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Archive for the ‘Plant Pathogens’ Category

NEWS RELEASE 29-JUN-2021

DNA barcodes decode the world of soil nematodes

To understand soil ecosystems and contribute to advanced agriculture

TOYOHASHI UNIVERSITY OF TECHNOLOGY (TUT)

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IMAGE: SOIL SAMPLING SITES (TOP). CLASSIFICATION OF SOIL NEMATODE COMMUNITIES BY FEEDING GROUP (RESULTS FOR BARCODE REGION 4) (BOTTOM). view more CREDIT: COPYRIGHT (C) TOYOHASHI UNIVERSITY OF TECHNOLOGY. ALL RIGHTS RESERVED.

Overview

The research team of Professor Toshihiko Eki of the Department of Applied Chemistry and Life Science (and Research Center for Agrotechnology and Biotechnology), Toyohashi University of Technology used a next-generation sequencer to develop a highly efficient method to analyze soil nematodes by using the 18S ribosomal RNA gene regions as DNA barcodes. They successfully used this method to reveal characteristics of nematode communities that inhabit fields, copses, and home gardens. In the future, the target will be expanded to cover all soil-dwelling organisms in agricultural soils, etc., to allow investigations into a soil’s environment and bio-diversity. This is expected to contribute to advanced agriculture.

Details

Similar to when the UN declared 2015 to be the International Year of Soils, there have recently been many efforts worldwide to raise awareness of the importance of the soil that covers our Earth and its conservation. Diverse groups of organisms such as bacteria, fungi, protists, and small soil animals inhabit the soil, and together they form the soil ecosystem. Nematodes are a representative soil animal; they are a few millimeters long and have a shape resembling a worm. They play an important role in the cycling of soil materials. Many soil nematodes are bacteria feeders, but they have a wide variety of feeding habits, such as feeding on fungi, plant parasitism, or being omnivorous. In particular, plant parasitic nematodes often cause devastating damage to crops. Therefore, the classification and identification of nematodes is also important from an agricultural standpoint. However, nematodes are diverse, and there are over 30,000 species. Additionally, because nematodes resemble one another, morphological identification of nematodes is difficult for anyone but experts.

The research team focused on “DNA barcoding” to identify the species based on their unique nucleotide sequences of a barcode gene, and they established a method using a next-generation sequencer that can decode huge numbers of nucleotide sequences. They used this to analyze nematode communities from different soil environments. Initially, four DNA barcode regions were set for the 18S ribosomal RNA genes shared by eukaryotes. The soil nematodes used for analysis were isolated from an uncultivated field, a copse, and a home garden growing zucchini. The PCR was used to amplify the four gene fragments from the DNA of the nematodes and determine the nucleotide sequences. Additionally, the nematode-derived sequence variants (SVs) representing independent nematode species were identified, and after taxonomical classification and analysis of the SVs, it was revealed that plant parasitizing nematodes were abundant in the copse soil and bacteria feeders were abundant in the soil from the home garden. It was also determined that predatory nematodes and omnivorous nematodes were abundant in the uncultivated field, in addition to bacteria feeders.

This DNA barcoding method using a next-generation sequencer is widely used for the analysis of intestinal microbiota, etc., but analyses of eukaryotes such as nematodes are still in the research stage. This research provides an example of its usefulness for the taxonomic profiling of soil nematodes.

Development Background

Research team leader Toshihiko Eki stated, “Through genetic research, I have been working with nematodes (mainly C. elegans) for around 20 years. As a member of our university’s Research Center for Agrotechnology and Biotechnology, I came up with this theme while considering research that we could perform that is related to agriculture. As a test, we isolated nematodes from the university’s soybean field and unmanaged flowerbed and analyzed the DNA barcode for each nematode. Bacteria feeders were abundant in the soybean field, and that was used for comparison with the flowerbed, where weed-parasitizing nematodes and their predator nematodes were abundant. This discovery was the start of our research (Morise et al., PLoS ONE, 2012). If that method using one-by-one DNA sequencing was the first generation, the current method using the next-generation sequencer is the second generation, and we were able to clarify characteristics of nematode communities representing the three ecologically different soil environments according to expectations.”

Future Outlook

Currently, the research team is developing the third-generation DNA barcoding method which involves purifying DNA directly from the soil and analyzing the organisms in the whole soil instead of isolating and analyzing any particular soil-dwelling organisms. They are currently analyzing the soil biota of cabbage fields, etc. They are aiming to precisely analyze how communities of soil-dwelling organisms including microbes change with crop growth, clarify the effects that cultivated plants have on these organisms, and investigate biota closely related to plant diseases. If this research moves forward, crops can be cultivated and managed logically based on biological data in agricultural soils, and it can contribute to advancing smart agriculture in Japan, such as in the prominent Higashi-Mikawa agriculture region and beyond.

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This research was performed with the support of the Takahashi Industrial and Economic Research Foundation.

Reference

Harutaro Kenmotsu, Masahiro Ishikawa, Tomokazu Nitta, Yuu Hirose and Toshihiko Eki (2021). Distinct community structures of soil nematodes from three ecologically different sites revealed by high-throughput amplicon sequencing of four 18S ribosomal RNA gene regions.
PLoS ONE, 16(4): e0249571.

Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.

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Kolar: Mangoes dumped by the roadside after steep fall in price

Since there is no factory for mango pulp in Kolar and Chikkaballapur districts, farmers have to depend on such units in Tamil Nadu and Andhra Pradesh.

Indian Express

Published: 26th June 2021 05:13 AM  |   Last Updated: 26th June 2021 05:13 AM  |  A+A-

By V Velayudham Express News Service

KOLAR: With a steep fall in prices of Benishan or Banganapalli and Totapuri varieties of mangoes, growers are dumping the ‘King of Fruits’ by the roadside in Srinivaspura of Kolar district. Adding to farmers’ woes, the Totapuri variety has been attacked by a fungal disease — anthracnose.

Growers are demanding compensation from the government. However, the government is yet to respond to their appeal.Speaking to TNIE, Kolar District Mango Growers Association president Neelaturu Chinnappa Reddy said as compared to previous years, mango growers are suffering losses this year and are unable to bear the burden as prices have crashed.

He said there are no takers for Benishan and Totapuri varieties. In 2019, each tonne of Benishan was sold at Rs 1 lakh, while last year it was Rs 50,000 to Rs 80,000. However, the prices have come down to as low as Rs 8,000 to Rs 15,000 this year. Farmers are finding it difficult to even cover the annual maintenance cost, he added.

Since there is no factory for mango pulp in Kolar and Chikkaballapur districts, farmers have to depend on such units in Tamil Nadu and Andhra Pradesh. With Totapuri being grown in both the neighbouring states, farmers belonging to Andhra Pradesh and Tamil Nadu are not heading to Srinivaspura for mangoes. 

Moreover, the Andhra government has passed an order that merchants should purchase the Totapuri variety from local growers at Rs 10,000 per tonne. Reddy said the variety is being grown in 60,000 hectares in Srinivaspura.

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JULY 2, 2021

Phys.Org

How the potato blight pathogen penetrates the plant

by Wageningen University

Scientists discover how the potato blight pathogen penetrates the plant
Credit: Wageningen University

In the 19th century, the notorious pathogen Phytophthora infestans caused a large famine in Ireland and other parts of Western Europe. To this day, it continues to pose a major threat to global food production. It has long been a mystery how this microscopically small organism and other members of the Phytophthora genus mechanically gain entry through the protective layer on the leaves of crops. In a unique collaboration, Wageningen University & Research experts in plant pathology, cell biology and physics have now found an answer to this question. Their discovery also provides new leads to making the control of Phytophthora more effective, more efficient and more sustainable on the long term. Their findings are published in Nature Microbiology.

Plants are under constant threat from all kinds of pathogens. A number of these intruders bearing the difficult name Phytophthora (literally: plant destroyer), cause enormous damage yearly to all kinds of crops, such as potatoes, tomatoes, eggplant, cocoa, peppers, soy and date palm, as well as to woodlands and nature reserves. Phytophthora not only poses a major threat to our food security, but also results in vast economic damages, causing annual damage to the potato sector of approximately 6-7 billion euros.

Combatting Phytophthora is and remains problematic, in part because the pathogen and its target are engaged in an ongoing arms race. Tremendous resources are invested in the development of resistant crops through plant breeding, with the aim of becoming less dependent on chemical crop protection. There is also increasing interest in new forms of mixed cropping.

Utilising Insights from Mechanics

Another option has now arisen; preventing Phytophthora from gaining access to a plant altogether. Plants come equipped with a protective layer that serves to keep intruders like Phytophthora out. Yet, this microscopically small pathogen (smaller than one tenth of the thickness of a human hair) is able to penetrate this layer and initiate its disease process in plants. Despite decades of research, it remained unknown how they mechanically penetrate this layer. To solve this problem, WUR plant pathologists and cellular biologists joined forces with WUR physicists. The latter are specialists in mechanics, a branch of physics that studies how objects and materials move and respond under the action of forces acting upon them. Their combined knowledge, and new research tools developed in collaboration, could finally bring resolution to this puzzle.

“We discovered that Phytophthora uses clever tricks to sharpen its tubular infection structure to then cut through the surface of the plant with a sharp knife. Using this strategy, Phytophthora is able to infect its host, without brute force and with minimal consumption of energy. This is the first time that this mechanism has been uncovered, and really a fundamental discovery,” Joris Sprakel, professor in Physical Chemistry and Soft Matter, says.

More effective and sustainable protection

Phytopathology Professor Francine Govers sees plenty of leads to make the control of Phytophthora more effective, more efficient and more sustainable in the long run, without the usual suspects—chemicals and plant breeding—to circumvent the arms race. “The laws of mechanics tell us that Phytophthora is unable to penetrate the plant without first attaching itself tightly to the leaf surface.” To test this idea, as initial proof of feasibility, the research team sprayed the leaves of potato plants with a non-toxic and inexpensive substance that removes the leaf’s stickiness. This resulted in a reduction of around 65% in the level of infection. The effect even rose towards 100% in an optimized trial on artificial surfaces.

Apart from the fundamental breakthrough and investigating tools for combatting this kind of plant disease from a new perspective, the research also resulted in a new methodology; a kind of rapid testing method, that can reveal the effect and efficiency of pesticides in a rapid, accurate and inexpensive way. These novel tools could also make a significant contribution to the ongoing battle against plant diseases.

“Thanks to the engagement of Joris Sprakel and his team, including Ph.D. candidate Jochem Bronkhorst, we now know that there are a number of fundamental physical principles that could give a new twist to the arms race between pathogens and plants,” says Govers. “All in all, this research is a truly wonderful example of how collaboration across disciplinary borders can lead to breakthroughs.”


Explore further New resistance gene to devastating potato disease that caused Irish Famine


More information: Jochem Bronkhorst et al, A slicing mechanism facilitates host entry by plant-pathogenic Phytophthora, Nature Microbiology (2021). DOI: 10.1038/s41564-021-00919-7Journal information:Nature Microbiology

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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.

Explore moreKnow How

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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Mushroom growing out of fossilized ant reveals new genus and species of fungal parasite

IMAGE
IMAGE: Oregon State University research has identified the oldest known specimen of a fungus parasitizing an ant, and the fossil also represents a new fungal genus and species. A mushroom is…
view more Credit: George Poinar Jr., OSU

CORVALLIS, Ore. – Oregon State University research has identified the oldest known specimen of a fungus parasitizing an ant, and the fossil also represents a new fungal genus and species.

“It’s a mushroom growing out of a carpenter ant,” said OSU’s George Poinar Jr., an international expert in using plant and animal life forms preserved in amber to learn about the biology and ecology of the distant past.

A mushroom is the reproductive structure of many fungi, including the ones you find growing in your yard, and Poinar and a collaborator in France named their discovery Allocordyceps baltica. They found the new type of Ascomycota fungi in an ant preserved in 50-million-year-old amber from Europe’s Baltic region.

“Ants are hosts to a number of intriguing parasites, some of which modify the insects’ behavior to benefit the parasites’ development and dispersion,” said Poinar, who has a courtesy appointment in the OSU College of Science. “Ants of the tribe Camponotini, commonly known as carpenter ants, seem especially susceptible to fungal pathogens of the genus Ophiocordyceps, including one species that compels infected ants to bite into various erect plant parts just before they die.”

Doing so, he explains, puts the ants in a favorable position for allowing fungal spores to be released from cup-shaped ascomata – the fungi’s fruiting body -protruding from the ants’ head and neck. Carpenter ants usually make their nests in trees, rotting logs and stumps.

The new fungal genus and species shares certain features with Ophiocordyceps but also displays several developmental stages not previously reported, Poinar said. To name the genus, placed in the order Hypocreales, Poinar and fellow researcher Yves-Marie Maltier combined the Greek word for new – alloios – with the name of known genus Cordyceps.

“We can see a large, orange, cup-shaped ascoma with developing perithecia – flask-shaped structures that let the spores out – emerging from rectum of the ant,” Poinar said. “The vegetative part of the fungus is coming out of the abdomen and the base of the neck. We see freestanding fungal bodies also bearing what look like perithecia, and in addition we see what look like the sacs where spores develop. All of the stages, those attached to the ant and the freestanding ones, are of the same species.”

The fungus could not be placed in the known ant-infecting genus Ophiocordyceps because ascomata in those species usually come out the neck or head of an ant, Poinar said, and not the rectum.

“There is no doubt that Allocordyceps represents a fungal infection of a Camponotus ant,” he said. “This is the first fossil record of a member of the Hypocreales order emerging from the body of an ant. And as the earliest fossil record of fungal parasitism of ants, it can be used in future studies as a reference point regarding the origin of the fungus-ant association.”

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Findings were published in Fungal Biology.

Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.

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JUNE 25, 2021

Kiwi disease study finds closely related bacterial strains display different behaviors

by American Phytopathological Society

Kiwi disease study finds closely related bacterial strains display different behaviors
Elodie Vandelle, Annalisa Polverari, Davide Danzi, Vanessa Maurizio, Alice Regaiolo, Maria Rita Puttilli, Teresa Colombo, Tommaso Libardi. Credit: Elodie Vandelle

Over the last decade, severe outbreaks of bacterial canker have caused huge economic losses for kiwi growers, especially in Italy, New Zealand, and China, which are among the largest producers. Bacterial canker is caused by the bacterial pathogen Pseudomonas syringae pv. actinidiae (Psa) and more recent outbreaks have been particularly devastating due to the emergence of a new, extremely aggressive biovar called Psa3.

Due to its recent introduction, the molecular basis of Psa3’s virulence is unknown, making it difficult to develop mitigation strategies. In light of this dilemma, a group of scientists at the University of Verona and University of Rome collaborated on a study comparing the behavior of Psa3 with less-virulent biovars to determine the basis of pathogenicity.

They found that genes involved in bacterial signaling (the transmission of external stimuli within cells) were especially important, especially the genes required for the synthesis and degradation of a small chemical signal called c-di-GMP, that suppresses the expression of virulence factors. Compared to other biovars, Psa3 produces very low levels of c-di-GMP, contributing to an immediate and aggressive phenotype at the onset of infection before the plant can corral a defense response.

“It was exciting to discover this diversified arsenal of pathogenicity strategies among closely related bacterial strains that infect the same hosts but display different behaviors,” said Elodie Vandelle, one of the scientists involved with this study. “Although their ‘small’ genomes mainly contain the same information, our research shows that bacterial populations within a pathovar are more complex than expected and their pathogenicity may have evolved throughout different strategies to attack the same host.”

Their research highlights the importance of working on a multitude of real-life pathogenic bacterial strains to shed light on the diversity of virulence strategies. This approach can contribute to the creation of wider pathogenicity working models. In terms of kiwi production, Vandelle hopes their findings can help scientists develop new mitigation methods. In the long-term, their research could lead to the identification of key molecular switches responsible for the transition between high and low bacterial virulence phenotypes.

“This identification would allow, at industrial level, to develop new targeted strategies to control phytopathogenic bacteria, weakening their aggressiveness through switch control, instead of killing them,” Vandelle explained. “This would avoid the occurrence of new resistances among bacterial communities, thus guaranteeing a sustainable plant protection.”


Explore furtherUnpacking the two layers of bacterial gene regulation during plant infection


More information: Elodie Vandelle et al, Transcriptional Profiling of ThreePseudomonas syringaepv.actinidiaeBiovars Reveals Different Responses to Apoplast-Like Conditions Related to Strain Virulence on the Host, Molecular Plant-Microbe Interactions (2020). DOI: 10.1094/MPMI-09-20-0248-RJournal information:Molecular Plant-Microbe InteractionsProvided by American Phytopathological Society

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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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East Africa’s growers welcome new banana varieties more resistant to disease and drought

Breeders in Uganda and Tanzania have developed drought-tolerant and disease-resistant banana hybrids that are should support the commercialization of East Africa’s banana sector. The general response to the new hybrids has been positive from more than 1,350 Ugandan and Tanzania smallholder banana growers. These have very often struggled to sustain their plantations beyond four or five years in the face of intense pressure from plant diseases like Xanthomonas wilt (BXW), fusarium wilt and black Sigatoka.

Some regional agricultural analysts predict that East Africa’s banana farmers will soon enjoy the best of both worlds: bananas developed from conventional breeding and emerging biotechnologies like genome editing. The new advances also mean it’s highly likely that the region will be able to control the devastating Xanthomonas wilt (BXW) disease that has stymied production.

Dr. Ivan Kabiita Arinaitwe of Uganda’s National Banana Research Program told the Alliance for Science that the high- yielding new hybrids were developed through conventional breeding by crossing an East African highland banana cultivar (Triploid 3x) and a male diploid (2x) parent of the wild species Musa acuminata, which contributes the source of resistance to pests and diseases.

For East Africa, giving farmers access to improved banana hybrids mean increased and sustained commercial banana productivity, hunger mitigation, better food security and increased interventions aimed at strengthening and widening banana value addition for greater income generating opportunities.

Publication date: Mon 21 Jun 2021

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How Some Fungi That Cause Diseases Can Grow Through Tiny Gaps

TOPICS:BiomechanicsCell BiologyFungusMicrobiologyMycologyUniversity Of Tsukuba

By UNIVERSITY OF TSUKUBA JUNE 19, 2021

A team led by the University of Tsukuba has found key differences that explain why some species of fungi can grow successfully through tiny gaps, whereas other fungi–typically those with faster growth rates–cannot squeeze through and stop growing. The trade-off between developmental plasticity and growth rate helps to understand how fungi penetrate surfaces or plant/animal tissues, with important implications for fungal biotechnology, ecology, and studies of disease. Credit: University of Tsukuba

University of Tsukuba research team sheds new light on how fungi that cause diseases can penetrate tissues by squeezing through tiny gaps between plant or animal cells.

Fungi are a vital part of nature’s recycling system of decay and decomposition. Filamentous fungi spread over and penetrate surfaces by extending fine threads known as hyphae.

Fungi that cause disease within living organisms can penetrate the spaces between tightly connected plant or animal cells, but how their hyphae do this, and why the hyphae of other fungal species do not, has been unclear.

Now, a team led by Professor Norio Takeshita at University of Tsukuba, with collaborators at Nagoya University and in Mexico, has discovered a key feature that helps explain the differences among species. They compared seven fungi from different taxonomic groups, including some that cause disease in plants.

The team tested how the fungi responded when presented with an obstruction that meant they had to pass through very narrow channels. At only 1 micron wide, the channels were narrower than the diameter of fungal hyphae, typically 2-5 microns in different species.

Some species grew readily through the narrow channels, maintaining similar growth rates before meeting the channel, while extending through it, and after emerging. In contrast, other species were seriously impeded. The hyphae either stopped growing or grew very slowly through the channel. After emerging, the hyphae sometimes developed a swollen tip and became depolarized so that they did not maintain their previous direction of growth.

The tendency to show disrupted growth did not depend on the diameter of the hyphae, or how closely related the fungi were. However, species with faster growth rates and higher pressure within the cell were more prone to disruption.

By observing fluorescent dyes in the living fungi, the team found that processes inside the cell became defective in the fungi with disrupted growth. Small packages (vesicles) that supply lipids and proteins (needed for assembling new membranes and cell walls as hypha extend) were no longer properly organized during growth through the channel.

“For the first time, we have shown that there appears to be a trade-off between cell plasticity and growth rate,” says Professor Takeshita. “When a fast-growing hypha passes through a narrow channel, a massive number of vesicles congregate at the point of constriction, rather than passing along to the growing tip. This results in depolarized growth: the tip swells when it exits the channel, and no longer extends. In contrast, a slower growth rate allows hyphae to maintain correct positioning of the cell polarity machinery, permitting growth to continue through the confined space.”

As well as helping explain why certain fungi can penetrate surfaces or living tissues, this discovery will also be important for future research into fungal biotechnology and ecology.

Reference: Trade-off between Plasticity and Velocity in Mycelial Growth” by Sayumi Fukuda, Riho Yamamoto, Naoki Yanagisawa, Naoki Takaya, Yoshikatsu Sato, Meritxell Riquelme and Norio Takeshita, 16 March 2021, mBio.
DOI: 10.1128/mBio.03196-20

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