Red-leaf virus - a newly recognized virus disease of subterranean clover (Trifolium subterraneum L.)

Abstract

A previously undescribed virus disease, for which the name subterranean clover red-leaf virus (SCRLV) is proposed, affects subterranean clover (Trifolium subterraneum L.) in the northern and southern pasture belts of Victoria. The leaves of infected plants are red and the plants may collapse and die. The virus was transmitted by the aphid Acyrthosiphon solani (Kltb.), but not by the aphids Myzus persicae (Sulz.), Aphis cracciuora Koch, or A. gossjpii Glover. The virus was not sap-transmissible nor was there any evidence of transmission through subterranean clover seed. A. solani transmitted the virus to 45 cultivars of subterranean clover, and also to white clover (T. repens L.), red clover (T. pratense L.), strawberry clover (T. fragiferum L.), strand medic (Medicago littoralis L.), and barrel medic (M. trunculata L.). The virus was not transmitted to several other indicator species. The virus persisted in the vector after a moult and thus the mode of transmission is of the circulative type. The acquisition, transmission, and availability thresholds were 6 hr, 20 min, and 4 days respectively. After an acquisition feed, the virus had a latent period of about 12 hr in the vector. SCRLV resembles other members of the leaf-roll group of persistent aphid-borne viruses. The present cryptogram for the virus is */* : */* : */* : S/Ap.