As featured in Arable Farming Magazine
First beet variety with partial BMYV tolerance joins RL
by Arable Farming
A difficult Sugar Beet Recommended List trials season due to adverse weather and Covid-19 restrictions was reflected in lower yields of control varieties.
However, there were some bright spots, including the first variety with partial tolerance to beet mild yellowing virus joining the list. Marianne Curtis reports.
With virus yellows causing major yield losses for many beet growers last season, it is timely that a variety offering partial tolerance to beet mild yellowing virus (BMYV) is among the six new varieties which have been added to the 2022 British Beet Research Organisation/British Society of Plant Breeders Recommended List (RL) of Sugar Beet Varieties.
While some way off the highest yielding varieties on the list, scoring 93.
5% of controls on yield, Maruscha KWS is said to provide partial tolerance to BMYV and hopes will surely be pinned on higher yielding varieties with tolerance to yellowing viruses coming forward in the future.
BCN New variety Katjana KWS, tolerant to beet cyst nematode (BCN) and from KWS, comes in second highest yielding on the list (102.
7% of controls) after BTS 1915, which keeps its lead for the second year running (107.3%).
In third place on yield is BTS 3020 from Limagrain (102.2%),
followed by Wren from SESVanderHave (101.7%), and BTS 5770 (101.5%).
The latter offers the second highest sugar content on the list (17.6%) after BTS 4100 (17.7%).
Smart Rixta KWS (92.2%) is an ALS herbicide-tolerant variety.
The claims for tolerances are based on breeders’ data as these characteristics are not tested in the RL trials.
Maruscha KWS and Smart Rixta KWS are not recommend ed for early sowing (before mid-March), but both have shown low bolting characteristics AT 0/hectare and 14/ha, respectively, when sown after that date in the last three years of RL trials.
Katjana KWS and BTS 5770 produced no bolters in those three years of normal sown RL trials.
All of the other four new varieties are recommended for early sowing.
Of existing varieties, the highest yielder, BTS 1915, is not recommended for early sowing and neither are Evalotta KWS and Philina KWS.
Mike May, chairman of the RL board, says that as well as having several new varieties yielding closer to the top-yielding BTS 1915, it is good to see that a variety, Maruscha KWS, with tolerance to some of the yellowing viruses is on the list.
“The trend is still to higher yields and new traits are coming in.
We need virus yellows tolerance and may well need cercospora tolerance.
If we breed these in it will have some effect on the system and may mean lower yields in the short term when the focus is on breeding for these traits.
An example is BCN tolerance.
Breeding “When it first arrived varieties with it were lower yielding as the breeding was going into that but after that yields improved,” says Mr May.
KWS says it has made developing varieties with tolerance to virus yellows a breeding priority for the UK as it has one of the highest seasonal risks of infection of any country in Europe.
Breeding varieties with strong tolerance remains a difficult and complicated process because of the different nature of the strains that make up the virus yellows complex.
In 2020 trials there was slightly more bolting than in previous years but as well as previously mentioned new varieties, Daphna and BTS 4100 continued to show good bolting suppression, with no bolters recorded in normal sown trials in the last three years, says Mr May.
Selecting tolerant varieties – the pros and cons
While sugar beet varieties tolerant to diseases, pests or herbicides perform a useful function on land where there is a problem, there can be a yield penalty and they are not appropriate in all situations.
In the case of beet cyst nematode (BCN), Mike May, RL board chairman, says the first step is to establish whether land destined for sugar beet is infested.
“Get it tested before sowing.
If you have it there are three varieties available – go with those.
“Katjana KWS is one of the highest yielding varieties [102.7%] and BCN-tolerant and it can be sown early as can Daphna and Lacewing [also BCN-tolerant].
” Unlike BCN, there is only a small area of sugar beet land affected by the rhizomania AYPR strain and only one variety with tolerance – Philina KWS.
“If you have AYPR strain that’s what you should use,” says Mr May.
He cautions that the variety is prone to bolting in the early sowing slot.
For growers sowing into fields with a weed beet problem, ALS tolerant (Conviso system) beet is ‘worth thinking about’, adds Mr May.
“Otherwise work out how you are going to control weeds and the cost and balance it up.
” Herbicides Although the two ALS herbicide tolerant beet varieties on the RL have a lower yield than conventional varieties, they are only tested with conventional herbicides in RL trials.
When used with Conviso herbicides the yield is higher ‘but I’m not sure they get to 100%’, says Mr May.
Knowing what yellows virus is most prevalent in the local area can help with the decision on whether to go for virus tolerant beet In virus yellows trials in East Anglia over three years, Maruscha KWS demonstrated tolerance to beet mild yellowing virus (BMYV) as well as a positive response to beet yellows virus, according to KWS.
“It is an option if you know you get BMYV but not, perhaps, if you are not sure,” says Mr May.
“It is a low-yielding variety [93.5%] if you only get mild infection. It is the first of a line. It will never be perfect. It is very unlikely you will get tolerance to all three or four of the viruses if bred normally.”
New Recommended List varieties What the breeders say
BTS 5770 BTS 5770 has one of the best disease resistance packages available along with high sugar content, says Ron Granger, arable technical manager for Limagrain.
“Sitting among the pack for highest yields [101.5%], BTS 5770 offers flexibility in drilling, showing excellent early sown bolters and normal sown bolters characteristics.
“BTS 5770’s robust disease resistance profile illustrates how sugar beet breeders are raising the bar when it comes to breeding for disease resistance.
“The variety has an 8.1 rating for rust, 5.2 for powdery mildew and the limited available data from both Betaseed trials and the RL trials suggests it has better than average cercospora resistance.”
BTS 3020 BTS 3020 joins the RL as the early bird variety in the Limagrain portfolio having consistently delivered three years of very low bolter counts in the early sowing period before March 5, says Mr Granger.
“This result has been consistent over the last three years, including data from 2020, which we know was a higher year for bolting.
“BTS 3020 has high adjusted tonne yields of 102.2%, the third highest yielding variety on the RL, and again also offers a very good disease resistance package with a rating of 7.5 for rust and 4.6 for powdery mildew.”
Katjana KWS With an adjusted yield of 102.7% of controls, Katjana KWS is the highest yielding variety with tolerance to beet cyst nematode (BCN).
Ben Bishop, KWS country manager for sugar beet in the UK, says: “Katjana KWS is our highest-yielding BCN-tolerant variety and, with its excellent low-bolting performance, will appeal to those seeking to reduce their risk from this pest for which there are few conventional methods of control.
“We expect it to find interest among those with a history of BCN as well as those looking to protect the viability of land for the long term.”
Smart Rixta KWS As growers ponder weed control strategies without desmedipham, the appeal of the Conviso Smart system continues to grow, says Mr Bishop.
“The addition of Smart Rixta to the BBRO RL marks the solid progress KWS is making in bringing varieties to market with tolerance to ALS herbicides.
Smart Rixta KWS is a good fit to this system, with low bolting when sown in the main drilling window and an adjusted yield close to the average of control when grown under the Conviso Smart system.”
Smart Rixta KWS offers a yield of 92.2% compared with existing RL variety Smart Janninka KWS at 88.6%.
Maruscha KWS Sugar beet growers will have the option of growing virus yellows-tolerant beet in 2022 with the addition of Maruscha KWS to the BBRO RL.
But the distinct nature of the viruses involved means that tolerance to one form of the virus does not necessarily confer equal protection against another, says Mr Bishop.
“Maruscha KWS is the first variety to come through the KWS breeding programme with a level of tolerance that supports commercially-viable yields. It has recorded minimal losses to beet mild yellowing virus infection and respectable losses with beet yellows virus compared to those seen in susceptible varieties,” says Mr Bishop.
The introduction of varieties with tolerance to yellowing viruses represents an opportunity to protect yields but exploiting this possibility will also involve the continued use of cultural measures, such as good field hygiene, adds Mr Bishop.
Wren Wren, from SESVanderHave, has been developed and tested under UK conditions and tailored to the needs of Britain’s sugar beet growers, according to the company.
SESVanderHave UK managing director Ian Munnery says: “UK growers face the twin challenges of an uncertain market and variable weather patterns every season.
“Wren has been selected from our extensive breeding programme, in which we have invested in more than 25,000 trial plots each year in the UK over the 10 years it takes with conventional breeding to bring a new variety to market. Therefore, we are confident it will perform consistently well regardless of what the environment throws at it and show the durability you would expect from our varieties.”
Wren has the highest root yield (104.5%) of the new entrants, second to BTS 1915 (107.3%) on the RL.