Vining Pea Trials - Perfecting peas

Research and trials are adding to the understanding of latest vining pea varieties, planting populations and their genetic make-up, says Sue Jupe.

Trial day updated growers on the progress made in assessing this year's varieties - image: Sue Jupe
Trial day updated growers on the progress made in assessing this year's varieties - image: Sue Jupe

This year is proving a challenging one for vining pea growers. Wet, cool weather that had an impact on crop establishment in spring is now playing havoc with harvest scheduling. Speaking at the recent Processors & Growers Research Organisation (PGRO) trial day at Thornhaugh near Peterborough in mid June, principal technical officer Stephen Belcher reported plots were lagging two-and-a-half weeks behind last year.

Alongside vining pea variety trials, the PGRO continues to attract funding and collaborate on broad research topics. These range from optimising plant populations for the best returns and evaluating new varieties sown at appropriate commercial timings to exploring nitrous oxide emissions and honing the make-up of the perfect pea for the future.

With a steady, although reducing, stream of new material from breeding companies, the 2012 main vining pea variety trial featured 17 varieties. These were selected from the previous preliminary trials plus four standards - Avola for maturity, Bikini for yield as well as Oasis and Ambassador. Plots were sown in 10 rows, 15cm wide at a target population of 90 plants per square metre at the Thornhaugh site on silty loam. The trial was replicated at Holbeach, in south Lincolnshire, on a silt soil.

"Thirteen of this year's varieties complete their assessment in 2012, including two conventionalleaved Limagrain UK varieties - Terrain and Tennessee," says Belcher. "Maturing a day ahead of Bikini, Terrain yields a little below it and produces similar size grade. Slightly later, Tennessee matures two days after Bikini, delivering slightly higher yields of similar size grade peas."

New Zealand varieties

Genesis, Cawood and Columbus are varieties bred at the New Zealand Institute for Plant & Food Research. Maturing a day after Bikini, Genesis produces higher yields of medium to large size grade peas. Cawood matures three days after Bikini with high yields of similar size grade peas. Five days after Bikini, and a day later than Ambassador, yields of Columbus have been similar to Bikini but smaller in size.

The trial featured two van Waveren varieties - Sienna and Fantasy. "A conventional-leaved second early, maturing five days later than Avola, Sienna produces high yields of large peas with a short haulm, like Bikini," Belcher explains. "Semi-leafless and maturing two days after Bikini, Fantasy delivers large grade peas with yields below Bikini."

Two semi-leafless varieties from Pure Line Seeds - PLS 560 and PLS 566 - both matured at the same time as Bikini. PLS 566 has been the higher yielding, a little below Bikini. Crites Seeds semi-leafless variety CMG 419 AF matures three days after Bikini, producing slightly lower yields and significantly smaller peas.

Nunhems Seeds semi-leafless variety Compana showed Bikini maturity and stood well. Yields are lower than Bikini but in the small to medium size grade. Also semi-leafless, Hyperion from Seminis matured three days later than Bikini, producing small to medium grade peas. Frisbee from Maribo is a second early, maturing three days after Avola but producing higher yields, although lower than Bikini. Produce is smaller than Avola in medium to large size grade.

With vining pea sowing dates dependent on their scheduled maturity, variety choice is key to ensuring a programmed harvest. In its third and final year, a Horticultural Development Company (HDC) funded project is evaluating varieties sown at appropriate commercial timings. Featuring eight varieties, and comparing these to Avola and Bikini for yield, maturities range from zero to +5.

"Unfortunately, two trials in the series were lost due to rook damage," says Belcher. "Sown after it had stopped raining on 11 May, the birds took the seeds from the plots before they emerged. The project concludes this year and the data will be added to the advisory leaflet on vining pea varieties. The additional information will give growers greater confidence in maturity and performance of varieties."

While the Martin pea tenderometer has been around for many years, the new digital instrument is starting to find a place in the industry. An HDC-funded project aims to standardise tenderometers by validating the digital version as a reliable substitute for the original Martin.

Target populations

In its second year, PGRO researchers are exploring recommended vining pea target populations to evaluate whether they should vary according to variety and/or plant type. The work is taking into account how much seed costs versus produce prices.

The trial features Biktop and Oasis sown at populations of 70, 90, 110, 120 and 140 plants per square metre at Thornhaugh. It is replicated at Holbeach, together with the petit pois variety Waverex. Plots of Oasis at Thornhaugh ranged from 89 to 176 plants/sq m and gave 91-105 tenderometer readings. "Any increase in yield covered the cost of extra seed giving the same return on investment," says PGRO principal technical officer Jim Scrimshaw.

At Holbeach, readings for the Oasis plots were 120 and populations ranged from 69-127 plants/sq m. Yields varied little from 16-16.3 tonnes per hectare and the optimum population proved to be 86 plants/sq m. Plots of Waverex at Holbeach produced tenderometer readings of 100-105. Populations of 67 plants/sq m produced yields of 9.5t/ha, whereas at 133 plants/sq m yields were 11t/ha. "Yields increased as population rose," says Scrimshaw. "The target population is between 100 and 110, statistically there was no different at populations of between 100 and 133."

Biktop at Holbeach produced excellent tenderometer readings of between 100 and 105. According to Scrimshaw, taking into account seed cost, yield and tenderometer readings, the best return would be at 99 plants/sq m.

Taste and tenderness

Scientists, pea breeders and the food industry are collaborating to discover how taste and tenderness can be determined by biochemistry and genetics. They are working together to hone the make-up of a perfect pea in a £1.5m project coordinated from the John Innes Centre (JIC) in Norwich. As well as finding ways to develop improved pea varieties, the project is studying the likely impact of greater uptake of legume farming on nitrogen fertiliser use.

To improve the market opportunities of peas, the Sustainable Arable LINK project is exploring quality determinants in vining and marrowfat pea seeds. It involves many industry players including Penguin, Princes, Birds Eye, Limagrain, Thermo Fisher, the PGRO, Aberystwyth University Institute of Biological, Environmental & Rural Sciences, the Biotechnology & Biological Sciences Research Council and JIC.

In simple terms, the project aims to assist pea breeding by improving understanding of the genes involved in producing good-quality peas. Researchers have characterised some of the changes occurring in peas leading up to, during and after optimum harvest time. Tenderometer readings are currently relied on to decide when to harvest. However, specific proteins and compounds can also be detected in peas at the optimum stages for harvest and these tests could prove to be more accurate. Compounds contributing to taste and flavour include saponins, associated with bitter flavours.

Peas from John Innes' gene bank are being characterised for the genes controlling concentrations of sugars in the crop. Teams of scientists are looking at variation and novel germ plasm in 3,000 lines.

"With a good understanding of how genes convert the sugar in peas to starch, we plan to exploit mutations to block this pathway," says JIC researcher Dr Claire Domoney. "Currently, 95-99 per cent of commercial pea lines in the UK rely on mutation 'r', where junk DNA inserted into a particular gene blocks part of the pathway leading to starch."

At the PGRO event, she explained that another "rb" mutation has also been identified where part of a gene is missing, which effectively blocks the pathway at an earlier stage. "While exploring 'r' and 'rb' mutations, researchers are using mutagenesis to create new mutations," says Domoney.

Standing in front of the recombinant inbred lines in the PGRO trial plot at Thornhaugh, Dr Mike Ambrose of the JIC says: "These plots display three weeks' variation in flowering time as well differing heights, flower and pod colour - they are very variable, which is exactly what we need." He continues: "In modern cultivars there is not enough variation to dissect the genetics. From a morphological point of view, these have lots of variation. Extensive mapping has been studied for the best part of three years."

Other research

As well as the research projects discussed in detail at the open day, Processors & Growers Research Organisation technical director Dr Anthony Biddle outlined other current research areas including managing Sclerotinia, identifying critical levels of phosphate for vining peas and involvement in a major new collaborative project exploring improvements in drought resistance.

Agronomy advice

Based at Thornhaugh near Peterborough, the Processors & Growers Research Organisation (PGRO) is the UK centre for applied research into temperate peas, beans and other legumes for animal feed and human consumption. Formed in the 1940s, it provides growers and agronomists with independent, well researched, practical agronomy advice on growing legumes and other field vegetables.

A registered charity, PGRO is funded by voluntary levy contributions, contract research and Government research grants. Managed by a board of trustees appointed from the NFU, grain traders, food processors and other agribusinesses, income is also derived from laboratory services and conference/meeting facilities.

According to PGRO chairman Mark Leggott, UK vining pea hectarage has had a few recent highs and lows but currently stands at around 30,000ha - down slightly from the previous year due to the tonnage reduction of one processor. Meanwhile, levy income remains fairly static at around £117,000 for vining peas.

Commenting on the challenges ahead, Leggott says: "We are well placed to collaborate in bids for sustainable ventures. We remain a thriving and relevant research station."


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