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Research reveals mechanism making banana fungus less responsive to crop protection

An international team of scientists led by Wageningen University & Research has discovered a new genetic mechanism that makes the notorious Black Sigatoka fungus less sensitive to the main chemical crop protection products used against the disease.
The discovery shines light on this increasingly reduced sensitivity and underlines the importance of developing banana varieties resistant to the fungus which causes Black Sigatoka.
Pseudocerospora fijiensis, the fungus causing the dreaded Black Sigatoka disease in banana cultivation, is tackled with chemicals. In practice, this requires farmers around the world to spray against the disease between 35 and 70 times a year. One specific type of fungicides, the so-called demethylase inhibitors (DMIs), form the backbone for managing the disease. Unfortunately, the fungus is becoming increasingly less sensitive to these products on a global scale.
Dr Pablo Chong conducted his PhD research under the supervision of Gert Kema, professor in tropical phytopathology at Wageningen University & Research. The working hypothesis was that “we thought that the reduced sensitivity of the fungus was caused by changes in the protein, a demethylase enzyme, which is the target of the DMIs” Kema says.
“As a result we only looked at mutations in the segment of the gene that encodes the enzyme. What we found is that the reduced sensitivity is also caused by changes in the promoter, the switch that controls the gene. In the promoter we discovered a segment of DNA that is concatenated up to six times. The larger the number of DNA-repeats in the promoter, the less sensitive the fungus.”
The less sensitive Black Sigatoka strains that were found in banana cultivation and studied by the team all had a combination of mutations in the encoding part of the gene as well as DNA-repeats in the promoter.
Kema: “Mutations in the coding segment of the gene reduces the ‘docking’ of the compound in the enzyme, while the DNA repeats in the promoter make the gene extra active. These two factors together appear to ensure that the fungus has so much well-functioning enzyme in its cells that it is far less affected by the crop protection. As a result, the banana plants develop disease despite the application of these products.”
The findings emphasise the importance of smart crop protection, using not only DMIs but also fungicides that function in a completely differently way. This will slow the pace of reduced sensitivity in the fungus.
“The results of our research also underline the importance of developing Black Sigatoka resistant banana varieties” concludes Kema. “This is the only way to make global banana cultivation more sustainable.”
For more information:
Erik Toussaint
Wageningen University & Research 
Tel: +31 651 56 59 49

Publication date: 11/22/2017

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The same Australian university that is trialing Vitamin A-enriched bananas in Uganda has successfully developed genetically modified Cavendish bananas with resistance to the deadly soil-borne fungus Panama Disease Tropical Race IV.

In their world-first GM field trial conducted in heavily TR4-infested soil, Queensland University of Technology (QUT) researchers found one Cavendish line – transformed with a gene taken from a wild banana – was completely free of the disease.

In addition, three others from the six lines tested also showed showed robust resistance, which is very exciting according to project lead Professor James Dale from QUT’s Centre for Tropical Crops and Biocommodities.

The results have just been published in Nature Communications.

Click here for a feature article we published back in 2013 with Dr Dale discussing his vision for improved nutrition and disease resistance through GMO bananas.

The field trial ran from 2012 to 2015 on a commercial banana plantation outside Humpty Doo in the Northern Territory previously affected by TR4. The soil was also heavily reinfested with disease for the trial.

Professor Dale said the outcome was a major step towards protecting the US$12 billion Cavendish global export business, which is under serious threat from virulent TR4.

“These results are very exciting because it means we have a solution that can be used for controlling this disease,” he said.

“We have a Cavendish banana that is resistant to this fungus that could be deployed, after deregulation, for growing in soils that have been infested with TR4.

 

 

 

 

 

 

“TR4 can remain in the soil for more than 40 years and there is no effective chemical control for it. It is a huge problem. It has devastated Cavendish plantations in many parts of the world and it is spreading rapidly across Asia. “It is a very significant threat to commercial banana production worldwide.”

They will have the capacity to grow up to 9,000 plants and quantify crop yield over the five-year trial.

“The aim is to select the best Grand Nain line and the best Williams line to take through to commercial release,” Professor Dale said. “While in Australia we primarily grow Williams, in other parts of the world Grand Nain is very popular.”

Professor Dale said the correlation demonstrated between the RGA2 gene activity and TR4 resistance opened up new research. 

“We can’t make the assertion that the RGA2 gene is the gene responsible for the resistance in the original wild diploid banana, because in the modified Cavendish we significantly increased the gene’s expression –  the level of its activity – over its activity in the wild banana,” he said.

“But we’ve established a correlation, and we’ve found that the RGA2 gene occurs naturally in Cavendish – it just isn’t very active.

“We are aiming to find a way to switch that gene on in the Cavendish through gene editing. We’ve started that project. It is not easy, it’s a complex process that is a way off, with four or five years of lab work.

“We’re also looking at as many genes as possible in the wild banana and screening them to identify other resistance genes, not only for resistance to TR4 but to other diseases.”

Other key findings of the field trial:

  • Nine lines of Cavendish Grand Nain transformed with the nematode-derived Ced9 gene were also trialled, with one line remaining TR4-free for the three years
  • There was no difference in observed mature bunch size between the transgenic bananas and healthy control Cavendish

The article, Transgenic Cavendish bananas with resistance to Fusarium wilt tropical race 4, can be accessed here.

www.freshfruitportal.com

 

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Via PestNet

hindu 2

http://www.thehindu.com/sci-tech/agriculture/icrisat-researchers-make-peanuts-free-of-aflatoxin/article20048362.ece

ICRISAT researchers make peanuts free of aflatoxin

R Prasad

Dual strategy involves inserting 2 alfalfa genes into the plants to boost immunity and gene silencing technique to prevent any toxin production

Researchers at the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) in Hyderabad have developed dual strategies to keep groundnuts almost free of aflatoxin — a toxin produced by the fungi Aspergillus flavus and Aspergillus parasiticus — contamination. While one strategy prevents groundnuts from being infected by the fungus thereby preventing the toxins from being produced, the other strategy prevents the fungus from producing the toxin even if groundnuts somehow get infected with the fungus.

Genetic engineering approaches were used for inserting two alfalfa genes into groundnut plants to enhance immunity against fungal infection and growth. Preventing aflatoxin production even in case of any infection was achieved through a plant-induced gene silencing technique.

While both strategies showed promising results, the ultimate goal is to combine the two traits into a single variety to offer double protection so that groundnuts do not accumulate any aflatoxin or the amount of toxin is well within permissible limits at or after harvest.

Combining the two traits

“It is a proof-of-concept study. We have individually tested each of the two mechanisms and it is a matter of using conventional plant breeding approaches to develop a variety that has both the traits in place,” says Kiran K. Sharma from ICRISAT.

The researchers plan to start field trials early next year. “It will take one-two years to breed the two traits into a single variety and another about three years to conduct biosafety trials followed by the development of regionally adapted groundnut varieties. So, if everything goes to plan and gets approved by the Genetic Engineering Appraisal Committee (GEAC), farmers will have a groundnut variety that is near-immune to aflatoxin contamination in five to seven years,” says Dr. Pooja Bhatnagar-Mathur from ICRISAT who led the team.

“We selected two specific genes from alfalfa and inserted them into groundnut plants to enhance the immunity against fungal infection and growth. Groundnuts showed very little fungal infection and negligible aflatoxin contamination,” says Dr. Bhatnagar-Mathur. “We choose alfalfa as it is a legume like groundnut.”

To further prevent toxin production even when groundnuts get infected with the fungus, the researchers designed two small RNA molecules that silence the fungal genes which produce aflatoxin.

“When the fungus and plant come in contact with each other the small RNA molecules from the plant enter the fungus and prevent it from producing aflatoxin,” says Mr. Sharma, who is the first author of the paper published in Plant Biotechnology Journal.

About 40 hours after infection with Aspergillus, six lines with alfalfa genes showed less than 1 part per billion (ppb) of toxin and another five lines showed 1-4 ppb compared with over 3,000 ppb in groundnuts that did not have these genes. Similarly, six lines carrying the RNA molecules, the toxin present was less than 1 ppb and two other lines showed 1-4 ppb of toxin. “It is much lower than the Indian and U.S. safety limit of 20 ppb and meets even the stringent European safety limit of 4 ppb,” Dr. Bhatnagar-Mathur says.

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From PestNet

LATE BLIGHT, POTATO – UK: STRAIN DARK GREEN 37

**********************************************
A ProMED-mail post
<http://www.promedmail.org>
ProMED-mail is a program of the
International Society for Infectious Diseases
<http://www.isid.org>

Date: Thu 26 Oct 2017
Source: Farmers Weekly [edited]
<http://www.fwi.co.uk/arable/potato-blight-strain-causes-resistance-concern-with-agronomists.htm>

The emergence of a new strain of late potato blight with signs of
resistance to the popular fungicide fluazinam is causing concern among
agronomists who suggest switching to other products. Fluazinam has
been one of the most effective actives against the disease, but
frequent use may have increased the selection pressure on the
fungicide.

After 5 cases of the 37_A2 (Dark Green 37) strain were confirmed in
the UK last year [2016], largely in the English Midlands, it has
spread to Kent, Shropshire, North Yorkshire, Cheshire and most
recently Derbyshire. It has not been seen in East Anglia yet.

Darryl Shailes, Hutchinsons advisory group, said from only a handful
of cases in 2016, there have been close to 20 confirmed cases this
year [2017]. “We don’t know where it will go next, but we do know it
is at least as competitive as the dominant strains Blue 13 and Pink 6
[see comments below],” he said. Although little is known about this
strain of the potato industry’s most damaging disease, it has proved
to be highly aggressive.

[Byline: David Jones]

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basmati-farmer

A farmer in Jind, Haryana in his  basmati paddy field. (Express photo: Renuka Puri)

Pesticide residues are an issue, more so when it concerns products such as basmati rice, fetching the country annual export revenues ranging from $ 3.23 billion in 2016-17 to $ 4.52 billion in 2014-15. The burden of consignments being rejected ultimately falls on the farmer, who has to, then, use new-generation pesticides that are safer, but costlier and very often proprietary/patented molecules.

The most recent example is of Tricyclazole. A single 120-gram spray of this common fungicide, against leaf and neck blast disease in paddy, hardly costs Rs 150-170 per acre. But with the European Union (EU) deciding not to allow import of any rice having Tricyclazole levels above 0.01 parts per million (ppm) from January 1, farmers would find it difficult to spray the generic chemical sold under assorted brands like ‘Sivic’, ‘Baan’ and ‘Beam’. The existing tolerance limit stipulated by the EU (which accounts for about 3.5 lakh tonnes of India’s total annual basmati shipments of 40 lakh tonnes) for Tricyclazole is one ppm or 1 mg/kg; 0.01 ppm will make it 1mg/100 kg!

With Tricyclazole ruled out, farmers may, henceforth, have to go for fungicides that are considered environmentally friendlier, though costing ten times more. These include Azoxystrobin (a single 200-ml spray, sold under the Swiss company Syngenta’s ‘Amistar’ brand, costs around Rs 900 per acre) and Picoxystrobin (the cost of a single 400-ml spray of this formulation, sold under DuPont’s ‘Galileo’ brand, comes to Rs 1,300 per acre). No less expensive is ‘Nativo’. This combination fungicide of Bayer CropScience, containing Tebuconazole and Trifloxystrobin, costs Rs 1,000 for a single 160-gram spray per acre.

However, an alternative approach to pesticide application — necessary, especially keeping in view basmati’s premium quality attributes and huge export market — is to “breed for disease resistance”. This involves transfer of specific disease-resistance genes, from both traditional landrace cultivars and wild relatives of paddy, into existing high-yielding basmati varieties. That is what scientists at the Indian Agricultural Research Institute (IARI) have sought to do.

The New Delhi-based institute — under a collaborative project with the Indian Council of Agricultural Research’s National Research Centre on Plant Biotechnology — has transferred the ‘Pi9’ gene into its popular Pusa Basmati-1 variety. This gene, sourced from Oryza minuta (a wild relative of Oryza sativa, which is the normal cultivated paddy), provides “very high resistance” against leaf blast and “moderate resistance” against neck blast fungus.

The resultant variety, which is called Pusa Basmati-1637, combines Pusa Basmati-1’s high-yielding trait with resistance against a fungus that infests the leaf and neck nodes of the rice plant’s main stem, from where the grain-bearing earheads (panicles) emerge. Blast disease affecting the leaf basically damages the chlorophyll, thereby impeding photosynthesis that involves absorption of sunlight and using its energy to synthesise carbohydrates. Neck blast, if severe, can cause the stem to even break. If the panicles at that point have only partially formed grains, in their early milky stage, the yield losses can be huge.

Rajeev Kharb, a farmer from Tito Kheri village in Safidon tehsil of Haryana’s Jind district, has grown Pusa Basmati-1637 in five out of his total 80-acre holding. The latter includes 28 acres of own and 52 acres of leased land. High temperatures and humidity levels this time round has resulted in the bulk of his planted area – mainly under Pusa Basmati-1401, Pusa Basmati-1 and Pusa Basmati-1509 – suffering gardan-marod (the local term for blast, whose literal translation is “curling of the neck”) to the extent of 10-20 per cent.

“But nothing has happened to my Pusa Basmati-1637 field. This, even without spraying any Tricyclazole,” says Kharb. A loss of 10-20 per cent isn’t small. Taking per-acre yields of 22-25 quintals for Pusa Basmati-1, 25-28 quintals for Pusa Basmati-1509 and 28-30 quintals for Pusa Basmati-1401, and current average price realisations of Rs 2,800/quintal, it works out to anywhere from Rs 7,000 to Rs 14,000 per acre.

“We will continue to have to spray for other diseases (bacterial blight and sheath blight fungus) and pests (brown plant hopper and stem borer). But with this new variety, there is still significant savings from not using Tricyclazole or other expensive fungicides against blast,” points out Pritam Singh Hanjra, a progressive farmer from Urlana Khurd village in Madlauda tehsil of Panipat district.

Hanjra, who has sown Pusa Basmati-1637 in five out of his 105-acre holding (30 acres own and the rest leased), estimates expenses on crop protection chemicals at Rs 3,000-4,000 out of the total cultivation costs of Rs 20,000-22,000 per acre for paddy. “It can go up, depending on the extent of pest and disease incidence. Either way, this is the second biggest expenditure head after manual harvesting-and-threshing (Rs 4,500-5,000), and more than fertilizers (Rs 2,100-2,200),” he claims.

A K Singh, head of IARI’s Division of Genetics, notes that Indian breeders have, over a period, managed to raise crop yields. The traditional tall basmati cultivars, for instance, gave barely 8-10 quintals of paddy per acre. With improved dwarf high-yielding basmati varieties, these have gone up to 25 quintals or so. “Our challenge now is to protect these yields and preferably through breeding for resistance, as opposed to pesticide application,” he adds.

IARI is, in fact, working on transferring other blast resistance genes as well — such as ‘Pi54’, ‘Pi25’, ‘Pi2’ and ‘Pib’, all from wild relatives and land races of rice — to high-yielding basmati varieties.

“We want to do pyramiding of these genes (combining two or more of them), in order to impart more durable resistance against blast. Besides, we have already developed and released two new varieties, Pusa Basmati-1718 and Pusa Basmati-1728, both of them incorporating the Xa21 and xa13 genes that confer resistance to the bacterial blight pathogen. The first variety is basically Pusa Basmati-1121 and the second one Pusa Basmati-1401, containing both these genes obtained from Oryza longistaminata (another wild relative of paddy) and BJ1 (a traditional land race), respectively,” informs Singh.

 

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SE farm press
BASF Oliver Gernsheimer
Oliver Gernsheimer, BASF Functional Crop Care, U.S. Crop Protection, highlights BASF‘s commitment to biologicals as another important crop protection tool for farmers.

BASF releases its first proprietary biological fungicide

Serifel, which is now labeled for use as a foliar fungicide in the United States, is based on viable spores of the beneficial bacterium Bacillus amyloiquefaciens strain MBI 600.

John Hart | Oct 23, 2017

BASF is committed to biologicals as another tool for growers to battle pests and disease. The introduction of Serifel, the first proprietary biological fungicide offered by the company, is an important step into the market.

Oliver Gernsheimer, responsible for BASF’s Functional Crop Care, U.S. Crop Protection business, said there is a growing interest in biologicals, particularly among specialty crop growers. “BASF is excited about new technologies in all areas that add value to our portfolio. Wherever we see a promising product and customers who are excited about it, we invest to develop these technologies further,” he said.

 “Strong grower interest and the realization that no one has focused on exactly how biologicals work are key drivers for BASF’s commitment to increase investment, science and research behind biologicals,” Gernsheimer said, noting that the company will introduce additional biological crop protection products in the near future.

Serifel, which is now labeled for use as a foliar fungicide in the United States, is based on viable spores of the beneficial bacterium Bacillus amyloiquefaciens strain MBI 600. It is targeted to specialty crops such as lettuce, spinach, grapes, wine grapes, strawberries, onions, carrots and tomatoes. It is currently labeled for foliar users, but BASF plans to add soil users to the label. Gernsheimer said the company hopes to have a label for soil use in the U.S. by next year.

Gernsheimer emphasizes that Serifel is a preventive fungicide designed to be used in a program with conventional fungicides or in an organic program. “Serifel is not designed as a stand-alone product,” he explained.

The product is effective on diseases such as powdery mildew because of its unique formulation. “Serifel is pure which allows the bacterium to work as it would in nature, making it  more efficacious without interference,” said Gernsheimer. “BASF is also the only company to provide a true resistance-management program by killing resistant diseases to some conventional chemistries and not just a rotational resistance program.”

“Serifel works best when applied early, before moderate disease infection. Once applied, the spores multiply very rapidly, covering anywhere on the leaf that a disease may try to inhabit. If the conditions are right for disease, the conditions are right for Serifel,” Gernsheimer said. “Additionally, a special feature of Serifel is rainfastness. Of the many metabolites produced by Serifel, one in particular, surfactin, is very sticky, allowing it to adhere to the leaf even during rain or irrigation. No longer will a grower have to decide about using a biological because of impending rain or a strict irrigation schedule.”

Gernsheimer said a key aim of BASF is to increase the credibility of biologicals as part of a pest management program and to understand biologicals with as much specification as the company’s conventional chemistry.

“We need to increase the confidence level of biologicals. We know when and how to apply Serifel because of novel research that looks at a multitude of parameters that may be faced in natural field scenarios. Parameters, that until now, have not been communicated to the grower,” he said. “Serifel works differently crop by crop. It’s not a one-size-fits-all solution. Every crop is a little different and every situation needs a different treatment. Helping growers to maximize the power of Serifel will give confidence in biologicals and prove that BASF is a trusted leader in this segment.”

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Australian scientists work to save the banana with fungus resistance trials

A slippery skid awaits the banana if the hazard is not removed. So in a field near Humpty Doo in Australia’s Northern Territory, scientists are racing to begin an experiment that could determine the future of the world’s most popular fruit.
Researchers will soon place into the soil plants that they hope will produce standard Cavendish bananas – the curved, yellow variety representing 99 per cent of all bananas sold in the United States.
The plants have been modified with genes from a different banana variety.
A fungus known as fusarium wilt has wiped out tens of thousands of hectares of Cavendish plantations in Australia and South-east Asia over the past decade and recently gained a foothold in Africa and the Middle East.
Scientists said Latin America, the source of virtually all the bananas eaten in the US, is next.
“These recent outbreaks confirmed that this thing does move,” said plant pathologist Randy Ploetz of the University of Florida, who identified the fungus in 1989 in samples from Taiwan.
Ever since, farmers have been trying to escape the effects of fusarium wilt, also known as Panama disease Tropical Race 4, or TR4. Once it hits a farm, the only recourse is to eradicate the plants and start over.
Ironically, a major obstacle to replacing today’s Cavendish with a TR4-resistant strain is the industry, which, for the most part, has dropped out of doing research, said Prof Ploetz. The result is that very few scientists have been focusing on the problem directly.
This means that even if Prof Dale’s transgenic experiment in Humpty Doo is successful, the TR4 fungus’ march to Latin America may be inevitable.

Publication date: 10/13/2017

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