Hetero­ge­neous wheat popu­la­tions: Stability for the future

Agron­o­mist Dr Odette Weedon from the Univer­sity of Kassel is scep­tical. Even today, poor weather condi­tions often prevents maximum yields and optimum quality. Bakeries and mills are increas­ingly reporting a decline in baking quality. “At the moment we are spoilt, but in the future, we will likely be discussing yield and protein stability more, rather than the best yield,” says Odette.

Hetero­ge­neous popu­la­tions – also known as popu­la­tion vari­eties, modern landraces, or composite cross popu­la­tions (CCP) – offer a solu­tion. Derived from the offspring of multiple hybrids that have been cross-bred, they are prop­a­gated over several years, resulting in excep­tional genetic diver­sity compared to conven­tional, uniform wheat vari­eties.

Diver­sity brings stability

“If a wheat variety grows in a field where all indi­vid­uals are genet­i­cally almost iden­tical, this means that each plant can only ever act in the same way, no matter what the stress factor is”, she explains. Within a popu­la­tion, however, there are always some plants that thrive under given condi­tions. Their yield and quality can buffer those of less well-performing indi­vid­uals. This diver­sity increases resis­tance to pests, diseases, and weather extremes and ensures more stable yields over time. However, there are always plants that cope less well with the condi­tions – this is the price for the higher buffer poten­tial.

“Popu­la­tions are a form of risk insur­ance against varying envi­ron­mental condi­tions,” adds Annette Haak, also an expert in hetero­ge­neous popu­la­tions. “While elite wheat often loses its baking quality in poor years, popu­la­tions continue to deliver the required qual­i­ties rela­tively reli­ably – even if not the top yields like elite vari­eties,” says Annette. Another benefit is that popu­la­tions can be repro­duced directly on-farm, giving growers greater inde­pen­dence.

Still a niche, but with poten­tial

Until now, this poten­tial has mainly been utilised in organic farming. So far, EU rules for conven­tional produc­tion are still catching up. Between 2014 to 2021, the commer­cial­i­sa­tion of hetero­ge­neous popu­la­tions was only allowed on a trial basis. Only since 2022 has an EU regu­la­tion on hetero­ge­neous plant mate­rial provided legal certainty that allowed breeders to market these seeds, even though they do not have plant variety protec­tion.

“Popu­la­tions simply do not meet the unifor­mity and stability criteria required for stan­dard vari­eties,” explains Annette. Instead, they go through a simpli­fied approval process, known as noti­fi­ca­tion. Under Regu­la­tion (EU) 2018/848 on organic produc­tion, hetero­ge­neous popu­la­tions may be sold as ‘organic hetero­ge­neous mate­rial’ (OHM).

As popu­la­tions are not protected by plant breeders’ rights, large conven­tional breeding compa­nies are unlikely to invest in their further devel­op­ment in the future. Breeding there­fore remains organic and focuses on cultivation under low-input condi­tions. However, because popu­la­tion breeding has hardly been econom­i­cally viable to date, it also falls short of its poten­tial, with too few breeders involved in it. Odette points out that like, conven­tional vari­eties, popu­la­tions should be contin­u­ously improved.

Despite these circum­stances, both experts see great poten­tial for the future including for conven­tional farmers. “Popu­la­tions will make it into wide­spread cultivation,” believes Annette. “It’s amazing how well popu­la­tions keep up with modern vari­eties, even though some of them are so old and so few breeders are engaged in this prac­tice,” adds Odette.

Hetero­ge­neous popu­la­tions in the field

But how do hetero­ge­neous popu­la­tions perform in the field? In the BAKWERT project (2020-2023), scien­tists, bakers, farmers, and millers tested hetero­ge­neous wheat popu­la­tions from cultivation to processing. Funded by the Federal Organic Farming Scheme, researchers from the Univer­sity of Kassel and the Compe­tence Centre of Organic Agri­cul­ture Baden-Würt­tem­berg (KÖLBW) compared two popu­la­tions – Brandex and EQuality  – with the organic elite wheat variety Aris­taro.

Across 10 farms, the popu­la­tions aver­aged EQuality: 5.8 t/ha on Equality and Brandex at  5.6 t/ha, and achieved higher yields on average over the two trial years than Aris­taro (5.1 t/ha). Condi­tions varied widely in 2021 and 2022: first wet, then dry. The popu­la­tions also matched or exceeded baking quality vari­eties seen in many organic national variety trials.

Researchers attribute this to struc­tural diver­sity. Differ­ences in ear height not only make the crop more perme­able to wind, allowing it to dry out more quickly, but also stabilise the crop – popu­la­tions barely tend to lodge under organic condi­tions. Each indi­vidual geno­type also has different resis­tance genes and can act as a barrier to prevent the spread of pathogens. Different root lengths also allow for better util­i­sa­tion of nutri­ents and water.

High stability among popu­la­tions

Organic farmer Volker Menthe from Hofgut Weiden in North Hesse confirmed the bene­fits. “On the contrary, there was no notice­able differ­ence in terms of harvest and yield.” Johannes Müller from the Müller-Oelbke organic farm has been using his own winter wheat variety mixtures for years. “However, the stability of the popu­la­tions was even better. We were very satis­fied, espe­cially with the qual­i­ties”.

BAKWERT also showed that the popu­la­tions were able to exploit loca­tion poten­tial better than the line variety Aris­taro. Compared with the line variety, they had a lower propor­tion of small grains and greater stability in all baking quality traits except for the falling number. “Cleaning and processing were just as effi­cient as with other wheat,” says Anna Schmieg from the OBEG Hohen­lohe growers’ asso­ci­a­tion. “Non-uniform genes do not neces­sarily mean non-uniform qual­i­ties.”

Another organic elite winter wheat popu­la­tion – Liocharls – has been included in the organic state variety trials in Baden-Würt­tem­berg for years. Yields and partic­u­larly the quality have remained stable over the years and across loca­tions. In compar­ison with other organic elite wheat vari­eties, Liocharls consis­tently ranks in the middle, says Annette.

Popu­la­tion Seeks Farm

In Germany, popu­la­tions remain a niche. Primarily, corn, wheat, and rye are grown as popu­la­tions. Winter wheat popu­la­tions are only found on about 300-400 hectares nation­wide. But repro­duc­tion and seed multi­pli­ca­tion are increasing each year. The currently noti­fied wheat popu­la­tions are grown for low-input condi­tions. With inten­sive fertil­i­sa­tion, organic popu­la­tions lose stability, as trials with Brandex show. For conven­tional farmers, the avail­able popu­la­tions are there­fore partic­u­larly inter­esting in chal­lenging loca­tions, such as water conser­va­tion areas, or with reduced fertil­i­sa­tion.

Popu­la­tions like Brandex which perform well across various condi­tions, are less suit­able for very dry, sandy soils, notes Odette. For such loca­tions, new short-season popu­la­tions are needed, like those already being devel­oped in Hungary and other coun­tries. She expects that in the future, vari­eties and popu­la­tions will be selected increas­ingly for local condi­tions tailored to suit the micro­cli­mate, cultivation system, or soil type, even with a single field.

A Valu­able Tool

Odette warns against narrowing the genetic base of crop breeding. “This restricts our genetic palette, which we actu­ally need in order to keep up. I find that really dangerous. Genetic diver­sity is the be-all and end-all of healthy, resilient agri­cul­ture – including within vari­eties.”

Hetero­ge­neous organic wheat popu­la­tions cannot yet compete with conven­tional high-perfor­mance vari­eties under optimal condi­tions, but they can with organic ones. “When we talk about stability, it’s a trade-off with maximum yields and quality,” she clar­i­fies. “I believe the real oppor­tu­nity for popu­la­tions lies in the fact that they can adapt better to diffi­cult condi­tions.” Popu­la­tions are not a replace­ment for line vari­eties, but a comple­ment. They are not a panacea, but they are a useful tool. “And we need as many tools as possible to be ready for the future.”