When the Growing Gets Tough, the Tough Get Pre-breeding
Much like dogs have wolves, our familiar crops have undomesticated relatives growing in the wild, which often have useful traits not found in their cousins grown on farms. As global food systems face increasing threats from climate change, scientists and breeders are figuring out how to use these wild relatives to produce new crop varieties that are more productive and resilient.
The latest issue of the journal Crop Science is dedicated exclusively to recent efforts to use crop wild relatives in pre-breeding for this purpose, all conducted through the Crop Wild Relatives (CWR) Project, a global initiative led by the Crop Trust.
“This special edition of Crop Science on the successful use of crop wild relatives in pre-breeding is incredibly significant,” says Benjamin Kilian, who leads the CWR Project. “The crops in these projects provide much of the sustenance that humanity relies on. Without developing varieties that can better tolerate a changing climate, many of the foods we see regularly on our plates could disappear.”
The research included in the special issue covers all the activities along the pre-breeding continuum—from isolating desirable genetic traits like disease resistance from crop wild relatives, to introducing them into new seeds that are then easier to cross with modern varieties. Thirteen major crops are featured: alfalfa (lucerne), barley, banana, carrot, chickpea, durum wheat, eggplant, finger millet, grasspea, pearl millet, rice, sorghum and sweetpotato.
Crop wild relatives often look very different from their cultivated counterparts—and are normally not even edible—but they offer a potentially valuable source of the genes needed to breed new, hardier seeds.
Humans have been taming the wild for millennia, domesticating plants to serve as food, or forage. But plant domestication has narrowed the genetic diversity of our crops in comparison with their wild ancestors, with scientific plant breeding often continuing this process in recent decades. The less genetic diversity crops have, the lower their potential to adapt to challenges, such as shifts in seasons, more intense rains, droughts, pests, and other effects of the changing climate.
“If we want to have crops that can cope with these challenges—if we want to ensure an ongoing food supply—then we need to go back to the wild, and give pre-breeding with crop wild relatives long-term investment,” says Kilian.
The starting point for pre-breeding is to investigate collections of genetic diversity housed in genebanks, and to fill any gaps that may exist. For example, researchers found that wild species of bananas in Papua New Guinea had not been fully conserved in genebanks, leading the group to collect 31 new samples of eight different Musa species. These samples included individuals with unique traits expected to be useful for drought tolerance breeding programs, which will be explored in future studies.
The next step in pre-breeding is to evaluate crop wild relatives for genes linked to useful traits. Traits that can make plants more tolerant to abiotic stresses, such as drought, heat and salinity, have been found in alfalfa, carrot, durum wheat, eggplant, sorghum and sweetpotato. Resistance to biotic stresses, such as pests and diseases, have been found and explored in barley, finger millet and grasspea. Traits in crop wild relatives can also be used to bolster nutrient content, as shown for chickpeas.
Then there is research that looks at combinations of useful traits. Using crop wild relatives for pre-breeding has been found to improve tolerance to drought, together with resistance to heat and certain diseases in both wheat, one of the world’s main food crops, and pearl millet, the world’s hardiest warm-season cereal crop.
Once the desired traits have been found in the crop wild relatives, they must be transferred to breeding lines—intermediate products of the plant breeding process—and from them, ultimately, to new commercial varieties. Scientists and breeders have already achieved these stages for sorghum and for alfalfa, an important forage crop.
To ensure extensive uptake by farmers, it is essential that pre-breeding efforts address their priority needs. Participatory evaluation, where scientists collaborate closely with farmers to assess plants, provides an opportunity to explore what these needs are in different regions. This method was used in two studies to investigate salt-tolerant crop wild relative-derived rice seeds adapted to the Mekong Delta. The resulting varieties were then enthusiastically taken up by local farmers.
The final step in a successful pre-breeding project with crop wild relatives is to ensure the data are available to as many people as possible—for that, the Germinate platform was further developed by the CWR Project to manage all pre-breeding data on 14 crops.
“Together, these findings add up to impressive progress—and they provide clear evidence that the benefits of pre-breeding are worth the time, effort and expense,” says Kilian. “But this is only the beginning. The pace of climate change is going to increase, and today’s extremes will become tomorrow’s normal. The next, crucial step is to move this work from pre-breeding into breeding so that, one day, farmers’ fields will be alive with crop varieties strengthened using traits from their wild relatives.”
This is the first article in this series highlighting the findings on pre-breeding with crop wild relatives as featured in the special issue of Crop Science: Adapting Agriculture: A Walk on the Wild Side.
This article was originally published on Landscape News.