Incidence and pathology of common viruses of nerine in Tasmania

This is the first study of the incidence of common viruses within bulb stoc ks of nerine in Australia. Five viruses were frequently found within commer cial stocks but were never associated with obvious viral symptom expression in the field. This study found cucumber mosaic virus (CMV) infections of N erine flexuosa, and nerine virus Y (NeVY) infections of N. flexuosa, N. bow denii and N. fothergilli which we believe to be new host records. Virus inc idence varied with virus species, host species, and sample site but did not vary within the same bulb stocks over a 2 yr period. Incidence of the majo r viruses appeared to correlate with the efficiency of transfer from mother bulb to offsets, suggesting that virus status in Tasmania may be largely d etermined by the incidence of viruses within original planting material and by subsequent vegetative spread. No effect of the most frequent virus infections was found on the efficiency of flowering, flower quality, and dormant bulb fresh weight in N. flexuosa and N. fothergilli with the exception of a small (16.8%), but economically unimportant decrease in scape length of N. flexuosa co-infected with NeLV and NeVY. It is concluded that current virus infections in nerine in Tasman ia pose little commercial significance to the developing cut flower industr y, however discovery of NeYSV in one sample of Lycoris aurea warrants monit oring to ensure that spread of this important pathogen does not occur.