How Plant Vaccines Could Save Us From a World Without Fruit

How Plant Vaccines Could Save Us From a World Without Fruit

2021-04-15 20:00:00

A future where chocolate, wine and oranges can only be afforded by the wealthy certainly feels dystopian. But it could be a reality if some of our favorite crops succumb to plant diseases – a reality that is already taking shape in some parts of the world. To tackle the problem, Anne Elizabeth Simon, a virologist at the University of Maryland, is trying a so-called 'vaccine' to create crops that could protect our food supply.

Like the current approach to the COVID-19 pandemic, researchers have long addressed the spread of pathogens among plants by quarantining infected flora to conserve surrounding flora. And, depending on the type of disease, plants can also be given pesticides or antibiotic sprays.

But to provide more reliable protection, Simon is part of a team developing a vaccine-like solution as an efficient and relatively rapidly deployable solution to prevent or possibly cure plant diseases.

This potential solution cannot come fast enough. The world is currently grappling with increasing dangers to vital agricultural sectors. In Europe a disease called Olive Quick Decoder Syndrome threatens Italy's treasured industry. Cocoa grown in West Africa, which provides about 70 percent of the world's chocolate, faces the debilitating cocoa-swollen shoot virus (CSSV). And now precious Napa Valley grapes struggle with the vine red spot virus

Most of these diseases do not have a simple treatment and require several costly, time-consuming strategies to reduce the diseases once they have spread. They can also be difficult to detect, as in some cases it may take several years for symptoms to appear.

Plant pandemics are, of course, not a new challenge For example, a disease caused by fungus in the first half of the 20th century killed more than 3 billion American chestnut treesBut overall, climate change, increased global travel, and government and industry neglect have combined to create a perfect pathogen storm that puts our food supply at risk. "The time has come to let people know that there are other pandemics going on," says Simon. "Several are happening with trees, and it will lead to a completely different world."

Why old solutions are no longer enough

The readily available tools cannot always contain the intrusive pathogens, as Florida quickly shows spiral citrus industry – although some argue that regulators and growers worsened conditions by not acting fast enough.

Citrus trees have struggled with multiple pathogens over the centuries, including the 19th century root rot epidemic and the citrus tristeza virus that surfaced in the 1930s. Most devastating of all huanglongbing (HLB) – also often referred to citrus greening – originated in China and has wreaked havoc over the past two decades.

Between 2013 and 2018, China & # 39; s top producing citrus region lost more than half of the area on HLB. By 2018 HLB an 83 percent decline in Florida citrus production between 2003 and 2018.

Changing temperatures and humidity levels have also complicated the battle. They can affect both plant immunity and pathogen strength, in a positive or negative sense, as vectors thrive in specific conditions. This brings disease to areas that were previously unsuitable for them; for example the bug that HLB will probably spread to northern Florida as states warm to its liking.

Because of these compounding challenges, some growers have pursued additional products or completely changed course. Some minor operations in Brazil and Mexico have been hit by citrus greening already considered growing sugar cane to make up for economic losses. Farms in Florida have the same way chose alternatives, planting crops such as mini pumpkins and avocado in an attempt to make up for lost income.

Where Tree "vaccines" come in

Simon accidentally joined the fight against plant pathogens: While studying plant RNA viruses in her lab, she came across a surprising sample in a genetic sequence database that contradicted her 30 years of research.

It turned out to be a new type of virus-like RNA she called iRNA. It shocked Simon because iRNA lacks certain genes found in all normal plant viruses, but can still move between cells in a plant's veins by attaching to plant-generated movement proteins.

By adapting the iRNA to carry small fragments of a virus, it can induce plant enzymes to cut the harmful virus into small pieces without harming the plant. “This could be a vehicle, not just for one type of tree, but for many,” says Simon. "It's all because of this very unusual, never-before-seen trait."

The iRNA sample was first discovered by researchers at the University of California, Riverside in the 1950s, when it appeared in lime trees. They found that the iRNA can infect many citrus species with very mild to zero symptoms. Yet its disease-eradicating properties were only recently discovered when Simon identified the missing genes that allow it to move through plant veins.

"This could become one of the most important tools in the industry and farmers to keep citrus going," said Georgios Vidalakis, a plant pathologist at the University of California, Riverside, and director of the Citrus Clonal Protection Program. "It looks promising. Still, there is still a lot of work to be done. "

Simon wanted to get the ball rolling and started a company by the name Silvec Biologics in 2019 and is working to develop a one-step vaccine-like preventative treatment that tricks trees into not only eradicating viruses that cause disease, but also fungi and bacteria – somewhat similar to how mRNA shots force our immune system COVID-19 to boil antibodies.

Since October 2020, Silvec has been conducting trials with UC Riverside's Citrus Clonal Protection Program to test the iRNA vaccines in citrus trees. Researchers can tailor treatment to ambush different pathogens based on their genetic sequences. This has enabled Simon & # 39; s team to work on vine viruses and bacteria targeting apple trees, and they have also begun to experiment with protecting cocoa trees from CSSV.

Because the trees with the original iRNA sample have survived for over 70 years, Simon says it suggests the vaccine could potentially provide lifelong protection against a variety of pathogens when placed in newly planted trees – similar to giving a standard set to children. What is less clear, however, is whether severely affected trees that have been infected for several years may still benefit from treatment.

Simon hopes that the iRNA therapy can save infected trees that are not yet showing signs of disease. It seems less likely for those with roots that have disintegrated due to disease, such as a growing number of Florida citrus trees. Even if the vaccine worked in those cases, she says, they would be too weak to recover.

How science can help sick plants

Simon's team is not alone in developing new techniques to combat devastating plant diseases. For example, some researchers have adapted relatively new technologies to address these threats. In recent years, scientists have to have suggested genome editing techniques such as CRISPR For this purpose. By manipulating specific parts of the plant DNA, breeders and researchers could work more accurately when designing disease-resistant varieties.

And as a safer, more efficient citrus green treatment, UC Riverside geneticist Hailing Jin has one antimicrobial peptide that can be injected or sprayed in place of antibiotics or pesticides. Jin and her colleagues isolated the peptide from a type of green-tolerant Australian limes, turning it into a natural plant product. In another nature-based solution, Vidalakis has worked liquid fertilizer made from fermented food waste. It contains beneficial bacteria that can strengthen crops' resistance to pathogens.

Ultimately, it will likely require a combination of approaches to keep our food system resilient to current and emerging diseases – just as we've combined masking and social aloofness along with different treatments and vaccines to counteract COVID-19.

But if scientists, governments and growers don't join forces quickly enough, some food production costs could skyrocket and affect consumer prices. The production price for oranges per acre in Southwest Florida, increased by 113 percent between 2003 and 2018, which is why Simon says plant epidemics are a Manhattan project of sorts, true scientists can bring their minds together and offer their individual expertise. Vidalakis agrees. “The clock is ticking and we won't be spending decades on this,” he says. "It has to be done quickly."


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