I noticed some subtle but consistent leaf malformation in some yacon that I am propagating this year. (This is not a named or publicly available variety – I use it for breeding.) I wasn’t sure if this was an intrinsic trait or externally caused, but I don’t remember seeing this before, so I decided to test the variety for a selection of common viruses for which we have had field positives in the past. 3 of 3 plants with deformed leaves tested positive for Tomato Spotted Wilt Virus by Immunostrip. 1 of 3 plants of the same variety without deformed leaves also tested positive. As far as I am aware, this is the first report of TSWV in yacon. I will follow this up with ELISA for confirmation in about a month. I didn’t notice any symptoms in the field last year, but if they remain subtle as the plant grows, they would have been easy to miss. I will grow one of the infected plants in isolation this year to see if it produces any more recognizable symptoms. If there are apparent symptoms, I will update this post with pictures.
There is probably something in our collection, as yet untested, that harbors TSWV, causing it to pop up occasionally in vulnerable plants. (The yacon in question grew near to Cannas that have not been virus indexed, so they are my top suspect and will be tested as soon as they sprout this year.) I doubt that this virus is widespread in yacon, because I have tested our varieties for it in the past, following positive tests in mashua. Nevertheless, you should be aware that TSWV can apparently infect yacon. This is a widespread virus that infects many species. It is not particularly surprising that it can infect yacon, since it also infects relatives like dahlia, Jerusalem artichoke, and sunflower. Thrips are the primary vector. The virus can be damaging in some plants. It is generally not a big problem in the northern part of the USA, but it can become a serious problem in greenhouses.
That’s all I know for now. This is probably not a matter of concern for the casual yacon grower, but it is a consideration for anyone trying to propagate virus free plants. I have randomly sampled the yacon varieties available for sale this year and got no positive results, so they are healthy within the limits of my testing. I will now begin routine testing for TSWV in yacon, at least for the foreseeable future.