Articles
FREESIA LEAF NECROSIS: SOME OF ITS MYSTERIES REVEALED
FLN can be recognized by chlorotic spots and stripes that start at the leaf tip, and then spread over the whole leaf.
Later, these chlorotic areas turn grey-brown, and become necrotic.
In mildly affected plants only the lower leaves show some light, chlorotic symptoms.
Flowers and corms do not seem to be affected by FLN. The disease is transmitted through the soil, probably by the chytrid fungus Olpidium brassicae. Until recently it was not possible to transmit the agent to freesia or any other plant by aphids, sap inoculation or by grafting, and no virus-like particles were found in diseased plants by electron microscopy.
On the whole very little was known about the agent that causes FLN. Now we can report some positive developments.
During a restricted period of the year it is possible to provoke virus-like symptoms on Chenopodium quinoa, Nicotiana hesperis-67A, and N. occidentalis-P1 by mechanical inoculation with sap of freesia showing FLN symptoms.
Back inoculations to freesia have been unsuccessful so far.
Attempts have been made to purity the FLN agent from freesia, and from test plants.
Only from freesia some positive results can be reported.
The purification procedure has to be short, because the agent seems to disintegrate easily.
The infectivity can be enhanced, but it is till now not possible to purity the agent sufficiently.
In electron microscopic studies virus-like particles were found that may be associated with FLN.