作物疾病大流行“早于

健康的小麦在乌干达,从哈几周rvest, turns into a tangle of black stems and shrivelled grains. As much as 80 per cent of the harvest is lost, a fate that destroys the farmer’s investment in the fields and damages the livelihood of the family.

Soon wheat fields in Kenya, Ethiopia and Egypt experience the same fate. Iran follows, along with India, Pakistan and Lebanon. Then countries in Asia and Europe show signs.

The culprit is wheat stem rust. A plant disease that has been known for decades, a virulent new strain, Ug99, emerged in 1999 to ravage wheat production across the globe — and was spread by the wind.

"Plant disease can be very cryptic and look like water stress or nutrient deficiencies. These tools enable someone to diagnose it effectively where it may have been missed before."

斯蒂芬·帕内尔（Stephen Parnell），索尔福德大学空间流行病学家

Wheat stem rust is just one example of plant pests and diseases that farmers and agricultural experts across the globe are battling. They are a silent threat to food security, responsible for up to40 per cent of global food crop losses根据食品和农业组织的说法。beplay下载官网西西软件

While crop pests and diseases can be spread by environmental factors, such as the wind, they also move into new places via global trade, traffic and transport. As the world prepares to feed its expected population of more than nine billion people by 2050, preventing plant disease outbreaks is becoming more urgent.

Indeed, this has been recognised on a global scale with the United Nation’s declaration of 2020 as the International Year of Plant Health. But experts say more research has to be done — and quickly — in order to prevent a global crop disease pandemic.

Evolutionary arms race

“There is a constant evolutionary battle between pathogens and their hosts,” Helen Fones, a plant pathologist from the University of Exeter, tellsscidev.net。“Each continually evolves to overcome the latest strategy that the other has created to infect or resist infection.”

Fones’ latest research, published with colleagues in the journalNature Food(8 June), points to this ‘evolutionary arms race’ to conclude that no interventions last forever. Fungi, such as wheat stem rust, pose the greatest threat, according to the researchers.

真菌具有高度适应性并能够迅速发展，具有较短的生成时间，并且可以在农业领域达到较高的人口规模。

“This aspect of their biology makes them hard to predict,” says Fones. As fungal pathogens are introduced through global trade systems, they attack crops that lack immunity.

“In a new location there are new, naïve hosts lacking immunity, a release from competition and other opportunities. For this reason, the transported fungus often thrives,” she says.

Exacerbating this is a global food system that emphasises monoculture practices — large-scale production of single crop species — which increases the devastating impact of a crop disease if it becomes resistant to defences.

脆弱的系统

While regional crop diversity has increased over the past 50 years, researchers say large industrial farms in Asia, Europe and South America are allgrowing the same one crop speciesacross thousands of hectares of land.

“在全球范围内,世界的农业地区ns are now starting to look more and more similar to one another than they did in the past,” Adam Martin, an ecologist from the University of Toronto, tellsscidev.net。

他说，随着这一趋势的继续，世界上许多不同的地区将受到相同的害虫和疾病暴发的影响。这可能会导致“重大和令人惊讶的破坏”。

马丁说，全球粮食系统中的内置备份可能会缓解作物损失的一些负面影响。尽管一个国家可能会从另一个国家进口疾病的农作物，但它可能会产生营养类似的农作物来取代它。但是这些缓冲区只能掩盖富裕国家。

“When the world has seen major shocks or disruptions to global food or economic systems, what we do know is that less-developed countries tend to bear the brunt of negative impacts,” he says.

Looking to theworld food crisis of 2007-2008, in which staple food prices soared, sheds some light on those impacts: poverty, malnutrition, and economic and social unrest. During the crisis, protests and riots broke out across48个国家, including Syria, Venezuela and 14 African countries.

Detect and treat

Smart technology, like disease mapping, could play a role in stopping a devastating plant pandemic in its tracks.

Mapping is especially helpful with early detection and treatment targeting, Stephen Parnell, a spatial epidemiologist at the University of Salford, says.

“Identifying plant disease is like a needle in a haystack problem. Maps are like a metal detector to show you where and how to target resources,” he says.

这些地图中的一些通过建模来起作用，将环境风险因素（例如风和降雨）与其他因素（例如作物传播以及先前检测到的疾病接近beplay足球体育的微博）结合在一起。其他人则依靠农民和社区成员使用智能手机应用程序来检测和记录疾病标志。

“植物疾病可能非常神秘，看起来像水应力或营养缺乏。这些工具使某人能够有效地诊断出可能错过的地方。”帕内尔说。

One challenge, however, is the ability to gather these data in time. “Some plant diseases express quickly, and others can be infectious for a year before showing symptoms,” he says.

How to treat the disease is another challenge. Fungicides are an effective first-line defence, but only for so long, says Fones.

她说：“真菌在不断发展，其中包括对新杀菌剂的耐药性。”她说，令人担忧的是，在人类医学中也使用了同样的杀菌剂。

例如，高唑是最广泛使用的植物杀菌剂类，同时是人类的一线抗真菌药物之一。研究表明，这种双重作用是促进抗烷基的抗性，荷兰的一项研究表明100 per cent mortality在患有相关真菌感染的患者中。

研究人员说，在农业环境中使用杀菌剂及其临床有效性之间的冲突凸显了抗真菌干预措施的局限性。

Still, Fones says not using fungicides is not an option. "Without fungicides we might expect to lose 30 to 50 per cent of the wheat harvest in the UK in a bad year. For crops that don't have resistance and rely only on fungicides for protection, it could be 100 per cent,” she says.

“Therefore, we really need new, agriculture-specific fungal control methods.”

Protecting the plant

Some biochemists argue that the most effective protection against a pandemic is to avoid plants getting sick in the first place.

2Blades Foundation总裁戴安娜·霍瓦斯（Diana Horvath）告诉他：“现代植物科学生产了更有针对性，有效的作物繁殖工具，使我们能够改变农作物的基因组。”scidev.net。

“Now we can extend a plant’s strong, existing resistance by enabling it to detect new pathogens.”

2Blades is a non-profit supporting genetic solutions for crop disease resistance. Horvath says its scientists can engineer seeds with gene stacks, where multiple resistance genes and modes of action make it much harder for a pathogen to infect the plant.

This multiple resistance approach for fighting infections is already seen in the biomedical world, she says, with AIDS ‘triple cocktail’ treatments and triple antibiotic ointments.

“With resistance genes, we have shown that we can prevent most of the damage caused by major diseases of major crops, such as wheat stem rust, and protect not only the individual plant, but also its progeny – its seeds and tubers,” Horvath says.

那么，全球农业beplay下载官网西西软件最好的武器可能正在加强植物病原体研究。但是霍瓦斯说，植物和农业研究长期资金不足，仅收到了生物医学研究的投资的十分之一。

这可能会受到19009年大流行的进一步影响。“我们已经看到许多全球发展组织将优先权转移到了Covid-19。您可以看到为什么这很重要，但是植物大流行的情况并没有消失。”她说。

What a crop disease pandemic will look like, and how the world will fight it, is difficult to predict. But, the University of Toronto’s Martin says, “both science and economics suggest we’re going to find out sooner rather than later.”