I had thought they were kaput with the recent shakeout of rose nurseries. However, I got a tour of the UC Davis Foundation Plant Services a few days ago and just outside their door is an AARS test garden that was installed ‘not too long ago’.
FPS is where virus indexing is performed, virii are eliminated and virus-free stock is maintained. I got a chance to witness the process, pretty cool. I can’t help wondering whether the installation of an AARS test garden twenty feet from their side-door is a sign that the industry plans to try to clean up its act.
I’ll do my best, Dr. Kuska, although I think mostly they are still using the protocols that were established back when the booklet was updated.
They focus mostly on grape vines, some other fruit trees especially prunus, strawberries and, to a much lesser degree than in the past, roses. One interesting development is that the USDA has been sending grape cultivars originating in Georgia (the country, not the state) to the FPS lab.
Virus indexing is done using a variety of techniques including infecting hyper-susceptable hosts which are observed for visible tissue symptoms; and ELISA and PCR screening using target sequences developed at FPS.
Virii are eliminated using one of three techniques.
Apical meristem excision and culture is the first thing they try because it requires the least effort and gives the best results. The idea here is that virii infect cells at some distance below the apical meristem so if you can isolate the apical meristem it is likely to be clean.
Heat treatment is another technique where a plant is grown at elevated temperatures it can barely tolerate but which the virii cannot. The drawbacks are that it sometimes kills the patient and it takes a very long time, usually months and months.
Oddly enough, one way they eliminate virii is by clonal propagation. Simply put, if you culture enough buds (~100) some small number of them (two or three maybe) will be virus free. The drawback is space, labor and the need to index all the test plants.
I learned how to graft one bit of strawberry vine onto another - honest! I didn’t have my camera but with luck I will have photos to share later on that proves it and shows some of the lab and grounds at the Foundation Plant Services.
Of particular interest (to me) is that Davis is able to get virus free roses from buds. This follows logically from the discovery around 2000 that the viruses were not distributed evenly in the plants.
It would be nice if Davis looked at this further with the idea of optimizing the conditions (what time of year should one take the buds to get the best yield, where on the plants does one have the highest probability of having “clean” buds, would treatment of the virused plant with an aspirin (or other readily available chemical immune system boosters such as a commercially available harpin) result in more clean buds, etc.
If the odds can be increased, we may have a practical “home remedy” after all.
Thanks for this link Henry!! Wow, it would sure be great to use the strong heat of some of climates to help clean roses of viruses. Even if whole plants are not cleaned up, if we can at least take cuttings or buds from the terminals produced under higher temperature conditions that limit virus replication, it would sure be a great and accessible method for us. Maybe even a hot greenhouse!!
That’s something I often wondered about at Sequoia. At the height of the season, those greenhouses could hit 120 F and they frequently propagated from the plants growing under those conditions. Budding was done infrequently with cuttings making up 99% of everything created. You haven’t lived until you’ve been “pressure cooked” at 120 F with 100% humidity while being dragged through them to “look at THIS one!” Kim
120 F with 100% humidity from intermitant misting is the kind of climate that are prevalent in dutch propagators greenhouses were florist roses cuttings and stentings are rooted.