Tag: wheat

UMD Scientist Helps Harvest Wheat’s Giant Genetic Code

The University of Maryland, as part of the International Wheat Genome Sequencing Consortium, has helped accomplish a feat once considered impossible, sequencing the full genome of wheat, the world’s most widely cultivated crop.

Experts say that the long-awaited mapping of wheat’s vast genetic territory opens up opportunities for creating new and better strains of wheat by improving complex traits such as crop yield, grain quality, resistance to diseases or pests, tolerance to heat and drought, and even characteristics like protein content or types and amounts of allergy causing compounds.

“The wheat genome gives us a complete picture that will be the key to unlocking genes controlling important traits for crop improvement,” said UMD consortium researcher Vijay Tiwari, who leads the Small Grain Breeding and Genetics program in the department of plant science & landscape architecture.  “When this discovery was made for rice and maize, rapid advances were made in those crops almost immediately after,” he said.

Wheat’s incredibly large and duplicative genome is not actually a single genome, but three overlapping and similar ones, the result of natural hybridisation of different grasses over thousands of years. The consortium research that has opened up its full genetic complexity was authored by Tiwari and more than 200 other scientists from a total of 73 research institutions in 20 countries. UMD is one of only seven US institutions involved as consortium partners. A paper about their work was published on August 17 in the journal Science.

“This was very much collaborative science at its best,” said Tiwari. “Without the consortium, this couldn’t have been accomplished in this amount of time.”

Wheat is the staple food of more than a third of the world’s people and accounts for almost 20 percent of the total calories and protein consumed by humans, more than any other single food source. It also serves as an important source of vitamins and minerals.

According to the International Wheat Genome Sequencing Consortium, which began in 2005 as an initiative by Kansas farmers, meeting future demands of a projected world population of 9.6 billion by 2050, will require wheat production to increase by more than 50 percent (1.6 percent each year). In order to preserve biodiversity, water, and nutrient resources, the majority of this increase has to be achieved through crop and trait improvement on land currently cultivated, the consortium said in a release.

The impact of their wheat sequencing findings has already been significant because the now published wheat reference sequence was made available to the scientific community in January 2017. More than 100 publications referencing the sequence have already been published. And a new publication in this same issue of Science features work using this resource done by UMD’s Tiwari as part of a collaborative team of researchers led by Professor Cristobal Uauy at the John Innes Centre in the United Kingdom. This team used the new genome sequence to study the expression in wheat of genes affecting resistance to heat, drought, and disease. Work they hope will pave the way for the production of wheat varieties better adapted to climate challenges, with higher yields, enhanced nutritional quality, and improved sustainability.

Numerous studies have shown the susceptibility of wheat to climate changes. For example, a 2011 study in Science showed that rising temperatures are already causing declines in wheat production. And a more recent Nature research article suggested that this trend will only get worse, with a 5 percent decline in wheat yields for every one degree (Fahrenheit) temperature increase.

Taken together, the two new publications in Science provide results that will give a major boost to wheat breeding and genetic research, said Tiwari.  “Now researchers will have direct access to all the genes in the genome and information about their expression patterns, and it will allow them to unravel the genetic basis of important agronomic traits,” he said.

In previous work at the John Innes Centre, Tiwari and his fellow researchers fine-tuned a technique called speed breeding, which uses glasshouses to shorten breeding cycles. They say that earlier work combined with the new genome resources provided in these two papers, will significantly shorten the time needed to test genetic markers for traits like drought, heat, and disease resistance, getting new varieties of wheat to the growers faster.

“We are in a better position than ever to increase yield, breed plants with higher nutritional quality, and create varieties that are adapted to climate changes thanks to the research we and the international community are publishing,” said Uauy, project leader in crop genetics at the John Innes Centre.

“It has been a bad year for wheat yields in Maryland, so we are excited to give growers and researchers this good news and bright hope. These landmark results and resources will allow us to address the imminent challenges of global food security in changing climatic conditions,” said Tiwari.

Original article can be found online by clicking here.

Guess the Pest! Week #10 Answer: Stagonospora nodorum Leaf Blight and Glume Blotch

Guess The Pest Logo

 

 

 

 

 

Bill Cissel, Extension Agent – Integrated Pest Management, University of Delaware; bcissel@udel.edu

Congratulations to Buzz Lowe for correctly identifying the disease in the photo as Stagonospora nodorum leaf blight and glume blotch and for being selected to be entered into the end of season raffle for $100 not once but five times. Everyone else who guessed correctly will also have their name entered into the raffle. Click on the Guess the Pest logo to participate in this week’s Guess the Pest challenge!

Stagonospora nodorum Leaf Blight and Glume Blotch

By Nancy Gregory

Stagonospora nodorum leaf blight and glume blotch can cause yield loss on wheat, especially if infection occurs before grain fill. Stagonospora overwinters in crop residue and can be spread in infected seed. Disease is favored by environmental conditions of high moisture and wind, resulting in spore movement up through the canopy. Disease spread slows when weather turns dry. Symptoms include oval to round, brown leaf spots with yellow halos. The glume blotch phase is characterized by gray to purple brown discoloration on the outer seed coverings. Closer look with a hand lens may show a dusty cast to the heads when the fungus is producing spores. Management strategies include rotation to soybean, corn, or other on-hosts, as well as proper plant density to avoid over-crowding. Fungicide applications of a labeled triazole or strobilurin product at heading can be a part of a management plan. Resistant varieties are available for fields with a known history of glume blotch.

What Can I Do To Manage Head Scab in 2019?

Andrew Kness, Agriculture Extension Educator
University of Maryland Extension, Harford County
akness@umd.edu

Wheat head with bleached spikelets from FHB
Figure 1. Wheat head with Fusarium head blight. Image: Andrew Kness, University of Maryland

If you grew wheat this year, chances are you don’t have to look too hard to find head scab/Fusarium head blight (FHB). The excessive rainfall, humidity, and warm temperatures that we had around wheat flowering provided the perfect habitat for Fusarium graminearum, the causal agent of FHB, to thrive. If you have FHB, you have few options to manage it at this point in the season as you read in Bob’s article above; but what can you do in 2019 to better your odds (besides hope for little rain during flowering)?

To understand your options you need to understand the lifecycle and biology of F. graminearum. The pathogen survives on residue, particularly that of wheat, barley, and corn and will persist through the winter on this material. During periods of wet, humid, and warm temperatures in the spring, the fungus will produce spores. If wheat or barley is growing in the field, the spores are splashed up onto the heads via rain or irrigation, or carried by the wind. If the wheat or barley is flowering, the spore can germinate and infect the plant through the flower; it cannot get into the plant any other way. This is why we recommend fungicide application at flowering. Once the pathogen infects the wheat, it grows within the spikelet, bleaching it in the process (Figure 1) and infects the developing grain, causing shriveled, light weight, discolored kernels called tombstones. Infected grain may contain deoxynivalenol (DON) vomitoxin. FHB not only reduces yield, but has the potential to contaminate your grain with DON.

With that in mind, here are some tips for managing FHB in 2019:

  • Know your variety! If you plan to grow and market quality grain, then you need to know your varieties. Unlike barley, wheat does have some resistance to FHB, although it is not complete resistance. Some varities are more resistant than others, so my suggestion is to grow a variety that has the best resistance and yield potential. Consult with your seed rep and utilize the data from our wheat variety trials. A collaborative project between the University of Maryland and University of Delaware screens wheat varieties for resistance to FHB. The data can be found here, or call your Extension Office for a copy.
  • Use a fungicide at flowering. Unless we have an exceptionally dry spring, you’ll likely need a fungicide application to protect against FHB. Use the Scab Risk Assessment Tool to help assess your risk. Time your application at the start of flowering (Feekes 10.5.1) and up to 5 days thereafter. Triazole fungicides work best, particularly Caramba (metconazole), Proline (prothioconazole), and Prosaro (prothioconazole + tebuconazole). Do not use strobilurin fungicides! See my article in the April issue for more information on fungicide strategies.
  • New for the 2019 growing season will be a new product from Syngenta, called Miravis Ace (adepidyn). This will be a new mode of action fungicide (SDHI) to be used on FHB, and should help us with managing resistance by rotating it with the Triazoles. Preliminary University testing shows that Miravis Ace does well against FHB; however, claims of a wider application window seems questionable at this point, so application timing will still be critical.
  • Select your best fields. Since F. graminearum can survive on small grain and corn residue, planting wheat or barley behind soybeans is better than following corn. F. graminearum doesn’t survive well on soybean residue. If you are following corn, consider a light tillage pass with a vertical till tool to size residue. This will accelerate residue decomposition, killing some of the surviving F. graminearum.

It is important to utilize as many management strategies as possible for FHB. Host resistance can only provide about 50% FHB suppression in wheat (and 0% in barley), and fungicides can only provide 50% suppression at best. Growers must use a combination of variety selection, fungicides, and cultural practices to achieve a high quality wheat or barley crop.

Fusarium Head Blight (Head Scab) in Small Grain This Year Cause for Concern

Bob Kratochvil, Extension Agronomist
University of Maryland, College Park
rkratoch@umd.edu

 

wheat heads infected with Fusarium graminearum
Figure 1. Healthy (outside two heads) and Fusarium head blight diseased wheat heads. Image: APS.net

During the past two weeks, I have had the opportunity to walk a number of small grain fields (wheat, barley, triticale) across the state. Many of those fields are infected with Fusarium head blight (FHB), aka head scab (Figure 1). I have seen fields with very low levels of infection (less than 1% of heads infected) to some that have over 50% infected heads. Thus, the reason for concern. The reason for the high number of infected fields this year is the rainy weather we have had during May. The rains coincided with flowering of the wheat, barley, and triticale. Rain splashes spores of the causal agent of the disease, F. graminearum, onto the heads allowing infection to occur. Temperatures ranging between 75 and 85°F are considered optimum but lower temperatures during periods of high humidity and moisture can also enhance infection. The over 10 inches of rain much of the state has received created ideal infection conditions.

Head scab often results in significant yield loss and grain quality reduction. Grain quality reduction is primarily the result of the mycotoxins (chemicals) that are produced by F. graminearum. These mycotoxins can be toxic for humans and animals if the concentrations exceed minimum limits. The most concerning mycotoxin is deoxynivalenol (DON), also known as vomitoxin. The Food and Drug Administration (FDA) advisory level for DON is 1 ppm for foods consumed by humans. In the case of wheat, the level is 1 ppm for the flour. Often elevators and mills will accept wheat with DON levels 1.5 – 2 ppm without penalty because they can blend infected grain with sound grain to meet the FDA advisory level. Wheat with DON levels that exceed 2 ppm can be acceptable livestock feed. Swine are the most sensitive with the recommended level of 5 ppm DON with the DON infected grain not to exceed 20% of the ration. For ruminants and poultry, grain with 10 ppm DON can be used as long as no more than 50% of the ration is composed of the infected grain.

 

FHB-infected wheat kernels (tombstones)
Figure 2. Healthy and head scab damaged wheat kernels.

When you harvest your grain and notice shriveled, whitish looking kernels (tombstones), there is a strong likelihood that DON is present (Figure 2). If you have head scab infected wheat or barley fields, you will want to do what you can to minimize the impact of DON that is concentrated in the shriveled tombstone kernels (Figure 2). These light-weight kernels can be separated from sound grain at harvest by increasing the combine’s fan speed so don’t be concerned that you are losing too much good grain if you see lots of tombstones behind the combine, because you are not.

combine harvesting wheat
If you are storing the grain do so properly to prevent further contamination. Dry newly harvested grain that is infected to 13-14 percent moisture. This will stop pathogen growth and mycotoxin production. DON is an extremely stable mycotoxin. This means that drying and properly storing grain will not reduce the DON levels, however, DON concentration will not increase in properly stored grain. Bin any infected grain you harvest separately from sound, good quality grain. If you have a cleaner, you can remove fines from the wheat before you bin it and possibly lower the DON concentration. Before you deliver your grain, I suggest you check with your elevator or mill to see if they test for DON. It will be easier to take samples to them for testing prior to delivery than to learn that your grain is rejected after you have loaded the truck and taken it to the elevator.

FHB Update: May 9, 2018

scab alert map
24 hour Risk for Fusarium Head Blight development on susceptible wheat varieties (eg Shirley) for May 9, 2018.

 

 

 

 

 

 

 

 

 

 

 

Wheat growers in Maryland have so far been fortunate this year for having
low disease pressure from leaf rust, powdery mildew and even scab!! In the
south (Eastern shore), wheat is flowering currently. With consistently
warmer temperatures now, a few incidences of leaf diseases are being
observed. Triazole fungicides: Prosaro/ Caramba/ Proline that are the scab
fungicides should provide control against these as well. Strobilurin
containing fungicides should not be sprayed at this stage, as they may lead
to DON accumulation in grains. Up in the north, flag leaves are emerging. No
diseases being seen so far here as well. Growers should keep an eye on the
FHB risk, as crop heads and flowers here in coming weeks.

–Nidhi Rawat, Small grains Pathologist, University of Maryland

For more details, go to the FHB Risk assessment tool at
http://www.wheatscab.psu.edu

For the latest news and updates from the U.S. Wheat & Barley Scab
Initiative, go to https://www.scabusa.org

 

 

Fusarium Head Blight Fungicide Recommendations

By Andrew Kness, Agriculture Extension Educator
University of Maryland Extension, Harford County

Wheat head infected with Fusarium graminearum
Figure 1. Wheat head with Fusarium head blight, which causes the premature dry-down and bleaching of florets. Image: A. Kness, University of Maryland

As wheat begins to head, growers will be considering fungicide applications for managing head scab/Fusarium head blight (FHB). The Fusarium Risk Assessment Tool (www.wheatscab.psu.edu) is a forecasting model that predicts your risk for developing FHB on your wheat based on the current and predicted weather forecasts. FHB infection is favored by wet weather and high humidity. You should use this tool to help assess your risk for developing FHB as your wheat approaches flowering. Historically, this tool has been about 70% accurate.

Management of FHB should start with seed selection, since fungicides can only achieve about 50% control under the best case scenario; so selecting resistant varieties is crucial for harvesting good quality grain. It should be noted that resistance to FHB in wheat is not complete; therefore, fungicide applications are often needed in order to achieve acceptable management of FHB and suppression of DON vomitoxin. The pathogen that causes FHB can only infect the plant through the flower, so fungicide applications should be targeted between early flowering (Feekes 10.5.1) and 5 days thereafter. Fungicides that are effective on FHB include the triazoles (FRAC group 3 fungicides), which are Caramba (metconazole), Proline (prothioconazole), and Prosaro (prothioconazole + tebuconazole). These fungicides will also do an excellent job on foliar diseases as well, helping to keep the flag leaf clean. Folicur (tebuconazole) is less effective, but provides some suppression of FHB and DON accumulation, but should not be used if FHB risk is high. Over the past few years, Tilt (propiconazole), has become less effective for managing FHB, and is currently providing poor control. Fungicides containing strobilurins (Qoi, FRAC group 11 fungicides and mix-mode of action fungicides) should not be used past flag leaf emergence on wheat because these fungicides can increase DON vomitoxin accumulation in the grain. For barley, fungicide applications should be made at head emergence. Unlike wheat, barley has no resistance to FHB, so if we get a highly favorable year for FHB development, the very best control you can hope to achieve of FHB and DON is about 50% suppression.

 

Know Your Insect Pest: Grass Sawfly

By Emily Zobel, Agriculture Agent Associate
University of Maryland Extension, Dorchester County

Grass sawflies can cause damage to both barley and wheat. Grass sawfly larvae hatch and feed on the lower leaf blade in early May. As it grows, the larvae will climb and continue to feed on stems and leaves. Stem and head clipping often occur before leaf feeding is complete and/or the grain reaches physiological maturity. A sawfly larva may clip >10 heads before it matures and drops to the ground.

The grass sawfly larvae can be distinguished from other pests by their solid green color, amber head with a brown band and many legs.   Sawfly larvae are often mistaken as caterpillars, but are actually in the insect order Hymenoptera (wasp, bees, and ants). You can tell the difference between a caterpillar and sawfly larvae by counting the number of prologs. Caterpillars will have 5 or fewer pairs of pro-legs while sawfly larvae will have 6 or more pairs of pro-legs (Figure 1).

sawfly and armyworm comparison
Figure 1. Proleg comparison between a sawfly larva and an armyworm. Sawflies have 6 or more pairs of prolegs. Images: University of Maryland and University of Delaware.

You can scout for sawfly larvae and armyworms by shaking stems. Shake both sides of 5 linear feet of row and examine any worms that fall off between the 2 rows and note any head clipping. Repeat for at least 10 sites. The threshold for sawfly larva and armyworm is when the larvae number more than 0.4 per linear ft. of row or 0.7 per square ft. and are smaller than ¾ inch. If the larvae are over 1 inch, have a dark bar on the head capsule, and have clipped many heads, it is probably too late to treat.

Some chemical control options are as follows: BaythroidXL (beta-cyfluthrin), Besiege (lambda-cyhalothrin+ chlorantraniliprole), Blackhawk 36WG(spinosad), Mustang MAXX 0.8 EC (zeta-cypermethrin), Radiant SC (spinetoram, Warrior II (lambda-cyhalothrin), and Tombstone 2 EC (cyfluthrin). Remember the label is the law. Be sure to read the label before making any pesticide applications and observe all label restrictions. Please check the label for rates and pre-harvest interval and restrictions.

Article adapted from information from University of Maryland and University of Delaware.

 

Spring Snow and Wheat

By Andrew Kness, Agriculture Extension Educator
University of Maryland Extension, Harford County
 

Even though the calendar says spring, the weather does not always cooperate. Snow is predicted to hit some parts of Maryland later this week, particularly Northern Maryland. Producer’s may be wondering what the risk for damage may be to their wheat with this late snowfall event.

Winter wheat is of course a cold-hardy crop. A good stand of wheat that was planted at the proper depth and has two or more tillers going into the winter has a very high tolerance for freeze injury; down to about –10°F. As the plants come out of their winter dormancy and begin to green up, their tolerance drops to about 10-15°F. Once the wheat reaches Feekes 6 and begins to joint, the main growing point and the grain head emerge from beneath the soil surface, thus exposing the most important parts of the plant to the elements. Once wheat reaches this stage, the plants can only tolerate temperatures as low as 15°F at the beginning of jointing, and 28°F towards the end of jointing.

For wheat that has jointed, exposure to temperatures below 28°F for more than two hours can cause noticeable damage, including leaf burn, which is mostly cosmetic and plants will generally grow out of it if sufficient nitrogen is present; but in more severe cases the developing grain head can be injured. In this case, significant yield reductions will occur.

Two developing wheat heads that were dissected to show freeze damage
Figure 1. Healthy wheat grain head (right) and freeze-damaged grain head (left). Image: Carrie Knott, University of Kentucky.

To assess the damage after a spring freeze, pull back the leaves and stems from the main tiller of some wheat plants, exposing the developing grain head. A healthy grain head will be plump, turgid, somewhat green/green-yellow, slightly translucent, with very distinct and well defined edges (Figure 1, right). A freeze-damaged grain head will be limp, shriveled, milky discoloration, and will not be well defined (Figure 1, left). Note that these growing points are very small, so you’ll likely need a hand lens to observe these structures and a very sharp razor blade to do the dissections.

Dr. Carrie Knott, agronomist at University of Kentucky, has a great instructional video on how to dissect a wheat plant and assess freeze damage. The video can be found here.

FHB Update – May 16, 2017

Nathan Kleczewski, Extension Field Crop Plant Pathologist, University of Delaware

We are through flowering in Delaware and Maryland wheat. Growers should assess wheat for FHB severity approximately 18-24 days after flowering or fungicide application. Check one transect per 1-2 acres of field. At each transect, pick 25 heads without looking at the field. Mark the number of heads with FHB out of the total heads collected (FHB incidence). Fields with high levels of FHB incidence should be harvested with increased fan speeds to remove tombstones and grain stored separately from that harvested from cleaner fields. If possible, harvest fields early and dry to at least 15% moisture to prevent continued growth of the FHB fungus and potential mycotoxin production.