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Archive for the ‘Fungi’ Category

New Threat to Oilseed Rape Emerges in UK

By European Seed

-December 17, 2021 Facebook Twitter Linkedin Email Print

A variety of the fungus that causes the disease Phoma on oilseed rape and other brassicas has been discovered in Europe for the first time, at sites in Southern England and Northern Ireland.

The Plenodomus biglobosus ‘canadensis’ variant was discovered last spring on wasabi plants, marking the first time the disease has been found on the vegetable.

Another variant of the fungus, P. biglobosus ‘brassicae’ was also discovered infecting wasabi at a third site in the West Midlands.

DNA analysis of cultures taken from the infected plants confirmed the identification, said Rothamsted plant pathologist, Dr Kevin King.

“Greenhouse testing then showed that both variants could cause disease not just on wasabi, but also oilseed rape, cabbage and pak choi.

“To date, ‘canadensis’ has been reported from brassica species in Australia, Canada, China, Mexico and the USA. However, the present study extends the known geographic range of it, which now includes Europe, having been found in the UK at two geographically distinct sites.

“Moreover, this study also represents, new discoveries for both ‘brassicae’ and ‘canadensis’ as causal agents of Phoma disease on wasabi plants, which previously was thought to be infected only by other variants in Canada, New Zealand and Taiwan.”

In recent years, there is evidence that P. biglobosus has become an increasingly problematic pathogen of UK oilseed rape crops.

Previously, only ‘brassicae’ has been reported on European OSR, and Dr King believes further work is needed to check whether this increase is as a result of the new ‘canadensis’ variant or down to recent varieties being more susceptible generally.

“Additional monitoring surveys are now required to understand the geographic distribution of the P. biglobosus variants present in current pathogen populations, both on wild and cultivated brassicas from throughout the British Isles and continental Europe.”

Source: Rothamsted Research

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Robot delivers ‘world-first’ season free of powdery mildew sprays

16 December 2021 | by FarmingUK Team | Farm ProductsMachinery and EquipmentNewsProduceThorvald performs light treatment to control mildew on strawberries, reducing the need for fungicidesThorvald performs light treatment to control mildew on strawberries, reducing the need for fungicides    

An autonomous robot which reduces powdery mildew through light treatment achieved complete control of the pathogen during this growing season.

‘Thorvald’ delivered UV-C treatment to protect strawberry plants on over 10 hectares of land at Clock House Farm and Hugh Lowe Farm, both in Kent.

The robot performs light treatment to control mildew on strawberries and vines, drastically reducing the need for fungicides.

During March to October, the farms did not spray their crops with any powdery-mildew-targeting chemical control agent, with Thorvald’s team calling this a ‘world-first’.

The autonomous robot was developed by Saga Robotics and has been on trial in the UK since 2019.

But 2021 has proven to be a watershed year due to an especially prevalent pathogen. Despite this, plant samples were examined having no traces of the fungal disease.

Oli Pascall, managing director at Clock House Farm, described the work undertaken by Thorvald as an ‘industry leading result’.The autonomous robot was developed by Saga Robotics and has been on trial in the UK since 2019The autonomous robot was developed by Saga Robotics and has been on trial in the UK since 2019

“The first three robots that Saga Robotics used to treat crops delivered positive results in 2020, although there was evidence that we needed a stronger intensity of UV-C.

“This has been addressed with a positive outcome, and the improved results seen in 2021 are of an outstanding level of protection.”

Pål Johan, CEO of Saga Robotics, said this year’s results had only increased what was already a strong interest in their service.

“Throughout the season, our robots have efficiently treated over 7,300 linear kilometres of strawberries with completely effective treatment, 100% robot service reliability and no failures.”

Dan Sargent, head of plant sciences at Saga added: “Not a single chemical has been needed to protect these plants from powdery mildew all season.

“And that’s great news for the growers, their customers, and the consumers.”

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2020 Integrated Pest Management Research, Data and Findings: A Look Back

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Integrated Pest Management Innovation Lab

Feb 09, 2021

Photograph of fall armyworm
Fall Armyworm.

2020 was a year like no other — researchers in search of answers to some of the world’s most pressing questions were forced to think outside the box when trials and experiments were put on hold due to the COVID-19 pandemic. Globally, communities are facing food insecurity challenges more intensely than ever before, emphasizing the ongoing value of research that looks at the sustainable production of crops. Despite a challenging year, Virginia Tech’s Feed the Future Integrated Pest Management Innovation Lab (IPM IL) and its partners aim to highlight some of the 2020 research outputs that will continue to help foster improved livelihoods around the world.

Fall armyworm

Tuta absoluta

Crop protection

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DECEMBER 1, 2021

Resolute scientific work could eliminate wheat disease within 40 years

by Lauren Quinn, University of Illinois at Urbana-Champaign

wheat
Credit: CC0 Public Domain

Wheat and barley growers know the devastating effects of Fusarium head blight, or scab. The widespread fungal disease contaminates grain with toxins that cause illness in livestock and humans, and can render worthless an entire harvest. As Fusarium epidemics began to worsen across the eastern U.S. in the 1990s and beyond, fewer and fewer farmers were willing to risk planting wheat.

But the battle to eliminate Fusarium head blight never went away. Public breeding programs, with support from the USDA-supported Wheat and Barley Scab Initiative, have been doggedly tweaking soft red winter wheat lines in hopes of achieving greater resistance to the disease.

In a new analysis, University of Illinois researchers say those efforts have paid off. Over the past 20 years, critical resistance metrics have improved significantly. And, they say, if breeding efforts continue, vulnerability to Fusarium head blight could be eliminated within 40 years.

“I don’t think anybody realizes it’s possible we could eliminate Fusarium head blight as a problem. Forty years sounds like a long time, but by the time I’m retired, the threat of disease could be gone. That would make a huge difference,” says Jessica Rutkoski, assistant professor in the Department of Crop Sciences at Illinois and co-author on the new paper.

Rutkoski and her colleagues examined 20 years of data from nine university breeding programs spanning 40 locations in the eastern U.S. That’s a whopping 1,068 wheat genotypes.

In each year and each location, researchers inoculated wheat plants with Fusarium spores. They evaluated both test entries (novel wheat lines) and check cultivars (standard across all locations and years) for various resistance traits. The long-term check cultivars act as a kind of barometer, accounting for agronomic practices and environmental factors.

The researchers looked at disease incidence, severity, Fusarium-damaged kernels, and deoxynivalenol (also known as Vomitoxin) content—the main toxin of concern in Fusarium-contaminated grain. And over 20 years and 1,068 lines, all the resistance traits improved.

“The genetic gain in disease resistance was significant for each of those four traits. Most importantly, we saw a 0.11 parts-per-million decrease in deoxynivalenol per year. Just to see any significant favorable trend is really good,” Rutkoski says. “It basically shows that everyone’s making progress, and that the investment in public breeding programs is paying off.”

Rutkoski says breeders have thrown nearly every technique at wheat to try to improve resistance to Fusarium head blight. It’s a tough nut to crack because resistance is controlled by multiple interacting genes.

“It’s quantitative resistance. There isn’t just one gene that’s going to solve it. On the breeding side, people have looked at exotic sources of resistance, such as Chinese lines that have high resistance. Then they’ll map the genes and introgress them,” Rutkoski says. “That’s been successful to some degree, but those genes tend to be associated with unfavorable traits, like lower yield. So, there have been issues.”

When Rutkoski analyzed the impact of germplasm introductions from Chinese wheat lines, they weren’t responsible for boosting resistance. In other words, progress over the past 20 years was mostly due to breeders exploiting native resistance—the locally adapted wheat‘s inherent genetic capacity to resist disease—rather than introducing resistance from exotic sources.

That’s not to say novel genetic sources of resistance don’t have their place. Rutkoski notes it’s important to try to identify major-effect genes because often they can help breeders achieve their goals faster.

Ultimately, Rutkoski hopes her results justify and encourage investments in public breeding programs.

“Nobody really notices the progress that’s being made. I think there’s some skepticism and suspicion that breeding isn’t that important. Or people think we need to focus more on genome editing or finding more exotic sources of resistance,” she says. “A lot of public breeding programs are getting shut down, and we risk losing all that progress. So, I was gratified to show that the improvement is very consistent over time. And if you just stick to this kind of strategy, you will have guaranteed results. It’s not risky.”

The article is published in Plant Disease.


Explore furtherScientists discover a protein that naturally enhances wheat resistance to head scab


More information: Rupesh Gaire et al, Genetic trends in Fusarium head blight resistance due to 20 years of winter wheat breeding and cooperative testing in the Northern US., Plant Disease (2021). DOI: 10.1094/PDIS-04-21-0891-SRProvided by University of Illinois at Urbana-Champaign

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DECEMBER 1, 2021

Resolute scientific work could eliminate wheat disease within 40 years

by Lauren Quinn, University of Illinois at Urbana-Champaign

wheat
Credit: CC0 Public Domain

Wheat and barley growers know the devastating effects of Fusarium head blight, or scab. The widespread fungal disease contaminates grain with toxins that cause illness in livestock and humans, and can render worthless an entire harvest. As Fusarium epidemics began to worsen across the eastern U.S. in the 1990s and beyond, fewer and fewer farmers were willing to risk planting wheat.

But the battle to eliminate Fusarium head blight never went away. Public breeding programs, with support from the USDA-supported Wheat and Barley Scab Initiative, have been doggedly tweaking soft red winter wheat lines in hopes of achieving greater resistance to the disease.

In a new analysis, University of Illinois researchers say those efforts have paid off. Over the past 20 years, critical resistance metrics have improved significantly. And, they say, if breeding efforts continue, vulnerability to Fusarium head blight could be eliminated within 40 years.

“I don’t think anybody realizes it’s possible we could eliminate Fusarium head blight as a problem. Forty years sounds like a long time, but by the time I’m retired, the threat of disease could be gone. That would make a huge difference,” says Jessica Rutkoski, assistant professor in the Department of Crop Sciences at Illinois and co-author on the new paper.

Rutkoski and her colleagues examined 20 years of data from nine university breeding programs spanning 40 locations in the eastern U.S. That’s a whopping 1,068 wheat genotypes.

In each year and each location, researchers inoculated wheat plants with Fusarium spores. They evaluated both test entries (novel wheat lines) and check cultivars (standard across all locations and years) for various resistance traits. The long-term check cultivars act as a kind of barometer, accounting for agronomic practices and environmental factors.

The researchers looked at disease incidence, severity, Fusarium-damaged kernels, and deoxynivalenol (also known as Vomitoxin) content—the main toxin of concern in Fusarium-contaminated grain. And over 20 years and 1,068 lines, all the resistance traits improved.

“The genetic gain in disease resistance was significant for each of those four traits. Most importantly, we saw a 0.11 parts-per-million decrease in deoxynivalenol per year. Just to see any significant favorable trend is really good,” Rutkoski says. “It basically shows that everyone’s making progress, and that the investment in public breeding programs is paying off.”

Rutkoski says breeders have thrown nearly every technique at wheat to try to improve resistance to Fusarium head blight. It’s a tough nut to crack because resistance is controlled by multiple interacting genes.

“It’s quantitative resistance. There isn’t just one gene that’s going to solve it. On the breeding side, people have looked at exotic sources of resistance, such as Chinese lines that have high resistance. Then they’ll map the genes and introgress them,” Rutkoski says. “That’s been successful to some degree, but those genes tend to be associated with unfavorable traits, like lower yield. So, there have been issues.”

When Rutkoski analyzed the impact of germplasm introductions from Chinese wheat lines, they weren’t responsible for boosting resistance. In other words, progress over the past 20 years was mostly due to breeders exploiting native resistance—the locally adapted wheat‘s inherent genetic capacity to resist disease—rather than introducing resistance from exotic sources.

That’s not to say novel genetic sources of resistance don’t have their place. Rutkoski notes it’s important to try to identify major-effect genes because often they can help breeders achieve their goals faster.

Ultimately, Rutkoski hopes her results justify and encourage investments in public breeding programs.

“Nobody really notices the progress that’s being made. I think there’s some skepticism and suspicion that breeding isn’t that important. Or people think we need to focus more on genome editing or finding more exotic sources of resistance,” she says. “A lot of public breeding programs are getting shut down, and we risk losing all that progress. So, I was gratified to show that the improvement is very consistent over time. And if you just stick to this kind of strategy, you will have guaranteed results. It’s not risky.”

The article is published in Plant Disease.


Explore furtherScientists discover a protein that naturally enhances wheat resistance to head scab


More information: Rupesh Gaire et al, Genetic trends in Fusarium head blight resistance due to 20 years of winter wheat breeding and cooperative testing in the Northern US., Plant Disease (2021). DOI: 10.1094/PDIS-04-21-0891-SRProvided by University of Illinois at Urbana-Champaign

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Over half of winter wheat varieties resistant to yellow rust at the young-plant stage

02 Dec 2021 ShareCategories: Agronomy / Arable

Farming Online

The UK Cereal Pathogen Virulence Survey (UKCPVS) has released its annual update on the varietal resistance of young winter wheat plants to yellow rust.

Conducted on AHDB Recommended Lists (RL) varieties, including candidates, the latest screens found that over half of the varieties tested were resistant at the young-plant stage.

A young pot-grown wheat plant showing severe yellow rust symptoms.

Growers should use the information, alongside the RL (adult plant) disease resistance ratings, to adapt spray programmes in 2022, particularly at the T0 spray timing.

Dr Charlotte Nellist, UKCPVS project lead at NIAB, said: “The pathogen that causes yellow rust is complex; some varieties are susceptible to the disease when plants are young but go on to develop some level of resistance after early stem extension. However, if young plants are susceptible and the RL disease resistance rating is also low, crops will require closer monitoring for active rust over the winter period.”

The screens use five pathogen isolates selected by UKCPVS to best represent the diversity in the yellow rust population at the time of testing. A variety is classified as susceptible at the young-plant stage if it is sufficiently susceptible to any one of the isolates.

Charlotte said: “The 2010s saw large changes in the UK yellow rust population, resulting in numerous reductions in resistance, at both the young-plant and adult-plant stages. For example, only three varieties were recorded as having young-plant stage resistance in 2016. Since then, the situation has improved somewhat, with over half of the varieties screened in 2021 classed as resistant during these early growth stages.” 

Relatively few yellow rust samples were received by the UKCPVS team in 2021, with 155 samples sent in (from 54 varieties and 19 counties) – around half the number recorded in 2020. The reduction is probably due to this year’s cool, dry spring, which helped reduce wheat yellow rust pressure. Similarly, for brown rust, only 10 samples were received.

Charlotte said: “It is important to send in material, irrespective of the disease pressure. It helps us provide a regional snapshot of the pathogen population and serves as a basis for early warnings of population change. While we cannot test every sample, we do preserve and archive all isolates, which provides an essential reference library for pathogen virulence research.”

The latest cereal pathogen developments, both in the UK and globally, will be in focus at the annual UKCPVS stakeholder meeting on 2 March 2022.

UKCPVS thanks everyone who submitted samples and looks forward to continued support in 2022.

For further information, including about the event and sampling instructions, visit: ahdb.org.uk/ukcpvs

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Bees deliver organic fungicide to crops while pollinating flowers

Sustainable farming technology company Bee Vectoring Technology (BVT) has created a natural fungicide powder that eliminates mold on growing fruits. The preventative measure is delivered by bees doing what they do best – pollinating flowers. They take it directly to the flower, rather than spreading it all over the plants and soil as a traditional spraying system does. This bee-based system has been dubbed ‘natural precision agriculture’.

The fungicide is dispensed through the openings of the hives. As bees leave the hive, they move through the powder, picking up a thick coating on their legs and wings. When they land on a flower to collect pollen, the powder naturally falls off.  

With bee populations all over the world declining in number, lessening environmental pollution is a necessity for their survival. As the bees deliver the fungicide, they are reducing the need for chemicals. Growers can rent or buy hives of bees for a season or full-time, and beekeepers monitor hive health and the needed volumes of fungicide for each crop. The fungicide is available as a single ingredient or a stackable mix of powders, depending on what crop is being protected.

“Spraying products onto crops is inherently inefficient. Only a small amount of what is sprayed on an acre of farm lands on the crop flower,” explains Ashish Malik, CEO of BVT. “On the other hand, bees only visit flowers, and so all of what they are carrying can be used to inoculate the crop with a beneficial microbe to help it fight diseases and pests.”

A number of innovations are focusing on ways to help improve the resilience of hives, with Springwise spotting several new designs. These include a hive that mimics the shape of a tree, and another made from mycelium that helps repel deadly mites. 

For more information:
Bee Vectoring Technologies International 
T: (647) 660-5119
info@beevt.com
www.beevt.com

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Global cooperation fights a potentially devastating banana pandemic

A potentially devastating banana disease (Fusarium TR4) is now spreading across the tropics, threatening the livelihoods of smallholders and large commercial farmers alike, especially growers of Cavendish, the main variety of dessert banana. There have been efforts to understand and control this devastating disease, but a real solution will require international cooperation across many disciplines. In 2020, RTB supported a virtual symposium and a masterclass to share information on how TR4 spreads, how to diagnose it and insights into future control methods.ImageTR4 kills the banana plant by attacking its vascular system. M. Dita (Alliance)

A virulent strain of a soil-dwelling fungus known as Fusarium Tropical Race 4 (TR4) is threatening the world supply of bananas, and the livelihood of millions of farmers. TR4 kills the banana plant by attacking its vascular system. Disease management is complex, as the fungus persists for decades in infected fields and there are no fully effective strategies for managing TR4. 

The pathogen spreads easily through spores, in contaminated soil and planting material. The spores even cling to farmers’ shoes and farming equipment. First identified in Taiwan in 1967, TR4 spread to other Asian countries by the early 2000s. Since 2014, the disease has expanded quickly across the greater Mekong Delta, especially in Laos and Vietnam. TR4 also emerged in 2013 in Mozambique, and was more recently identified on Mayotte, an island in the Indian Ocean. In August 2019, TR4 was reported in organic banana plants in La Guajira, Colombia, while in April 2021, TR4 was spotted in northern Peru, also on an organic banana farm. So far, the Colombians have managed to contain TR4 in the department of La Guajira, although the pathogen has spread from two farms to ten. The Cavendish variety, which dominates the market for dessert bananas, is widely grown as a monocrop, facilitating the spread of the disease. However, TR4 is also starting to gradually spread into smaller-scale, more diversified banana farming systems in various Asian countries.ImageSampling a diseased banana in northern Mozambique. Surveys like this help to map the spread of TR4. G. Blomme (Alliance)

The Alliance of Bioversity and CIAT and the International Institute of Tropical Agriculture (IITA), with the support of RTB, held a two-day virtual mini-symposium which presented a state-of-the-art overview of research on this disease. In addition, a virtual Masterclass for anyone interested in the pathogen, diagnostic tools, control strategies and the impact was organized by The Alliance and IITA in the framework of ProMusa and RTB. 

During the Masterclass, banana researchers from across the globe presented current knowledge on Fusarium spread, epidemiology and control. At the virtual symposium, novel research insights were communicated. For example, how to detect viable Fusarium inoculum from environmental samples, or insights in the survival and treatment of Fusarium in water. In addition, weevils and nematodes were reported to contribute to disease spread and infection intensity. The symposium also presented new tools to detect and map TR4.

The symposium discussed biocontrol approaches, including use of the beneficial fungus Trichoderma to control TR4. The substrate left over after harvesting cultivated mushrooms could be applied to the soil to stop the spread of the disease. Groundcover root flavonoids and phenolic acids may also help stop the fungus in the soil. Researchers in China have identified beneficial bacteria closely related to the well-known Bt. Two of these Bacillus bacteria are now being screened to find the best strains for biological control of TR4. Colombian scientists are testing ammonia-based soil disinfectants to eliminate the pathogen from locations where infected mats had been removed.ImageInternal symptoms of Fusarium wilt, TR4 affecting Cavendish bananas in Colombia. M. Dita (Alliance)

The key option to mitigate the impact of Fusarium is through the use of resistant or highly tolerant germplasm. Some promising genetic material is currently available and is being used, and many other banana types are being screened for resistance. Therefore, conventional breeding, in addition to GM and CRISPR, will most likely widen the pool of resistant germplasm in the years to come. 

“The rapid spread of TR4 threatens food security across the tropics on three continents. The banana also creates lots of jobs, including many for women and youth, from farming to packing houses to retail sales. It’s heartening that the world’s experts have been able to start working together to develop the technologies that will solve this crisis,” says James Legg, leader of FP3, which helped to sponsor the symposium.ImageFemale banana exporter in Uganda. (CIP)ImageLeaves turn yellow on a diseased plantain plant. A Fusarium Race 1 affected Bluggoe plant in northern Moza

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NOVEMBER 23, 2021

For a fungus, the right ‘accessories’ can make or break a relationship with a plant

by American Phytopathological Society

Plants interact with a diversity of organisms over the course of their lifetime, but even very similar microbes can cause opposite reactions. Two strains of the fungus Fusarium oxysporum (Fo) share a core genome, but one is a beneficial endophyte while the other is a detrimental pathogen causing wilt and death. A new study, published in the Molecular Plant-Microbe Interactions journal, tried to tease apart why these two strains cause such opposite reactions, and more generally how plants respond differently to useful and harmful microbes, by exploring the interaction of these two strains with the model plant Arabidopsis.https://171f00c1a52866b7097ffbff08524c56.safeframe.googlesyndication.com/safeframe/1-0-38/html/container.html

As explained by senior author Li-Jun Ma, “strain-specific interactions with a common host are likely dictated by the accessory chromosomes from each F. oxysporum genome.” Accessory chromosomes are extra pieces of genetic material that are considered to be more plastic in that they move and change based on the lifestyle that the fungus has, unlike the core genome. Like the gadget laboratory in a spy movie, the accessory chromosomes of Fo strains contain tools used to infiltrate the plant and shut down defenses. Using closely related strains that differ in accessory chromosomes “allows a comparative study that minimizes genetic differences between strains to address the underlying mechanism that results in distinct phenotypes (growth promotion or disease or even death),” says leading author Li Guo.

In this study, metatranscriptomic data reveals that most plant genes (about 80%) are expressed similarly in response to both fungal strains across timepoints over four days. By just twelve hours, the most obvious differences in plant response are occurring. Co-first author Houlin Yu explains that “it is important to realize that plants can rapidly react to signals of microbial presence by changing their gene expression.” For example, plant defense-related genes are induced by both the endophytic and pathogenic strains, but the endophyte is better able to suppress these genes. The other host genes that varied include plant growth-related genes that were reduced in expression when the pathogen was present, whereas nitrogen uptake and metabolism genes were increased in expression (upregulated) when the endophyte was present.

The accessory chromosomes are also where a lot of the gene expression changes were seen in the fungal strains. The endophytic strain upregulated genes involved in cell signaling and nutrient transport, while the pathogenic strain unsurprisingly upregulated those enriched for virulence or detoxification roles. Identifying the fungal genes with changes in expression on the accessory chromosomes that correspond to the ultimate outcome of plant health tell researchers what to investigate further to increase disease resistance and promote plant growth. Ma emphasizes that, “This research has a profound effect on plant and perhaps even animal immunology, suggesting that cells have a remarkable flexibility and plasticity in response to microbes of same species but genetically different.”


Explore furtherFungal transplants from close relatives help endangered plants fight off disease


More information: Li Guo et al, Metatranscriptomic Comparison of Endophytic and Pathogenic Fusarium–Arabidopsis Interactions Reveals Plant Transcriptional Plasticity, Molecular Plant-Microbe Interactions (2021). DOI: 10.1094/MPMI-03-21-0063-RJournal information:Molecular Plant-Microbe InteractionsProvided by American Phytopathological Society

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New paddy variety on 250 acres hit by rice blast disease in Wayanad

E.M. ManojKALPETTA, NOVEMBER 12, 2021 21:45 ISTUPDATED: NOVEMBER 12, 2021 21:45 IST

Scientists of the Regional Agricultural Research Station, Ambalavayal, visiting a paddy farm affected by the rice blast disease, under the Cheekkallur Padashekhara Samiti in Wayanad district.   | Photo Credit: Special Arrangement

Expert says ‘Manuvarna’ strain was intended for cultivation in kole fields and wetland ecosystems

Rice blast, a fungal disease affecting paddy, is haunting farmers who had raised “Manuvarna”, a new rice variety released by the Kerala Agricultural University recently, on more than 250 acres in Wayanad district.

K. Kesava Marar, president of the Cheekkallur Padashekhara Samiti, cultivated the new rice variety on 70 acres of rented land after learning from some farmers in Palakkad district that it had given higher yields than the traditional rice varieties.

Mr. Marar, along with 60 other farmers of the samiti, procured the 4,600 kg of seeds from the Kerala Agricultural University at a cost of ₹42 kg.

However, they noticed a few weeks ago that the crop cultivated on more than 250 acres of land was damaged owing to the blast disease.

The blast disease is caused by the fungus Pyricularia oryzae which is non-systemic in action. The spores of the fungus could have been released from hosts like Purple nutsedge and Echinochloa crusgalli (Muthanga and Kavada respectively in local parlance) which are abundantly present in the paddy fields, bunds, and on sides of irrigation channel of the affected area. This would have resulted in an increased concentration of spores in the air. Relative humidity of more than 93% and rainfall below 5 mm per day are the major predisposing factors especially during the mid tillering stage of the crop for the incidence of the blast, RARS sources said.

The ‘Manuvarna’ variety of paddy was released for the low lands of Kerala, especially for the kole lands, wetland ecosystem, K. Ajith Kumar, Associate Director, RARS, told The Hindu.

Adoption of prophylactic measures of management would have substantially reduced the severity of blast disease incidence, Dr . Ajithkumar said. However, such measures were not taken properly in the affected area which led to severe damage due to the incidence of neck blast, he said.

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Tar spot gains attention of USDA-ARS

Tom J. Bechmancorn leaf with signs of tar spotEARLY STAGES: Agronomists say growers need to learn to identify tar spot at this stage. This specimen was growing in Bayer’s fungicide demonstration plots at the Farm Progress Show.Hi-Tech Farming: The newest corn disease in the U.S. is targeted by researchers.

Tom J Bechman | Nov 18, 2021

Tar spot was first detected in the U.S. in 2015, but it now has the undivided attention of a USDA Agricultural Research Service research team based in West Lafayette, Ind. Growers fight this corn disease with fungicides. However, Steve Goodwin, an ARS plant pathologist, says plants that have resistance to tar spot are preferable.

While participating universities conduct research on timing of fungicides and other control measures, Goodwin and his team are concentrating on four fronts:

1. Screening current material. The team is screening existing commercial varieties and germplasm lines for resistance or susceptibility to tar spot. The goal is to help growers adjust management practices as soon as possible depending upon which hybrids they grow.

2. Developing molecular markers. These tools will identify Qrtsc8, the gene that confers tar spot resistance. Investigators are also exploring why some plants that lack this gene are still resistant, since an unknown gene or genes could be involved.

3. Determining biocontrol potential. A microbiome of organisms was found on tar spot-resistant plants, but not on susceptible plants. Researchers want to know how these organisms, plant growth stage and the environment are interconnected in the progression of tar spot.

4. Understanding how tar spot works. Scientists also want to learn how the tar spot fungus uses several proteins to short-circuit defenses of susceptible plants. Identification of these proteins could lead to better detection of different strains of the fungus and its severity in the field.

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