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Archive for the ‘Host plant resistance’ Category

Scientists decode chemical defense against plant sap-sucking leafhoppers

Date:February 3, 2022 Source: Max Planck Institute for Chemical Ecology Summary: Given the sheer number of potential enemies, plants are resistant to most pests, even if they can cause damage to other plants. Researchers describe a newly discovered mechanism that protects a wild tobacco species from plant sap-sucking leafhoppers. By combining different genetic screening methods with the study of chemical changes in tobacco leaves, they identified a previously unknown defense substance important for the tobacco’s resistance to leafhoppers and characterized the genes for its biosynthesis.Share:

FULL STORY


Plants are at the bottom of the food chain and are continually threatened by pathogens and herbivorous insects. But the vast majority of attackers are unable to cause any damage due to a broadly based plant resistance, also known as non-host resistance. This resistance is permanent and effective. However, the mechanisms that lead to this resistance, particularly to herbivorous pests, are largely unknown. In a new study, researchers at the Max Planck Institute for Chemical Ecology were able to identify a chemical substance responsible for the resistance of Nicotiana attenuata plants to sucking leafhoppers (Empoasca spp.) and the genes needed for its production. “Our research uncovered how native plants use chemical reprogramming to defend themselves against opportunistic leafhoppers in nature,” first author Yuechen Bai says, summarizing the results.

In 2004, scientists at the institute had already discovered in field studies that tobacco plants impaired in their defense-signaling cascade based on the plant hormone jasmonic acid were attacked by leafhoppers, insects that are usually not able to harm tobacco plants with functional defenses. The work proved that, in nature, plants are permanently “tested” by herbivorous insects in order to find out whether they can serve as a food source; however, in most cases the plants are able to defend themselves effectively. Consistent with these findings, another study by the institute showed that leafhoppers colonized the very plants in natural tobacco populations whose jasmonic acid signaling pathway was weaker than in other tobacco plants. “However, at that time, it was still unknown which specific defense mechanisms triggered by jasmonic acid were responsible for resistance to the leafhoppers,” explains Dapeng Li, one of the study leaders.

To answer this question, the scientists crossed 26 genetically different natural parental lines. This population, which the research team had crossed according to a fixed scheme over a total of nine years, was planted out in its natural habitat in Arizona, USA, where it could be attacked by opportunistic leafhoppers. When leafhoppers attacked these plants, the severity of the damage helped identify the genetic basis that made this particular plant a host plant for leafhoppers taking advantage of weak defenses.

The researchers also investigated which chemical changes are elicited in the plants after attack and which genes are activated. They found a new unstable substance, for which they used the abbreviation CPH (caffeoylputrescine-green-leaf-volatile compound), which was responsible for permanent resistance to leafhoppers. Through bioinformatic detective work and by using plants that were specifically modified in certain defense and signal transduction genes, they were able to show which three metabolic pathways were involved in the production of this chemical. Finally, the researchers even succeeded in reconstituting the biosynthetic pathway for the defense substance CPH in two related plants, the field bean Vicia faba and the tomato species Solanum chilense, and demonstrating its efficacy against leafhoppers.

“By combining sophisticated molecular biology and chemical analysis methods, we were able to identify and characterize not only a previously unknown defense substance, but also the genes responsible for its synthesis,” explains Ian Baldwin, and continues: “Our approach can be described as “natural history-guided forward genetics. Natural history and the observation of the feeding behavior of leafhoppers has driven our discovery process. Because when it comes to chemistry, nature remains the mother of invention.”

In further studies, the researchers want to find out how the synthesis of this chemical defense is coordinated in the plant and which other factors and specific regulators are crucial for its production, especially under natural conditions. Leafhoppers of the genus Empoasca, especially the potato leafhopper Empoasca fabae, can cause major crop damage by sucking on the leaves of young plants and transmitting viral diseases. Higher temperatures have led to a threatening spread of these insects. This basic research to control such a pest can provide valuable insights with regard to permanently improved resistance in crops, especially in the context of new demands on agriculture caused by climate change.


Story Source:

Materials provided by Max Planck Institute for Chemical EcologyNote: Content may be edited for style and length.


Journal Reference:

  1. Yuechen Bai, Caiqiong Yang, Rayko Halitschke, Christian Paetz, Danny Kessler, Konrad Burkard, Emmanuel Gaquerel, Ian T. Baldwin, Dapeng Li. Natural history–guided omics reveals plant defensive chemistry against leafhopper pestsScience, 2022; 375 (6580) DOI: 10.1126/science.abm2948

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Anthracnose-resistant sorghum is a gene away

Courtesy of Purdue University and Tom CampbellTesfaye Mengiste, professor of botany and plant pathology at Purdue University, looks at sorghum infected with anthracnose. Mengiste RESISTANCE: Tesfaye Mengiste, a professor of botany and plant pathology at Purdue University, looks at sorghum infected with anthracnose. Mengiste led a team of researchers of the Feed the Future Innovation Lab for Collaborative Research on Sorghum and Millet (SMIL) that identified a single gene conferring broad resistance to the fungal disease.Kansas State University scientists are working on a sorghum variety with natural resistance to pathogens and pests.

Anthracnose resistance in sorghum is just a gene away. Scientists with the Feed the Future Innovation Lab for Collaborative Research on Sorghum and Millet (SMIL) recently announced they have developed a sorghum variety they say will provide natural resistance to pathogens and pests that have crippled the crop in humid lowland areas of western Ethiopia.

Their research is reported in the Jan. 9 issue of The Plant Cell, a journal of the American Society of Plant Biologists.https://0621facf49cfb5973b607839954903fe.safeframe.googlesyndication.com/safeframe/1-0-38/html/container.htmlJennifer M. LatzkeSorghum

SORGHUM: Farmers could soon have sorghum varieties with built-in anthracnose resistance, which will boost yields.

Timothy Dalton, director of SMIL, based at Kansas State University, says the researchers’ work will “serve the broader sorghum development community and is a flagship global good, public characteristic of the U.S. land-grant mission.

Sorghum map

The K-State lab led by Dalton funded work in Ethiopia and West Africa to map genes and explore more than 2,000 pieces of germplasm in numerous field trials over several years.

“The new variety, called Merera, has multiple benefits, including resistance to pathogens and birds, and it yields better than current varieties that Ethiopian farmers have,” says Tesfaye Mengiste, a professor of botany and plant pathology at Purdue University and the principal investigator for the research.

Mengiste says Merera has shown resistance to anthracnose, a devastating fungal disease that attacks all parts of the plant — leaves, stalk, and head — leaving almost nothing to be used for food, biofuels or animal feed.

“With these improved traits and yield potential, it can mean a better livelihood for [farmers],” Mengiste says.

Discovery

A newly discovered gene named anthracnose resistance gene1, or ARG1, is unique, according to Mengiste.

“Although some natural resistance to fungal disease was known in sorghum, genes that confer widespread resistance have not been identified,” he says. “It is remarkable that a single gene leads to resistance across a broad spectrum of fungi and multiple strains of the anthracnose fungus.”

Mengiste cited recent results with Merera that indicate up to a 43% increase in sorghum yields, which has led to increased income for smallholder farmers.

USAID

In 2013, the U.S. Agency for International Development invested $13.7 million to establish the Feed the Future Innovation Lab for Collaborative Research on Sorghum and Millet at K-State. The lab’s primary focus is to improve the productivity, disease resistance, agronomy and economy of sorghum and millet in six partner countries. In 2018, USAID renewed its commitment to SMIL, awarding $14 million over five years to continue the project’s work.

USAID funds several Feed the Future Innovation Labs across the country to harness the capacity of U.S. land-grant institutions, other universities and the private sector to improve food security globally.

The sorghum variety recently developed for Ethiopia — while directly benefiting farmers in that country — is much like many other Feed the Future projects that aim to build knowledge to help farmers throughout the world, including in the U.S.

“Through this collaborative research supported by SMIL and the funding through USAID, we will continue to explore the rich Ethiopian germplasm to come up with the next resilient and high-yielding varieties,” Mengiste says. “With better leveraging of recent genetic technologies, we will expedite the development of the new generation of varieties or those in the pipeline.”Source: Kansas State Research and Extension is solely responsible for the information provided and is wholly owned by the source. Informa Business Media and all its subsidiaries are not responsible for any of the content contained in this information asset.

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DECEMBER 20, 2021

Microbe sneaks past tomato defense system, advances evolutionary battle

by Lauren Quinn, University of Illinois at Urbana-Champaign

tomato
Credit: CC0 Public Domain

When we think of evolution, many of us conjure the lineage from ape to man, a series of incremental changes spanning millions of years. But in some species, evolution happens so quickly we can watch it in real time.

That’s the case for Xanthomonas, the organism that causes bacterial leaf spot disease in tomato and pepper plants. Like many microbes with short generation times, it can evolve at lightning speed to acquire beneficial traits, such as the ability to elude its host’s defense system.

New research from the University of Illinois shows one Xanthomonas species, X. euvesicatoria (Xe), has evolved to avoid detection by the immune system of tomato plants.

“It’s part of the evolutionary warfare between plants and pathogens, where the plant has some defense trait and then some portion of the pathogen population evolves to escape it. The plant has to develop or acquire a new defense trait, but the process is much slower in plants compared to microbes. This study is a great example of that ongoing battle in progress. It tells us we can’t completely rely on this trait to combat bacterial spot disease caused by Xe,” says Sarah Hind, assistant professor in the Department of Crop Sciences at Illinois and co-author on a pair of recent studies published in Molecular Plant-Microbe Interactions and Physiological and Molecular Plant Pathology.

The tomato defense system keeps tabs on Xanthomonas and other bacteria with immune receptors that chemically detect flagella, the long whip-like tail structures that allow bacteria to move or “swim” through soil and plant tissues. Hind and her colleagues used laboratory and genomic modeling techniques to show one of tomato’s receptors, FLS3, no longer works to detect flagellin proteins in Xe.

Their work shows Xe’s flagellin proteins have changed by just one amino acid, but it’s enough to escape detection by tomato’s FLS3 receptors.

Graduate student and study co-author Maria Malvino says, “It was surprising to see that only one amino acid change was making all the difference. It made us wonder how binding between flagellin and FLS3 could be so dramatically altered.”

The fact that Xe can sneak past tomato’s defenses means farmers can rely even less on inherent disease resistance. Instead, they’ll have to combat the disease in other ways, such as spraying copper-based pesticides.

In some locations, including the Midwest region and in Illinois specifically, Xe isn’t as much of a problem as two other Xanthomonas species, X. perforans and X. gardneri (Xp and Xg). Tomato can still hold its own against these species for the time being, but Hind is concerned Xe will share its evasion strategy.

“X. euvesicatoria [Xe] had been the predominant strain for a long time, but within the last decade or two, it’s become less prominent and has been overtaken by another species, Xp,” she says. “Xp and Xe are really genetically close, and it’s been shown that they can share their genetic material with each other. So it wouldn’t be out of the realm of possibility that that Xe’s evasion strategy could make its way into Xp and provide the same advantage against tomato.”

Hind says the tendency of these bacteria to defeat host defenses through rapid evolution makes breeding for disease resistance difficult in tomato.

“It’s like whack-a-mole for breeders. It takes a long time to release a resistant variety. Often, by the time they go to release a new one, the pathogen population shifts,” Hind says. “And when you add to that the difficulty of maintaining all the desirable traits of a tomato, it’s a tough situation. Again, that leaves us relying on fungicides and copper treatments to keep tomato production profitable here in Illinois.”


Explore furtherScientists find new system in tomato’s defense against bacterial speck disease


More information: Maria Laura Malvino et al, Influence of flagellin polymorphisms, gene regulation, and responsive memory on the motility of Xanthomonas species that cause bacterial spot disease of solanaceous plants, Molecular Plant-Microbe Interactions (2021). DOI: 10.1094/MPMI-08-21-0211-R

Julius Pasion et al, Utilizing Tajima’s D to identify potential microbe-associated molecular patterns in Xanthomonas euvesicatoria and X. perforans, Physiological and Molecular Plant Pathology (2021). DOI: 10.1016/j.pmpp.2021.101744Journal information:Molecular Plant-Microbe InteractionsProvided by University of Illinois at Urbana-Champaign

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LSU awarded $5 million to look into invasive species harmful to sweet potatoes

A team of LSU AgCenter researchers, collaborating with scientists from four other universities, have been awarded a USDA National Institute of Food and Agriculture grant of more than $5 million, aiding them in developing sweet potato varieties resistant to the invasive guava root-knot nematode.

The AgCenter team is spearheaded by nematologist Tristan Watson. It has also received a sub-grant for $990,000 to support research on sweet potato breeding and characterization of resistance mechanisms and associated genes as well as extension of research findings to regional and national stakeholders.

Watson: “Root-knot nematodes are particularly damaging to the sweet potato. The overall goal of this project is to provide Louisiana sweet potato growers effective tools for the management of established and emerging root-knot nematode species.”

Source: lsuagcenter.com

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Novel Plantibodies show promise to protect citrus from Greening Disease

Citrus greening [huanglongbing (HLB)] has emerged as the most significant disease in citrus (Citrus sp.) agriculture. The disease is associated with the Candidatus Liberibacter species of bacteria. The most prevalent and virulent species in this group is Candidatus Liberibacter asiaticus. It is primarily vectored by the Asian citrus psyllid [ACP (Diaphorina citri)]. 

The bacteria and insect vector are present in many citrus orchards worldwide, including the United States, China, and Brazil. HLB often has a devastating impact on infected citrus; causing a rapid decline, with loss of fruit yield and quality and potentially leading to tree death. The bacteria has had a significant negative impact on the citrus industry, causing loss of fruit quality and yield, as well as loss of root mass, leading to tree decline. Finding a cure has been challenging due to the complexity of the CLas bacteria interactions with the citrus host and the Asian citrus psyllid. Another factor that has made it hard to recover from the disease is the tendency of the citrus industry to focus on a small number of cultivars with commercially desirable traits, but little genetic diversity.

Researchers who are working to find a citrus cultivar that is HLB resistant have a choice of either adding genetic variation through breeding with distant relatives or modifying the trees transgenically. In an article published this month in the Journal of the American Society for Horticultural Science, scientists present promising results from transgenic populations that produce antibodies that can bind with CLas proteins and reduce the bacteria’s ability to replicate. 

This study advances the research needed to test the durability and strength of any resistance conferred by expression in rootstocks to a grafted tree and will hopefully lead to the development of a novel protection strategy for HLB.

According to Ed Stover, a Research Horticulturalist with the USDA Agricultural Research Service, “The Florida citrus industry desperately needs more HLB tolerant trees. If sufficient tolerance can be conferred by a single transgenic rootstock then it will greatly expedite implementation. Any transgenic solution will require extensive validation and analyses for non-target effects and food safety.” 

For more information: doi.org

Publication date: Wed 15 Dec 2021

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“What we saw convinced us again that the ToBRFV resistance is holding very well”

In October 2020, Enza Zaden announced the discovery of the High Resistance gene to ToBRFV. The one and only solution to beat this devastating tomato virus.

Fast forward to today, one year later: what has happened in the past year? Where are we now? And what is yet to come? 

Martijn van Stee, Crop Breeding Manager Tomato, gives an insight into the process to create high-resistant varieties: “Since we discovered the ToBRFV high resistance gene we worked hard on introducing it in our elite parent lines. At this moment we have high-quality parent lines with the ToBRFV resistance. This helps us to make high resistance tomato varieties.”  

Check out the video here.

Trials confirm high resistance 
Besides working on the parent lines, Enza Zaden has done some extensive trials with high resistant varieties in the past year. Martijn: “We trialed the first tomato varieties already in Europe, Mexico, and the Middle East. And what we saw there really convinced us again that the ToBRFV resistance is holding very well.” 

Kees Konst, Crop Research Director, continues: “In the meantime, we started up also the seed production of the hybrids. We already have some examples of high resistance varieties in our hands.” 

Importance of high resistance to ToBRFV 
The gene that Enza Zaden has discovered provides high resistance to ToBRFV. Kees explains the importance of high resistance. “With high resistance, you will not have any problems, because there is no virus in the plant or the fruit. You keep your soil, your water, everything clean.” 

What’s next? 
Eradicating the virus remains our top priority. This is something we can only achieve together with the growers and the fresh produce industry. Martijn: “Our breeders are very busy filling the pipeline. To make more elite parent lines with resistance, to make more varieties with resistance. The solution is right around the corner.”\For more informationEnza Zaden
info@enzazaden.com
www.enzazaden.com

Publication date: Wed 1 Dec 2021

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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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SCN: What you can do to fight soybeans’ top yield robber

DFP Staffsoybean fieldRotating SCN-resistant sources of resistance is an active management strategy advised by the SCN Coalition, but easier said than done for Midsouth growers.”We’re seeing bushels upon bushels of soybeans lost.”

Ginger Rowsey | Dec 02, 2021

Soybean cyst nematode continues to rank as the top yield robber of soybeans in the U.S. and Canada and it’s showing no signs of stopping. Since 2017 SCN has continued to move into new areas, and, according to experts is becoming harder to control. 

“We’re seeing bushels upon bushels of soybeans lost. The biggest challenge is yield loss can occur in the absence of symptoms. We’ve observed yield loss of up to 30% in fields that looked fine,” said Kaitlyn Bissonnette, Extension specialist with the University of Missouri. Bissonnette was speaking at a Grow in the Know SCN webinar, sponsored by the SCN Coalition and BASF. https://31ff83a5596d5b2313020cd4368ba0f3.safeframe.googlesyndication.com/safeframe/1-0-38/html/container.html

In addition to SCN expanding to new geographic areas, there is evidence these nematodes are also adapting to PI 88788 — the most common source of SCN resistance that is available in about 95% of SCN-resistant varieties. In Tennessee, for example, the SCN Coalition reports that 93% of fields planted to soybean varieties with PI 88788 sources of resistance have seen SCN numbers increase more than 10%. 

“This elevated reproduction tells us these sources are no longer as resistant as they once were,” said Bissonnette. 

Rotating sources of resistance 

Rotating sources of resistance would slow SCN’s growing tolerance to one source. The problem for Midsouth growers is there are few desirable alternatives to PI 88788. Peking is the second most widely used source of SCN resistance, but it is not a major player in southern soybean genetics. A search of seed companies’ websites revealed Peking resistance could only be found commercially available in maturity groups earlier than MG3.  

Expanding the sources of SCN resistance is not an easy task. Public soybean breeders have spent years working with SCN resistance breeding lines other than PI 88788. Unfortunately, breeding resistance genes from those other sources — such as Peking and Hartwig — into elite varieties has been challenging. 

Vince Pantalone, soybean breeder with the University of Tennessee said Hartwig resistance is the better option for the South. This year, UT’s breeding program released TN14-5021, which Pantalone says contains multiple SCN resistance as well as resistance to many southern plant pathogens. Other universities, such as University of Illinois and University of Nebraska have also developed cultivars with the Hartwig resistance source. 

If growers can only get soybeans with PI 88788 resistance, the SCN Coalition recommends rotating different varieties of soybeans with PI 88788 because not all PI 88788 varieties are the same. 

“Ideally, we’d like growers to rotate among several different modes of action of SCN resistance,” said Melissa Mitchum, University of Georgia molecular nematologist. “That’s what we’re working to provide.”  

More resistance genes on the way 

However, Mitchum says there are additional resistance genes that haven’t been used yet in commercial soybean varieties. “We’ve only utilized Rhg1 and Rhg4, and that’s what you see in growers’ fields, but we can breed with other sources to introduce other resistance genes.” 

Mitchum is working closely with soybean breeders to investigate other sources of resistance. “We’ve already found new genes and gene combinations that are different from Rhg1b in PI 88788 and the Rhg1a/Rhg4 combination in Peking to help fight back against virulent SCN.”  

SCN research 

For several years, checkoff-funded researchers have been working to identify novel types of nematode resistance. Advances in technology, such as the ability to clone resistance genes and the development of precise molecular markers, have allowed university soybean breeders to speed up the process of getting resistant cultivars out to commercial breeders.   

“Today, we can quickly test more soybean germplasm for nematode resistance,” Mitchum explains. “We’re also looking at which genes we should combine, which genes we shouldn’t, and the best rotation strategies for different modes of action.”   

The goal is to get more SCN-resistant modes of action on the market for farmers and protect existing SCNresistance sources. “We want to keep PI 88788 in the toolbox and offer growers other options to protect their soybean yields,” Mitchum says.  

Beyond variety selection 

Beyond variety selection, crop rotation is still effective within reason, according to Bissonnette.  

“We can’t get rid of this through crop rotation alone, but cultural practices like that along with planting certain species of cover crops and improving weed management can help,” she said.  

“Growers could also consider using SCN seed treatments, especially where SCN populations have gotten out of control,” she added. Results from an SCN Coaltion survey showed the number of growers using nematode protectant seed treatments has almost doubled over the past five years. 

“Soil testing will always be the first step in SCN management. Those results will give you a better idea of how intensively to manage, but it’s much easier to keep counts down than reduce high numbers,” Bissonnette said. “The most important steps will be selecting resistant varieties and using different resistance sources. If that’s not an option for you, at least rotate varieties within PI 88788.”  

Learn more 

To learn more about the checkoff-funded research that’s focused on bringing new tools to soybean growers in the fight against parasitic nematodes, watch the Research Collection of “Let’s Talk Todes” videos. 

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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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IAPPS Region X Northeast Asia Regional Center (NEARC)

Present committee members

Dr. Izuru Yamamoto, Senior Advisor

Dr. Noriharu Umetsu, Senior Advisor

Dr. Tsutomu Arie, a representative of the Phytopathological Society of Japan, the chair of Region X

Dr. Tarô Adati, a representative of Japanese Society of Applied Entomology and Zoology

Dr. Hiromitsu Moriyama, a representative of Pesticide Science Society of Japan, the secretary general of Region X

Dr. Rie Miyaura, a representative of The Weed Science Society of Japan

The Phytopathological Society of Japan and Pesticide Science Society of Japan became official partners of IYPH2020 by FAO of UN and Ministry of Agriculture, Forestry and Fisheries (MAFF) of Japan and endeavored to educate the society on plant protection. https://www.maff.go.jp/j/syouan/syokubo/keneki/iyph/iyph_os.html

Annual activities related to IAPPS especially to IPM of plant diseases, insects and weeds, and plant regulation (from April 2020 to March 2021)

The Phytopathological Society of Japan (PSJ)

2020 Kanto District Meeting, Online; Sep 21–22, 2020

2020 Kansai District Meeting, Online; Sep 21–22, 2020

2020 Tohoku District Meeting, Online; Oct 12–14, 2020

2020 Hokkaido District Meeting, Online; Oct 15, 2020

2020 Kyushu District Meeting, Online; Nov 24–26, 2020

2021 Annual Meeting, Online; Mar 17–19, 2021

Japanese Society of Applied Entomology and Zoology (JSAEZ)

65th Annual Meeting, online, March 23-26, 2021

28th Annual Research Meeting of the Japan-ICIPE Association, online, March 25, 2021

Pesticide Science Society of Japan

37rd Study Group Meeting of Special Committee on Bioactivity of Pesticides, online, Sep 18, 2020

40th Symposium of Special Committee on Agricultural Formulation and Application, Yokohama, Kanagawa; Oct 15–16, 2020 (Cancelled due to the spread of COVID-19)

43th Annual Meeting of Special Committee on Pesticide Residue Analysis, online, Nov. 5–6, 2020

46th Annual meeting, Fuchu, Tokyo and Online, March 8–10, 2021

The Weed Science Society of Japan (WSSJ)

2020 Annual Meeting, The Weed Science Society of Kinki, Online; Dec 5, 2020

35th Symposium of Weed Science Society of Japan, Online; Dec 12, 2020

2020 Annual Meeting, Kanto Weed Science Society, Online; Dec 22, 2020

22th Annual Meeting, The Weed Science Society of Tohoku, Japan, Online; Feb 25, 2021

2020 Study Group Meeting of Weed Utilization and Management in Small Scale Farming, Online; Feb 26, 2021

Hono-Kai (means, Meeting who are appreciating agriculture)

35th Hono-Kai Symposium was cancelled due to the epidemic of COVID-19

Japan Biostimulants Association

rd Symposium, Online; Nov 2–30, 2020

Nodai Research Institute

2020-1 Biological Control Group Seminar, Setagaya; Tokyo; Jun 16, 2020 (Cancelled due to the epidemic of COVID-19)

2020-2 Biological Control Group Seminar, online, Nov 13, 2020

2021-1 Biological Control Group Seminar, online, Jun 15, 2021

2021-2 Biological Control Group Seminar, online, Nov 9, 2021

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