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Saturday, 14 January 2023 16:05:11

PestNet

Grahame Jackson posted a new submission ‘Bacterial volatile organic compounds attenuate pathogen virulence via evolutionary trade-offs’

Submission

Bacterial volatile organic compounds attenuate pathogen virulence via evolutionary trade-offs

Nature

Jianing WangWaseem RazaGaofei JiangZhang YiBryden FieldsSamuel GreenrodVille-Petri FrimanAlexandre JoussetQirong Shen & Zhong Wei 

The ISME Journal (2023)

Abstract

Volatile organic compounds (VOCs) produced by soil bacteria have been shown to exert plant pathogen biocontrol potential owing to their strong antimicrobial activity. While the impact of VOCs on soil microbial ecology is well established, their effect on plant pathogen evolution is yet poorly understood. Here we experimentally investigated how plant-pathogenic Ralstonia solanacearum bacterium adapts to VOC-mixture produced by a biocontrol Bacillus amyloliquefaciens T-5 bacterium and how these adaptations might affect its virulence. We found that VOC selection led to a clear increase in VOC-tolerance, which was accompanied with cross-tolerance to several antibiotics commonly produced by soil bacteria. The increasing VOC-tolerance led to trade-offs with R. solanacearum virulence, resulting in almost complete loss of pathogenicity in planta. At the genetic level, these phenotypic changes were associated with parallel mutations in genes encoding lipopolysaccharide O-antigen (wecA) and type-4 pilus biosynthesis (pilM), which both have been linked with outer membrane permeability to antimicrobials and plant pathogen virulence. Reverse genetic engineering revealed that both mutations were important, with pilM having a relatively larger negative effect on the virulence, while wecA having a relatively larger effect on increased antimicrobial tolerance. Together, our results suggest that microbial VOCs are important drivers of bacterial evolution and could potentially be used in biocontrol to select for less virulent pathogens via evolutionary trade-offs.


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Science News

from research organizations


Molecular mechanism behind nutrient element-induced plant disease resistance discovered

Date:January 10, 2023Source:American Phytopathological SocietySummary:In one of the few studies to directly investigate the mechanism underlying the effect of essential elements on plant disease resistance, scientists demonstrate that nutrient elements activate immune responses in tomato plants through different defense signaling pathways.Share:

    

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Just like humans can’t subsist on a diet of only French fries and brownies, plants must also consume a balanced diet to maintain optimal health and bolster their immune responses. Nutrient element uptake is necessary for plant growth, development, and reproduction. In some cases, treatment with essential elements has been shown to induce plant disease resistance, but conclusive research on the molecular basis of this remedy has been limited.

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In one of the few studies to directly investigate the mechanism underlying the effect of essential elements on plant disease resistance, Rupali Gupta of Volcani Institute and colleagues demonstrate that nutrient elements activate immune responses in tomato plants through different defense signaling pathways.

Their paper, recently published in Phytopathology, outlines the molecular mode of action that potassium, calcium, magnesium, and sodium take to minimize both fungal and bacterial plant diseases. Using straightforward laboratory methods, the authors demonstrate that essential element spray treatment sufficiently activates immune responses in tomato — including defense gene expression, cellular leakage, reactive oxygen species production, and ethylene production — leading to disease resistance. Their results suggest that different defense signaling pathways are required for induction of immunity in response to different elements.

Understanding the genetic mechanism underlying this process may provide new insights into crop improvement. Corresponding author Maya Bar comments, “We are excited to probe the molecular basis of this phenomenon, define another facet of induced resistance, and provide data that will assist in applying this principle to agricultural systems in a more purposeful, reproducible manner.”

The tenets of mineral nutrient-induced disease resistance discovered in this study can be exploited in agricultural practices — benefiting growers/farmers and protecting valuable crops.

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Story Source:

Materials provided by American Phytopathological SocietyNote: Content may be edited for style and length.


Journal Reference:

  1. Rupali Gupta, Meirav Leibman-Markus, Gautam Anand, Dalia Rav-David, Uri Yermiyahu, Yigal Elad, Maya Bar. Nutrient Elements Promote Disease Resistance in Tomato by Differentially Activating Immune PathwaysPhytopathology®, 2022; 112 (11): 2360 DOI: 10.1094/PHYTO-02-22-0052-R

Cite This Page:

American Phytopathological Society. “Molecular mechanism behind nutrient element-induced plant disease resistance discovered.” ScienceDaily. ScienceDaily, 10 January 2023. <www.sciencedaily.com/releases/2023/01/230110150941.htm>.

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DECEMBER 20, 2022

Researchers analyze performance of bacterium in combating coffee rust

by Ricardo Muniz, FAPESP

Researchers analyze performance of bacterium in combating coffee rust
The research is part basic science, investigating the bacterium’s resilience in a hostile environment—coffee leaves—and part biotech, seeing whether the bacterium inhibits the development of a pathogen. Credit: Jorge Mondego/IAC

A new study has analyzed the potential of a bacterium for biological control of the fungus Hemileia vastatrix, which causes coffee rust, a major challenge for Brazilian coffee growers. An article on the study is published in the journal BMC Microbiology.

The symptoms of coffee rust are yellow spots like burn marks on the leaves of the plant. The disease impairs photosynthesis, making foliage wither and preventing bean-producing cherries from growing until the tree resembles a skeleton. It is typically controlled by the use of copper-based pesticides, which can have adverse effects on the environment.

“This was a basic science study, in which we set out to understand the behavior of bacteria that inhabit the leaves of coffee trees. First of all, there are several compounds that are harmful to bacteria and can be used to attack them,” said Jorge Maurício Costa Mondego, last author of the article.

“Second, leaves are environments that undergo significant environmental pressures, such as sunlight and rain. We wanted to understand how bacteria that live on coffee leaves can withstand both the compounds produced by the coffee plant and the stresses of rain and sun,” he said.

Besides this basic science front, the study also addressed applied science challenges. The researchers decided to find out whether bacteria that inhabit coffee leaves can combat the fungus that causes coffee rust. The first step consisted of identifying the expressed sequence tags (ESTs) of Coffea arabica and C. canephora produced by the Brazilian Coffee Genome Project (Projeto Genoma EST-Café).

“I was the first author, alongside Ramon Vidal, a professor at UNICAMP, of an article in which we compiled the sequences expressed by C. arabica. It was published in 2011. We weren’t yet thinking in terms of metagenomics, but that’s what we did, more or less accidentally,” Mondego said.

Accidental metagenomics

The researchers found sequences they considered contaminating in the midst of the coffee leaf ESTs. “We took these sequences, fed them into the database, and concluded that they appeared to be from Pseudomonas spp, a genus of bacteria.,” Mondego said. “This stimulated the curiosity of our research group, which was led by Gonçalo Pereira, also a professor at UNICAMP. We asked ourselves, ‘What if we’ve done metagenomics without meaning to? Do these bacteria really live on coffee leaves?'”

At the time, Mondego was already a researcher at IAC. A few years later, he was able to join forces with Leandro Pio de Sousa, first author of the article published in BMC Microbiology. Sousa was a student who had a scientific initiation scholarship and now holds a Ph.D. in genetics and molecular biology from UNICAMP.

“I invited Leandro to work with me on this study, which was designed to see if Pseudomonas really does live on coffee leaves. If so, the previous findings would be confirmed. He agreed immediately,” Mondego said.

They isolated bacteria from the coffee leaves and put them in a culture medium. Under ultraviolet light, it is possible to characterize Pseudomonas, which looks purple and can easily be selected in the medium. “We collected the bacteria, extracted their DNA and sequenced one, which we called MN1F,” he said.

They made several interesting discoveries about MN1F, which has a secretion system that reflects its need to survive in a hostile environment full of fungi and other bacteria. “The secretion system produces antibacterial and antifungal compounds. That suggested it could be used for biological control,” Mondego said. They also detected a number of proteins associated with protection against water stress.

The next step entailed physiological experiments, whereby bacteria were cultured in different media to confirm the researchers’ observations regarding the genome. “The biological experiments proved several inferences correct. We showed that the bacterium does indeed have a considerable capacity to withstand strong osmotic pressure, which can be considered analogous to the effects of drought on coffee leaves,” Mondego explained. “Furthermore, MN1F is capable of degrading phenolic compounds that can be harmful to it. It breaks down these compounds from the plant and converts them into material for its own survival.”

The researchers then conducted a battery of tests to find out if MN1F could be used for biological control, preventing or inhibiting the development of H. vastatrix, the fungus that causes coffee rust. The tests took place under greenhouse and laboratory conditions, including an attempt to inhibit in vitro germination of the fungus. In all of the experiments, the bacterium proved capable of inhibiting the development of spores (reproductive units) and mycelium (the filamentous network containing the fungus’s genetic material).

More information: Leandro Pio de Sousa et al, Functional genomics analysis of a phyllospheric Pseudomonas spp with potential for biological control against coffee rust, BMC Microbiology (2022). DOI: 10.1186/s12866-022-02637-4

Journal information: BMC Microbiology 

Provided by FAPESP 


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Fungus that eats fungus could help coffee farmers

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Bacterial wilt still threatens crops in tropical and subtropical areas

For tomatoes and more than 200 other plant species, bacterial wilt is an extremely destructive disease. Although some may not show symptoms, they keep the pathogen alive in the soil. The disease is caused by Ralstonia solanacearum, a bacterium found mainly in moist, hot areas.

The first sign of R. solanacearum is plants that start to wilt during the day and recover by nightfall. Later, they remain wilted and die. The disease usually starts in patches and spreads fairly rapidly to neighboring plants. It is almost impossible to control once it takes hold.

Fortunately for farmers, resistant genes are available. However, there are several races of R. solanacearum, with only one occurring in South Africa, namely race 1 biovar 2. It is therefore crucial to choose a tomato variety that has resistance to this race, or it will be ineffective. Varieties with the resistant gene can extend the harvest season into warmer conditions, but when the soil becomes too hot, the gene becomes less effective.

The resistant gene for race 1 biovar 2 was developed at the Agricultural Research Council station in Mbombela, and the resistant variety is named Rodade. This gene is used by other countries for our strain of the pathogen, and was hailed as a major breakthrough at the time.

Source: farmersweekly.co.za

Publication date: Thu 22 Dec 2022

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DECEMBER 5, 2022

Researchers discover a master regulator of plant immunity

by King Abdullah University of Science and Technology

A master regulator of plant immunity
KAUST plant scientists have revealed the role that the regulatory protein OXI1 plays in anti-pathogen immunity in plants. In this image, the plant specimens overexpressed OXI1, which manifests in the brown coloring when stained with a special dye. Credit: KAUST

The demonstration that a regulatory protein linked to stress responses in plants also serves as a master switch for anti-pathogen immunity could help breeders develop more pest-resistant and climate-resilient crops.

The KAUST-led discovery suggests that, rather than focusing on individual immune signals involved in plant defenses, agricultural scientists looking to implement sustainable crop protection strategies could simply focus their efforts on this one all-important protein.

“The identification of OXI1 as a single molecular switch of immunity offers a number of big advantages in molecular breeding,” says study lead Heribert Hirt, a professor of plant science at KAUST.

Hirt’s finding was nearly two decades in the making. In 2004, he and his colleagues first identified a gene called OXI1—short for oxidative signal-inducible 1 kinase—that was critical to plant responses in the face of environmental stresses.

Over the next 18 years, Hirt and others then connected OXI1 with various aspects of plant immunity and growth, but it was not entirely clear how the protein exerted its biological effects. And while scientists had detailed the ways in which three key immune-related metabolites—salicylic acid (SA), N-hydroxy pipecolic acid (NHP) and camalexin—contribute to pathogen defenses, their connection to OXI1 signaling was unknown.

It took Hirt and Anamika Rawat, a postdoctoral research fellow in his lab, to connect the dots. The researchers created mutant forms of Arabidopsis plants that either lacked OXI1 function or had elevated expression of the regulatory protein. Together with collaborators in Germany and France, they then comprehensively profiled gene activity patterns, protein abundances and metabolite levels in these plants.

Collectively, the researchers showed how OXI1 triggers a handful of genes that promote the synthesis of SA, NHP and camalexin. The buildup of these three immune-promoting molecules then confers greater protection against plant pathogens.

But the extra immunity brought on by OXI1 activity comes at a cost: it makes for stunted plants that show a greater propensity for cell death. Plants with lower OXI1 levels, while more susceptible to infection by bacterial and fungal pests, tend to grow bigger, with more active photosynthetic machinery.

Crop developers will therefore have to find the right balance of OXI1 activity for their agricultural applications. As a protein kinase, OXI1 should be amenable to manipulation, Hirt points out.

Already, there are dozens of kinase-targeted small-molecule drugs in widespread use in human medicine. Knowledge gleaned from the development of those agents, he says, should now be put to use in the discovery of OXI1 modulators for crop improvement.

The group’s findings are published in New Phytologist.

More information: Anamika A. Rawat et al, OXIDATIVE SIGNAL‐INDUCIBLE1 induces immunity by coordinating N‐hydroxypipecolic acid, salicylic acid, and camalexin synthesis, New Phytologist (2022). DOI: 10.1111/nph.18592

Journal information: New Phytologist 

Provided by King Abdullah University of Science and Technology 


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Discovery of plant immune signaling intermediary could lead to more pest-resistant crops

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Western Farmer-Stockman

Nate LongWFP-nate-log-juniper-control-web.jpg

Junipers on a hillside are controlled through chaining.

Large populations of the tree can negatively impact sage grouse habitat and diminish sustainability of grazing land.

Heather Smith Thomas | Jul 28, 2022

Farm Futures Summit and Boot Camp 2022

Western juniper is a native shrub that grows to tree size, thriving in the Great Basin, which spans most of Nevada, much of Oregon and Utah, and portions of California, Idaho, Wyoming, and Mexico.   

In recent decades, hardy junipers have been dominating vast areas, crowding out other plant species.  Large populations of juniper can negatively impact sage grouse habitat and diminish sustainability of grazing land.

The goal of many rangeland managers has been to restore ecologic balance.  Juniper removal on the Modoc National Forest in California, for instance, is part of an effort to improve sage grouse habitat, but there are many other ecological benefits resulting from removing the encroaching juniper stands.

These trees pull more water from the ground than the surrounding vegetation does, leaving less moisture for the other plants. With loss of understory vegetation in juniper woodlands, there is soil loss and erosion during intense rain storms. They outcompete most other plants; with their efficient root system they consume a lot of water that would have helped the survival of other plants.

Effect on watersheds has been noticed; with increased demand for water by juniper, combined with several years of drought in Northeast California, many springs and streams have dried up.

Removal projects

Kyle Sullivan, District Manager, Soil and Water Conservation District, Grant County, Ore., says there were government projects in earlier years to help ranchers remove juniper; there was funding for mechanical removal—sawing the trees, piling and burning them.  “Logging crews brought equipment to take out the trees, with hand-labor follow-up for the smaller trees,” Sullivan said.

Loggers piled the trees, and after they dried out the landowners burned the piles during winter when there was no risk of fire danger.

“Our Soil and Water Conservation District received grants to try to control juniper with herbicide.  A dozen years ago we did an experiment, cutting incisions into the trunk with a chain saw, then squirted herbicide into the trunk with a spray bottle. But juniper is so bushy that it is difficult to get to the base of the tree,” he said.

The crew tried different herbicides and different concentrations. It was effective for killing the trees, but the time and labor involved didn’t pencil out, economically.  The Forest Service preferred that method, however, because it left the dead trees standing and didn’t tear up the ground or disrupt surrounding vegetation.

A landowner might choose this method, to kill some of the larger trees and keep them from reproducing, but dead trees on the range might be fuel for wildfires.

“If standing trees are limbed high enough, a grass fire might quickly burn through underneath, but many junipers have low branches under the duff which could raise the fire higher off the ground and into the tree itself,” said Sullivan.

Junipers proliferate

“We left a few trees on the landscape to provide shade for livestock and wildlife, but they had to be trees with no berries (seeds).  Juniper trees have genders, and some can have both male and female characteristics.  If a tree isn’t producing berries it doesn’t spread seeds,” he explained.

“We also learned the importance of maintenance after trees are cut/piled/burned, because the seed source is still there.”  The seeds are viable for years, to produce new seedlings.  The problem will re-emerge if you don’t keep after it.

“After you cut them down you may get a new flush of young trees in 7 to 10 years, but you can do periodic controlled burning or remove the young ones, or use herbicide and eventually get rid of most of them.”            

Junipers are tough and hardy, with high survival rate.  If they take over a range or watershed, they can be detrimental.  “Research is still ongoing in central Oregon, looking at the effects of hydrology, and how a canopy of juniper can keep snow from coming to the ground.  This watershed study is providing new information; we realize what an aggressive root system they have.  If there is a high population of junipers, they have a negative effect on the watershed,” he said.

Herbicide pellets can be used for juniper control. Wilburn Ranches in Oregon started using chemical control of juniper invasions on their range pastures a few years ago, with good results. They took photos of trees afterward, showing how it killed them.

Label directions suggest putting one tablet on the ground in the drip zone of the juniper if it is 3 feet tall.  For every additional 3 feet, you add another tablet– up to about 10 feet of tree height.  The pellets can be applied when moisture is sufficient to dissolve them.  The smaller trees tend to die all at once and the larger ones die by degrees until they completely brown and dead.

Cost per tree for this method is lower than using chain saws or heavy equipment, but the herbicide pellets may need to be repeated every 3-4 years to keep juniper contained.  This is another option for people who don’t want to mechanically remove and then burn them.  Ranchers can hike around and distribute the pellets, or do it from horseback while checking cattle, tossing pellets around the outside edges of the junipers. 

Chains and excavators

Sullivan said one method still used in some parts of the West is chaining.  An old ship anchor chain (with huge, heavy links) is secured between two big Cat tractors to mow down the trees.  The heavy chain pulls on the trees and uproots them.

Another method is to tip the juniper tree over with the boom of an excavator.  The machine can then grab it, pick it up and shake the soil off the roots so the trees can be piled easier.  It costs more for this method but has the advantage of uprooting the trees without much damage to the surrounding terrain.  “A machine can also be used to pile them and clean up the area afterward.  This way you get some of the smaller branches that are underneath the soil; they pull up with the tree roots,” he said.

“This is probably one of the more expensive alternatives but leaves a cleaner site.  Depending on your goals, budget, and equipment, one method may be more attractive than another.”

In his region many ranchers use chain saws and cut down the larger trees, then go back later to get the little ones—and pile them all up with machines. 

“We try to keep abreast of research that keeps evolving on the impacts of these plants, and how to deal with them.  Oregon State University has published a number of guidelines with advice on managing western juniper,” Sullivan said.

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Rijk Zwaan launches ToBRFV-resistant tomato varieties

The Tomato Brown Rugose Fruit Virus or ToBRFV has been causing major economic losses in tomato cultivation worldwide. Rijk Zwaan’s team of researchers found new ToBRFV-resistant genetics .

HR ToBRFV – Rugose Defense
Soon after this discovery, breeders started to develop resistant varieties in all worldwide breeding programs and extensively tested these varieties internally as well as with growers to assess their agronomic value. Rijk Zwaan now offers growers the best-performing hybrids under the Rugose Defense label, including mini plum, cherry TOV, cocktail, and medium TOV tomato varieties.

Compatible with all commercial rootstocks
Rijk Zwaan tomato varieties with high resistance to ToBRFV are compatible with all commercially available rootstocks. Trials have shown that rootstock variety Suzuka RZ performs strongly in combination with both susceptible and resistant tomato varieties.

Contact for more information
In the coming period, Rijk Zwaan will continue to introduce new varieties suitable for high-tech and protected cultivation. Rijk Zwaan would like to thank all growers who supported the company in testing the first HR resistant tomatoes for high-tech cultivation. Keen to know more? Visit Rijk Zwaan’s local Rugose Defense page.

For more information:
Rijk Zwaan
info@rijkzwaan.com
www.rijkzwaan.com

Publication date: Tue 6 Dec 2022

   

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Climate change means farmers in West Africa need more ways to combat pests

by Loko Yêyinou Laura Estelle, The Conversation

worm on corn
Credit: Unsplash/CC0 Public Domain

The link between climate change and the spread of crop pests has been established by research and evidence.

Farmers are noticing the link themselves, alongside higher temperatures and greater variability in rainfall. All these changes are having an impact on harvests across Africa.

Changing conditions sometimes allow insects and diseases to spread and thrive in new places. The threat is greatest when there are no natural predators to keep pests in check, and when human control strategies are limited to the use of unsuitable synthetic insecticides.

Invasive pests can take hold in a new environment and cause very costly damage before national authorities and researchers are able to devise and fund ways to protect crops, harvests and livelihoods.

Early research into biological control methods (use of other organisms to control pests) shows promise for safeguarding harvests and food security. Rapid climate change, however, means researchers are racing against time to develop the full range of tools needed for a growing threat.

The most notable of recent invasive pests to arrive in Africa was the fall armyworm, which spread to the continent from the Americas in 2016.

Since then, 78 countries have reported the caterpillar, which attacks a range of crops including staples like maize and has caused an estimated US$9.4 billion in losses a year.

African farmers are still struggling to contain the larger grain borer, or Prostephanus truncatus Horn, which reached the continent in the 1970s. It can destroy up to 40% of stored maize in just four months. In Benin, it is a particular threat to cassava chips, and can cause losses of up to 50% in three months.

It’s expected that the larger grain borer will continue to spread as climatic conditions become more favorable. African countries urgently need more support and research into different control strategies, including the use of natural enemies, varietal resistance and biopesticides.

My research work is at the interface between plants, insects and genetics. It’s intended to contribute to more productive agriculture that respects the environment and human health by controlling insect pests with innovative biological methods.

For example, we have demonstrated that a species of insect called Alloeocranum biannulipes Montr. and Sign. eats some crop pests. Certain kinds of fungi (Metarhizium anisopliae and Beauveria bassiana), too, can kill these pests. They are potential biological control agents of the larger grain borer and other pests.

Improved pest control is especially important for women farmers, who make up a significant share of the agricultural workforce.

In Benin, for example, around 70% of production is carried out by women, yet high rates of illiteracy mean many are unable to read the labels of synthetic pesticides.

This can result in misuse or overuse of chemical crop protection products, which poses a risk to the health of the farmers applying the product and a risk of environmental pollution.

Moreover, the unsuitable and intensive use of synthetic insecticides could lead to the development of insecticide resistance and a proliferation of resistant insects.

Biological alternatives to the rescue

Various studies have shown that the use of the following biological alternatives would not only benefit food security but would also help farmers who have limited formal education:

  1. Natural predators like other insects can be effective in controlling pests. For example I found that the predator Alloeocranum biannulipes Montr. and Sign. is an effective biological control agent against a beetle called Dinoderus porcellus Lesne in stored yam chips and the larger grain borer in stored cassava chips. Under farm storage conditions, the release of this predator in infested yam chips significantly reduced the numbers of pests and the weight loss. In Benin, yams are a staple food and important cash crop. The tubers are dried into chips to prevent them from rotting.
  2. Strains of fungi such as Metarhizium anisopliae and Beauveria bassiana also showed their effectiveness as biological control agents against some pests. For example, isolate Bb115 of B. bassiana significantly reduced D. porcellus populations and weight loss of yam chips. The fungus also had an effect on the survival of an insect species, Helicoverpa armigera (Hübner), known as the cotton bollworm. It did this by invading the tissues of crop plants that the insect larva eats. The larvae then ate less of those plants.
  3. The use of botanical extracts and powdered plant parts is another biological alternative to the use of harmful synthetic pesticides. For example, I found that botanical extracts of plants grown in Benin, Bridelia ferruginea, Blighia sapida and Khaya senegalensis, have insecticidal, repellent and antifeedant activities against D. porcellus and can also be used in powder form to protect yam chips.
  4. My research also found that essential oils of certain leaves can be used as a natural way to stop D. porcellus feeding on yam chips.
  5. I’ve done research on varietal (genetic) resistance too and found five varieties of yam (Gaboubaba, Boniwouré, Alahina, Yakanougo and Wonmangou) were resistant to the D. porcellus beetle.

Next generation tools

To develop efficient integrated pest management strategies, researchers need support and funding. They need to test these potential biocontrol methods and their combinations with other eco-friendly methods in farm conditions.

Investing in further research would help to bolster the African Union’s 2021–2030 Strategy for Managing Invasive Species, and protect farmers, countries and economies from more devastating losses as climate change brings new threats.

Initiatives like the One Planet Fellowship, coordinated by African Women in Agricultural Research and Development, have helped further the research and leadership of early-career scientists in this area, where climate and gender overlap.

But much more is needed to unlock the full expertise of women and men across the continent to equip farmers with next generation tools for next generation threats.

Provided by The Conversation 

This article is republished from The Conversation under a Creative Commons license. Read the original article.


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Why African farmers should balance pesticides with other control methods

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Combatting soil-borne pathogens and nematodes vital for food security

   Delhi Bureau  0 Comments CIMMYT  9 min read

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08 November 2022, Mexico: The International Maize and Wheat Improvement Center (CIMMYT) coordinated the VIII International Cereal Nematode Symposium between September 26-29, in collaboration with the Turkish Ministry of Agriculture and Forestry, the General Directorate of Agricultural Research and Policies and Bolu Abant Izzet Baysal University.

As many as 828 million people struggle with hunger due to food shortages worldwide, while 345 million are facing acute food insecurity – a crisis underpinning discussions at this symposium in Turkey focused on controlling nematodes and soil-borne pathogens causing reduced wheat yields in semi-arid regions.

A major staple, healthy wheat crops are vital for food security because the grain provides about a fifth of calories and proteins in the human diet worldwide.

Seeking resources to feed a rapidly increasing world population is a key part of tackling global hunger, said Mustafa Alisarli, the rector of Turkey’s Bolu Abant Izzet Baysal University in his address to the 150 delegates attending the VIII International Cereal Nematode Symposium in the country’s province of Bolu.

Suat Kaymak, Head of the Plant Protection Department, on behalf of the director general of the General Directorate of Agricultural Research and Policies (GDAR), delivered an opening speech, emphasizing the urgent need to support the CIMMYT Soil-borne Pathogens (SBP) research. He stated that the SBP plays a crucial role in reducing the negative impact of nematodes and pathogens on wheat yield and ultimately improves food security. Therefore, the GDAR is supporting the SBP program by building a central soil-borne pathogens headquarters and a genebank in Ankara.

Discussions during the five-day conference were focused on strategies to improve resilience to the Cereal Cyst Nematodes (Heterodera spp.) and Root Lesion Nematodes (Pratylenchus spp.), which cause root-health degradation, and reduce moisture uptake needed for proper development of wheat.

Richard Smiley, a professor emeritus at Oregon State University, summarized his research on nematode diseases. He has studied nematodes and pathogenic fungi that invade wheat and barley roots in the Pacific Northwest of the United States for 40 years. “The grain yield gap – actual versus potential yield – in semiarid rainfed agriculture cannot be significantly reduced until water and nutrient uptake constraints caused by nematodes and Fusarium crown rot are overcome,” he said.

Experts also assessed patterns of global distribution, exchanging ideas on ways to boost international collaboration on research to curtail economic losses related to nematode and pathogen infestations.

A special session on soil-borne plant pathogenic fungi drew attention to the broad spectrum of diseases causing root rot, stem rot, crown rot and vascular wilts of wheat.

Soil-borne fungal and nematode parasites co-exist in the same ecological niche in cereal-crop field ecosystems, simultaneously attacking root systems and plant crowns thereby reducing the uptake of nutrients, especially under conditions of soil moisture stress.

Limited genetic and chemical control options exist to curtail the damage and spread of these soil-borne problems which is a challenge exacerbated by both synergistic and antagonistic interactions between nematodes and fungi.

Nematodes, by direct alteration of plant cells and consequent biochemical changes, can predispose wheat to invasion by soil borne pathogens. Some root rotting fungi can increase damage due to nematode parasites.

Integrated managementFor a holistic approach to addressing the challenge, the entire biotic community in the soil must be considered, said Hans Braun, former director of the Global Wheat Program at CIMMYT.

Braun presented efficient cereal breeding as a method for better soil-borne pathogen management. His insights highlighted the complexity of root-health problems across the region, throughout Central Asia, West Asia and North Africa (CWANA).

Richard A. Sikora, Professor emeritus and former Chairman of the Institute of Plant Protection at the University of Bonn, stated that the broad spectrum of nematode and pathogen species causing root-health problems in CWANA requires site-specific approaches for effective crop health management. Sikora added that no single technology will solve the complex root-health problems affecting wheat in the semi-arid regions. To solve all nematode and pathogen problems, all components of integrated management will be needed to improve wheat yields in the climate stressed semi-arid regions of CWANA.

Building on this theme, Timothy Paulitz, research plant pathologist at the United States Department of Agriculture Agricultural Research Service (USDA-ARS), presented on the relationship between soil biodiversity and wheat health and attempts to identify the bacterial and fungal drivers of wheat yield loss. Paulitz, who has researched soil-borne pathogens of wheat for more than 20 years stated that, “We need to understand how the complex soil biotic ecosystem impacts pathogens, nutrient uptake and efficiency and tolerance to abiotic stresses.”

Julie Nicol, former soil-borne pathologist at CIMMYT, who now coordinates the Germplasm Exchange (CAIGE) project between CIMMYT and the International Center for Agricultural Research in the Dry Areas (ICARDA) at the University of Sydney’s Plant Breeding Institute, pointed out the power of collaboration and interdisciplinary expertise in both breeding and plant pathology. The CAIGE project clearly demonstrates how valuable sources of multiple soil-borne pathogen resistance in high-yielding adapted wheat backgrounds have been identified by the CIMMYT Turkey program, she said. Validated by Australian pathologists, related information is stored in a database and is available for use by Australian and international breeding communities.

Economic losses

Root-rotting fungi and cereal nematodes are particularly problematic in rainfed systems where post-anthesis drought stress is common. Other disruptive diseases in the same family include dryland crown and the foot rot complex, which are caused mainly by the pathogens Fusarium culmorum and F. pseudograminearum.

The root lesion nematode Pratylenchus thornei can cause yield losses in wheat from 38 to 85 percent in Australia and from 12 to 37 percent in Mexico. In southern Australia, grain losses caused by Pratylenchus neglectus ranged from 16 to 23 percent and from 56 to 74 percent in some areas.

The cereal cyst nematodes (Heterodera spp.) with serious economic consequences for wheat include Heterodera avenae, H. filipjevi and H. latipons. Yield losses due to H. avenae range from 15 to 20 percent in Pakistan, 40 to 92 percent in Saudi Arabia, and 23 to 50 percent in Australia.

In Turkey, Heterodera filipjevi has caused up to 50 percent crop losses in the Central Anatolia Plateau and Heterodera avenae has caused up to 24 percent crop losses in the Eastern Mediterranean.

The genus Fusarium which includes more than a hundred species, is a globally recognized plant pathogenic fungal complex that causes significant damage to wheat on a global scale.

In wheat, Fusarium spp. cause crown-, foot-, and root- rot as well as head blight. Yield losses from Fusarium crown-rot have been as high as 35 percent in the Pacific Northwest of America and 25 to 58 percent in Australia, adding up losses annually of $13 million and $400 million respectively, due to reduced grain yield and quality. The true extent of damage in CWANA needs to be determined.

Abdelfattah Dababat, CIMMYT’s Turkey representative and leader of the soil-borne pathogens research team said, “There are examples internationally, where plant pathologists, plant breeders and agronomists have worked collaboratively and successfully developed control strategies to limit the impact of soil borne pathogens on wheat.” He mentioned the example of the development and widespread deployment of cereal cyst nematode resistant cereals in Australia that has led to innovative approaches and long-term control of this devastating pathogen.

Dababat, who coordinated the symposium for CIMMYT, explained that, “Through this symposium, scientists had the opportunity to present their research results and to develop collaborations to facilitate the development of on-farm strategies for control of these intractable soil borne pathogens in their countries.”

Paulitz stated further that soil-borne diseases have world-wide impacts even in higher input wheat systems of the United States. “The germplasm provided by CIMMYT and other international collaborators is critical for breeding programs in the Pacific Northwest, as these diseases cannot be managed by chemical or cultural techniques,” he added.

Road ahead

Delegates gained a greater understanding of the scale of distribution of cereal cyst nematodes and soil borne pathogens in wheat production systems throughout West Asia, North Africa, parts of Central Asia, Northern India, and China.

After more than 20 years of study, researchers have recognized the benefits of planting wheat varieties that are more resistant. This means placing major emphasis on host resistance through validation and integration of resistant sources using traditional and molecular methods by incorporating them into wheat germplasm for global wheat production systems, particularly those dependent on rainfed or supplementary irrigation systems.

Sikora stated that more has to be done to improve Integrated Pest Management (IPM), taking into consideration all tools wherever resistant is not available. Crop rotations for example have shown some promise in helping to mitigate the spread and impact of these diseases.

“In order to develop new disease-resistant products featuring resilience to changing environmental stress factors and higher nutritional values, modern biotechnology interventions have also been explored,” Alisarli said.

Brigitte Slaats and Matthias Gaberthueel, who represent Swiss agrichemicals and seeds group Syngenta, introduced TYMIRIUM® technology, a new solution for nematode and crown rot management in cereals. “Syngenta is committed to developing novel seed-applied solutions to effectively control early soil borne diseases and pests,” Slaats said.

It was widely recognized at the event that providing training for scientists from the Global North and South is critical. Turkey, Austria, China, Morocco, and India have all hosted workshops, which were effective in identifying the global status of the problem of cereal nematodes and forming networks and partnerships to continue working on these challenges.

Also Read: Agriculture and the agricultural economy is the strength of India: Union Agriculture Minister

(For Latest Agriculture News & Updates, follow Krishak Jagat on Google News)

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Potential use of entomopathogenic and mycoparasitic fungi against powdery mildew in aquaponics

Aquaponics has the potential to produce sustainable and accessible quality food through the integration of hydroponics and aquaculture. Plants take up dissolved nutrients in fish wastewater, allowing water reuse for fish. However, the simultaneous presence of fish and plants in the same water loop has made phytosanitary treatments of diseases such as powdery mildew problematic due to risks of toxicity for fish and beneficial bacteria, limiting its commercialization.

Entomopathogenic and mycoparasitic fungi have been identified as safe biological control agents for a broad range of pests. This study aimed to investigate the efficacy of entomopathogenic fungi, Lecanicillium attenuatum (LLA), Isaria fumosorosea (IFR), and mycoparasitic fungus Trichoderma virens (TVI) against Podosphaera xanthii. Also, we investigated the possible harmful effects of the three fungal biocontrol agents in aquaponics by inoculating them in aquaponics water and monitoring their survival and growth. The findings showed that the three biocontrol agents significantly suppressed the powdery mildew at 107 CFU/ml concentration.

Under greenhouse conditions (65-73% relative humidity (RH)), a significant disease reduction percentage of 85% was recorded in L. attenuatum-pretreated leaves. IFR-treated leaves had the least AUDPC (area under disease progress curve) of ~434.2 and disease severity of 32% under 65-73% RH. In addition, L. attenuatum spores were the most persistent on the leaves; the spores population increased to 9.54 × 103 CFUmm-2 from the initial 7.3 CFUmm-2 under 65-73%. In contrast, in hydroponics water, the LLA, IFR, and TVI spores significantly reduced by more than 99% after 96 hrs. Initial spore concentrations of LLA of 107 CFU/ml spores were reduced to 4 x 103 CFU after 96 hrs. Though the results from this study were intended for aquaponics systems, the relevance of the results to other cultivation systems are discussed.

Read the complete research at www.researchgate.net.

Folorunso, Ewumi Azeez & Bohata, Andrea & Kavkova, Miloslava & Gebauer, Radek & Mraz, Jan. (2022). Potential use of entomopathogenic and mycoparasitic fungi against powdery mildew in aquaponics. Frontiers in Marine Science. 9. 10.3389/fmars.2022.992715. 

Publication date: Wed 9 Nov 2022

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Saturday, 19 November 2022 15:31:49

Grahame Jackson posted a new submission ‘Effect of marigold (Tagetes erecta L.) on soil microbial communities in continuously cropped tobacco fields’

Submission

Effect of marigold (Tagetes erecta L.) on soil microbial communities in continuously cropped tobacco fields

Nature Scientific Reports

Scientific Reports volume 12, Article number: 19632 (2022) Cite this article

Abstract

Root-knot nematode disease is a catastrophic soil-borne disease in tobacco production. The regulation of natural microbial communities is considered a good disease management approach to suppress the incidence of soilborne diseases. In this study, the effects of tobacco (Nicotiana tabacum L.)-marigold (Tagetes erecta L.) rotation on the diversity and structure of soil microbial communities in continuously cropped tobacco fields were analyzed to manage this devastating pathogen. The results showed that the soil bacterial OTUs increased after marigold rotation and that the bacterial Shannon, ACE, Chao1 index, and fungal Shannon index were higher in the tobacco-marigold rotation fields than in the continuously cropped tobacco fields by 3.98%, 10.37%, 5.46%, and 3.43%, respectively. After marigold rotation, the relative abundances of Actinobacteria, Acidobacteria, and Ascomycota increased by 28.62%, 107.50%, and 57.44%, respectively, and the proportion of beneficial bacterial genera such as NocardioidesGemmatimonas, and Bradyrhizobium increased. In addition, our results also showed that rotation of marigold could effectively reduce the incidence of root-knot nematodes in the next crop of tobacco. These results indicate that marigold rotation had a positive effect on the soil microecological environment of continuously cropped tobacco fields, reducing the obstacles to continuous cropping of tobacco.

Read on: https://www.nature.com/articles/s41598-022-23517-x

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