Virus yellows –
a big problem that can be solved!
Virus yellows has been known since the 1930s as a sugar beet disease that can drama-tically reduce the sugar yield. After the most recent years of phasing out effective plant protection products (neonicotinoids) for seed treatment of sugar beet seed, the virus yel-lows has returned as a serious plant disease in several European countries. E.g. in France the yield has decreased with up to 70% in some areas due to this disease.
DLF Beet Seed has therefore intensified the breeding of new varieties with virus yellows resistance/tolerance, and in the DLF Beet Seed gene pool strong tolerance and resistance to virus yellows has been identified. Progress is so good that we will soon be offering the beet grower the first varieties that are partially resistant to virus yellows.’
The disease can be caused by single or mix in-fections of aphid transmitted viruses such as beet mild yellowing virus (BMYV), beet chlorosis virus (BChV) and beet yellows virus (BYV). Many different aphid species can transmit one or more of the viruses, but the principal vector is the green peach aphid (Myzus persicae Sulzer).
In surveys during the past years, it has been shown in e.g. France, that mix infections of the mentioned viruses occur frequently. The combinations can change from year to year. Therefore, it is important for DLF Beet Seed to breed for resistance/tolerance to more than one of the viruses.
The breeding story started in the 1980s
DLF Beet Seed could already in the past provide farmers with varieties resistant to the disease, and during the 1980s and 1990s there were dedicated breeding programs on virus yellows. During the past years extensive breeding is again ongoing.
A high number of elite lines, sources from gene banks, own wild beet collections, test hybrids and hybrids are now continuously under evaluation for tolerance/resistance to the different types of viruses.
The evaluation is done in greenhouses, in semi field trials and in field trials. The plants are inoculated and the virus content is quantified in the plants and development of symptoms is observed. In the inoculated field trials the yield is measured.
The Greenhouse Experiment
Set up of the greenhouse experiment where plants were inoculated with different combinations of BMYV, BChV, BYV and BtMV. The plants were kept in the tents during the whole experiment to avoid contamination.
Plants are inoculated with viruses in semifield trials and development of symptoms are observed. Tolerant and resistant plants stay green.
VYtech® variety and traditional varieties in field trials with artifi-cial infection with virus yellows. The VYtech® variety has a low virus content and retains its green colour compared to traditional varieties which, when infected, have a high virus content and be-come strongly yellow.
Virus yellows can be seen as at least three different diseases and it is a challenge to combine all genetic components to get a good final product, but in the near future DLF Beet Seed will be able to provide sugar beet growers with the first hybrids partially resistant to virus yellows.
VYtech® varieties on the market in 2023
The first partially resistant varieties will be available on the market in 2023. The varieties will be marketed under the name VYtech® varieties.
In 2024, we plan to launch a range of VYtech® varieties on the market with slightly different profiles to suit different markets.
The VYtech® varieties will protect the crop and give a good yield in case of a viral infec-tion, but during the first years on the market the yield is expected to be slightly lower than non-resistance varieties in the areas without infection.
DLF Beet Seed expect that the yield in the VYtech® varieties will compete with non-resistant varieties by 2025.
Mix infection of four viruses in Vytech® (a) and Vy Suspectible (a) Lines
Plants of a VYtech® line (A) and a susceptible VY line (B) inoculated with BMYV, BChV, BYV and BtMV.