infect any other species out of all 40 species of thirteen plant families tested in total. JINRV particles were isometric about 35nm in diameter and showed rounded outlines with rough surfaces when negatively stained in uranyl acetate. In ultrathin sections, virus particles could be consistently observed in the cells of most tissues of infected Japanese iris leaves. They occurred in the ground cytoplasm of which they were scattered or in clusters in the central vacuoles in some cells