Cycas necrotic stunt virus, a new member of nepoviruses found in Cycas revoluta host range, purification, serology and some other properties.

Abstract

A new disease of cycas (Cycas revoluta) characterized by dwarfing and twisting of young leaves and chlorotic or necrotic spots on mature leaves was shown to be caused by a small spherical virus of 28nm in diam. By sap inoculation the virus was easily transmitted to some Chenopodium spp. in which chlorotic local lesions and systemic mottlings were produced. The host range of the virus was limited. Out of 39 species in 12 families tested, only ten species in Aizoaceae, Amaranthaceae and Cycadaceae were susceptible to the virus. The virus was transmitted through seeds from diseased plants of C. amaranticolor and C. serotinum at the rate of 29 and 82 per cent, respectively. The virus was inactivated after 10min at 60-65 C, and 18-24 days at room temparature. The dilution end point lay between 1×10-3 and 5×10-3. The virus particles were observed to show a linear arrangement in tubular structures in both cytoplasm and plasmodesmata, and to form crystalline aggregates in cytoplasm. The virus was purified from systemically infected C. quinoa leaves, and the purified virus was separated into three components after sucrose density gradient centrifugation. The properties of the virus were very similar to those of nepoviruses so far described, but no serological reaction was found between the virus and nine known nepoviruses tested. The virus was concluded to be a new member of nepoviruses, and was named the cycas necrotic stunt virus. This disease designated as the cycas necrotic stunt disease was newly described.