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‘Coconut palm seeds thoroughly assessed before importation’ — Plant Protection Unit

10 June 202103 Share

The lethal yellowing disease has decimated the coconut palm population here in Antigua and Barbuda. Many hope that the importation and replanting exercises will be completed as soon as possible.

Authorities looking to rebound from impact of lethal yellowing disease

By Orville Williams

orville.williams@antiguaobserver.com

In a bid to restock the majestic coconut palms that once adorned Antigua and Barbuda in abundance, the government has already put plans in motion to import 100,000 coconut seeds from Costa Rica.

In light of this, the Plant Protection Unit is assuring that the seeds have been thoroughly vetted to prevent a recurrence of the devastation that nearly rid the country of the plant over the past years. 

The lethal yellowing disease – first discovered in the island in 2012 – has decimated the coconut palm population, setting back beautification efforts and impeding the efforts of small business owners whose livelihoods depend on the sale of coconuts and/or its byproducts. 

During the worst period of the outbreak, a solution was introduced and a formula – Oxytetracycline Hydrochloride (OTC) – developed to “control the amount of the disease agent in the plants”. However, that formula was rather costly and many trees were deemed too far gone to even consider the expensive treatment. 

Fast forward to early this month, the government announced plans to import the seeds from Costa Rica, “for propagation of new coconut palms”. These seeds, the government said, are expected to “produce trees resistant to [the] disease, grow about six feet tall and begin producing fruit shortly after three years of growth”.

The idea to import and replant coconut palms is not new to the government, as consideration was given to acquiring seeds/seedlings/saplings, most recently from Suriname. The Agriculture Ministry’s Plant Protection Unit opposed that idea, however, amid concerns of pests being introduced into the island as a result.

Chief Plant Protection Officer, Dr Janil Gore-Francis, had aired those concerns back then, but speaking to Observer on these current plans, she said strict measures have been enforced to ensure safety.

“There has been a process of assessment, we have done our research and our risk assessment with regard to the seeds coming from Costa Rica via the US. [The seeds] have to go through a very stringent process, they have to be certified and so on, so there are specific requirements that have to be met for those seeds to come into Antigua, and that is what has been applied. 

“Some of those seeds have come in already, they must have import permission, they have to be certified, they must be unsprouted [and] a number of [other factors] that would ensure they do not come in with lethal yellowing or any other disease that could be spread by the foliage – which is why we insist that they must come in unsprouted. 

“So, all of that would have been taken into consideration with the risk assessment that would have been done, in order for us to arrive at the approval of those specific nuts coming through that process, under very stringent conditions,” Dr Gore-Francis explained. 

She also disclosed that, based on their observations, the disease is not as prevalent at this point as it had been in the past. 

“We have not really been having as many calls as we were having [for example] back in 2019, with respect to plants that are suspected to have contracted the disease. So, I think we have reached a sort of equilibrium, where I guess those palms that have some sort of tolerance or just have not been infected by lethal yellowing are what remain right now.”

In regard to the treatment formula – OTC – a programme was put in place to provide some relief to homeowners or business operators whose coconut palms were struggling with the disease. 

The formula is injected into the trunk of the plants to keep the level of the phytoplasma down, to allow the plant to thrive. After a while, however, the amount of formula within the plant decreases, which means the plants have to be treated at regular intervals – three to four months – to maintain control of the disease and keep them alive. 

These plants are assessed after interested persons apply to the programme and depending on the condition of the plants, they are either chosen to be treated or rejected if they are “too far gone”.

The plant owners are then allowed to import the formula under specific regulations, which include refraining from using the OTC on plants that are meant for consumption. These regulations, Dr Gore-Francis says, are closely monitored to reduce the various risks associated.

The entire importation and dissemination process of the new plants can’t come soon enough for many, including Barbara Japal, the President of the local Horticultural Society. 

She told Observer, upon news of the importation, “The old saying is, ‘the palm is the charm’. Palm trees are part of the lifeblood [of the country], it’s the industry of so many people in Antigua. Coconuts provide food, they provide medicine to some [and] they provide a tourist attraction in every way.”

Similarly, ‘Granma Aki’ – who makes products including sauces and dips from coconuts – said getting the plants and the coconut industry back in full swing was vital to herself and many others. 

“It’s very urgent and small producers like me, we are suffering. The products that we use coconuts for are in demand, great demand. So, I suppose, if we don’t have any coconuts, they have to come from abroad, the price is going up [and] the quality is not so good.”

As Dr Gore-Francis mentioned, some of the seeds have already arrived in Antigua, but there is no indication as to when the entire bunch will be on island. 

‘Granma Aki’ would certainly hope that it’s sooner, rather than later. 

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Why demand is expected to be strong for virus-resistant wheat

Wheat with the Bdv2 gene (left) and a non-Bdv2 crop © RAGTWheat with the Bdv2 gene (left) and a non-Bdv2 crop © RAGTf

Farmer’s Weekly

Insecticide-free wheat has moved a step closer with the arrival of the hard Group 4 winter wheat variety Wolverine, which is the first to offer barley yellow dwarf virus (BYDV) resistance.

Added to the latest AHDB Recommended List on a yield of 102%, Wolverine has a specific recommendation for resistance to BYDV and sets an exciting tone for future wheat variety introductions from breeder RAGT, many of which will have resistance to both BYDV and orange wheat blossom midge.

While Wolverine is a high-yielding feed variety, the company also has bread-making wheats with both types of resistance in development – many of which should eliminate the need to apply insecticides throughout the entire growing season.

Against a background of the loss of insecticidal seed treatments, rising resistance levels in pests to the remaining foliar sprays and greater scrutiny of pesticide use, the development of these varieties is a breakthrough.

Their arrival is expected to be as well-received by the supply chain as it is by farmers, in the industry’s quest to sharpen its environmental credentials.

Seed demand

After a limited seed release last year ahead of the recommendation decision, there is enough seed of Wolverine available to meet demand for this autumn’s wheat plantings, RAGT managing director Lee Bennett confirms.

He believes the variety could take a significant market share.Lee Bennett in a trial plot

Lee Bennett © RAGT

“The ideal situation is to have this BYDV resistance in a variety that suits early drilling,” he says. “That’s exactly what we have in Wolverine.”

After two consecutive wet autumns and difficulties with wheat drilling schedules, the opportunity for farmers to get under way while conditions are good, without putting the crop at unnecessary risk from virus-carrying aphids, is a bonus, he notes.

“This will be the second year without the Deter (clothianidin) seed treatments that gave such cost-effective control. The approval of Wolverine gives them a different, more environmentally friendly solution.”

Genetic solution

The genetic alternative to chemical control is performing well in the field, says his colleague Tom Dummett, who confirms that the Bdv2 gene used in Wolverine brings season-long protection from the aphids that transmit the virus.

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Visit our Know How centre for practical farming advice

“The aphids still arrive, but Wolverine doesn’t express any virus symptoms and the virus doesn’t multiplicate in the plant,” he explains.

“We’re very happy with the way that the gene is working. It’s proved effective in Australia for almost 20 years and is now in the right genetic background to work well in the UK.”

Having previously conducted trials to look at the value of the resistance at different sowing dates and whether the use of one insecticide spray could protect the gene or give a yield uplift, this year’s work by RAGT has a different focus.

The plots were all drilled in early September and then inoculated with aphids infected with the PAV strain of BYDV, both in the autumn and the spring.

BYDV pressure

The idea was to create severe BYDV pressure, explains Mr Dummett, with one-third being left untreated, one-third receiving an autumn insecticide, and the remaining plots getting both an autumn and spring insecticide.

At the time of Farmers Weekly‘s visit in June, varieties without the BYDV resistance gene were showing clear symptoms of the virus in the untreated plots.

Wolverine and the other RAGT lines with the Bdv2 gene were symptom-free.

The PAV strain of BYDV is the most common, Mr Dummett says, but the company is confident that the resistance is broad-spectrum as tests have confirmed that it also controls the MAV and RPV strains.

Wolverine’s agronomic features

Agronomically, Wolverine is a later-maturing type, with a +2 for ripening.

It has stiff straw and good resistance to brown rust, but is middle-of-the-road for septoria (5.3) and did take on some yellow rust last year, so has a score of 5. As such, it needs to be grown with care and frequent monitoring.

Seed cost

The previous cost of using Deter (clothianidin) seed treatments and an insecticide for BYDV control has been factored into the cost of growing Wolverine.

As it was last year, the variety will be sold via the Breeders’ Intellectual Property Office system, which means that the value of the trait will be charged direct to farmers on an area basis rather than by tonnage.

That charge will be £33/ha, and RAGT points out that it covers season-long protection and eliminates the need to monitor aphid populations or repeatedly spray at a busy time of year.

Competitive advantage

RAGT has a head start over other breeding companies when it comes to BYDV resistance, as it is the only UK plant breeder with Bdv2.

The company has two feed wheat varieties coming along closely behind Wolverine, followed by four bread-making types with both BYDV and orange wheat blossom midge resistance.

The Bdv2 gene originated in goat grass and was translocated onto a wheat chromosome by Australian researchers, who went on to breed BYDV-resistant wheats.

There are four other known BYDV resistance genes, most of which are being investigated by RAGT. Bdv3 and Bdv4 work differently to Bdv2, for example, but may bring other benefits when put into the right genetic background.

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PepMV brings a halt to New Zealand tomato exports

New Zealand tomato exports to six countries have been stopped, after the pepino mosaic virus (PepMV) was discovered on crops.

According to local website www.rnz.co.nz The Ministry for Primary Industries (MPI) has notified Australia, Japan, Thailand, Fiji, Tonga, and New Caledonia about the disease affecting New Zealand tomatoes, because these countries consider PepMV a quarantine risk. MPI had temporarily suspended export certification to these markets, the ministry’s response controller David Yard said.

Discovery of PepMV
For some weeks Biosecurity New Zealand and the tomato industry have been investigating the discovery in New Zealand of the pepino mosaic virus (PepMV). The virus was first detected in an Auckland glasshouse operation and has subsequently been found in a handful of tomato production facilities in the wider Auckland region.

The premises where PepMV has been found are able to continue operating and selling fruit under strengthened hygiene conditions. However, there may be restrictions on exporting to markets who are known to consider PepMV of quarantine concern.

PepMV is a virus that can cause pepino mosaic disease – predominantly in tomatoes, but potentially in other solanaceous plants including potatoes and eggplants. “It’s not yet certain how badly PepMV would affect tomato crops in New Zealand. It appears to have minor foliage effects on younger plants, but as the plant ages, can cause mottling of the fruit itself,” the team with TomatoesNZ shares. They have developed advice on Pepino Mosaic Virus for growers.  

“Now the virus has been confirmed in several facilities, it is considered possible that it may be distributed more widely in the country’s tomato growing operations. For this reason, we strongly encourage all growers of tomatoes to follow careful biosecurity procedures on their properties,” they say. The virus can be asymptomatic or have very mild symptoms so it is important that you remain vigilant with hygiene, especially with equipment, plant material and people that are moving on and off site.   

The risk of transmission of the disease through selling fruit is considered low. 

It is important to note that while PepMV can affect tomato production, it does not present any food safety concern or risk to people. New Zealand grown tomatoes are perfectly safe to eat.

Read more about the precautions and the actions to take at TomatoesNZ.

Publication date: Fri 25 Jun 2021

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Identifying ToBRFV and ToMV using CRISPR/Cas

CRISPR/Cas12a-based detection is a novel approach for the efficient, sequence-specific identification of viruses. In new research,  CRISPR/Cas12a is used to identify the tomato brown rugose fruit virus (ToBRFV), a new and emerging tobamovirus that is causing substantial damage to the global tomato industry.

Specific CRISPR RNAs (crRNAs) were designed to detect either ToBRFV or the closely related tomato mosaic virus (ToMV). This technology enabled the differential detection of ToBRFV and ToMV.

Sensitivity assays revealed that viruses can be detected from 15–30 ng of RT-PCR product, and that specific detection could be achieved from a mix of ToMV and ToBRFV.

“In addition, we show that this method can enable the identification of ToBRFV in samples collected from commercial greenhouses. These results demonstrate a new method for species-specific detection of tobamoviruses,” the researchers explain. “A future combination of this approach with isothermal amplification could provide a platform for efficient and user-friendly ways to distinguish between closely related strains and resistance-breaking pathogens.” 

Read the complete research here.

Alon, Dan & Hak, Hagit & Bornstein, Menachem & Pines, Gur & Spiegelman, Ziv. (2021). Differential Detection of the Tobamoviruses Tomato Mosaic Virus (ToMV) and Tomato Brown Rugose Fruit Virus (ToBRFV) Using CRISPR-Cas12a. Plants. 10. 1256. 10.3390/plants10061256. 

Publication date: Fri 25 Jun 2021

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International collaboration receives regulatory approval of cassava brown streak disease resistant cassava in Kenya

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St. Louis, Missouri, USA
June 23, 2021

The Kenya Agricultural and Livestock Research Organization (KALRO) has received approval from the Kenyan National Biosafety Authority (NBA) for environmental release of cassava that is resistant to cassava brown streak disease (CBSD). The approval paves the way for conducting national performance trials (NPTs), the final step of testing new varieties before they can be registered and released to farmers.

The disease-resistant cassava was developed under the Virus Resistant Cassava for Africa Plus (VIRCA Plus) project, an international collaboration between the Kenya Agricultural and Livestock Research Organization (KALRO), the National Agricultural Research Organisation (NARO) in Uganda, the Rwandan Agriculture Board (RAB), Mennonite Economic Development Associates (MEDA) and the Donald Danforth Plant Science Center in St. Louis, MO.

In parallel with the NPTs, the VIRCA Plus team is working to multiply, deliver and steward the improved varieties to Kenyan farmers once they are registered and fully approved by regulatory authorities.

Through a decision document dated June18, 2021, the NBA Board approved the application following necessary review in accordance with the country’s Biosafety Act. The researchers used modern biotechnology to introduce a small part of two viruses that cause CBSD into the cassava plant to make it resistant. The process used augments a naturally occurring plant defense mechanism against viruses. The improved cassava was evaluated over a period of five years, in confined field trials (CFTs) in six different locations in Kenya and Uganda, and showed high and stable defense against CBSD, a disease that can result in up to 100 percent loss of usable storage roots in severe infection.

According to NBA’s Chief Executive Officer, Prof. Dorington Ogoyi, the decision was arrived at following a rigorous and thorough review, taking into account food, feed, and environmental safety assessment as well as consideration of socio-economic issues. The review process also factored public comments for 30 days, in line with the Kenyan constitution that calls for public participation.

“This is a welcome decision and a significant step to getting disease-resistant cassava into the hands of Kenyan farmers for addressing food security challenges,” said KALRO Director General Dr. Eliud Kireger. “We thank the NBA and all those who participated in the review for their diligent consideration of the application.”

More details about next steps of the project will be coming soon.

About VIRCA Plus
VIRCA Plus, a multi-institutional project working to improve resistance to viruses that cause cassava brown streak disease (CBSD) and to increase levels of iron and zinc in the storage roots, the edible part of the plant. VIRCA Plus collaborates with research scientists, regulatory experts and communication specialists with the National Agricultural Research Systems (NARS) in Kenya, Uganda, Nigeria and Rwanda. For more information please visit, cassavaplus.org.

More news from:
    . Donald Danforth Plant Science Center
    . Kenya Agriculture and Livestock Research Organisation (Kalro)

Websitehttp://www.danforthcenter.org

Published: June 23, 2021

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Decoded genome of little-known disease offers hope for citrus

Benign infection can potentially send medicine into plants

11-Jun-2021 2:25 PM EDT, by University of California, Riversidefavorite_border

Newswise: Decoded genome of little-known disease offers hope for citrus

Gerardo Uribe/UCR

Progression of citrus yellow vein disease, from left to right.

Newswise — Scientists are hoping the RNA of an obscure infection can one day be used like a Trojan horse to deliver life-saving treatments to citrus trees.

The infection, citrus yellow vein disease, was discovered 64 years ago in Riverside and has never been seen elsewhere in the world. Decades later, UC Riverside researchers have finally unraveled the associated pathogen’s genetic codes — a significant step toward harnessing its unique properties.

A paper describing this work was published recently in the journal Frontiers in Microbiology. It opens the door to testing whether this apparently benign infection could be used as a vehicle to transport antibacterial and antiviral agents into citrus plants’ vascular systems, where infections usually take place.

Citrus crops face a highly uncertain future due to Huanglongbing, also known as citrus greening disease. In the past decade, the disease has caused a 72% decline in oranges used for juice, and a 21% decrease in the American fresh citrus fruit market. Growers in other parts of the world are similarly affected, and it continues to spread unabated.

Though there are promising treatments and disease-resistant hybrids being developed for Huanglongbing, none are yet commercially available.

Cells use RNA to convert the information stored in DNA into proteins that carry out different functions. Yellow vein disease is associated with small, independently mobile RNA, called iRNA, which spreads through a plant’s vascular system. This spreading mechanism could be a new way to send treatments for Huanglongbing or other diseases into plants.

The story of this promising research starts in 1957 with Lewis Weathers, a UC Riverside plant pathology professor.

“He found four limequat trees with beautiful, bright veins on their leaves, almost fluorescent yellow,” said Georgios Vidalakis, a plant pathology professor at UCR, UC-ANR cooperative extension specialist, and principal investigator on the new paper.

“That color was recognized as a disease, and samples of it were deposited at the Citrus Clonal Protection Program disease bank where it was waiting for us to study decades later,” Vidalakis said.

Based on Weathers’ experiments, it did not appear as though the disease is carried by any animal or other microorganism, Vidalakis said.

“We think it was introduced into the limequats in a single event, and once those plants were destroyed, it never spread to other citrus in California.”

Researchers have learned, however, how the disease spread between cells in infected plants. The iRNA disguises itself with plant proteins that lets it pass through cellular connective tissue. This ability to travel inside citrus trees may allow the iRNA to send protective molecules into noncitrus plants as well, including grapes, olives, and cacao.

Yellow vein disease iRNA is also surprisingly small, even for a microscopic organism. Plant viruses typically have four to 10 genes on an average, each with at least one function. The iRNA of this disease has only one functional gene.

“The iRNA is amazing because it’s able to manipulate plant cells to help it replicate, despite having only one functional gene,” explained Kiran Gadhave, a UCR microbiologist, corresponding author of the paper, and lead researcher of the iRNA project. “In addition to its potential therapeutic value, it’s just a scientific curiosity. This is as small as it gets.”

Though they believe the pathogen to be benign, the research team is doing additional testing to make sure it won’t affect fruit quality or quantity, tree height, or any other markers of health. Symptoms in greenhouse-grown trees were mild. Now this is being tested in a field trial in the living laboratory at the UCR Agricultural Experiment Station AgOps.

“The support of the Citrus Research Board and our close collaborations with the University of Maryland and Silvec Biologics are proving to be crucial in taking this technology from lab to the farm,” Gadhave said.

One day, iRNA could be used alongside gene editing technologies like CRISPR, in which cells are trained to recognize and destroy nucleic acids from invading plant pathogens. There are challenges with both methods that need to be overcome first, like managing unintended effects, costs, and efficient delivery.

“The common limitations of both approaches can be overcome by matching their strengths, the same way we integrate different disease management solutions,” Gadhave said.

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Costa Rica updates the requirements to import avocado from Honduras due to sunspot detection

Costa Rica’s State Phytosanitary Service (SFE) has updated the requirements for the entry of avocados from Honduras after authorities detected the sunspot disease, a quarantine disease not present in the country caused by the viroid Avocado Sunblotch (ASBVd), in 5 different shipments.

From now on, Costa Rica will require all avocados from Honduras to undergo a molecular biology laboratory analysis to rule out the presence of the pest. The cost of the test will be assumed by the importer and the shipments will be retained awaiting the results of the test, Costa Rican authorities stated. If the viroid is detected, the shipments will be returned.

Costa Rica has already informed the World Trade Organization (WTO) about this new requirement.

Honduras is currently Costa Rica’s main supplier of Hass avocado, after the country banned the entry of this fruit from Mexico, the world’s leading exporter, and from eight other markets (Australia, Spain, Ghana, Guatemala, Israel, South Africa, Venezuela, and the state of Florida, in the United States) in 2015 to prevent the entry of the sunspot disease into the country. The measure, therefore, may pose a market supply problem.

The 2015 measure caused a trade clash with Mexico, the resolution of which is currently in the hands of a panel of experts at the WTO.

Last year, Costa Rica invested 3.64 million dollars in avocado purchases from Honduras, while total imports of the fruit totaled 12 million.

In the first four months of this year, imports from Honduras totaled 3.9 million dollars, i.e. 77.5% of all fresh avocado imports, which totaled 5.03 million dollars, according to data from the Statistical portal of the Foreign Trade Promoter (Procomer).

Source: nacion.com 

Publication date: Thu 27 May 2021

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Virus free asparagus seed improves grower’s bottom line

The asparagus seed harvest in New Zealand is started two weeks earlier than previous seasons. The harvest of asparagus seeds would normally run from mid-March through to the end of April. Dr Peter Falloon from Aspara Pacific is excited about the earlier harvest and explains, “We have had the perfect combination of warm dry weather since spring and excellent pollination, so we are predicting one of the best yields on record.”

The excellent conditions have come at a great time for Aspara Pacific who have begun full production of ground-breaking varieties that are virus free and Phytophthora tolerant.

“We have long known that Asparagus Virus 2 is one of the main contributors, if not the primary cause of asparagus decline in New Zealand.

Asparagus decline had previously been associated with the soil borne fungus Fusarium but research at Michigan State University and Lincoln University, New Zealand has since shown that Fusarium is more of a problem when asparagus plants are already infected with the virus.

Since effective control of Fusarium has proven almost impossible we have attacked the problem from the other direction and chosen to eliminate asparagus virus 2 by breeding varieties that are free of the disease.”

Virus free plants live longer and have considerably higher yields of better quality spears.

One of the main sources of asparagus virus 2 has been in imported asparagus seed. So our goal has been to develop varieties for the New Zealand industry that are free of the virus.

One of these varieties Challenger 2 also has high levels of tolerance to the soil borne fungus Phytophthora. Phytophthora rot is a world-wide problem reducing yields by up to 50% in asparagus in Europe, Asia, North Central and South America and Australasia. The wetter the harvest, the greater the losses due to Phytophthora.

Aspara Pacific’s new variety Challenger 2, is one Dr. Falloon is especially proud of after breeding asparagus for over 40 years. “It has shown excellent tolerance of Phytophthora rot, it is less affected by Purple Spot (caused by Stemphylium) and is especially useful under organic conditions.. Not only that, but International asparagus variety trials carried out over 8 harvest seasons have shown Challenger 2 to be the top yielding variety, out-yielding Eclipse, Sequoia, Millenium and Equinox.

Aspara Pacific has a number of other virus free varieties, each producing excellent results in different growing conditions around the world. They export seed to over 20 countries with Dr. Falloon “looking forward to exporting larger volumes of premium seed around the world. With such a fantastic harvest this season we are in a position to supply the bigger asparagus producers who are looking for high yielding, virus free asparagus seed.”

For more information:
Dr. Peter Falloon
Aspara Pacific
peter@asparapacific.co.nz
www.asparapacific.co.nz 

Publication date: Mon 19 Apr 2021

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ToBRFV resistant tomatoes

In 2020, Enza Zaden announced the discovery of the tomato brown rugose fruit virus (ToBRFV) High Resistance gene, a complete solution for ToBRFV. Since the announcement, we’ve worked hard with resistant trials material achieving excellent results. “We see no symptoms at all in the plants, while the disease pressure is very high,” says Oscar Lara, Senior Tomato Product Specialist, about the first trials in Mexico.

No symptoms at all
At the Enza Zaden trial location in Mexico, the high resistance (HR) varieties are placed next to susceptible ones. There you can clearly see the difference. The susceptible tomato varieties show different foliage disorders such as a yellow mosaic pattern. The affected plants also stay behind in growth.

“You can clearly see how well our high resistant varieties withstand ToBRFV,” says Oscar Lara. “In comparison to the plants of susceptible varieties, the resistant ones look very healthy with a dark green colour, show no symptoms at all and have good growth. All our trialled HR tomato varieties do not show any symptoms at all.”

Exciting news
Enza Zaden is running parallel tests in different countries with varieties with high resistance to ToBRFV. “Our trials in Europe, North America, and the Middle East show that we have qualitatively good tomato cultivars with a confirmed high resistance level,” says Kees Könst, Crop research Director. “This is exciting news for all parties involved in the tomato growing industry. We know there is a lot at stake for our customers, so we continue to work hard to make HR varieties available for the market. We expect to have these ready in the coming years,” says Könst.

High performing and high resistance
Enza Zaden has a long history in breeding tomatoes. “We have an extended range of tomato varieties, from large beef to tasty vine tomatoes (truss tomatoes) and from baby plum tomatoes to pink varieties for the Asian market. This basis of high performing varieties combined with the gene we discovered, will enable us to deliver the high performing varieties with high resistance to ToBRFV.”

Why is a high resistance level so critical?
“With an intermediate resistance (IR) level, the virus propagation is delayed but ToBRFV can still enter tomato plants – plants that may eventually show symptoms,” says Könst. “With a high resistance level, plants and fruits do not host the virus at all. This means they won’t be a source for spreading the virus and that the detection test will come back negative. Growing a variety with high resistance can be the difference between making a profit or losing the crop.”For more information Enza Zadeninfo@enzazaden.com
www.enzazaden.com

Publication date: Tue 13 Apr 2021

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Fighting HLB disease with finger limes?

Could finger limes be part of the solution in Florida’s struggle with the HLB disease affecting its grapefruit?

Dr. Manjul Dutt thinks possibly so. Dutt, a research assistant scientist in Horticultural Sciences with the University of Florida has been observing finger lime growth in Florida for almost a decade and has made an interesting discovery. “It seemed that when the surrounding trees around the finger lime trees started getting HLB and declining, the finger lime trees continued thriving,” says Dutt. He collected leaf samples from the trees every year to test for HLB, a disease that continues to significantly impact Florida’s citrus crops and the finger lime trees proved tolerant of the disease—unlike other citrus variety trees such as grapefruit, oranges, mandarins and pomelos.

It was then Dutt launched a pilot program with finger lime trees to try integrating the HLB-resistant genes from the finger limes into conventional citrus. “And since then, we’ve generated a large population of trees that we’re evaluating against HLB,” he says.

Why finger limes?
What is it though about finger lime trees that keeps them protected? While there’s no strong evidence pointing in one direction, Dutt has several theories. “We think something could be different in the phloem chemistry. There was earlier work done in collaboration with Dr. Nabil Killiny, looking at the finger lime phytochemicals in the phloem and we found they were quite different from HLB-sensitive cultivars,” he says.

Leaf color could also play a role. “Young leaves in finger limes are always dark red in color. The citrus psyllid move around using visual cues and we think this red color may disorient them and make them less appealing than other citrus which have young green leaves for example,” he says.

Whatever it is, the finger limes at least seem more tolerant—but not 100 percent resistant—to the disease. “If you infect a finger lime tree and a sweet orange tree at the same time and test them a year or two later, you’ll always see the rate of infection is much lower in finger limes than in oranges. There’s something going on in the phloem that we need to understand.”

Tapping into their genetics
While finger limes aren’t exactly set out to be the new crop replacing Florida’s longstanding orange and grapefruit industry, Dutt believes finger lime trees can provide a strong assist. “Hybrids between finger limes and sweet orange down the road may have sweet orange-like traits that can be acceptable to the grower and consumer. It would create a sweet orange-like fruit with finger lime genetics that allow it to be tolerant to HLB,” he says. “Many people in the industry realize it’s a long-term process. Some are skeptical but overall, people are hopeful that the finger-lime genetics play an important role in providing HLB-tolerant trees in the future.”

To date, finger limes are more of a niche crop in North America with only a few growers in California, Hawaii and Florida.

In the meantime, Dutt has produced a finger lime hybrid that looks like a larger finger lime. “We’ll be releasing it this summer—it’s similar to the finger lime but it has more pulp and the same “pearls” that finger limes do,” he says. He adds that it’s a commercial release as a niche crop and hopes the limes will be available in stores in the next three to four years.

For more information:
Dr. Manjul Dutt
University of Florida
Tel: +1 (863) 956-8679
manjul@ufl.edu
https://crec.ifas.ufl.edu/

Publication date: Tue 23 Mar 2021
Author: Astrid Van Den Broek
© FreshPlaza.com

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