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Archive for the ‘Fungi’ Category

Fresh Plaza

Research and production experiences in Asia

Western media is fixated with reporting that Panama Disease caused by Fusarium oxysporum f. sp. cubense (Foc TR4) will lead to the disappearance of Cavendish bananas from supermarkets. This is in reaction to certain researchers predicting the unavoidable incursion of the fungus into Latin American banana plantations, which are the major supplier of western markets. These researchers further claim that only molecular-based breeding, more specifically genetic engineering, can be used to develop resistant Cavendish bananas as a solution to the problem.

Epidemics of Panama disease on Cavendish banana plantations are common in Asia. They have been reported in Taiwan as early as 1967, in Indonesia and Malaysia in 1990, and in the Philippines and China in 2001. These epidemics have caused significant damage to the commercial banana plantations. Containing build ups of epidemics in infested plantations is extremely difficult to achieve. The Taiwan banana Research Institute (TBRI) developed resistant Cavendish varieties through non-conventional way of selecting resistant variants from Giant Cavendish. These varieties became the corner stone of an integrated disease management that make Cavendish production still sustainable in Taiwan, and in Indonesia as well.

Foc TR4- resistant Giant Cavendish Tissue Culture Variants (GCTCVs), are becoming practical options in managing epidemics of Foc TR4 in commercial plantations in the Philippines to sustain the more than 80,000 hectares Cavendish plantations that is  bringing more than US$800 million annual export revenue, and more than 320,000 direct employments. Shared by Taiwan Banana Research Institute (TBRI), Bioversity International carried out a series of field evaluations in public-private partnerships. Two GCTCV varieties, namely, GCTCV 218 and GCTCV 219 proved to be the most acceptable options in managing Foc TR4 epidemic. In commercial trials these varieties remained resistant even after 4 ratoons, while Gran Naine became severely infected even in the  primary crop. GCTV 218, moderately resistant to Foc TR4, is more acceptable by growers. It has big bunches thus good box stem ratio, and fruit   quality as good as Gran Naine. Fruits can be packed and ripened together with Gran Naine, and acceptable in current markets. Agronomically, GCTCV 218 is taller than Gran Naine, similar to Tall Williams, but has longer maturity by two to three weeks.

GCTCV 219, a variant of another resistant GCTCV 119, is highly resistant to Foc TR4. It is recommended for the rehabilitation of severely affected and abandoned farms of small growers. While GCTCV 219 is resistant and has sweet fruit thus has an opportunity for a special market, its bunch and agronomic characteristics are more inferior than that of GCTCV 218 and Gran Naine. GCTCV 219 is taller, longer maturing, less box-stem ratio and more of a floater thus prone to yield decline with time. Growers are satisfied with the level of resistance of GCTCV 219, but productivity and fruit quality are main concern.

The use of GCTCV 218 is now gaining wide acceptance by banana growers and companies. The Philippine government launched a $ 2.2 million programme to help small growers to rehabilitate affected farms and sustain livelihoods by an integrated approach around  the use of GCTCV 218 and 219. The planting of these varieties with tissue culture seedlings in commercial scale also provides an opportunity to select for improved phenotypes.

The fundamental approach of preventing the incursion of Foc TR4 into new areas is essential. However, in the presence of Foc TR4, production and disease management paradigms have to change to sustain the industry. In the absence of other varieties from other breeding programmes, the GCTCVs seem to be the best our farmers could have at this time to save their livelihoods. The approach of using somaclonal selection is definitely a viable approach in Cavendish banana improvement. The prediction that Foc TR4 will cause the demise of the Cavendish-based export industry unless a GMO-resistant variety is developed appears a gross exaggeration.

For more information:

Agustin Molina
Bioversity International, Philippine Office and Regional Coordinator Banana Asia Pacific Network
Email: a.molina@cgiar.org
http://www.cgiar.org

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Southern corn rust has arrived earlier and earlier in Georgia in recent years, but this year is the earliest in recent memory the yield-stealing disease has been confirmed in the state. Corn growers need to decide whether to make a fungicide treatment.

If southern corn rust is not spotted or treated quickly, it can be devastating to corn production in the Southeast, particularly in Georgia where yield losses can be as high as 80 bushels per acre if conditions are favorable for its spread, said Bob Kemerait, University of Georgia Extension plant pathologist.

“If you don’t protect against southern rust early enough and it starts to spread, it’s hard to stop. Once it escapes the bottle, it’s hard to put back in the bottle,” Kemerait said.

Southern corn rust was found June 1 in “very small amount in Seminole County on corn at the R2/blister stage, which is older than most corn in the state,” he says.

The disease was confirmed in the state last year on June 5.

The disease spreads rapidly in storms and with irrigation. And conditions in the region the previous week were favorable for development and spread of the disease, he said.

Kemerait sent an alert about the discovery of the disease to county UGA Extension agents. Growers are encouraged to contact their agents if they have questions or concerns about the disease.

“Now that we have found it, I have enough respect for the disease to say that growers in the southwestern part of the state whose corn has reached or is about to reach tassel apply a fungicide to protect the crop,” he says in an alert. “Growers in other areas removed from extreme southwest Georgia should monitor the spread of the disease. Some may want to make fungicide application either as a safeguard or because they are already making a trip across the field to spray something else.”

If northern corn leaf blight is not a problem in a field, he says, growers have many fungicide options including tebuconazole to manage rust. For longer protective windows or where NCLB is also a problem, growers should apply strobilurin or fungicides that include some combination of strobilurins, triazoles and SDHI active ingredients.

Asian soybean rust continues to spread in southwest Georgia. As of June 1, the disease has been found in small amounts on kudzu in the Miller, Baker and Grady counties. “But we can assume that soybean rust is present in low amounts throughout southwest Georgia,” Kemerait said.

 

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As Georgia’s corn crop enters the tassel stage, farmers are weighing whether to make a fungicide application. And Asian soybean rust is in the state now, the earliest the troubling disease has been detected in Georgia in more than a decade.

The Asian soybean rust was confirmed in Miller County, Ga, located in southwest Georgia May 17, and this means the disease will likely be problematic for Georgia soybean producers this year, said Bob Kemerait, University of Georgia Extension plant pathologist. Growers are advised to stay alert and scout soybean fields. Current conditions favor the spread of the disease within kudzu.

And as Georgia corn progresses, rapidly entering the tassel stage, Kemerait advises growers, at the least the more disease aggressive growers, to consider a protective fungicide application. “This is especially true if southern corn rust has been detected in the area, if northern corn leaf BLIGHT is problematic in a field (typically with a less-resistant hybrid), conditions have been favorable for disease (very wet), the corn was planted LATE or if the grower is aggressive in a disease management program and wants to make sure the crop is protected,” he said.

Kemerait’s further thoughts on corn disease management at this time for Georgia are:

  • As of May 17, we have not found SOUTHERN CORN RUST in Georgia and conditions have not been especially favorable for southern rust.
  • As of May 17, we have had one report of common corn rust from Mitchell County. Common rust typically forms pustules on both sides of the leaf and does NOT need a fungicide application.
  • As of May 17, the only report of northern corn leaf BLIGHT in Georgia is from Ty Torrance in Decatur County. Northern corn leaf blight can be an important problem that requires a fungicide treatment IF it is severe (e.g., a susceptible variety and favorable weather). The NCLB in Decatur County was confined to the bottom leaves and there were only a few lesions on about one plant out of 15. The grower is right to be aware of the problem but I do not think a fungicide is needed for NCLB in that particular field.
  • Northern corn leaf SPOT has been found in Mitchell County by Andy Shirley.  Typically we do not spray for this disease, except in severe cases. The northern corn leaf spot in this field was confined to the lower leaves and did not appear to be spreading.
  • We have not detected southern corn rust in Georgia yet. Conditions over the next few days are more favorable for disease spread, but (overall) conditions have been unfavorable. I would not argue with a grower who wants to apply a fungicide at this time (to corn) as it reaches the tasseling growth stage; HOWEVER I think the grower is better advised to DELAY a fungicide application at this point and wait at least a week or so.

Information in this article courtesy of Andrew Sawyer, UGA Extension agent in Thomas County, at Thomas County Ag.

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NATURE International weekly journal of science

Devastating wheat fungus appears in Asia for first time

Scientists race to determine origin of  Bangladesh outbreak, which they warn could spread farther afield.

27 April 2016 Updated:

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Ruth Fremson/NYT/eyevine

Wheat in northern India could be threatened by an outbreak of fungal disease in Bangladesh.

Update: On 26 April, a team led by microbial population geneticist Daniel Croll, who is at the Swiss Federal Institute of Technology in Zurich, reported on github.com that the Bangladeshi wheat-blast strain is closely related to those collected in Brazilian wheat fields and on nearby weeds. His team’s analysis, which uses the data on the website Open Wheat Blast, reveals that the sample is not closely related to known rice-blast-causing strains of M. oryzae. Croll’s team concludes that wheat blast was probably introduced to Bangladesh from Brazil, and warns that other Asian countries that import Brazilian wheat, including Thailand, the Philippines and Vietnam, should be on the lookout for the disease.

Fields are ablaze in Bangladesh, as farmers struggle to contain Asia’s first outbreak of a fungal disease that periodically devastates crops in South America. Plant pathologists warn that wheat blast could spread to other parts of south and southeast Asia, and are hurrying to trace its origins.

“It’s important to know what the strain is,” says Sophien Kamoun, a biologist at the Sainsbury Laboratory in Norwich, UK, who has created a website, Open Wheat Blast (go.nature.com/bkczwf), to encourage researchers to share data.

Efforts are also under way to find wheat genes that confer resistance to the disease.

First detected in February and confirmed with genome sequencing by Kamoun’s lab this month, the wheat-blast outbreak has already caused the loss of more than 15,000 hectares of crops in Bangladesh. “It’s really an explosive, devastating disease,” says plant pathologist Barbara Valent of Kansas State University in Manhattan, Kansas. “It’s really critical that it be controlled in Bangladesh.”

After rice, wheat is the second most cultivated grain in Bangladesh, which has a population of 156 million people. More broadly, inhabitants of south Asia grow 135 million tonnes of wheat each year.

Wheat blast is caused by the fungus Magnaporthe oryzae. Since 1985, when scientists discovered it in Brazil’s Paraná state, the disease has raced across South America.

The fungus is better known as a pathogen of rice. But unlike in rice, where M. oryzae attacks the leaves, the fungus strikes the heads of wheat, which are difficult for fungicides to reach. A 2009 outbreak in wheat cost Brazil one-third of that year’s crop. “There are regions in South America where they don’t grow wheat because of the disease,” Valent says. Wheat blast was spotted in Kentucky in 2011, but vigorous surveillance helped to stop it spreading in the United States.

In South America, the disease tends to take hold in hot and humid spells. Such conditions are present in Bangladesh, and the disease could migrate across south and southeast Asia, say plant pathologists. In particular, it could spread over the Indo-Gangetic Plain through Bangladesh, northern India and eastern Pakistan, warn scientists at the Bangladesh Agricultural Research Institute (BARI) in Nashipur.

Bangladeshi officials are burning government-owned wheat fields to contain the fungus, and telling farmers not to sow seeds from infected plots. The BARI hopes to identify wheat varieties that are more tolerant of the fungus and agricultural practices that can keep it at bay, such as crop rotation and seed treatment.

Guillermo Isidoro Barea Vargas

Wheat blast strikes the heads of wheat, which are difficult for fungicides to reach.

It is unknown how wheat blast got to Bangladesh. One possibility is that a wheat-infecting strain was brought in from South America, says Nick Talbot, a plant pathologist at the University of Exeter, UK. Another is that an M. oryzae strain that infects south Asian grasses somehow jumped to wheat, perhaps triggered by an environmental shift: that is what happened in Kentucky, when a rye-grass strain infected wheat.

To tackle the question, this month Kamoun’s lab sequenced a fungus sample from Bangladesh. The strain seems to be related to those that infect wheat in South America, says Kamoun, but data from other wheat-infecting strains and strains that plague other grasses are needed to pinpoint the outbreak’s origins conclusively.

The Open Wheat Blast website might help. Kamoun has uploaded the Bangladeshi data, and Talbot has deposited M. oryzae sequences from wheat in Brazil. Talbot hopes that widely accessible genome data could help to combat the outbreak. Researchers could use them to screen seeds for infection or identify wild grasses that can transmit the fungus to wheat fields.

Rapid data sharing is becoming more common in health emergencies, such as the outbreak of Zika virus in the Americas. Kamoun and Talbot say that their field should follow suit. “The plant-pathology community has a responsibility to allow data to be used to combat diseases that are happening now, and not worry too much about whether they may or may not get a Nature paper out of it,” says Talbot.

Last month, Valent’s team reported the first gene variant known to confer wheat-blast resistance (C. D. Cruz et al. Crop Sci. http://doi.org/bfk7; 2016), and field trials of crops that bear the resistance gene variant have begun in South America. But plant pathologists say that finding one variant is not enough: wheat strains must be bred with multiple genes for resistance, to stop M. oryzae quickly overcoming their defences.

The work could help in the Asian crisis, says Talbot. “What I would hope for out of this sorry situation,” he says, “is that there will be a bigger international effort to identify resistance genes.”

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WGCU News

npr News

By Jessica Meszaros • Apr 27, 2016
orange pfd_1
You can find these “buttons” on some orange trees across Florida. They’re indicators of a fungus known as PFD, or post bloom fruit drop. An infected tree will drop fruit prematurely and leave these behind. They normally fall off with healthy oranges.

Jessica Meszaros / WGCU News

A fungal disease is affecting all types of orange trees statewide right now. It’s called PFD, or post bloom fruit drop. The fungus causes oranges to fall off prematurely. El Niño weather patterns that brought rainy, foggy days this winter helped spread the disease.

orange pfd_2

Bryan Beer is a fifth generation orange grower in Southwest Florida. At one of the groves he manages in Hendry County, Beer said he’s heard “horror stories” about PFD from growers.

“This disease has just annihilated their whole crop for next year that they won’t even have anything to pick,” said Beer. “And you can see how bad it is on just this one tree.”
Grower Bryan Beer at one of the orange groves he manages in Southwest Florida.

Beer grabbed an orange tree branch and pointed to what’s called a “button.” When the orange falls off, it leaves what the fruit would normally be attached to. He said it’s a sign the tree is in trouble.

University of Florida researcher Megan Dewdney has studied citrus trees for nearly a decade. She said there’s a combination of factors contributing to the current fungal spread in Florida.

For one, the orange trees are already stressed from battling the citrus greening disease, so they’re blooming at odd times. And then El Niño brought more rain than normal for winter. Dewdney said the unusual blooms plus unusual rains allowed the fungus to thrive.

“The flowers were stimulating a small amount of the fungus ‘til the major bloom showed up and then that coincided with the El Niño patterns of wet, cool-ish winter, which was perfect for the fungus,” she said.

Dewdney said this is a widespread problem throughout the state. But she said we won’t know the extent of crops lost until the summer.

Local grower Bryan Beer said he thinks it’s going to be “very, very, very bad.”

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  • GM banana resistant to fungus shows promise

[KAMPALA] A banana strain resistant to a common fungal disease could help smallholder farmers in East Africa better control the crippling disease, which has been spreading across the region over the last three decades.

The results of confined field trials of a genetically modified (GM) banana with improved resistance to a black sigatoga disease, the devastating leaf spot fungus, are promising, researchers have told SciDev.Net.

The disease is caused by the fungus Mycosphaerella fijiensis and it can halve fruit production in affected plantations. It is easily spread by airborne spores, rain, planting material, irrigation water and packing material used in transporting goods between banana-growing countries.

The dark leaf spots caused by the fungus eventually enlarge and merge together, causing much of the leaf area to dry.

The team led by Andrew Kiggundu — head of banana biotechnology research at the Uganda’s National Agricultural Research Laboratories Institute (NARL) in Kawanda — analysed 19 lines of GM bananas and found promising results in five of them. Andrews told SciDev.Net further research is needed to calculate the exact yield gains from using the resistant banana strain.

The researchers inserted genes for chitinase — an enzyme that breaks down chitin, the hard substance that makes up the cell walls of the invading fungi — preventing the fungus from invading the plant cells and causing the disease.

Kiggundu said laboratory tests using leaves from transgenic plants showed almost full immunity when cultured fungi were applied to the leaves.

Researchers collaborated closely with the Catholic University of Leuven in Belgium, where several banana lines were engineered to include the chitinase gene before being brought to NARL for testing.

However, Settumba Mukasa, resident banana expert in the department of crop science at Uganda’s Makerere University, said the field trials had more significance for building research capacity in Uganda than the development of a new disease-resistant banana.

“[The project] is a stepping stone for subsequent breeding programs and genetic engineering programmes. As a consequence of this project we can now do transformations of other varieties of bananas and other crop species,” said Mukasa.

While black sigatoka is among the top three diseases affecting bananas in Uganda it mainly affects Cavendish, which are not as widely cultivated as other types of bananas.

But for the few farmers in Uganda who do grow Cavendish bananas, the development may be useful since the disease is currently controlled by aerial pesticide spraying which is expensive for smallholders and affects their health.

“Farmers cannot afford that because they are small and they have few plants. Here, chemical control is not viable, so this approach may be the only available method to manage the disease,” Mukasa said.

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  • Fungus-resistant gene found in rice

   

Scientists in Japan have found a way to create high-yielding rice with long-lasting resistance to the devastating rice blast fungus.

Sufficient rice to feed 60 million people is destroyed by the blast fungus, Magnaporthe grisea — also known as Magnaporthe oryzae — every year.

Some rice is naturally resistant but is often also of lower yield. Now a team led by Shuichi Fukuoka from the National Institute of Agrobiological Sciences in Japan has engineered good quality rice that is both resistant to blast disease and high-yielding.

Their research was published in Science last week (21 August).

By comparing japonica rice that is resistant to blast disease with rice that succumbs to infection, Fukuoka found that a change in a key gene called Pi21 can mean the difference between devastating infection and mild disease.

Fukuoka says even plants with the resistant form of the gene become infected, but “The damage they suffer is not so serious, making it possible to reduce the amount of fungicide used by 50 per cent.”

He says his team’s findings will be particularly useful in mountainous areas where blast disease is a serious threat.

There have been many previous attempts to engineer resistant rice strains by making specific adjustments to plant immunity to allow the plants to recognise and resist the fungus.

But according to Nick Talbot, professor of molecular genetics at Exeter University in the UK, many of these modifications have a field life of just 2–3 years, as the fungus is quick to find ways to circumvent them and avoid being recognised.

Having the resistant form of Pi21, however, means a plant increases its defences against infection in general, making it much harder for the blast fungus to find a way to take hold, says Talbot.

He says the Japanese researchers have made a big discovery with universal applicability. When this is combined with other methods of engineering rice, scientists may be in a position to “exclude blast infections in a durable manner”.

Fukuoka has also managed to isolate the resistant form of Pi21, meaning it can be separated from other genes associated with poor yield. Previously this has been difficult because when scientists have tried to transfer the resistant Pi21 gene into new strains of rice, the genes affecting quality have also hitched a ride.

Fukuoka says the fact that his research has shown the exact location of the Pi21 gene means scientists can ensure it is not replaced by a more vulnerable form when breeding new rice strains.

Link to full article in Science

 

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