When Marie Noelle Ndjiondjop was a child in Cameroon, she spent every school holiday at her grandmother’s farm. ‘My grandmother was a lovely person, and she was a brilliant farmer,’ Ndjiondjop remembers fondly. ‘I was very close to her.’ She tells me how she spent hours by her grandmother’s side learning to cultivate maize, cassava, peanut, sweet potato, yams and cacao. As the school holidays came and went, she observed the cyclic rhythm of sowing and harvesting. She was still quite young when she began to wonder: where do all these plants keep coming from? One day she asked her grandmother, who answered: ‘Okay, come and see, I have a room here.’
Ndjiondjop still remembers that room. It was small and dark and smelled of sawdust. This was where cuttings of tubers were kept, such as yams and cassava. Her grandmother showed her how she cut the yams and covered them in sawdust, then packed them away for the following year. Next, she explained how she would save seeds from every harvest, how she took them to her kitchen where she laid them out to dry. When the seeds were ready, she placed them in envelopes. There was a special place for these, too. Ndjiondjop recalls another small room, so much cooler than everywhere else, that was full of these envelopes. This is how she learned the importance of saving cuttings and seeds, of treating them carefully and storing them in a special place, because they are the source of every future harvest.
There were other valuable lessons, Ndjiondjop tells me. ‘She [taught] me that the time you spend working is important,’ she says, recalling her grandmother’s words of advice: ‘You need to be passionate, you need to invest your time in something.’ Ndjiondjop didn’t know then that she would grow up to become a scientist, but that time with her grandmother had planted the seed of an idea. Today, Ndjiondjop is a plant biologist and molecular geneticist at AfricaRice, where she heads the Rice Biodiversity Center for Africa. A major part of this role, she explains, involves managing the Genetic Resources Unit, which is the seed genebank for crop species and wild relatives of African rice, Oryza glaberrima. When people talk about rice, they often think of Asia, says Ndjiondjop, ‘but there is rice in Africa, too!’ Indeed, rice is grown in nearly 75 per cent of African countries and represents a major source of calories for the entire continent. In west-central Africa, where Ndjiondjop lives, it is the primary source.
Ndjiondjop explains that Africa is the only continent where two cultivated species of rice are grown: O. sativa and O. glaberrima. The latter, she reminds me, originated in West Africa, but then sometime around the 16th century, Asian rice varieties began to arrive via explorers from abroad, and African farmers were impressed by the higher yields compared to their own local rice. Part of the reason for the difference in yield, she explains, is that the stems of O. glaberrima are weaker than those of O. sativa, which was the case even before the Green Revolution came along and produced O. sativa varieties with shorter, stronger stems. Even to this day, O. glaberrima has a problem with its stems weakening and lodging. Moreover, O. glaberrima – though domesticated – never became fully non-shattering, so it loses a lot of grains when this happens.
Yet, although the shift towards Asian rice varieties made sense in terms of yield, some farmers still preferred African rice to the introduced varieties, and many generations later they continue to farm it. Ndjiondjop decided to find out why. ‘I went and I met one of those farmers, they are in the Togo Mountains,’ she says. ‘They told me that they keep this species, they still grow it, because it is healthy. When they eat it, it [provides] the nutritional value that they expect from their food for their family. Also, when they eat it, it stays longer in their stomachs, so they don’t feel hungry very quickly.’ O. glaberrima also grows in places where Asian rice varieties simply cannot grow, such as in the uplands where irrigation is difficult and farmers rely on a single annual rainy season to get them through months-long stretches of dry weather. With its deep root system and minimal water loss, it is able to endure such conditions. Moreover, the gene variants or ‘alleles’ that confer these traits could be useful in developing new drought-tolerant crossbreeds.
Ndjiondjop is particularly interested in the way certain O. glaberrima varieties respond to disease. ‘The most damaging virus disease that we have in Africa is rice yellow mottle virus,’ she says. It can wipe out entire harvests and is a big contributor to food insecurity. Ndjiondjop has been studying rice yellow mottle virus (RYMV) and its effect on rice for more than twenty years and is delighted to report that, as a species, O. glaberrima is ‘a reservoir of resistant genes’. She and her colleagues have discovered three RYMV-resistant genes, highlighting why it’s important that traditional African landraces and crop wild relatives are preserved. The genetic resources in the AfricaRice genebank are precious to her precisely because they have the potential to help so many people.
The story of AfricaRice extends back to the early 1970s, when eleven West African countries created an association to focus on rice development in the region. By the 1990s its headquarters had been established in the town of M’be, which sits just outside the city of Bouaké in Côte d’Ivoire, and by 2002 the genebank facility was up and running. They built an active seed collection that was used for in-house research and for distributing seeds to breeders and other collaborators. The facility was just hitting its stride, with the collections growing nicely and regularly backed up in long-term −20°C storage, when there was an outbreak of civil unrest in Côte d’Ivoire. The conflict began near Korhogo in the country’s north and within days it had reached Bouaké and M’be.
‘I was here,’ Ndjiondjop recalls. She was working in the biotechnology laboratory, looking for disease-resistant genes. One day she was in the lab, her research progressing well, and then suddenly everything changed. ‘From one day to another I was not able to access the lab,’ she says. ‘I had to run away. I just carried my bag and I ran away.’
She tells me that the genebank manager at the time also managed to escape, like her to Benin, and brought the active collection with him. Another small mercy was that the long-term backup wasn’t in M’be at all – it had been established in Nigeria. That meant the seed collection was safe for the time being, but most of the research had stalled. The team made a brief attempt to return to the Côte d’Ivoire facility in 2004, but a deadly bombing in Bouaké made it clear that it still wasn’t safe, so in Benin they stayed. Ndjiondjop sourced whatever funding and instruments she could to re-establish her seed research program.
Time passed and the civil war in Côte d’Ivoire ended, with the ensuing peace flagging the possibility of a return to M’be. By this time, Ndjiondjop had taken over as genebank manager and she was eager to return the seed collection to the original facility, but that was now in disrepair. ‘Being the leader of rice in Africa, we had to have a facility in line with our leadership,’ says Ndjiondjop. So she secured funding for the construction of a new genebank facility in M’be. When the laboratories were ready, the refrigeration rooms were humming and the paint was dry, it was time to move the seeds into their new home. The problem then, Ndjiondjop informs me, was that transporting an entire seed collection from the temporary facility in Benin to the new facility in M’be wasn’t going to be easy.
Picture, for a moment, a map of the world. However big you have just imagined Africa to be in relation to the other continents, it is far, far bigger. Thanks to the distortion effect of most flat maps, which artificially stretch geographic entities the further from the equator they are, many of us grow up with a woefully inaccurate perception of the proportional sizes of Earth’s major landmasses. If I were to walk into my daughter’s classroom and take a pair of scissors to the world map hanging on the wall, then place my cut-out of Greenland on top of my cut-out of Africa, I might be convinced that they’re roughly the same size. But not only would I draw ire for damaging school property, I would not even come close to the truth of the matter, which is that Africa is actually about fourteen times bigger than Greenland. Indeed, it would be possible to fit into Africa the contiguous United States, as well as all of India, most of China and most of Europe, with plenty of room to spare for Japan, New Zealand and probably Indonesia, too. All of which is to point out that when you look at the distance from Benin to Côte d’Ivoire on a flat map, it might seem like they’re not all that far apart, but in fact the distance is equivalent to that between New York and Chicago.
For Ndjiondjop, it entailed a three-day journey from Benin through Togo and Ghana and then into Côte d’Ivoire, which involved multiple border crossings and all the pauses and paperwork that entails. The entire route never strayed more than 600 kilometres from the equator, so the outdoor temperature was certain to quickly compromise the integrity of the seed collection if given half a chance to do so. Which is why Ndjiondjop hired three refrigerated trucks: two to carry the seed collection and ‘one empty refrigerated truck following the collection to ensure that if one breaks down, we could quickly transfer the material to the third one’. She also arranged for a mechanic and an electrician to accompany the convoy, to make sure both the trucks and the refrigeration units ran smoothly, and she was there for the whole journey, too, to ensure her seeds made it safely to M’be – which, she is happy to report, they did.
That was just the active collection. A few years later, Ndjiondjop coordinated a similarly nerve-racking seed-transport operation for the long-term collection that had been stored in Nigeria. This venture involved refrigerated air transport in addition to ground transport, border crossings and sleepless nights. This, too, was a success, and today both the active and long-term collections are in the AfricaRice genebank in M’be, where Ndjiondjop keeps a close eye on them. But even now, she is not one to take any chances. Two backups of the long-term collection have been made, one housed at the USDA’s genebank in Fort Collins and the other in Svalbard. Before they are sent, the seeds are placed in special envelopes. Water-tight and vacuum-sealed, these envelopes are a lot more high-tech than the ones her grandmother used, but at its heart, the idea is the same.
Currently, Ndjiondjop and her colleagues are characterising and adding new accessions to the collection in M’be and conducting research that ultimately will help farmers. ‘Our centre was built in response to problems that farmers face in their field,’ says Ndjiondjop. ‘Because farmers are our beneficiaries, our end users, the purpose of our work is to really change the life of the farmer. Their problem becomes our research topic.’ She continues to hunt for pathogen-resistance traits to help mitigate crop losses, while also searching for the most nutrient-rich varieties.
The point of farming is to feed people, she says. ‘You want the rice you are giving to them to have all the nutritional value that will fill them, so when they eat that rice they will be healthy.’ As a genebank manager, Ndjiondjop believes her job is to ensure she has a large, genetically diverse collection full of traits that will make that possible.
*
AfricaRice belongs to a global network of agricultural research centres that came together with the common aims of reducing world hunger and poverty. It is called the Consultative Group on International Agricultural Research (CGIAR), and as the name suggests, there is a lot of research going on. For example, researchers in Bangladesh are helping farmers to identify and combat outbreaks of fall armyworm, a species of moth with ravenous, crop-devouring larvae. They’ve even developed a pest-identifying app that crowdsources data from farmers across the region so that infestations can be quickly tracked and headed off. Meanwhile, scientists in Colombia are breeding varieties of cassava resistant to whitefly, while seed specialists in Kenya are working to increase the presence of species of fodder trees on farms. CGIAR staff spend a great deal of time working directly with smallholder farmers to provide training and access to agricultural technology. It’s a big task, and an important one because smallholder farms, each less than 2 hectares in size, account for 90 per cent of the world’s 570 million farms and produce around one-third of the world’s food.
CGIAR also supports a partnership involving some of the world’s largest and most important genebank collections of crop species and crop wild relatives. There are eleven CGIAR genebanks in all. AfricaRice is one, so is ICARDA. There is also the International Rice Research Institute, which holds more than 132,000 accessions of rice, from traditional landraces and wild relatives to emerging hybrid varieties, making it the largest collection of rice biodiversity in the world. Meanwhile, in Mexico, the International Maize and Wheat Improvement Center hosts a genebank containing a vast number of wheat varieties, as well as the world’s largest collection of maize seeds. Maize originated in Central America, after all, and that is where the greatest diversity of maize landraces and wild varieties still exist. In a similar vein, it makes sense that the biggest genebank housing potato biodiversity is in South America, at the International Potato Center, the headquarters of which are in Lima, Peru. Across the border in Colombia is another CGIAR genebank: the International Center for Tropical Agriculture. If it’s beans you’re interested in, this is where to go because they have almost 38,000 varieties stored there, from faba beans and kidney beans to the incredibly rare Phaseolus albicarminus beans which are only found on a few mountain slopes in southern Costa Rica.
India is home to ICRISAT, the International Crops Research Institute for the Semi-Arid Tropics, which houses thousands of accessions of chickpea, pigeon pea, sorghum, ground nuts and a substantial variety of millets in its central genebank just outside Hyderabad. In recent years, ICRISAT has also established additional genebanks in Niger, Zimbabwe and Kenya. There is the World Agroforestry genebank in Kenya, which focuses on tree crop species. The International Livestock Research Institute in Ethiopia stores the seeds of over 1000 species of forage plants, while the genebank at the International Institute of Tropical Agriculture in Nigeria stores seeds and plant tissue from important crops in sub-Saharan Africa, including cowpea, soybean, maize, cassava, plantain, banana and yam.
These CGIAR genebanks hold more than 760,000 distinct accessions of crop and tree species from around the world. Indeed, many CGIAR collections can be traced to plant-collection missions as far back as the 1960s, and there has been a lot of change in political and ecological landscapes since then. Boundaries have changed and so have many habitats. There are species in genebanks that are now extinct in the wild, and even the species that have thrived are no longer quite the same as they were.
‘Collection is an ongoing process,’ says ICARDA’s Mariana Yazbek. ‘We are nowhere near “Okay, we’re fine! We’ve conserved everything!”,’ she says. There are many crop species and crop wild relatives that have not yet been collected. Moreover, she notes, ‘Even if you have collected something thirty years ago, now, it’s thirty years later, it’s a different thing, it’s not the same thing anymore. It’s been changing.’
Charlotte Lusty of Crop Trust agrees. She tells me that, depending on when it was collected, a genebank accession is ‘a snapshot of that particular crop at that particular time’. Crop Trust was established by CGIAR and the FAO to help secure and distribute funding to major global genebanks. ‘We realised that it wasn’t going to be easy to fund all of the different kinds of storage facilities that there were, but at least it would be possible to save the biggest collections,’ she says, explaining that, after many years of struggling to fund the genebanks, the FAO and the CGIAR set up the endowment fund ‘to finance the most important global collections.’
As for the nature of the CGIAR genebanks, some of the genetic material is stored in the form of plant tissue, which is the case for most tubers such as potatoes and potato relatives. However, the majority of the stored genetic material takes the form of seed collections. About two-thirds of the accessions stored in the Svalbard Global Seed Vault come from CGIAR genebanks, but the idea here is not to just store the seeds away in anticipation of catastrophe. Long-term backups are critical, but the active collections are – as the name suggests – where all the action happens. They serve as a direct resource for researchers, plant breeders and farmers, with CGIAR genebanks distributing tens of thousands of accessions annually to users in over 100 countries. As such, the genebanks are always being expanded, managed, shared and replenished. Furthermore, all those accessions must be characterised, conditions monitored, and collections checked and double-checked. And as both Yazbek and Lusty point out, there is always more collecting to do, always more traits and alleles to explore.
At present there are over 1750 formally established crop genebanks operating around the world, Lusty tells me. ‘There are probably genebanks in every country,’ which makes sense, she adds, ‘because there are always locally adapted varieties and local needs.’ Most of these genebanks operate under the International Treaty on Plant Genetic Resources for Food and Agriculture, which she says was set up as a way to make sure landraces and varieties of key staple crops could be shared. There are also general guidelines for how these genebanks function so that there’s consistency in the way seeds are harvested, prepared, stored and transferred.
To find one of the largest crop seed collections in the world outside Svalbard, you just need to head to the Rocky Mountains in Colorado, not far from the Wyoming border. There, between the eastern foothills of the Rockies and the vast expanse of prairie grasslands, you will come to the mid-western town of Fort Collins. I’m told it’s a nice place to go if you are fond of craft beer and good views, and it’s so quintessentially American that it helped inspire Disneyland’s ‘Main Street, USA’. Fort Collins is also the location of the US Department of Agriculture’s National Laboratory for Genetic Resources Preservation, referred to earlier in this book. This is where you can find the National Plant Germplasm System which houses more than 600,000 accessions, mostly seeds. Christina Walters, who manages the collection, says there are somewhere between 1000 and 3000 seeds in each accession, which means the facility is in possession of a few billion seeds, and counting. Roughly, it equates to about 10 per cent of the global plant genebank accessions. It’s a lot of diversity, and much of it is ‘active’, meaning researchers and plant breeders can request samples. As such, the centre distributes somewhere around 250,000 samples each year. Walters once likened it to an ‘eBay of genetic resources’.
Walters also appreciates the architectural design of the building in which the enormous, refrigerated genebank is housed. With its long, vaulted roofs and small windows, it gives off a kind of Noah’s Ark vibe, or at least the version of Noah’s Ark as imagined by 19thcentury artists who almost unfailingly rendered the storied vessel as more barn-like than seaworthy. That said, the parallels evoke an interesting idea: what was the biblical story of the ark, or indeed the older, strikingly similar tale in Babylonian lore, if not an ancient concept of a genebank?
Plants have learned numerous ways to adapt to different habitats, climates, diseases and other environmental pressures over time, and that knowledge is written in their genes. We can’t let what has been learned be unlearned says Charlotte Lusty. ‘Why would you throw knowledge away? You wouldn’t! You would make sure it was stored somewhere.’
Take any one seed and you will hold in your hand the product of millions of years of evolution, and, for a crop seed, the additional effects of thousands of years of human intervention. That seed’s genetic code can tell a story of past climates, adaptations and biological mechanisms we don’t yet fully understand. There might be genes for more efficient photosynthesis that fumbled their way into existence millions of years ago. Alleles for deep roots may have emerged as a molecular counterpoise to some bygone epoch of drought. A sea rises and in time recedes, leaving genetic echoes in the form of salinity tolerance.
Plants have always pushed the boundaries of what’s possible. That’s how they got started, after all, with a foot – so to speak – in both the world of water and the world of dry land. All the while, they’ve been very good at repurposing existing genes to suit new needs, or breaking those genes down and making new ones from the spare parts. Occasionally, the act of survival is simply a matter of allowing a once-useful but now obstructive gene to slide, one mutation at a time, into obsolescence. Such is the evolutionary gamble, a vast and patient exercise in combinations played out on timescales with few analogies on Earth, but which can be discerned more readily in the stars.
There is a galaxy called Messier 83, which is also known, more cheerfully, as the Southern Pinwheel. It is a spiral galaxy, much like our own, and it’s located fifteen million light years away. This means that the light now reaching us here on Earth began its journey fifteen million years ago, which was roughly when the genus Oryza evolved. From that first Oryza followed the evolution of all known species of wild rice, and, with some added pressure from Neolithic humans, it culminated in domesticated rice. A recent study of O. sativa revealed that the long, starlit path to its evolution involved the fine-tuned repurposing of genes, as well as some wholesale building of new genes from bits of old genes. Most intriguingly, it seems that the evolution of O. sativa also involved the birth of at least 175 entirely new genes from non-coding ‘junk’ DNA just in the last few million years. Such is the unique genetic story contained within one seed of one crop species, and this is why genebank scientists have a long history of going to extraordinary lengths to find and save seeds. Further, they know it’s worth it because they’ve seen the real-world impact of seed genebanks time and time again.
Back in the 1960s, for example, the International Rice Research Institute (IRRI) began training agricultural scientists in Cambodia as part of efforts to support the country’s burgeoning rice sector. Back then, in the early days of the Green Revolution, Cambodia’s rice production was on the rise, rice yields were in surplus, and the country had become one of the world’s major rice exporters. But as conflict escalated in the region and the country not only became embroiled in the Vietnam War but also saw the outbreak of its own civil war, rice production plummeted. The Khmer Rouge took power in 1975 and enacted a brutal regime of large-scale population resettlements, mass executions and disastrous agricultural initiatives, such as the construction – by forced labour – of thousands of kilometres of poorly designed irrigation canals, dams and reservoirs. The misguided pursuit of improved rice yields decimated what remained of Cambodia’s rice production and ushered in one of the worst famines in the country’s history. Many of those who were not killed by violence faced disease and starvation. By the late 1970s, food shortages were so bad that whatever rice seeds could be found were eaten, including the last grains of Cambodia’s traditional rice varieties. By the time the Khmer Rouge fell from power in 1979, millions of Cambodians had died and there was nothing left to plant.
Nothing can undo something so horrific, but IRRI was at least able to help rebuild Cambodia’s food system. In December 1972, while the civil war was underway but before the Khmer Rouge had seized power, IRRI scientists went out to Cambodian farms and collected thousands of rice samples representing hundreds of traditional rice varieties. These were then stored at the IRRI genebank in the Philippines. In the 1980s, IRRI returned to Cambodia to repatriate more than 760 traditional rice varieties that had been lost. Today, Cambodian rice production is doing well, but like all rice producers they are in need of varieties that can better withstand extreme weather events, pests and diseases while producing enough to feed a growing population. To this end, breeding research is underway, and IRRI’s genebank is playing a significant role in this as a valuable genetic diversity resource.
There are other stories, including one that has recently emerged from Rwanda, which shows how the genetic resources found in seed genebanks might be used to improve human health.
Anaemia most often arises from a profound deficiency in iron, which is a major problem because iron is integral to the function of red blood cells. Healthy blood cells contain a special protein called haemoglobin which is able to carry a ‘haem’ molecule. Thanks to the iron atom at the centre of this haem, it is able to bind oxygen in parts of the body where oxygen levels are high, specifically the lungs, and release that oxygen where it’s needed elsewhere in the body. Around two-thirds of the body’s iron is found in the blood – in fact, it’s responsible for blood’s red colour. Iron is also crucial to a long list of other essential functions in the body, from cognitive processes to the ability to make new blood cells, so when iron levels dip too low, a lot can go wrong. The most pronounced effect of anaemia occurs when blood cells can no longer transport oxygen properly. According to a recent review in the medical journal Lancet, there were 1.2 billion cases of iron deficiency anaemia in 2016 alone, making it a leading contributor to the global disease burden.
In Rwanda, 19 per cent of women of reproductive age have iron deficiency anaemia. Rwanda also happens to have the highest percapita consumption of beans in the world, up to 66 kilograms per person per year, so researchers at the International Center for Tropical Agriculture (CIAT) saw an opportunity. Since the 1970s, CIAT had been amassing the world’s largest collection of beans. Searching the conserved accessions, the researchers found native American beans with high iron levels. These were unlikely to grow well in Rwanda’s tropical climate, so breeders crossed them with other species that do. In doing this, they produced a new variety of beans that was high in iron and grew well in Rwanda. CIAT researcher Mercy Lung’hao and her colleagues recently conducted an eighteen-week trial in which these iron-rich beans were included in the diets of a cohort of iron-deficient women. The series of studies, published in the Journal of Nutrition, showed that participants who received the hybrid beans experienced an increase in blood-ferritin levels as well as a reduction in anaemia symptoms.
Next, we come to millets, which are both interesting and rather underappreciated. Millets were among the first grains to be domesticated and were a dietary mainstay from the Indian subcontinent to the Korean peninsula for thousands of years. Gradually they fell out of favour, especially as rice and wheat production boomed during the Green Revolution. But, as befits the story of a steadfast underdog, millets may turn out to be precisely what the world needs. Not only are they full of nutrients, fibre and protein, but they are also impressively stress-tolerant. ICRISAT has been collecting and storing millet seeds for decades, including a number of varieties which are now endangered. Meanwhile, staff at ICRISAT’s genebanks have been steadily characterising their millet accessions, identifying those with the highest nutrient content and finding some other very useful traits along the way, such as resistance to drought, blast fungus and parasitic Striga weed. As promising accessions are being incorporated into breeding programs, agronomists and nutritionists are working with smallholder farmers across India – many of whom are women – to reintroduce millets, particularly in areas where malnutrition is rife. In addition to supplying high-nutrient varieties bred for local conditions, they’re also providing training in millet cultivation and seed production, as well as cooking demonstrations to increase the popularity of millets. It seems to be working: yields have gone up, smallholder incomes have improved, and a lot more millet is being consumed.
*
In 1936, the remarkable but ill-fated Russian botanist Nikolai Vavilov embarked on one of his final plant-collecting journeys. Though Vavilov and Trofim Lysenko were not yet at odds, Vavilov was already on uncertain ground. He had been forbidden from leaving the USSR, so he went as far as political boundaries would allow, into what was then Soviet Central Asia. They focused on hunting for crop species in Turkmenistan, Uzbekistan, Kazakhstan, and likely Tadjikistan, too, because Vavilov was reportedly fascinated by the rich diversity of flowering plants there. A picture was taken during this time that shows Vavilov walking along a bright mountain path, nonetheless dressed in shirtsleeves and a tie, his trademark fedora shading his eyes. There is another photo of him standing smiling beside a small passenger plane, not far from the Aral Sea. He seemed, if not happy, then at least content and in his element. At some point during these months, some of the team ventured further south-east into what is now Pakistan. While there they collected a number of local wheat landraces and returned with them to Russia. The seeds were catalogued and stored at the institute in Leningrad, becoming part of the collection that staff members died to protect during the siege of that city by the Nazis. Today, they are part of the seedbank at the N.I. Vavilov All Russian Institute of Plant Genetic Resources (VIR) in what is now called St Petersburg.
The seeds Vavilov collected on his journeys provided the foundation for the vast crop species collection at the institute named in his honour, which has since expanded to around 350,000 seed accessions. More than 38,000 of these are varieties of wheat. Lee Hickey, a plant breeder and crop geneticist at the University of Queensland, has been collaborating with scientists at the VIR for some years now and also building a mirror collection of the Vavilov wheat ‘panel’ in Australia. So far, he’s been able to duplicate around 300 of the Vavilov wheat lines, and he plans to keep going because genetic diversity is already proving incredibly useful for protecting modern-day wheat crops from disease or drought. Hickey is steadily analysing the genomes of those old wheat landraces, and while this work is turning up some interesting information, he cautions that when it comes to crop traits, genome information on its own doesn’t reveal as much as he’d like. You can’t necessarily predict the phenotype of wheat from the genotype, he tells me, meaning that you can’t deduce all of a plant’s traits just by perusing a list of its genes. Hickey tells me that the genomes of crop species are incredibly complex, with vast amounts of interactions between genes constantly in play.
As it happens, it’s often the meticulous notes kept by Vavilov and others that provide useful hints: the location where the seed was collected, the habitat, the features of the landscape – such information increases the odds of finding a trait of interest. Hickey gives the example of stripe rust. ‘Stripe rust prefers cooler environments, so you look for stripe-rust resistance in plants found in higher altitudes,’ he says. ‘You can narrow down regions of the world where you’d expect there to be natural variation for this trait.’
One of the traits Hickey is particularly interested in is resistance to yellow spot, a fungal disease caused by Pyrenophora tritici-repentis. It’s the number-one wheat disease in Australia, he tells me. It’s particularly nasty because the fungus has figured out how to weaponise the plant’s own defence mechanisms. When the plant detects a pathogen infection in some of its cells, it will kill those cells, sacrificing them for the greater good. For pathogens that need living plant tissue in order to survive, the game is over, but P. tritici-repentis happens to really like dead plant tissue, says Hickey. As the pathogen spreads, necrosis continues until the plant is unable to produce healthy grain. Sometimes the entire plant dies. The disease earned its name because as the infection spreads, the leaves become covered with yellowy blotches of dead tissue. Yellow spot reduces yields and has contributed to the increased use of fungicides in Australia. It also costs the national wheat industry more than $200 million annually.
As Hickey and his colleagues were working through the Vavilov wheat panel, they came across that traditional wheat landrace from Pakistan, the one collected in 1936. It turned out to be resistant to yellow spot. Curiously, a genetic analysis revealed the presence of a gene called Tsn1, which is known to make wheat more sensitive to yellow spot, not less. Yet, the trait studies were clear: adult plants did just fine in the presence of the fungus. Further investigation revealed a collection of genes and genomic regions that appeared to confer disease resistance, which just goes to show that deciphering the mysteries of wheat genetics can turn up all sorts of surprises. In the case of this Vavilov accession from Pakistan, it seems the presence of Tsn1 doesn’t matter so much as a whole cast of other genes all interacting just so.
Hickey tells me that he and his fellow researchers were able to ‘back-cross’ the trait, by which he simply means they took a few varieties of high-quality, high-yield modern wheat and bred them with Vavilov’s landrace from Pakistan. Metaphorically, it’s sort of like teaching new dogs an old trick, but in reality, breeding an old trait – or any trait really – into a new plant takes a lot of time and patience. It requires various attempts at crossbreeding, and multiple generations, to get the trait of interest to show up where you want it to. Fortunately, it just so happens that Hickey and his team have been honing a new technique. It’s called speed breeding and, as the name suggests, it hustles things along. By exposing the plants to certain wavelengths of light for longer hours, the researchers are able to trigger early flowering. This won’t work out in the field on a large scale, but in the tightly controlled environmental conditions of a specially designed greenhouse, it works a treat. Using this approach, breeders can reduce the timescale of breeding experiments by months or even years. In the case of yellow spot, a new line of modern high-quality wheat resistant to the disease was quickly produced.
Hickey is hopeful that incorporating this trait into Australian wheat varieties will have the effect of boosting wheat yields while reducing the reliance on fungicides. And to think it was just sitting there in a packet of seeds collected more than eighty years ago. Vavilov was right all along.