Viroids, Viruses and Phytoplasmas of Mulberry

Mulberry virus-like disorders which can be attributed to viroids, viruses and phytoplasmas have been known for many years and are currently reported from many parts of the world. With symptoms such as mosaic, vein clearing, yellowing, leaf deformation, dwarfing, necrosis and die back, they often affect plant health and are associated with economic losses. Variants of Hop stunt viroid, several viruses, and a Candidatus Phytoplasma species have been found associated with the diseases. Depending on the disease agent, transmission may take place by infected vegetative propagating material, pollen and seed, specific insects, nematodes and/or mechanical inoculation. However, in most cases the cause-and-effect relationship of disease symptoms is uncertain and Koch postulates still remain to be fulfilled. Management of mulberry virus-like diseases is mainly based on preventive measures such as quarantine, sanitation and selection of healthy propagating material. Despite presence of hundreds of mulberry varieties, information on genetic resistance to these agents is lacking.