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Researchers develop strategy that could lead to environmentally friendly fungicide to fight pathogens that cause billions of dollars in crop loss

gray mold on fruit, vegetables and flowersThe images third from the bottom and at the bottom show fruit, vegetables and flowers treated with pathogen gene-targeting RNA molecules. The other images represent various control methods.

 

RIVERSIDE, Calif. (www.ucr.edu) — Have you ever bought strawberries or other fruits and vegetables, forgot to put them in the refrigerator and later noticed they had gray mold on some of them?

That’s Botrytis cinerea, a fungal pathogen that can infect more than 1,000 plant species, including almost every fruit and vegetable and many flowers. Wine grapes are also a notable host – in grapes the condition is known as bunch rot. It causes billions of dollars in crop loss annually.

A team of researchers, led by Hailing Jin, a University of California, Riverside professor of plant pathology and microbiology, have developed a new strategy that could provide an easy-to-use and environmentally friendly fungicide to fight B. cinerea and other fungal pathogens that harm crops.

The findings were just published in the journal Nature Plants.

These findings build on a paper by Jin’s group published in 2013 in the journal Science. In that paper, they outlined how they discovered the mechanism by which B. cinerea infects plants.

Many pathogens secrete protein effectors molecules to manipulate and – eventually – compromise host immunity. The researchers, led by Jin, found three years ago for the first time that B. cinerea can deliver small RNA effector molecules to the host cells to induce cross-kingdom RNA interference (RNAi) to suppress host immunity.

Building on that work, in the just-published study in Nature Plants, they discovered that such cross-kingdom RNAi is bidirectional, meaning small RNAs can flow from the pathogen to the host and from the host to the pathogen.

Furthermore, they found that B. cinerea is capable of taking up RNA molecules from the environment, which makes it possible to use such external RNAs in fungicidal sprays to manage diseases.

The researchers tested that idea and found that applying those pathogen gene-targeting RNA molecules to the surface of fruits and vegetables and flowers – they used tomato, strawberry, grape, lettuce, onion, and rose – can control gray mold diseases.

The findings outlined in the Science and Nature Plants papers have significant implications for farmers looking to control fungal pathogens. Currently, fungicides and chemical spraying are still the most common disease control strategy. But, these treatments pose serious threats to human health and environments. RNA, which is present in all living organisms, doesn’t present problems for human health and it naturally degrades in soil.

While the research focused on the fungal pathogens B. cinerea and Verticillium dahliae, another fungal pathogen that causes wild disease on dozens of trees, shrubs, vegetables, and fields crops, the researchers believe this RNAi-based technique could be used to control multiple pathogens at the same time.

While the research focused on the fungal pathogen B. cinerea, the researchers believe the technique could be used to control other fungal pathogens, such as Verticllium dahliae, which causes wild disease on dozens of trees, shrubs, vegetables, and fields crops.

It also has the potential to decrease the use of GMOs by providing an effective, environmentally friendly way to control plant diseases.

The Nature Plants paper is called “Bidirectional cross-kingdom RNAi and fungal uptake of external RNAs confer plant protection.” In addition to Jin, the authors are Ming Wang and Arne Weiberg, both of UC Riverside; Arne Weiberg, who recently got a faculty position at the University of Munich; Feng-Mao Lin and Hsien-Da Huang, both of National Chiao Tung University in China; and Bart P. H. J. Thomma of Wageningen University in the Netherlands.

This research was supported by grants Jin received from the National Science Foundation and National Institutes of Health.

The invention has a patent pending status.

 

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Sudden drop in disease resistance in SA chickpea crop raises concern

Updated Mon at 11:16pm

A sudden loss of disease resistance in the expected bumper chickpea crop in South Australia this year is raising concerns.

South Australian Research and Development Institute (SARDI) pathologist Dr Jenny Davidson said she was concerned about the level of infection in varieties thought to be resistant to the disease.

Authorities have approved minor use permits for farmers to use chemicals to spray their crops to limit the spread of ascochyta blight.

Ascochyta blight has been detected in several cropping regions over the past few weeks — including the Mid North, Lower North and Yorke Peninsula.

Dr Davidson said not only was the extent of the disease concerning, but so too the pace of the outbreak had been unexpected.

“Suddenly this year, which we assume is to do with the rain in winter, the disease is creating some really severe problems.

“This sudden loss of resistance is something that is a little bit surprising, [given] the speed with which it has happened.”

“We were aware that something was changing and we gave information out to industry last year to monitor their crops because something was changing.

“But suddenly we’ve got a dramatic shift in the whole spectrum of what’s going on.”

Scientists are urging farmers to get on top of the outbreak as soon as possible, and by doing this farmers can help reduce its severity.

“If they get out there and spray their fungicides, and continue to put out sprays, they should be able to get those crops through.

Dr Davidson said to use protectant fungicides ahead of rain fronts, starting at the next rain front.

“They need to get a fungicide spray out, then during podding. They really need to be very diligent about getting those sprays on the crops,” Dr Davidson said.

Topics: agricultural-crops, agricultural-chemicals, earth-sciences, port-pirie-5540

First posted Mon at 10:56pm

 

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Growers say the fungal disease is piling on their miseries brought about by distribution of substandard fertiliser that affected germination of the crop

Wednesday August 17 2016

Mr Jeremiah Kipyego inspects maize on his farm in Uasin Gishu County in May.

Mr Jeremiah Kipyego inspects maize on his farm in Uasin Gishu County in May. Maize farmers in the region expressed fears of yield decline this season due to attack by head smut disease. FILE PHOTO | NATION MEDIA GROUP 

In Summary

  • Growers expressed fears of serious yield decline this season due to the disease referred to as head smut.
  • Maize farmers asked to practice crop rotation to break the cycle of the fungal disease.
  • The fungal attack follows repeated outbreak of Maize Lethal Necrosis (MLN) disease that ravaged parts of the country last season, forcing some farmers to uproot the crop.
  • Maize production in Rift Valley dropped from 21 million bags to 16 million bags last season due to erratic rainfall pattern and repeated outbreak of MLN disease.

By BARNABAS BII
More by this Author

An outbreak of a maize disease has left many farmers in the North Rift uncertain of their harvests putting the country’s food security at risk.

Growers yesterday expressed fears of serious yield decline this season due to the disease referred to as head smut, which is adding to the miseries bought about by distribution of sub-standard fertiliser that affected germination patterns of maize.

“We are worried that fungal disease will add to the miseries of high cost of production, rendering agriculture a non-profit investment,” said Mr Patrick Kemboi from Chepkumia, Nandi County.

The disease has been reported in parts of Uasin Gishu, Nandi  and Elgeyo Marakwet County.

Maize producers are now accusing the Kenya Seed Company of supplying them with poor seeds that has led to the outbreak of the fungal disease.

“I wonder why our crop has been attacked yet I planted certified seed from the company sourcing from the Kenya Seed Company,” said Mr Wilson Sang from Chembulet, Uasin Gishu County.

Growers have taken issue with the Kenya Seed management due to alleged failure in cracking down on traders dealing in sub-standard planting materials.

“Poor quality seed and a failure to crack down on fake seed being supplied by Kenya Seed’s accredited stockists,” said Mr Andrew Rotich, a maize farmer from Cherang’any.

Kenya Seed managing director Azariah Soi has, however denied responsibility for the outbreak of the fungal disease saying that studies conducted in conjunction with the Kenya Plant and Health Inspectorate Services (Kephis) have shown that the head smut disease has nothing to do with seed.

PRODUCTION OF DISEASE RESISTANT SEEDS

“The head smut disease that has affected maize in Rift Valley is not as a result of seed distributed by our company,” said Mr Soi noting that the disease was in the soil.

He asked maize farmers to practice crop rotation to break the cycle of the fungal disease. “Our researchers are working closely with those from Kephis to come up with further remedies that can be employed by farmers in future including a possible production of seeds, which are disease-resistant,” Mr Soi said.

The fungal attack follows repeated outbreak of Maize Lethal Necrosis (MLN) disease that ravaged parts of the country last season, forcing some farmers to uproot the crop.

“The recurrence of MLN disease and attack of the crop by head smut is a serious challenge to maize cultivation,” said Mr Isaac Kibogy from Sergoit, Uasin Gishu County.

Farmers have been asked to implement crop rotation to break the cycle of the disease that damaged over 260,000 hectares of maize valued at Sh2 billion in Rift Valley last season.

“Feeding the plants to cattle is not appropriate because the fungus which cannot be digested is passed out through dung and later reproduces posing threat to crops again,” said Mr Soi.

Maize production in Rift Valley dropped from 21 million bags to 16 million bags last season due to erratic rainfall pattern and repeated outbreak of MLN disease.

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From PestNet@yahoogroups.com

This is a summary of the research at UC Davis that the other email was referring to. It would have been better to have put both out together …

Crop Biotech Update

Banana Fungus DNA Unravelled; Findings to Lead to Hardier Bananas

Researchers at the University of California Davis and Wageningen UR have unravelled the DNA of Pseudocercospora fijiensis, the fungus that causes black Sigatoka disease in bananas globally.

The Sigatoka complex’s three fungal diseases — yellow Sigatoka (P. musae), eumusae leaf spot (P. eumusae) and black Sigatoka (P. figiensis) — emerged as destructive pathogens in the last century. Eumusae leaf spot and black Sigatoka are now the most devastating, with black Sigatoka posing the greatest constraint to banana production worldwide. Farmers need to apply fungicide at least 50 times per year to control the disease.

UC Davis plant pathologist Ioannis Stergiopoulos and colleagues sequenced the genomes of eumusae leaf spot and black Sigatoka, and compared their findings with the previously sequenced yellow Sigatoka genome sequence. They discovered that Sigatoka Complex has become lethal to banana plants not just by shutting down the plant’s immune system, but also by adapting the metabolism of the fungi to match that of the host plants. As a result, the attacking fungi can produce enzymes that break down the plant’s cell walls, allowing the fungi to feed on the plant’s sugars and other carbohydrates.

For more details, read the news release at the UC Davis website.

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Manila Times logo

Fungal disease reduces onion produce

July 27, 2016 9:53 pm

AGGRAVATED by climate change, fungal disease infection resulted in yield losses in the onion supply in Badoc town in Ilocos Norte. An assessment by the municipal agriculture office revealed that the areas planted to the red onion variety have decreased by almost 50 percent because of the sudden occurrence of the plant’s disease during this year’s planting season. Cornelio Dinong, Badoc municipal agricultural technologist, said the dominant fungal diseases that hit the growing onions are the “anthracnose” and the purple blotch, which usually develop during drizzles and the rainy season, and are further aggravated by climate change. To eliminate the fungal disease causing microorganisms, intensified information campaign was staged urging local farmers to practice soil sterilization and crop rotation at the onset of planting season. Farmers, meanwhile, have chosen to grow hybrid corn, mungbean and high value vegetables in their field in lieu of onion.

 

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Fresh

Plaza

Concern about the lack of controls

The banana crops of Colombia and other Latin American producers faces the risk of being affected by the arrival of a harmful fungus due to the increase in illegal migration from Asia and Africa, as well as the low health controls in Venezuela, said an official from the agricultural sector.
The Fusarium Tropical Race 4 fungus, which causes the Panama disease and can remain in the soil for up to 30 years, attacks the roots of the Cavendish banana variety and plantain.
The eventual arrival of the Fusarium to the region would negatively affect the economies of the banana producing countries and jeopardize food security, said the assistant manager of plant protection at the Colombian Agricultural Institute, Carlos Soto.
“It would be devastating if the fungus arrived, it would destroy everything. We can only take preventive actions, there is no cure for this fungus,” Soto said in a telephone interview with Reuters.
Colombia, the world’s fourth largest banana exporter after Ecuador, Costa Rica, and Guatemala, is working with Peru, Ecuador and Bolivia on a regional campaign to identify the presence of the disease and to increase health checks at borders.
The plan will also be presented to Central America in the coming weeks.
The fungus, which can be transported from one continent to another by migrants  shoes, clothing or agricultural products, has been detected in Indonesia, China, Philippines, Malaysia, Pakistan, Australia, and Mozambique.
Colombia leads the regional campaign because it has become an important transit country for migrants from Asia and Africa that walk across the border with Panama, one of the main areas of cultivation, as they seek to reach the United States illegally through Central America.
Even though the fungus has not been detected in Latin America yet, Soto expressed concern about Venezuela’s lack of controls.
“I’m very concerned about Venezuela because it has no health management and that means they can have the disease and not know they have it, since there is a lot of migration and illegal trade coming from that border, it can be a real danger for us,” he said.
Colombia has 47,000 hectares of banana that generates 30,000 direct jobs. Additionally, the country has over 400,000 hectares of bananas for domestic consumption.
In 2015, Colombia exported 92 million boxes of bananas worth 800 million dollars to the European Union and to the United States.
In the middle of the last century, several banana plantations in Latin America and the Caribbean were infected with a strain of the fungus and had to be replaced by more resistant crops.
Source: gestion.pe

 

Publication date: 7/28/2016

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Chiapas, Mexico, July 25, 2016

Felix Corzo Jimenez , a farmer in Chiapas, Mexico, examines one of his maize plants infected with tar spot complex.
Felix Corzo Jimenez , a farmer in Chiapas, Mexico, examines one of his maize plants infected with tar spot complex. Photo: J. Johnson/CIMMYT.

In southern Mexico and Central America a fungal maize disease known as tar spot complex (TSC) is decimating yields, threatening local food security and livelihoods. In El Portillo, Chiapas, Mexico, local farmer Felix Corzo Jimenez sadly surveys his maize field.

“It’s been a terrible year. We’ll be lucky if we harvest even 50 percent of our usual yields,” he said, examining a dried up maize leaf covered in tiny black dots, and pulling the husk off of an ear to show the shriveled kernels, poorly filled-in. “Tar spot is ruining our crops.”

Named for the black spots that cover infected plants, TSC causes leaves to die prematurely, weakening the plant and preventing the ears from developing fully, cutting yields by up to 50 percent or more in extreme cases. Caused by a combination of three fungal infections, the disease occurs most often in cool and humid areas across southern Mexico, Central America and South America. The disease is beginning to spread – possibly due to climate change, evolving pathogens and susceptible maize varieties – and was reported in important maize producing regions of central Mexico and the northern United States for the first time last fall. To develop TSC resistant maize varieties that farmers need, the Seeds of Discovery (SeeD) initiative is working to “mine” the International Maize and Wheat Improvement Center’s (CIMMYT) genebank for native maize varieties that may hold genes for resistance against the disease.

The first stage of fungal maize disease TSC, with tiny, black “tar spots” covering the leaf. The spots will soon turn into lesions that kill the leaf, preventing photosynthesis from occurring.

The majority of maize varieties planted in Mexico today are susceptible to TSC, meaning that farmers would have to spray expensive fungicides several times each year to protect their crops against the disease, a huge financial burden that few can afford. Creating varieties with natural resistance to tar spot is an economical and environmentally friendly option that will protect the livelihoods of the region’s smallholder maize farmers.

“This project targets the many farmers in the region with limited resources, and the small local seed companies that sell to farmers at affordable prices,” says Terry Molnar, SeeD maize breeder.

The key to developing maize varieties with resistance to TSC lies in the genetic diversity of the crop. For thousands of years, farmers have planted local maize varieties known as landraces, or descendants from ancient maize varieties that have adapted to their environment. Over centuries of selection by farmers these landraces accumulated specific forms of genes, or alleles, which helped them to resist local stresses such as drought, heat, pests or disease.

These novel genetic traits found in landrace maize can help breeders develop improved maize varieties with resistance to devastating diseases such as TSC. However, it is quite challenging for breeders to incorporate “exotic” landrace materials into breeding programs, as despite their resistance to stresses found in their native environment, they often carry unfavorable alleles for other important traits.

A maize ear with shriveled kernels that are poorly filled, a major side effect of TSC that reduces farmer’s tields.

To help breeders incorporate this valuable genetic diversity into breeding programs, SeeD works to develop “bridging germplasm” maize varieties, which are created by transferring useful genetic variation from landraces held in the CIMMYT genebank into plant types or lines that breeders can readily use to develop the improved varieties farmers need. These varieties are created by crossing landrace materials with CIMMYT elite lines, and selecting the progeny with the genetic resistance found in a landrace without unfavorable traits breeders, farmers and consumers do not want.

“The CIMMYT maize genebank has over 28,000 maize samples from 88 countries, many of which are landraces that may have favorable alleles for disease resistance,” Molnar says. “We all know that there is good material in the bank, but it’s scarcely being used. We want to demonstrate that there are valuable alleles in the bank that can have great impact in farmers’ fields.”

A susceptible maize variety infected with TSC (left) compared to a healthy maize plant , a resistant variety immune to the disease (right).

SeeD scientists began by identifying landrace varieties with genetic resistance to TSC. Trials conducted in 2011, 2012 and 2014 evaluated a “core set” – a genetically diverse subset of the maize germplasm bank – in search of resistant varieties.  Of the 918 landrace varieties planted in 2011 and 2012, only two landraces—Oaxaca 280 and Guatemala 153—were outstanding for tolerance to the disease.  Genotypic data would later confirm the presence of unique resistant alleles not currently present in maize breeding programs that could be deployed into SeeD’s bridging germplasm. This bridging germplasm will be available to breeders for use in developing elite lines and varieties for farmers.

“As a breeder, I’m excited to work with SeeD’s bridging germplasm as soon as it is available,” said Felix San Vicente, CIMMYT maize breeder working with the CGIAR Research Program on Maize and the Sustainable Modernization of Traditional Agriculture (MasAgro) project.

Terry Molnar, maize breeder with SeeD, and Enrique Rodriguez, field research technician with SeeD, evaluate bridging germplasm for resistance to TSC.

Up to this point, most breeders have only used elite lines to develop hybrids, because landraces are extremely difficult to use. This practice, however, greatly limits the genetic diversity breeders employ. Using novel alleles from maize landraces allows breeders to develop improved hybrids while broadening the genetic variation of their elite germplasm. This novel genetic diversity is very important to protect crops from evolving pathogens, as it means the varieties will have several resistant alleles, including alleles that have never been used in commercial germplasm before.

“The more alleles the better,” said San Vicente, “as it protects the line longer. It provides a form of insurance to smallholder farmers as these varieties will have more genes for resistance, which reduces their risk of losing their crop.”

To ensure that farmers can access this improved seed, CIMMYT works with small local seed companies. “The price of seed will be very affordable,” according to San Vicente. “As CIMMYT is a non-profit, we provide our improved materials to seed companies at no cost.”

The TSC resistant bridging germplasm developed by SeeD has been tested in on-farm trials in TSC-prone sites in Chiapas and Guatemala, with promising results, and will be publicly available to breeders in 2017. In the meantime, local farmers look forward to seeing the results of this research in their own fields. “A variety with the disease resistance of a landrace and the yield and performance of a hybrid is exactly what we need,” says Corzo Jimenez.

Corzo Jimenez in his maize field infected with TSC. Varieties made from SeeD bridging germplasm would allow him to protect his crop without applying expensive fungicides.

Corzo Jimenez in his maize field infected with TSC. Varieties made from SeeD bridging germplasm would allow him to protect his crop without applying expensive fungicides. CIMMYT/Jennifer Johnson.

SeeD is a multi-project initiative comprising: MasAgro Biodiversidad, a joint initiative of CIMMYT and the Mexican Ministry of Agriculture (SAGARPA) through the MasAgro (Sustainable Modernization of Traditional Agriculture) project; the CGIAR Research Programs on Maize (MAIZE CRP) and Wheat (WHEAT CRP); and a computation infrastructure and data analysis project supported by the UK’s Biotechnology and Biological Sciences Research Council (BBSRC). To learn more about the Seeds of Discovery project, please go to http://seedsofdiscovery.org/.

 

More news from: CIMMYT (International Maize and Wheat Improvement Center)

 

Website: http://www.cimmyt.org

Published: July 26, 2016

 

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