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LSU student identifies fungus causing soybean taproot decline

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TAGS: CROP DISEASELSUGarciaArocajpg.jpgTeddy Garcia-Aroca, an LSU Ph.D. student, holds a sample of a fungus he found and named that causes the disease soybean taproot decline.Discovery just “tip of the iceberg” as scientists strive to learn more about this devastating soybean disease.

Bruce Shultz, Louisiana State University | Apr 13, 2021

An LSU graduate student has identified and named a new species of fungus that causes a devastating soybean disease. 

LSU doctoral student Teddy Garcia-Aroca identified and named the fungus Xylaria necrophora, the pathogen that causes soybean taproot decline. He chose the species name necrophora after the Latin form of the Greek word “nekros,” meaning “dead tissue,” and “-phorum,” a Greek suffix referring to a plant’s stalk. 

“It’s certainly a great opportunity for a graduate student to work on describing a new species,” said Vinson Doyle, LSU AgCenter plant pathologist and co-advisor on the research project. “It opens up a ton of questions for us. This is just the tip of the iceberg.” 

Taproot decline

The fungus infects soybean roots, causing them to become blackened while causing leaves to turn yellow or orange with chlorosis. The disease has the potential to kill the plant. 

“It’s a big problem in the northeast part of the state,” said Trey Price, LSU AgCenter plant pathologist who is Garcia-Aroca’s major professor and co-advisor with Doyle. 

“I’ve seen fields that suffered a 25% yield loss, and that’s a conservative estimate,” Price said. Heather Kellytaproot decline in soybeans

Yellowing leaves are early symptoms of taproot decline in soybeans.

Louisiana soybean losses from the disease total more than one million bushels per year. 

Price said the disease has been a problem for many years as pathologists struggled to identify it. Some incorrectly attributed it to related soybean diseases such as black-root rot. 

“People called it the mystery disease because we didn’t know what caused it.” 

Price said while Garcia-Aroca was working on the cause of taproot decline, so were labs at the University of Arkansas and Mississippi State University. 

Price said the project is significant. “It’s exciting to work on something that is new. Not many have the opportunity to work on something unique.” 

Research 

Garcia-Aroca compared samples of the fungus that he collected from infected soybeans in Louisiana, Arkansas, Tennessee, Mississippi and Alabama with samples from the LSU Herbarium and 28 samples from the U.S. National Fungus Collections that were collected as far back as the 1920s. 

Some of these historical samples were collected in Louisiana sugarcane fields, but were not documented as pathogenic to sugarcane. In addition, non-pathogenic samples from Martinique and Hawaii were also used in the comparison, along with the genetic sequence of a sample from China. 

Garcia-Aroca said these historical specimens were selected because scientists who made the earlier collections had classified many of the samples as the fungus Xylaria arbuscula that causes diseases on macadamia and apple trees, along with sugarcane in Indonesia. But could genetic testing of samples almost 100 years old be conducted? “It turns out it was quite possible,” he said. 

DNA sequencing showed a match for Xylaria necrophora for five of these historical, non-pathogenic samples — two from Louisiana, two from Florida, and one from the island of Martinique in the Caribbean — as well as DNA sequences from the non-pathogenic specimen from China. All of these were consistently placed within the same group as the specimens causing taproot decline on soybeans. 

Why now? 

Garcia-Aroca said a hypothesis that could explain the appearance of the pathogen in the region is that the fungus could have been in the soil before soybeans were grown, feeding on decaying wild plant material, and it eventually made the jump to live soybeans. 

Arcoa’s study poses the question of why the fungus, after living off dead woody plant tissue, started infecting live soybeans in recent years. “Events underlying the emergence of X. necrophora as a soybean pathogen remain a mystery,” the study concludes. 

But he suggests that changes in the environment, new soybean genetics and changes in the fungal population may have resulted in the shift. 

The lifespan of the fungus is not known, Garcia-Aroca said, but it thrives in warmer weather of at least 80 degrees. Freezing weather may kill off some of the population, he said, but the fungus survives during the winter by living on buried soybean plant debris left over from harvest. It is likely that soybean seeds become infected with the fungus after coming in contact with infected soybean debris from previous crops. These hypotheses remain to be tested. 

Many of the fungal samples were collected long before soybeans were a major U.S. crop, Doyle said. “The people who collected them probably thought they weren’t of much importance.” 

Garcia-Aroca said this illustrates the importance of conducting scientific exploration and research as well as collecting samples from the wild. “You never know what effect these wild species have on the environment later on.” 

What’s next? Now that the pathogen has been identified, Price said, management strategies need to be refined. Crop rotation and tillage can be used to reduce incidence as well as tolerant varieties. 

“We’ve installed an annual field screening location at the Macon Ridge Research Station where we provide taproot decline rating information for soybean varieties,” Price said. “In-furrow and fungicide seed treatments may be a management option, and we have some promising data on some materials. However, some of the fungicides aren’t labeled, and we need more field data before we can recommend any.” 

He said LSU, Mississippi State and University of Arkansas researchers are collaborating on this front. 

Doyle said Garcia-Aroca proved his work ethic on this project. “It’s tedious work and just takes time. Teddy has turned out to be very meticulous and detailed.” 

The final chapter in Garcia-Aroca’s study, Doyle said, will be further research into the origins of this fungus and how it got to Louisiana. Source: Louisiana State University, which is solely responsible for the information provided and is wholly owned by the source. Informa Business Media and all its subsidiaries are not responsible for any of the content contained in this information asset.  

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Taken from PestNet

Sunday, 18 April 2021 15:03:00

Grahame Jackson posted a new submission ‘How Plant ‘Vaccines’ Could Save Us From A World Without Fruit’

Submission

How Plant ‘Vaccines’ Could Save Us From A World Without Fruit

Discover
https://www.discovermagazine.com/environment/how-plant-vaccines-could-save-us-from-a-world-without-fruit

Researchers are formulating unconventional solutions for tree diseases that harm beloved foods like oranges and chocolate. These include a potential RNA therapy, similar to certain COVID-19 vaccines.

A future where chocolate, wine and oranges can be afforded only 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 attempting to create what she calls a “vaccine” for crops that could protect our food supply.

Like the current approach to the COVID-19 pandemic, researchers have long dealt with pathogen spread among plants by quarantining infected flora to spare surrounding ones. And, depending on the type of disease, plants may also receive pesticides or antibiotic sprays.

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

This potential fix can’t come fast enough. Currently, the world grapples with increasing perils to vital agricultural sectors. In Europe, a disease called olive quick decline syndrome threatens Italy’s treasured industry. Cacao grown in West Africa, which provides about 70 percent of the world’s chocolate, faces the debilitating cacao swollen shoot virus (CSSV). And precious Napa Valley grapes now contend with the grapevine red blotch virus. 

Most of these diseases don’t have a simple treatment, and require several costly, time-consuming strategies to mitigate the diseases once they’ve spread. They can also be difficult to detect because, in some cases, several years pass before symptoms appear.

Of course, plant pandemics are no new challenge. In the first half of the 20th century, for instance, a disease caused by fungus killed more than 3 billion American chestnut trees. But overall, climate change, ramped-up global travel and neglect by governments and industry have combined to create a perfect pathogen storm that endangers our food supply. “The time has come to let people know that there are other pandemics going on,” Simon says. “There’s multiple ones happening with trees, and it’s going to lead to a very different world.”

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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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GarciaArocajpg.jpg

Teddy Garcia-Aroca, an LSU Ph.D. student, holds a sample of a fungus he found and named that causes the disease soybean taproot decline.Discovery just “tip of the iceberg” as scientists strive to learn more about this devastating soybean disease.

Bruce Shultz, Louisiana State University | Apr 13, 2021

An LSU graduate student has identified and named a new species of fungus that causes a devastating soybean disease. 

LSU doctoral student Teddy Garcia-Aroca identified and named the fungus Xylaria necrophora, the pathogen that causes soybean taproot decline. He chose the species name necrophora after the Latin form of the Greek word “nekros,” meaning “dead tissue,” and “-phorum,” a Greek suffix referring to a plant’s stalk. https://f51f4f44a38d9cb02edf74f97f4f06e6.safeframe.googlesyndication.com/safeframe/1-0-38/html/container.html

“It’s certainly a great opportunity for a graduate student to work on describing a new species,” said Vinson Doyle, LSU AgCenter plant pathologist and co-advisor on the research project. “It opens up a ton of questions for us. This is just the tip of the iceberg.” 

Taproot decline

The fungus infects soybean roots, causing them to become blackened while causing leaves to turn yellow or orange with chlorosis. The disease has the potential to kill the plant. 

“It’s a big problem in the northeast part of the state,” said Trey Price, LSU AgCenter plant pathologist who is Garcia-Aroca’s major professor and co-advisor with Doyle. 

“I’ve seen fields that suffered a 25% yield loss, and that’s a conservative estimate,” Price said. Heather Kellytaproot decline in soybeans

Yellowing leaves are early symptoms of taproot decline in soybeans.

Louisiana soybean losses from the disease total more than one million bushels per year. 

Price said the disease has been a problem for many years as pathologists struggled to identify it. Some incorrectly attributed it to related soybean diseases such as black-root rot. 

“People called it the mystery disease because we didn’t know what caused it.” 

Price said while Garcia-Aroca was working on the cause of taproot decline, so were labs at the University of Arkansas and Mississippi State University. 

Price said the project is significant. “It’s exciting to work on something that is new. Not many have the opportunity to work on something unique.” 

Research 

Garcia-Aroca compared samples of the fungus that he collected from infected soybeans in Louisiana, Arkansas, Tennessee, Mississippi and Alabama with samples from the LSU Herbarium and 28 samples from the U.S. National Fungus Collections that were collected as far back as the 1920s. 

Some of these historical samples were collected in Louisiana sugarcane fields, but were not documented as pathogenic to sugarcane. In addition, non-pathogenic samples from Martinique and Hawaii were also used in the comparison, along with the genetic sequence of a sample from China. 

Garcia-Aroca said these historical specimens were selected because scientists who made the earlier collections had classified many of the samples as the fungus Xylaria arbuscula that causes diseases on macadamia and apple trees, along with sugarcane in Indonesia. But could genetic testing of samples almost 100 years old be conducted? “It turns out it was quite possible,” he said. 

DNA sequencing showed a match for Xylaria necrophora for five of these historical, non-pathogenic samples — two from Louisiana, two from Florida, and one from the island of Martinique in the Caribbean — as well as DNA sequences from the non-pathogenic specimen from China. All of these were consistently placed within the same group as the specimens causing taproot decline on soybeans. 

Why now? 

Garcia-Aroca said a hypothesis that could explain the appearance of the pathogen in the region is that the fungus could have been in the soil before soybeans were grown, feeding on decaying wild plant material, and it eventually made the jump to live soybeans. 

Arcoa’s study poses the question of why the fungus, after living off dead woody plant tissue, started infecting live soybeans in recent years. “Events underlying the emergence of X. necrophora as a soybean pathogen remain a mystery,” the study concludes. 

But he suggests that changes in the environment, new soybean genetics and changes in the fungal population may have resulted in the shift. 

The lifespan of the fungus is not known, Garcia-Aroca said, but it thrives in warmer weather of at least 80 degrees. Freezing weather may kill off some of the population, he said, but the fungus survives during the winter by living on buried soybean plant debris left over from harvest. It is likely that soybean seeds become infected with the fungus after coming in contact with infected soybean debris from previous crops. These hypotheses remain to be tested. 

Many of the fungal samples were collected long before soybeans were a major U.S. crop, Doyle said. “The people who collected them probably thought they weren’t of much importance.” 

Garcia-Aroca said this illustrates the importance of conducting scientific exploration and research as well as collecting samples from the wild. “You never know what effect these wild species have on the environment later on.” 

What’s next? 

Now that the pathogen has been identified, Price said, management strategies need to be refined. Crop rotation and tillage can be used to reduce incidence as well as tolerant varieties. 

“We’ve installed an annual field screening location at the Macon Ridge Research Station where we provide taproot decline rating information for soybean varieties,” Price said. “In-furrow and fungicide seed treatments may be a management option, and we have some promising data on some materials. However, some of the fungicides aren’t labeled, and we need more field data before we can recommend any.” 

He said LSU, Mississippi State and University of Arkansas researchers are collaborating on this front. 

Doyle said Garcia-Aroca proved his work ethic on this project. “It’s tedious work and just takes time. Teddy has turned out to be very meticulous and detailed.” 

The final chapter in Garcia-Aroca’s study, Doyle said, will be further research into the origins of this fungus and how it got to Louisiana. Source: Louisiana State University, which is solely responsible for the information provided and is wholly owned by the source. Informa Business Media and all its subsidiaries are not responsible for any of the content contained in this information asset.  

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Damage from invasive species ‘trebling every decade’

Mosquitoes, rats and termites among species that have hitched ride on trade routes, causing at least $1.3tn of damage

Fall armyworm
The fall armyworm arrived in Africa in 2016 and has now invaded dozens of countries. Photograph: Grant Heilman Photography/Alamy

Damian Carrington Environment editor@dpcarringtonWed 31 Mar 2021 11.00 EDT

The costs of damage caused by invasions of alien species across the world is trebling every decade, research has found.

Mosquitoes, rats, ragweeds and termites are among the species that have hitched a ride on globalised trade routes, bringing disease, crop destruction and damage to buildings. The scientists calculated the costs at $1.3tn (£944bn) since 1970, and said even this “staggering sum” was likely to be a big underestimate as much damage is unreported.

The rapidly growing costs show no sign of slowing down, the researchers said, and are more than 10 times higher than the funding for preventing or dealing with these biological invasions. They said global action to combat invasive species remained limited, mostly because the “profound” impacts are poorly understood by the public and politicians.

Mosquitoes from the Aedes genus, such as the tiger mosquito, spread Zika, dengue, yellow fever and other viruses, and were responsible for the biggest recorded costs. Invasive rodents such as the black rat, grey squirrel, coypu and house mouse also cause severe damage to human health, crops and food stores and to native wildlife.

Formosan termites, voracious consumers of wood, are a particular problem in the US, while the red fire ant has spread from its South American home to Australia, New Zealand, several Asian and Caribbean countries and the US. The fall armyworm, which can destroy many crops, arrived in Africa in 2016 and has now invaded dozens of countries.

“The economic costs of invasive alien species since 1970 are tremendous, steadily increasing, but still massively underestimated,” said Christophe Diagne, at the Université Paris-Saclay, France, and who led the research. He said the rising damage mirrored the growth of international trade and the expanding area of farmland and settlements that the invaders can damage.Advertisement

Prof Corey Bradshaw, of Flinders University in Australia, who was part of the study team, said: “The quicker you detect invasive species and the quicker you act, the cheaper it is in the long run. So really good detection at ports and airports and then rapid responses are going to cost you orders of magnitude less money than the damage.”

He said consumers ended up paying for the damage via increased prices for food and other products, and higher healthcare costs.

The research, published in the journal Nature, analysed more than 1,300 estimates of damage by invasive animals and plants. Costs were highest in the US, India, China and Brazil, but this probably reflects where the problems have been most reported. There is little or no data in many other parts of the world.

Some earlier cost estimates indicated much higher damages – as much as $1.4tn a year – but Bradshaw said these were largely based on poor or speculative assessments. “Some were not even ‘back of the envelope’ – there was no envelope,” he said.

The new analysis was deliberately conservative, using only estimates based on observed data. “But there are so many unquantifiables from a monetary perspective, like ecosystem damage and lost productivity, so it’s still the tip of the iceberg,” said Bradshaw. The true costs could be 10 times higher, he said.

Biological invasions are known to be increasing and so the rising cost estimates are unlikely to be solely the result of increased reporting of damage. Either way, the scientists said, “they robustly show staggering amounts” and “a huge economic burden”.

Prof Helen Roy, of the UK Centre for Ecology & Hydrology, who was not part of the research team, said: “The most important aspect of this research is showing the rising costs, regardless of the exact figure. Overall it is a very useful paper and has some excellent recommendations. It also gives some cause for optimism – there are ways to prevent arrival or manage invasive alien species that become established.”

Bradshaw said cinnamon fungus, which rots the roots of plants including grape vines, was one of Australia’s most damaging invasive species. “I have a little farm and it’s killed all of my chestnuts. So we’re slowly replacing those with trees that are resistant”.

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DMI resistance in wheat powdery mildew confirmed for the first time

Date: 17 Mar 2021

image of powdery mildew
Powdery mildew in a head of wheat. Photo: CCDM

New South Wales and Victorian grain growers are urged to be on alert following confirmation that difficulties experienced in 2020 controlling wheat powdery mildew are linked to resistance of the pathogen to demethylase inhibitor (DMI, Group 3) fungicides.

Fungicide resistance was detected at frequencies ranging from 50 to 100 per cent in samples collected from paddocks around Albury, Rennie, Balldale, Deniliquin and Jerilderie in NSW, and Cobram and Katamatite in Victoria.

Further sampling revealed a wider NSW distribution, from around Hillston and Yenda in south-west NSW, as well as Edgeroi and Wee Waa in northern NSW, in similar frequencies. This marks the first time that resistance in wheat powdery mildew to DMIs has been detected in Australia.

Researchers from the Fungicide Resistance Group at the Centre for Crop and Disease Management (CCDM) – a co-investment by the Grains Research and Development Corporation (GRDC) and Curtin University – confirmed the presence of DMI resistance in a range of samples sent by agronomists who were concerned about disease levels in their clients’ wheat crops during the 2020 season.

The wheat samples from across NSW and into Victoria were from predominantly Vixen and Scepter bread wheat varieties, and a lower number of durum wheat varieties.

NSW Department of Primary Industries (DPI) cereal pathologist Steven Simpfendorfer says he is not entirely surprised some level of resistance was detected, but is surprised by the high frequency of the detections. He describes the detections as alarming and a wake-up call for industry.

“These detections have occurred predominantly in high-value, irrigated cropping regions, which create ideal conditions for wheat powdery mildew disease development,” Dr Simpfendorfer says.

He says that the reliance on DMI fungicides by many growers in the region over many years contributed to selecting for the fungicide resistance detected during this past season.

Strong collaborative networks were key to the rapid detection of this case of wheat powdery mildew DMI resistance.

Agronomists and growers collected 40 samples from 20 paddocks across NSW and Victoria and these were analysed by CCDM researchers in the laboratory.

image of Powdery mildew on leaves
Powdery mildew on leaves in a wheat crop. Photo: CCDM

Director of the CCDM, Mark Gibberd, praised his colleagues and collaborators for how quickly and effectively they worked together to detect this case of resistance.

“Recent case studies of fungicide resistance detections in WA, South Australia and now Victoria and New South Wales, demonstrate the importance of strong relationships and cross-institutional collaboration to deliver robust results that growers can act on,” Professor Gibberd says.

CCDM researcher Steven Chang says genetic and phenotypic analyses of the wheat powdery mildew pathogen isolated from the samples showed a combination of mutations in the DMI fungicide target gene that were associated with the resistance observed to some DMIs. Additionally, all samples tested had some level of strobilurin fungicide (Group 11) resistance.

CCDM’s fungicide resistance group leader Fran Lopez-Ruiz says CCDM researchers have run a monitoring program for fungicide resistance in wheat powdery mildew for many years. Thanks to this, they could determine that the mutations now found in NSW and Victoria were the same as those previously detected in Tasmania and SA.

The Australian grains crop protection market is dominated by only three major mode of action (MoA) groups to combat diseases of grain crops in Australia: the DMIs (Group 3), SDHIs (Group 7) and strobilurins (or quinone outside inhibitors, QoIs, Group 11). Having so few MoA groups available for use increases the risk of fungicide resistance developing, as growers have very few alternatives to rotate in order to reduce selection pressure for these fungicide groups.

With two of the three fungicide MoA groups now compromised in some paddocks in NSW and Victoria, all growers need to take care to implement fungicide resistance management strategies to maximise their chances of effective and long-term disease control.

The Australian Fungicide Resistance Extension Network (AFREN), a GRDC investment, suggests an integrated approach tailored to local growing conditions. AFREN has identified the following five key actions, ‘The Fungicide Resistance Five’, to help growers maintain control over fungicide resistance, regardless of their crop or growing region:

  1. Avoid susceptible crop varieties
  2. Rotate crops – use time and distance to reduce disease carry-over
  3. Use non-chemical control methods to reduce disease pressure
  4. Spray only if necessary and apply strategically
  5. Rotate and mix fungicides/MoA groups

Growers and agronomists who suspect DMI reduced sensitivity or resistance should contact the CCDM’s Fungicide Resistance Group at frg@curtin.edu.au. Alternatively, contact a local regional plant pathologist or fungicide resistance expert to discuss the situation. A list of contacts is on the AFREN website.

Further information on fungicide resistance and its management in Australian grains crops is also available via the AFREN website.

Contact Details

For interviews

Steven Simpfendorfer, NSW DPI
0439 581 672
steven.simpfendorfer@dpi.nsw.gov.au

Kylie Ireland, Curtin University
(08) 9266 3541
ccdm@curtin.edu.au

Contact

Sharon Watt, GRDC
0409 675 100
sharon.watt@grdc.com.au

GRDC Project code: MSF2007-001SAX

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

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Fusarium fujikuroi may be an emerging problem for plum cultivation in China

Plums are commercially cultivated worldwide for the rich nutrient value of their fruit. In May 2019, plums with symptoms of fruit rot were collected from fields located in Liuma town, Guizhou Province, China. The incidence of the disease varied from 10 to 20%, which was observed in 15 plum orchards (18 hectares) surveyed. Estimated yield loss was from 5 to 10% for each field. Diseased fruits showed deformity, wilting and sunken lesions, and subsequently became melanized and rotted.

Scientists at Guizhou University have collected diseased tissues and conducted morphological analyses. Based on the cultural and conidial morphology, the isolates were identified as Fusarium fujikuroi. To confirm the morphological diagnosis, DNA sequencing and pathogenicity assay were performed.

“Fruit were artificially inoculated and maintained in a growth chamber with 90% relative humidity at 25°C, and a daily 12-h photoperiod. After 5 days, the artificially inoculated fruit showed blotches with sunken lesions similar to those observed in the orchards, whereas no symptoms were observed on the control fruit. The experiment was repeated twice with similar results. Fusarium fujikuroi was reisolated from infected tissues and confirmed by sequence analysis. To our knowledge, this is the first report of F. fujikuroi causing fruit blotch of plum in China. Considering the economic importance of plum in China and throughout the world, F. fujikuroi may be an emerging problem for plum cultivation. Thus, further study of fruit blotch of plums is warranted,” the scientists explain.

Source: Haijiang Long, Xianhui Yin, Zhibo Zhao, Youhua Long, Juan Fan, Ran Shu, Guifei Gu, ‘First Report of Fruit Blotch on Plum caused by Fusarium fujikuroi in China’, 2021, Plant Disease.

Publication date: Thu 11 Mar 2021
Author: Emanuela Fontana
© FreshPlaza.com

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New tomato varieties in the fight against ToBRFV

The Italian company TomaTech is making great progress in the fight against ToBRFV. Starting next season, commercial varieties with intermediate resistance will be available. These include date tomatoes, midi plum and a number of colored varieties, both loose and on the vine.

This variety renewal starts with the date variety Dormaplum, which is described by TomaTech as the perfect tomato. It is very sweet, with a bright color and a uniform size, a weight of 16 grams and a Brix degree between 9 and 10. The balance between sweetness, acidity and structure is excellent.

The plant has an extraordinary high yield, suitable for long cycles and ideal for unheated greenhouses. TomaTech recommends grafting with two buds, and can be transplanted between the end of August and October.

The tomatoes have a long shelf life and are resistant to ToMV, Ff, TYLCV, ToBRFV. For those interested, seeds are available for trials.

Dormaplum, moreover, is a variety launched in southern Europe in 2020 which, despite numerous difficulties and limitations due to Covid-19, is proving to be an exceptional agronomic and commercial success.

For those who are instead looking for larger fruits, TomaTech offers cluster plums – still in the research phase – which seem very promising and are already available for long cycles with transplanting in August/October in Sicily and springtime in Lazio and Campania. Here too, free samples are available on request. To complete the current ToBRFV resistant/tolerant variety range there are three coloured specialities: ‘Tomelody’, ‘Cantando’ and ‘Tiny Tom Orange’.

Tomelody stands out for its sweetness, a tasty lemon-colored date variety with a distinctive shape and rich flavor. Perfect as a snack, light and healthy. High yield with more than 25 fruits per cluster of 15-17 grams each. The plant is resistant to Fol:0, ToMV, ToBRFV and is extremely versatile and suitable for all seasons.

Cantando is an orange date tomato with a high palatability, a Brix value between 8 and 10 and a smooth texture. The plant is very generative, well balanced with short internodes and resistant against Vd, Fol:0.1, ToMV, Mj, ToBRFV. The variety is suitable for transplanting between September and October.

Tiny Tom Orange is a sweet, fruity and aromatic orange date tomato. They weigh only 12 grams and have a Brix value ranging from 9 to 10. The variety is resistant to Vd, Fol:0.1, ToMV, Mj and ToBRFV.

 “At TomaTech, we are aware that the fight against ToBRFV is far from over, but we are confident in the work done. We are now able to launch these promising varieties and more will follow. So far, we have a valuable tool to contain this disease,” said the TomaTech research team.

For more information:
TomaTech
+39 351 7614 587
www.tomatech.it

Publication date: Wed 17 Mar 2021
© HortiDaily.com

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