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Archive for the ‘Plant Pathogens’ Category

From PestNet

Previously Unknown Rice Blast Resistance Isolated

By Sharon Durham
May 23, 2018

A never-before-described gene that gives rice resistance to a disease that has been costing about $66 billion a year in global damage has been isolated by a team of scientists led by Agricultural Research Service (ARS) plant pathologist Yulin Jia.

Rice blast, caused by the fungus Magnaporthe oryzae, results in annual yield losses large enough to have fed 60 billion people each year, according to the team’s paper just published in the journal Nature Communications.

In the United States’ mid-south rice-growing region, the cost of mitigating rice blast infection with fungicide applications can reach almost $20 per acre; plus, the fungus may still cause significant yield loss depending on the susceptibility of each rice variety and the degree of infection at the time of fungicide application, according to the U.S. Department of Agriculture’s (USDA) Economic Research Service.

Amazingly, Ptr, the disease resistance gene Jia and his team found, has a structure that has not been seen in plants before. It has been previously deployed unknowingly in blast-resistant rice cultivars because it has been tightly linked to another disease resistance gene, Pi-ta, which has a genetic structure that is well-described in scientific literature.

Ptr has essentially been living in the shadow of Pi-ta.. “Our research was able to separate the two genes and demonstrate that Ptr is independently responsible for its own broad-spectrum blast resistance without Pi-ta,” says Jia. “This will provide a new strategy for developing blast-resistant rice cultivars.” The full genomic sequence of the Ptr gene was put into GenBank for use by public researchers worldwide.

Jia, along with his colleagues Haijun Zhao, Melissa H. Jia and Jeremy D. Edwards, is with the ARS Dale Bumpers National Rice Research Center in Stuttgart, Arkansas. Other contributors include Xueyan Wang and Yeshi Wamishe at the University of Arkansas Rice Research and Extension Center (Stuttgart, Arkansas); Bastian Minkenberg, Matthew Wheatly and Yinong Yang at the Pennsylvania State University (University Park, Pennsylvania); Jiangbo Fan and Guo-Liang Wang at the Ohio State University (Columbus, Ohio); Adam Famoso at Louisiana State University (Rayne, Louisiana); and Barbara Valent at Kansas State University (Manhattan, Kansas).

The Agricultural Research Service is the U.S. Department of Agriculture’s chief scientific in-house research agency. Daily, ARS focuses on solutions to agricultural problems affecting America. Each dollar invested in agricultural research results in $20 of economic impact.

This is one of the news reports that ARS Office of Communications distributes to subscribers on weekdays.
Send feedback and questions to the ARS News Service at NewsService@ars.usda.gov.

 

 

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From PestNet

penn state

UNIVERSITY PARK, Pa. — Use of the powerful gene-editing tool CRISPR-Cas9 could help to breed cacao trees that exhibit desirable traits such as enhanced resistance to diseases, according to Penn State plant scientists.

The cacao tree, which grows in tropical regions, produces the cocoa beans that are the raw material of chocolate. Reliable productivity from cacao plants is essential to the multibillion-dollar chocolate industry, the economies of producing countries and the livelihoods of millions of smallholder cacao farmers.

But each year, several plant diseases severely limit global production, with 20-30 percent of cocoa pods destroyed preharvest, noted lead author Andrew Fister, postdoctoral scholar in plant science, College of Agricultural Sciences, Penn State.

“In West Africa, severe outbreaks of fungal diseases can destroy all cacao fruit on a single farm,” said Fister. “Because diseases are a persistent problem for cacao, improving disease resistance has been a priority for researchers. But development of disease-resistant varieties has been slowed by the need for sources of genetic resistance and the long generation time of cacao trees.”

The researchers reported recently, in Frontiers in Plant Science, the study results, which were thought to be the first to demonstrate the feasibility of using cutting-edge CRISPR technology to improve Theobroma cacao.

CRISPR stands for clustered regularly interspaced short palindromic repeats. It is a way to modify an organism’s genome by precisely delivering a DNA-cutting enzyme, Cas9, to a targeted region of DNA. The resulting change can delete or replace specific DNA pieces, thereby promoting or disabling certain traits.

Previous work in cacao identified a gene, known as TcNPR3, that suppresses the plant’s disease response. The researchers hypothesized that using CRISPR-Cas9 to knock out this gene would result in enhanced disease resistance.

Andrew Fister with cacao trees

Andrew Fister, postdoctoral scholar in plant science, stands among cacao trees in the African country of Ivory Coast. Pods turning yellow and black are infected with black pod disease.

Image: Désiré Pokou

 

To test their hypothesis, they used Agrobacterium — a plant pathogen modified to remove its ability to cause disease — to introduce CRISPR-Cas9 components into detached cacao leaves. Subsequent analysis of treated tissue found deletions in 27 percent of TcNPR3 copies.

When infected with Phytopthera tropicalis, a naturally occurring pathogen of cacao and other plants, the treated leaves showed greater resistance to the disease. The results suggested that the mutation of only a fraction of the copies of the targeted gene may be sufficient to trigger downstream processes, resulting in systemic disease resistance in the plant.

The researchers also created CRISPR gene-edited cacao embryos, which they will grow into mature trees to test the effectiveness of this approach at a whole-plant level.

This research builds on more than 30 years of biotechnology research aimed at building a better cacao tree, according to senior author Mark Guiltinan, professor of plant molecular biology and leader of Penn State’s endowed cocoa research program.

“Our lab has developed several tools for the improvement of cacao, and CRISPR is just one more tool,” he said. “But compared to conventional breeding and other techniques, CRISPR speeds up the process and is much more precise. It’s amazingly efficient in targeting the DNA you want, and so far, we haven’t detected any off-target effects.”

In addition to providing a new tool to accelerate breeding, CRISPR-Cas9 technology can help deliver insights into basic biology by offering a method to efficiently assess gene function, the researchers said.

“With CRISPR, we can quickly ‘break’ a gene and see what happens to the plant,” Guiltinan explained. “We have a list of genes in the pipeline that we want to test.”

There may be thousands of genes involved in disease resistance, Fister added.

“We want to evaluate as many as we can,” he said.

The ultimate goals of Penn State cacao research are to help raise the standard of living for smallholder growers and stabilize a threatened cocoa supply by developing plants that can withstand diseases, climate change and other challenges, according to co-author Siela Maximova, senior scientist and professor of horticulture.

“Any production increases in the last 20 years have been mostly due to putting more land into production,” said Maximova, who co-directs the cacao research program. “But land, water, fertilizer and other inputs are limited. To enhance sustainability, we need plants that are more vigorous and disease resistant and that produce more and better-quality beans.

“This study provides a ‘proof of concept’ that CRISPR-Cas9 technology can be a valuable tool in the effort to achieve these goals,” she said.

Lena Landherr Sheaffer, research assistant in plant science, Penn State, also was a co-author on the paper.

This work was supported by the Penn State College of Agricultural Sciences, the Huck Institutes of the Life Sciences, the Penn State Endowed Program in the Molecular Biology of Cacao, the National Science Foundation and the U.S. Department of Agriculture’s National Institute of Food and Agriculture.

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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.

 

cocoa

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

https://www.candyindustry.com/articles/88175-mars-aims-to-triple-cocoa-yield-through-development-of-disease-resistant-cocoa

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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
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.

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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

Reporter

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

cotton-june-ala-17-a1a_1

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

unb

Rice blast hits Boro corps in Sirajganj

UNB NEWS

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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