Infectious diseases of almond with special reference to the Mediterranean area ¹

Abstract

The major and most widespread virus‐induced disorder of almond is a complex disease called mosaic. The disease is characterized by a variety of symptoms ranging from bright chrome‐yellow (calico) to chlorotic discolorations, localized necrosis of the leaf blade, leaf curling, bud failure, fasciations, rosetting, stunting and bushy growth. Three ilarviruses, apple mosaic (ApMV), prune dwarf (PDV) and prunus necrotic ringspot (PNRSV), are associated with almond mosaic throughout the Mediterranean, and are involved to different extents in its aetiology. Apple chlorotic leaf spot trichovirus (ACLSV) may also be present in mosaic‐affected plants, and is sometimes associated with a chlorotic leafroll condition. Two epoviruses, tomato ringspot (ToRSV) and tomato black ring (TBRV), have been reported from the USA and Europe as the agents of diseases called yellow bud mosaic and enations, respectively. Plum pox potyvirus (PPV) and another filamentous virus, prunus latent virus (PLV), can also infect almond. Brown line and decline, a putative phytoplasma disease, occurs in California, together with the leaf scorch induced by the xylem‐limited bacterium Xylella fastidiosa. A stem pitting lot associated with nepovirus infection and a graft‐union necrosis apparently not caused by phytoplasmas have been reported from Italy. Infections by hop stunt viroid (HSVd) were recently reported from Spain.

The Incidence and Genetic Diversity of Apple Mosaic Virus (ApMV) and Prune Dwarf Virus (PDV) in Prunus Species in Australia

“…ApMV infection in many Prunus trees is characterised by yellow discolorations, line or oak-leaf patterns, and vein banding of leaves, but it may also be latent [ 9 ]. ApMV infection causes significant crop yield reduction of up to 25% in some commercial Prunus species [ 10 ]. PDV infection can induce a variety of symptoms which may include chlorosis, mosaic, ringspot symptoms on leaves, and stunting [ 7 ].…”