Research: Disease and Climate Stress Resistant Wheat Varieties for Global South

The review looked at two different studies and found that using the ancient genetic diversity of wild relatives of wheat, which provides 20 percent of the world's calories and protein, could lead to weather- and disease-resistant varieties of the crop. This could ensure food security around the world.

The study led by the International Maize and Wheat Improvement Centre reveals that "long overlooked" wild wheat relatives have the potential to revolutionise wheat breeding, with new varieties capable of withstanding climate change and associated threats, including heat waves, droughts, flooding, and emerging and current pests and diseases.

Wild wheat relatives, which have endured environmental stresses for millions of years, possess genetic traits that modern varieties lack—traits that, when integrated into conventional varieties, could make wheat farming more possible in ever more hostile climates, the study published today (August 26, 2024) explains.

By farming the more resilient wheat, productivity could increase by an estimated USD 11 billion worth of extra grain every year, says the authors in the review paper titled ‘Wheat genetic resources have avoided disease pandemics, improved food security, and reduced environmental footprints: A review of historical impacts and future opportunities' published by the journal Wiley Global Change Biology.

The review suggests that the use of plant genetic resources (PGR) helps against various diseases like wheat rust and defends against diseases that jump species barriers, like wheat blast. It gives nutrient-dense varieties and polygenic traits that create climate resilience.

The study points to a vast, largely untapped reservoir of nearly 800,000 wheat seed samples stored in 155 gene banks worldwide that include wild varieties and ancient farmer-developed ones that have withstood diverse environmental stresses over millennia. This is despite the fact that only a fraction of this genetic diversity has been utilised in modern crop breeding.

The findings, according to co-author Mathew Reynolds, will have major implications for food security, particularly in the Sub-Saharan Africa region, where the world's most food-insecure populations live.

"The discoveries are very promising, as Africa has a lot of new environments in terms of potential wheat cultivation," he told IPS.

Based on the research findings, significant environmental benefits have been realised thanks to various scientific efforts that have successfully integrated wild genes into modern species.

The study acknowledges that the use of PGR in wheat breeding has improved the nutrition and livelihoods of resource-constrained farmers and consumers in the Global South, where wheat is often the cereal of choice in parts of Asia and Africa

"We're at a critical juncture," says Reynolds. "Our current breeding strategies have served us well, but they must now address more complex challenges posed by climate change."

He observes that breeding that helps in maintaining genetic resistance to a range of diseases improves "yield stability" and avoids epidemics of devastating crop diseases that ultimately threaten food security for millions.

"Furthermore, post-Green Revolution genetic yield gains are generally achieved with less (in the Global North) and often no fungicide in the Global South, and without necessarily increasing inputs of fertilizer or irrigation water, with the exception in some high-production environments," the study contends.

As a result, there has been an increase in grain yield and millions of hectares of "natural ecosystems" have been saved from cultivation for grain production. These include millions of hectares of forests and other natural ecosystems, Reynolds and colleagues found.

Equally promising is the discovery in some experimental wheat lines incorporating wild traits that show up to 20 percent more growth under heat and drought conditions when compared to current varieties, and the development of the first crop ever bred to interact with soil microbes that has shown potential in reducing production of nitrous oxide, a potent greenhouse gas. This enables the plants to use nitrogen more efficiently.

"The use of PGR wild relatives, landraces, and isolated breeding gene pools has had substantial impacts on wheat breeding for resistance to biotic and abiotic stresses while increasing nutritional value, end-use quality, and grain yield," the review further finds.

Without the use of PGR-derived disease resistance, fungicide use to fight fungal diseases, the main threat to the crop, would have easily doubled, massively increasing selection pressure that would come with the need to avoid fungicide resistance, the review finds.

Remarkably, it is estimated that in wheat, a billion litres of fungicide application have been avoided, saving farmers billions that would go into the purchase and application of the chemicals, it adds.

The authors note that as weather becomes more extreme, crop breeding gene pools will need to be further enriched with new adaptive traits coming from PGR to survive the vagaries of climate change.

These ‘definitely' include stubborn diseases that have plagued wheat farming in the tropics, such as the Ug99, a devastating stem rust fungal disease that, at its worst, wipes out entire crops in Africa and parts of the Middle East, Reynolds said.

Modern crop breeding, it says, has largely focused on a relatively narrow pool of star athletes—elite crop varieties that are already high performers and that have known, predictable genetics.

The genetic diversity of wild wheat relatives, on the other hand, offers complex climate-resilient traits that have been harder to use because they take longer, cost more, and are riskier than the traditional breeding methods used for elite varieties.

"We have the tools to quickly explore genetic diversity that was previously inaccessible to breeders," explains Benjamin Kilian, co-author of the review and coordinator of the Crop Trust's Biodiversity for Opportunities, Livelihoods and Development (BOLD) project, that supports conservation and use of crop diversity globally.

Among the tools are next-generation gene sequencing, big-data analytics, and remote sensing technologies, including satellite imagery. The latter allows researchers to routinely monitor traits like plant growth rate or disease resistance at unlimited numbers of sites globally.

While the collection and storage of PGR since early in the 20th century have played a key role, especially in breeding of disease-resistant plant varieties, the study concludes that a massive potential remains unexploited.

With wild relative varieties having survived millions of years of climate variance compared with our relatively recent crop species, more systematic screening is recommended to identify new and better sources of needed traits not just for wheat but for other crops as well, the study advises.

It calls for more investments in studying resilient wild varieties of common crops, taking advantage of widely available, proven and non-controversial technologies that present multiple impacts and a substantial return on investment.

"With new technologies emerging all the time to facilitate their use in plant breeding, PGR should be considered the best bet for achieving climate resilience, including its biotic and abiotic components," the authors said.

Source: Global Issues