NIAB Set Onion Demonstration - Breeding remains strong in sets

Sets bridge the gap between stored and new season crop, reducing the need for imports, says Sue Jupe.

Hylander by Bejo: the late brownset variety is mildew resistant but it has not been put through its paces in recent mildew-free years - image: HW
Hylander by Bejo: the late brownset variety is mildew resistant but it has not been put through its paces in recent mildew-free years - image: HW

Breeding progress remains strong in sets, an important sector of the UK onion market that is helping to reduce imports by bridging the gap between stored bulbs and the new season crop. This year's NIAB set onion demonstration in July, assessing field and storage potential, boasted a record number of plots.

Conditions have been somewhat problematic for the crop this year. "The plots were slow to get underway, with planting delayed due to wet and cold weather," says NIAB vegetable specialist Bruce Napier. "Then followed a prolonged cold and dry period and, when it finally warmed up, it remained dry.

"Lack of rainfall in subsequent months has made it particularly challenging at sites without irrigation, such as at this year's trial site near Spalding in Lincolnshire. As a consequence, the onions have fallen over earlier than at the replicated trials site in Suffolk, where there is irrigation."

NIAB trials manager Shaun Coleman explains: "These plots are hand-planted, because it's easier to get the right density and very difficult to machine plant short plots to get required population. Commercially, early sets are planted from January onwards, often into frosty ground, and harvesting begins mid to late June, depending on the geography, soil and weather.

"In particular, the early non-heat treated sets, which are normally planted mid to late February, were delayed. Meanwhile, heat-treated varieties are usually planted mid March. This year, all trial plots were hand planted in mid March. Considering the Lincolnshire trials site does not have irrigation, the bulb size is good."

These Horticultural Development Companyand set company-funded trials were held courtesy of R Oldershaw, sandwiched in the centre of a large commercial onion crop. On 6 July, growers and seed company representatives gathered to assess the performance of 26 brown and red varieties supplied by the English Set Company (ESC), Allium & Brassica Supplies (ABS) and Elsom Seeds (Bejo). All three have promising new selections.

The 16 brown varieties include two newcomers - mildew-resistant Hylander (Elsoms) and a very early brown set ABS106. The 10 red plots include new ABS varieties - Garnet and Red Queen.

"Mildew needs warm and wet conditions," explains Napier. "With little around this year, the two resistant brown set varieties - Santero (ESC) and Hylander - haven't been put through their paces. In certain years, mildew resistance would be crucial."

Brown sets

The trials feature three very early brown set varieties. Tending to be thin-skinned, they are not recommended for storage. Having produced some good yields, VCS6003 (ESC) produced below average yields last year. Equally early, ABS101 is characterised by its fine, dark erect foliage and produces respectable yields for an early.

Making its debut in the trials, ABS106 is a promising newcomer maturing a week later. "From what we've seen it looks very early," says Napier. "Early varieties don't tend to store well, so growers need to have a market to shift it relatively quickly."

Slightly later but still in the early slot, Forum (Bejo) has produced average yields in past NIAB trials. "Last year Forum had a problem with rots - although it was dry through June and July, the heavens opened when it was harvested," says Napier. "In previous years, rots have not been a problem."

Characterised by its pale colour and thin-skinned bulbs, Alpha (ABS) is generally slow to sprout but can rot. Last year yields were a little down, but it was only planted on the Suffolk trials site, which is lower yielding.

Fractionally later in maturity is Elite Jagro, produced in France by ABS, and Jagro, produced in the UK by ESC. Proving high yields in previous NIAB trials, Elite Jagro produces large uniform bulbs, maturing two weeks after ABS106, but is not a variety lending itself to storage. With the same genetics, Jagro produces similar results.

Main slot

The trials feature seven varieties looking to take a share of the main maturity slot. A few days earlier than Sturon, Elite Rumba (ABS) offers similar qualities, namely uniformity, well protected bulbs and suitability for storage.

All three set companies have their own Sturon selections. A good reliable variety, all three are jockeying for position over yield and quality. "Sturon is characterised by producing good quality for storage to Christmas or the end of January - but you wouldn't want to store longer in an ambient store," says Napier.

According to last year's trials, Setton (ABS), VCS5004 and VCS6005 all produced average yields of uniform well-protected round bulbs suitable for storage.

Both late varieties - Santero (ESC) and Hylander F1 (Bejo) - offer the bonus of mildew resistance. "With two relatively mildew-free years, neither has had an opportunity to show its true worth," says Napier.

"Now in its second year in the trials, Santero has produced below average yield - in a mildew year it will get the benefit of green foliage for longer." Commenting on newcomer Hylander, he says it appears to be quite late maturing, because the foliage was still quite erect at the time of the open day on 6 July.

Red sets

"Although only accounting for approximately 20 per cent of set crops, red onions tend to attract a premium," says Napier. As with early brown varieties, early maturing red set varieties are not renowned for their storage potential.

Results from last year showed Reddawn (Elsoms), although very early, achieved very high yields and scored well for uniformity. With similar maturity, Red Emperor - produced in France by ABS and in the UK by ESC - produced average yields of pale, thin-skinned bulbs.

Red Barron continues to dominate UK red onion production, both drilled and from sets. Originally available from Elsoms, sets are now produced by all three companies. "An open-pollinated variety, Red Barron produces an assortment of shapes and sizes, but yields are good and it stores reasonably well," says Napier. "Hybrids have to compete with it."

He is keen to see how Broer variety Hyred performs this year, having not performed as well as was hoped in 2008. In other years it has yielded well, producing a uniform globe shaped bulbs.

Its second year in trials, Red Queen (ABS203) produced a smaller yield than last year - although data was only available from the lower yielding Suffolk site. "Red Queen may prove to be earlier than some of the others in the main/late slot," says Napier. "We don't have any storage data available yet."

Offering greater uniformity than Red Barron, the hybrid Kamal (ESC) falls in the main/late maturity slot. An average yielder, it stores well. Another ESC newcomer produced in the UK, Romy, is characterised by its uniformity, good quality and storage but has below average yields.

Bred by ABS and produced in France, Garnet is a promising newcomer to the reds trial. It appears to have a slight bolting issue this year, believed to be due to temperature changes causing the crop to stop start. However, bolting can generally be resolved with heat treatment. "While not an early variety, it is too early to say which slot Garnet falls into," says Napier.

As several set varieties are available from more than one company, the country where the sets are produced has become an important marketing point of difference. The ESC, based in Norfolk, produces its sets at isolated sites throughout the UK.

"We employ very tight fungicide programmes and set production is under our control," explains the ESC's Bob Lawrence. "Export markets are opening up for us - we are trading with Sweden, Czechoslovakia and Poland."

Commenting on this season, Lawrence is not alone in forecasting that yields will be down at sites without irrigation. "Success will depend on several factors - when the sets were planted, the site and whether the crop has had access to irrigation," he says.

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