Articles
NARCISSUS TIP NECROSIS VIRUS
In naturally infected narcissus plants no symptoms were found in flowers and leaves were either symptomless (e.g. cvs Fortune, King Alfred, Magnificence, Yellow Cheerfulness) or produced necrotic symptoms (e.g. cvs Barrett Browning, Goblet, Flower Record, Redmarley). The effect of NTNV infection on the growth of narcissus has yet to be assessed but because plants which develop leaf symptoms senesce prematurely infection probably reduces bulb weight increase.
The virus is manually transmissible to narcissus but failed to infect forty-six other plant species from fourteen families.
Good yields of virus were obtained from narcissus by differential centrifugation of leaf extracts clarified with either di-ethyl ether, n-butanol or a mixture of n-butanol and chloroform.
The virus particles are isometric c. 30 nm in diameter, sediment as a single component with a sedimentation coefficient (s20o,w) of 123 S, have a buoyant density of 1.356 g/cm3 and contain a single RNA species of mol. wt 1.6 x 106. Two major polypeptides of mol. wt 42 000 and 39 000 were observed in polyacrylamide gel electrophoresis.
In these properties, NTNV most closely resembles the tombusvirus group but showed no serological relationship either to the type member of the group, tomato bushy stunt virus, or to six putative members of the group, carnation mottle, carnation ringspot, elderberry latent, pelargonium flower break, Saguaro cactus and turnip crinkle, or to thirty-six other isometric plant viruses.
Thus it seems likely that NTNV is a previously undescribed virus.
The natural mode of transmission of NTNV is unknown and apart from the one instance when affected plants in a field stock of cv.
Goblet occurred in patches, diseased plants usually appear to be randomly distributed in crops.
It is suggested that, like other tombusviruses in vegetatively propagated crops, natural transmission of NTNV is rare and spread probably occurs by contaminated equipment and hands during cultural operations and flower harvesting.