Archive for the ‘Plant Pathogens’ Category

From PestNet

Mars aims to triple cocoa yield through development of disease-resistant cocoa

Company, cocoa farmers to tap genetic knowledge to improve crops, reduce pesticide use.



Mars, Inc., plans to triple its global cocoa yield by developing more disease-resistant clones and continuing to improve farmer practices based on genetic knowledge of cocoa.

The global confectionery/pet food conglomerate has published research in the journal Frontiers of Plant Science that builds on work done by Mars, IBM and the USDA to help sequence the cocoa genome and make it publicly available.

The research also adds to work on higher-yielding pest- and disease-resistant clonal varieties Mars has helped develop with cocoa-growing countries. Applying this knowledge is expected to help farmers produce more cocoa on less land and with fewer pesticides, which can improve farmers’ livelihoods.

Specifically, Mars, Inc., in partnership with governmental and academic research organizations, used genetic markers to connect genetically-related cocoa trees and identify genes related to resistance of frosty pod, black pod and Ceratocystis wilt diseases.

In a keynote speech he delivered at the Fourth World Cocoa Conference in Berlin last month, Frank Mars, fourth-generation family member and member of the company’s board of directors, outlined Mars’ objectives in relation to this research.

“Over the next 10 years, Mars aims to develop even better disease-resistant clones,” Mars told conference attendees. “We’ll focus on both simple and advanced production methodologies and improved farmer practices with a goal to triple cocoa yields globally. This would free up land occupied with unproductive cocoa trees for farmers to grow other crops, including those for their own consumption. But to achieve this will require all of us in this room to think differently and work harder together; not only on better plant varieties and farming practices and models, but also on pest and disease control.”

Mars cited the need for continuing innovation, such as the company’s work through the Mars Center for Cocoa Science in Bahia, Brazil. Opened in 1982, the center has evolved to include private-public plant science partnerships with researchers and governments around the world. The center helps lead Mars’ efforts in areas such cocoa breeding, farming best practices, and pest and disease research and management.

Nonetheless, Mars said action the industry has taken so far hasn’t been sufficient to move the needle on sustainable cocoa.

“My hope is that 10 years from now, I can reflect on our efforts, both individually, and collaboratively,” Mars said. “I hope that I can look in the mirror and say I am proud of what we have achieved together. And know that cocoa does in fact have a sustainable future. And it’s one that uses science and technology to put farmers first.”

–Candy Industry


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Study could spawn better ways to combat crop-killing fungus

Rutgers-led genome research finds fungus that causes disease in rice became harmful 21 million years ago

Rutgers University

IMAGE: Ning Zhang, associate professor in the Department of Plant Biology and the Department of Biochemistry and Microbiology at Rutgers University-New Brunswick, holds a Petri dish with switchgrass seedlings inoculated with… view more 

Credit: Nick Romanenko/Rutgers University

About 21 million years ago, a fungus that causes a devastating disease in rice first became harmful to the food that nourishes roughly half the world’s population, according to an international study led by Rutgers University-New Brunswick scientists.

The findings may help lead to different ways to fight or prevent crop and plant diseases, such as new fungicides and more effective quarantines.

Rice blast, the staple’s most damaging fungal disease, destroys enough rice to feed 60 million people annually. Related fungal pathogens (disease-causing microorganisms) also infect turfgrasses, causing summer patch and gray leaf spot that damage lawns and golf courses in New Jersey and elsewhere every summer. And now a new fungal disease found in wheat in Brazil has spread to other South American countries.

Results from the study published online in Scientific Reports may lead to better plant protection and enhanced national quarantine policies, said Ning Zhang, study lead author and associate professor in the Department of Plant Biology and the Department of Biochemistry and Microbiology in the School of Environmental and Biological Sciences.

“The rice blast fungus has gotten a lot of attention in the past several decades but related species of fungi draw little attention, largely because they’re not as severe or not harmful,” Zhang said. “But they’re all genetically related and the relatives of severe pathogens have been little-studied. You have to know your relatives to have a holistic understanding of how the rice blast pathogen became strong and others did not.”

The study is the outcome of a 2016 international symposium at Rutgers-New Brunswick hosted by Zhang and Debashish Bhattacharya, study senior author and distinguished professor in the Department of Biochemistry and Microbiology. The National Science Foundation, Rutgers Center for Turfgrass Science, and School of Environmental and Biological Sciences funded the symposium by researchers from the U.S., France and South Korea.

The scientists studied Magnaporthales, an order of about 200 species of fungi, and some of the new members were discovered in the New Jersey Pine Barrens. About half of them are important plant pathogens like the rice blast fungus – ranked the top fungal pathogen out of hundreds of thousands. After the first sign of infection, a rice field may be destroyed within days, Zhang said.

To get a holistic understanding of how the rice blast fungus evolved, scientists genetically sequenced 21 related species that are less harmful or nonpathogenic. They found that proteins (called secretomes) that fungi secrete are especially abundant in important pathogens like the rice blast fungus.

Based on previous research, the proteins perhaps became more abundant over time, allowing the fungi to infect crops, Zhang said. The researchers identified a list of genes that are abundant in pathogens but less so in nonpathogens, so the abundant genes might promote pathogens that can infect crops. The results will allow scientists to look into the mechanism behind the infection process.

“With climate change, I think the rice blast problem can only get worse because this is a summer disease in warm climates where rice is grown,” Zhang said, adding that wheat, turfgrass and other important plants may also be affected.


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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Alberta farmer

Key source of clubroot resistance goes AWOL

‘Grandparent’ can defeat new mutated clubroot strains but somehow it doesn’t get passed down

The ‘grandparent’ of clubroot resistance in most Canadian canola varieties is resistant to new virulent strains of clubroot — but its offspring aren’t.

“It’s possible that, in the course of breeding, some of the resistant genes were lost,” said provincial research scientist Rudolph Fredua-Agyeman.

European clubroot differential (ECD) 04 is a key source of clubroot resistance for canola-breeding programs around the world, including in Canada, Fredua-Agyeman said at Alberta Canola’s Science-O-Rama last month.

Because of its resistance to all the clubroot strains found in Canada so far, ECD 04 has been bred into most clubroot-resistant canola varieties, including Mendel — a European winter canola cultivar that has also been used as a source of resistance for Canadian varieties.

“When clubroot was found in Alberta, the natural source of resistance was ECD 04 and Mendel, which were resistant to most of the strains of clubroot that we had at the time,” said Fredua-Agyeman.

But in 2013, clubroot strains started to shift to overcome the resistance, and new, more virulent strains of the disease began to appear in Alberta canola fields. As of 2017, these new strains have been confirmed in at least 104 fields in Alberta — a conservative estimate, as researchers only test fields that have been brought to their attention. Most notable of these strains is 5x, which can cause disease severity of up to 90 per cent.

“We’ve found that these strains are causing much more severe disease on canola than the other strains,” said Fredua-Agyeman, adding at least nine other strains have also been identified.

“The challenge posed to the canola industry by these new strains is real and very aggressive.”

The good news is that ECD 04 still shows complete resistance to these new strains, including 5x. Unfortunately, Mendel — and the commercial varieties that were spawned from it — are not.

“We went from ECD 04 — complete resistance — to Mendel, where we’re getting resistance to only 50 per cent of the new strains, and then to the commercial varieties, none of which are resistant to these new strains,” he said. “Not all the resistant genes were passed on from ECD 04 to Mendel, and from Mendel to the commercial varieties.

“The loss of this gene has contributed significantly to the breakdown of resistance.”

Integrated approach needed

Until new resistant varieties can be developed and new resistant sources found, canola growers will need to take a more “integrated” approach to clubroot management.

“Our resistance is very good, but it’s not a magic bullet,” said Stephen Strelkov, a plant pathologist and professor at the University of Alberta.

“Resistance is vulnerable, and we need proper resistance stewardship.”

When clubroot was first discovered in Alberta in 2003, producers were interested in finding a variety of tools to manage the disease. But when the first clubroot-resistant canola variety came online in 2009, farmers began to rely heavily on resistance instead of integrated disease management (which includes equipment sanitation and extended rotations).

“Clubroot resistance was such a strong tool that the extension messaging probably fell on deaf ears a little bit, and farmers grew resistant varieties in very short rotations,” said Strelkov, who also spoke at Science-O-Rama.

“People thought, ‘We have resistant varieties that do so well now — why should we worry about it?’”

But that reliance on resistant varieties has caused resistance to break down in record time. It only takes about two crops of a resistant variety for the pathogen to start to shift to overcome the resistance, and if those two crops are seeded back to back, it takes less than three years for the resistance to break down — not nearly enough time to find new sources of resistance or breed new resistant varieties.

“Resistance is the most widely used management strategy — nothing really compares to genetic resistance,” said Strelkov. “But these new strains highlight that our crop is still at risk from clubroot.”

Researchers are exploring other tools for clubroot management — including soil fumigants, liming, and bait crops — but until producers have more tools to add to their tool box, they need to take care of the ones they already have. That means using resistant varieties, rotating sources of resistance, sanitizing equipment, and (yes) extending rotations to four years.

If they don’t, they risk finding themselves in the same boat if and when new sources of resistance are found.

“It’s not a stable situation. The pathogen is changing and evolving,” said Strelkov.

“We’ll need a more integrated way of thinking to sustainably manage clubroot. Resistance will need to be used in conjunction with other tools.”

About the author


Jennifer Blair is a Red Deer-based reporter with a post-secondary education in professional writing and nearly 10 years of experience in corporate communications, policy development, and journalism. She’s spent half of her career telling stories about an industry she loves for an audience she admires–the farmers who work every day to build a better agriculture industry in Alberta.


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SE farm press


Aphid-transmitted virus found in lower Southeast cotton

Cotton blue disease is a big problem in Brazil, and it seems to have come to the U.S. by a hurricane, like soybean rust did with Hurricane Katrina.

Patrick R. Shepard | May 03, 2018

A virus that is previously known to be vectored by aphids into cotton has been recently identified as the primary suspect virus from limited samples of cotton in Alabama. Similar symptomology has been reported in the coastal counties of Alabama, Georgia and the Florida Panhandle.

“The cotton blue disease (CBD) symptomology was observed at the end of 2016 by one of my former graduate students, Drew Schrimsher, in his grower cotton variety trials,” says Auburn University plant pathologist Dr. Kathy Lawrence.

“He observed it again at the end of 2017 and it was much worse; symptomology was observed in areas beyond the area where it was first observed. CBD is a big problem in Brazil, and we hypothesize it may have come to the U.S. by a hurricane, like soybean rust did with Hurricane Katrina.”

Symptoms include mosaic cupping and thickening of the dark blue/green leaves, yellowed leaf veins, and dwarfing of the plant. Other symptoms include no boll set on new growth, swollen and brittle stems, and decreased yields; fields with symptoms in early bloom had fewer bolls per plant.

“Once the virus starts showing its symptoms, the plant stops producing any more cotton,” Lawrence adds. “There’s not a top crop, which many growers depend on for income.

 “We seldom spray for aphids in cotton, and we don’t recommend spraying for them to prevent this suspect disease, which would take out beneficials and flare other insect pest problems. We do encourage growers and consultants to watch for the CBD virus symptomology, and if they find it, to call their state plant pathologist to help us keep up with it.

“We also recommend keeping cotton fields and surrounding areas weed-free, especially of legume and malvaceae weeds including pigweed and sida as the literature shows they harbor the virus. If the virus is in the weeds, aphids can pick it up and transmit it to cotton. So management might come down to taking out weed host plants.”

Schrimsher, who is now an agronomist with AGRI AFC, observed mild leaf crumpling symptoms in his cotton variety trials that he was conducting in growers’ fields in south Alabama and the Florida Panhandle in late summer to early fall 2016. He observed extensive severe leaf crumpling in 2017.

Lawrence says, “The virus was much worse by that time; CBD had progressed beyond the area where it was found in 2016. However, infected areas were patchy like aphid infestations are patchy along the outer edges of a field, and close to areas with other plants and trees. It didn’t take over the whole field.

“Schrimsher told me about the symptoms in August 2017. We took samples, and found it’s a virus. We normally don’t have viruses in Alabama, so to get an identification, leaves, petioles and stems were collected from the newest terminal of plants expressing leaf crumpling symptoms and sent to University of Arizona plant pathologist Dr. Judy Brown, who researches the viruses in her state. She tested the samples and ruled out leaf crumple or leaf curl virus; instead, she found a virus associated with aphids that matches the one in Brazil.”

It appears from Schrimsher’s variety trials that the U.S. cotton varieties that were in the trials and are grown in the Southeast region all demonstrated the symptomology. “He saw the virus’ symptoms across all company varieties in his tests,” Lawrence says. “CBD is a big problem in Brazil, but they do have cotton varieties that are tolerant to the disease. The U.S. seed companies have gene markers in their breeding program. It’ll take time to develop resistant varieties for the U.S., but it’s not like starting from scratch.

“We will observe CBD closely this year. We’ve seen it for two years and hope it’s not here to stay. We hope that it will have a limited economic impact like soybean rust did.”

Official confirmation of the suspect virus will require additional sampling and verification by APHIS.


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Bangladesh: Rice blast


Rice blast hits Boro corps in Sirajganj


Wednesday 18 April, 2018 12:38:55 pm

Rice blast hits Boro corps in Sirajganj

Sirajganj, Apr 18 (UNB) – Farmers of nine upazilas in the district are worried of getting poor yield of Boro crops due to fungal disease blast attack during the harvesting season.

The fungal attack has spread all over the upazilas, according to sources at the Department of Agricultural Extension (DAE) department.

Some 20,000 hectares of land have been affected by the fungal disease in the last three days. The worst affected areas are: Sadar, Raiganj, Chouhali, Ullapara, Belkuchi and Kamarkhand upazilas of the district.

In an instant measure, the DAE authorities cancelled the leave of all employees and staffs in effected upazilas for bringing the situation under control as well as to protect the paddy field from the attack, said Agriculturist Arshed Ali, deputy director of DAE.

The DAE sources said the blast disease affected the paddy fields as farmers did not put fertiliser in a proper way. Besides, the hot temperature in daylight and fall of the same in night has pushed up the epidemic.

Due to the fungal infection, the plants became white in colour, Agriculturist Arshed Ali told UNB.

He advised the farmers to spray medicines on the paddy field to protect the corps.

Some 1.40 lakh hectares of land in the area have been brought under Boro cultivation this year.

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Mexico: Coconut production falls by 99% in Veracruz

Coconut production in the state of Veracruz has fallen by 99 percent due to the lethal yellowing disease and a complete lack of replanting, said the representative of the Coastal Society of Mexico and Coordinator of the National Council of Producers in the State, Carmen Belen Lihaut Sequera.
She also stated that during the 2013-2014 project, producers had planted 1,700 hectares of coconut that were tolerant to the lethal yellowing disease.
“Coconut production has fallen by 99 percent since 2008, when we started to see the disease, but since 2010 production began to disappear completely. Currently we are awaiting the production of the 1,700 hectares that were replanted here in Veracruz. Other producers have managed to make a successful plantation, but we need to take care of the problems in Veracruz,” she said.
More than 700 producers, who were dedicated to the plantation of coconut, are affected by this crisis across the entire state of Veracruz, she said. Currently, there are only 1,200 coconut producers, who are still reluctant to leave this market.
“The coconut plant is going to die. It is going to become extinct. The Creole variety of the coasts of the Gulf of Mexico is dying, and replanting them is urgent,” she added.
She also said that the producers of coconut had been forced to bring the plant that is 85 percent tolerant to the lethal yellowing disease from the certified nurseries of Colima, themselves.
This disease attacks many species of palms, including some species of commercial interest such as Cocos nucifera (the coconut tree), she stated.
Finally, she urged the authorities of the Ministry of Agriculture, Livestock, Rural Development, Fisheries and Food (Sagarpa), the Secretariat of Agricultural Development, Rural and Fisheries (Sedarpa) and the Secretariat of the Environment (Sedema), to solve the problem by replanting the coconut trees.
Source: eldictamen.mx


Publication date: 4/24/2018

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Path of Panama disease fungus established for the first time

The much-feared Tropical Race 4 strain of the Fusarium oxysporum soil fungus which causes Panama disease in Cavendish bananas has now been discovered in Myanmar. This follows closely on the heels of its discovery in Vietnam and Laos. The fungus is expected to have disastrous consequences on individual banana growers and the global banana industry. Scientists from Wageningen University & Research working with colleagues abroad have detected the fungus and used advanced techniques to find out where it came from.

Panama disease is a form of Fusarium wilt, caused by Fusarium oxysporum. The strain of this fungus known as Tropical Race 4 (TR4) affects many local banana varieties as well as the Cavendish cultivar, which accounts for 85% of world trade in bananas. Since all Cavendish bananas are clones of each other and there is little variation, they are highly susceptible to TR4, making the sector extremely vulnerable.

As explained on phys.org, the fungus, which appeared several decades ago, infects the roots, attacks the vascular system and eventually kills the plant. Once a plot is infected, bananas can no longer be cultivated there. This is a major threat to the global monoculture of Cavendish bananas.

TR4 has now been detected in Myanmar for the first time and its presence in Vietnam and Laos has been confirmed. In addition, research has made it possible to see which path it took to get there. There are links between the strains found in TR4 in China and these countries and in Pakistan and the Philippines, and between those detected in Lebanon and Jordan.

After sampling missions, the fungus was isolated from infected plants and then further studied by means of DNA testing. By determining the number and nature of mutations in the fungus, scientists were able to see exactly which strains are related. “This has reaffirmed the need for quarantine measures to prevent international spread and the need for sustainable solutions,” states Gert Kema, professor by special appointment of tropical phytopathology at Wageningen University & Research.

Publication date: 4/26/2018

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