Another Canna virus discovered

Samples of Canna plants coming into the Central Science Laboratory's (CSL's) plant clinic have been found to carry a new virus - Canna yellow streak virus (CaYSV), so reports The Commercial Greenhouse Grower in its June 2007 edition. Dr Rick Mumford, the senior virologist at CSL, said "Typical virus symptoms include flecking, mosaic, leaf streaking and necrosis, which in severe cases renders plants unsaleable. With individual Canna specimens retailing for 15-20 pounds, the losses for commercial growers can be large."

Until CaYSV was found, four different viruses have been reported to infect Cannas, with Canna yellow mottle virus traditionally considered the most important.

Rick Mumford explained: "We are still trying to establish how widespread this new virus is, but preliminary findings show it is consistently found in plants showing severe virus symptoms and hence is likely to be an important cause of virus disease in Canna."

My first feeling was one of despair, yet another virus! But, in fact, this is good news. At last scientists are starting to find out what is wrong. The virus has obviously been there, unrecognised, for many years, now at last it is identified. This also explains why plants that had been cleared of virus in laboratory testing, were subsequently found to exhibit the symptoms described by Doctor Mumford.

We are one step nearer to being able to establish which are clean specimens and which are carrying virus, and corrective action in the form of segregation and culling then becomes a fully practical possibility.

Incidentally, Dr Mumford mentioned 5 separate viruses. The RHS laboratories at Wisley identified three viruses after the 2002 Canna Trials (CYMV, BYMV and Tomato aspermy virus), and I seem to have missed the identification of another one in the interim.