Now firmly established as a regular fixture in many growers' diaries, the annual September Dutch open days held in north-west Holland by leading vegetable breeders once again attracted visitors from around the world - including a strong UK presence.

A key element of the week is the sheer diversity of material on display, with breeders showcasing everything from leafy salads and brassicas to root crops, onions and even sweetcorn.

Brassica ranges continue to dominate the events, something that is unsurprising given the local area's strength in production. This is underlined by Rijk Zwaan, which had a specific brassica field near Medemblik that mirrored the company's approach to catering for specific sectors.

One of the highlights of this display was the new red cabbage Resima RZ, the first of a new series building on Rijk Zwaan's strength with this particular vegetable. With a more intense internal colour than other varieties, the new variety is performing well and particularly excels at high densities (such as 60,000 plants/ha), producing a 1.2kg head weight. However, the company's Dick Van Pelt points out that it also works well at wider spacings in Germany.

Another development on display was a semi-savoy type designed as a cross between a white and savoy cabbage, but with a milder taste than typical savoy varieties - 29-409 RZ produces a 1kg head and is mild enough to be eaten as a salad. It is also ideal for stir-frying - a growing market in northern Europe, where white varieties can suffer from a longer cooking time.

Also at an experimental stage is a similar but larger trial variety that is claimed to have an even better taste and produces heads between 2.5kg and 3kg, although at the moment it is still unclear whether there is a real market demand for such a variety.

Tourima RZ is a pointed cabbage that is five to six days later than Sonsma RZ, itself an early variety, and has a wider base that makes it especially suitable for fresh sales rather than wrapping, where Sonsma is preferred. Tourima has proved particularly popular in France, but Rijk Zwaan continues to work on its range and further, more slender varieties are in the pipeline.

Rijk Zwaan's cauliflower breeder Cees Bregman says that autumn production appears to still be the main UK market, while the USA favours long-cycle types. He points out that the effects of climate change are already being seen with the later production window for cauliflower in northern Europe. "There is interest in long-cycle types to increase the harvesting window around the world," he explains. Consequently the company has established a new breeding programme to capitalise on these developments.

Broccoli breeding programme

Despite Rijk Zwaan's strength in cabbage, Bregman and Van Pelt are keen to point out that it continues to have an active broccoli breeding programme in Spain and Holland. There are also ongoing developments in minor crops including kohl rabbi (which enjoys strong sales in Germany and Eastern Europe), Romanesco and green cauliflower. While Romanesco continues to attract a significant following in the UK, it is proving a profitable line for Rijk Zwaan, which boasts a 60 per cent share of the European market.

Nickerson Zwaan showed a potential replacement for its Duchy Sweetheart pointed cabbage. Dutchman F1 is very similar but with improved taste and colour. At 70-75 days maturity, it is also more uniform than Duchy and suitable for higher-density planting for baby production. Alongside the Sweetheart types was Winterjewel F1 (formerly NiZ 15-824) - a new over-winter spring green type.

In its final year of UK trials is the new early cauliflower, NiZ 10-378 F1, designed for spring, summer and autumn production. It has performed well in summer screening trials in the Pfalz region of Germany, showing strong perforce for curd hairiness and giving a uniform cut. A compact base facilitates bagging and commercial seed is expected in 2012.

Also at an early stage of development - but showing promise - is broccoli NiZ 18-603 F1, which appears suitable for October sowing and displays good resistance to blindness. Nickerson Zwaan's Nick Bolton adds that it has good shelf life characteristics and is slow to yellow.

Nickerson Zwaan's carrot programme remains "very focused on the UK market", says vegetable seed sales specialist John De Soyza. An example of this is new variety Attillo F1 (formerly Vac 55 F1). "It has earlier maturity than previous Nickerson varieties," he adds.

"It also has enhanced cavity spot resistance, which has been confirmed in the last two years of Processors & Growers Research Organisation trials." Performing well on sandy soils, it displays some frost tolerance, something it shares with very late variety Eskimo F1.

"This year we harvested Eskimo from open fields after 15 degrees of frost," he adds. Having looked into the carbon emissions associated with producing strawed carrots over the whole growing season, de Soya remains hopeful that Eskimo has potential to be the UK's first low-carbon carrot.

In lettuce, Nickerson has high hopes for its Antarctica iceberg, says Bolton. "The objective was to breed a lettuce with long holding ability that could be cut over five to seven days. It's all about the harvest window and Antarctica is very reliable and slow growing. When everything else is dead you can still cut this." It boasts full Bremia resistance and strong tip-burn resistance.

Redsea F1 is a new second early red cabbage from Clause for the storage market. In the UK it has undergone trials with two large growers and produces an erect, well-protected head of 2.5kg to 4kg. "It's one of the first cabbages into store," points out Clause's John Ward, adding that the small core is ideal for maximising processing yield. "It's all good, useful leaf."

Brassicas are not limited to those above the ground and a new turnip, Clovis F1 (CLX 3632), brings hybrid uniformity to this specialist market. With a globe shape and strong purple colouration at the shoulder, the smooth-skinned variety will be commercially available in the UK for the first time next year, where its shape and colour are expected to prove popular with buyers.

Pumpkins ready for Halloween

With Halloween approaching, two new pumpkins are performing well. In the 20-24cm size, Gomez F1 fits the UK market requirement and has a strong handle-forming stem, typically producing two fruits per plant. Ward says it stores well with few losses and bulks uniformly with early September cutting.

For culinary use, the smaller Spitfire F1 has proved popular with growers since its commercial launch two years ago. The single yellow fruit on each plant turns to orange from mid July onwards and, at 15-17cm across, it fits in perfectly with supermarket requirements. Another advantage for growers is its ability to reduce the need for thermo-curing in a late year, adds Ward.

Also in the squash range is Tosca F1, a late maincrop courgette for open field production. High yielding, it produces up to 16t/acre of 21cm-long fruit that has a small flower scar and is held high up in the plant, protecting it from wind damage and rubbing.

The fruit is easily seen in the open plant structure and presented at an ideal angle for picking. The straight, dark-green fruit has proved popular with growers and it has topped the tables for quality yield in this year's National Institute of Agricultural Botany (NIAB) trials. Ward is confident that when grown for larger specification European markets, yields could exceed 70 tonnes per acre.

With its large demonstration field next to their production facilities and laboratories at Warmenhuizen, Bejo Zaden continues to hold one of the largest open days of the week, showcasing dedicated fields of both conventional and organic crops.

This year Bejo also underscored its commitment to developing a full range of varieties supplied as organic seed by holding a seminar on the Tuesday morning exploring the latest European developments in organic markets and research and development.

According to Bejo Germany director Pieter Gabriels: "Our complete range of organic vegetable seeds is helping the organic sector to create an integrated organic chain from farm to fork. We have more than 120 varieties of organic seed available and we are seeing an increasing demand for it."

On the trial field, Bejo displayed a number of promising carrot varieties, including the multi-coloured Rainbow F1 that produces a range of shades from white through to orange. Of more interest to most UK producers will be Newcastle F1 (formerly known as Bejo 2799), a new mid-early Nantes type that produces a good yield of bulky cylindrical carrots for maincrop production after approximately 110 days. Whether or not Newcastle will finally become a challenger to industry standard Nairobi remains to be seen, but it is likely to find a place in many production programmes. For earlier production, Nominator F1 is a very smooth Nantes type that matures just 96 days after sowing.

Like many other breeders, Bejo has a wide-ranging portfolio including red beet, fennel and radicchio. Red beet Pablo is still doing well in the UK market, but Rhonda F1 has higher sugar levels and should be sweeter to taste. Rhonda also has good bolting tolerance and is well shaped with a good internal quality and dark colour. Maturing after 119 days, it is recommended for drier areas, while Bettollo F1 (Bejo 2731) should perform better in continental and sub tropical climates.

New radicchio lines include Lava and Rubro (Bejo 2710), which Elsom's Keely Watson says would be "a better bet for the UK market. Rubro can be harvested from mid January until late February. It produced excellent quality heads during the extremely cold conditions in the winter of 2009-10." Fennel varieties Rondo and Orion have been around for a while, but Keely describes new variety Solaris F1 as "an all rounder that does early and late production".

Harvesting experience

The theme of S&G and Syngenta Seeds was innovation and "harvesting the company's experience". Head of vegetable seeds Michael Kester says: "Syngenta's vision is to have growers and partners play a central role in innovation in breeding, mechanisation and protection."

In terms of alliums, new leek 1683 F1 will be trialled next year and, subject to performance, could be commercially available in the UK for the 2012 season. It has a similar maturity date to Antiope, but with a dark blue-green colour.

Meanwhile, the company is hoping that new onion ONL 353 can repeat the success of NIAB award-winner Vision. "Our varieties are all about long-term storage," says Syngenta's Nigel Kingston. This is a trait shared by ONL 353, which performed well in NIAB trails last year and will be commercially available for the first time in 2011.

Syngenta has also put considerable effort into crop security, with a particular emphasis on club root resistance. "There is big pressure from club root in the UK," explains James Gray.

Under its TopRes brand, the firm has developed club root resistant varieties of Brussels sprouts, cauliflower and cabbage. "We want to encompass club root resistance in the crop range for all brassicas," adds Gray. Crispus is a club root resistant sprout for harvesting in October and November. As a hybrid, the plants have more vigour and better root development while still producing a large quantity of smooth buttons.

One of the key traits that white cabbage growers look for is consistency of head size, something which Kilazol and Kilaton both deliver. Kilazol is a 1kg cabbage for the fresh market, which Gray describes as a club root resistant version of Unifor, while Kilaton produces 2-3kg heads ideal for processing.

For cauliflower, Clarfiy and Clapton both boast club root resistance, with the summer/autumn variety Clapton being most suitable for UK conditions.

Since its launch, Syngenta's range of multi-leaf BellaGio salad varieties has proved popular with growers and processors. LS9424 is a new green BellaGio baby leaf with a high yield and good leaf volume when cut. It has a range of Bl 1 and 3-26 Bremia resistance and Nasonovia resistance.

Also new is LS9498, a brilliant dark-green oak leaf type with a strong colour and robust leaves. It is complemented by red oak leaf LS7994, which will be named Rougini for commercial production. It has an excellent dark cherry-red colour and full Bremia and Nasonovia resistance.