Posts Tagged: Fusarium
UC Davis releases 5 strawberry varieties resistant to deadly fungal disease
Strawberries selectively bred for Fusarium wilt resistance and high yields
The University of California, Davis, is releasing five new strawberry varieties that are resistant to the soilborne disease Fusarium wilt, have high yields and improved fruit quality.
UC Eclipse, UC Golden Gate, UC Keystone, UC Monarch and UC Surfline will be available for sale to California nurseries from Foundation Plant Services in April.
Roughly 88% of strawberries grown in the nation come from California. Fusarium wilt is one of the most common reasons for crop loss and death and yet 55 to 59% of cultivars planted in the state since 2014 have not been resistant, according to UC Davis research.
This is the first release from the UC Davis Strawberry Breeding Program where all the cultivars have Fusarium wilt resistance. They are meant to replace susceptible plants on the market such as Monterey, UCD Royal Royce and UCD Valiant.
Monarch was also developed specifically as a prototype for mechanical harvesting – another first out of the breeding program, which dates to the 1930s and has released 72 patented cultivars over the decades.
“These provide the same yield or better and they are Fusarium resistant,” said Steve Knapp, a Distinguished Professor in the Department of Plant Sciences and director of the UC Davis Strawberry Breeding Program. “They have a better collection of traits. They're superior.”
Knapp is a faculty member based in the College of Agricultural and Environmental Sciences at UC Davis and shares the UC Agriculture and Natural Resources land-grant mission of the Agricultural Experiment Station.
Dangerous pathogen
Fusarium wilt didn't present much of a danger to strawberry crops until after the fumigant methyl bromide was phased out of use in the United States in 2005. But the pathogen had always been in the soil, and cases of wilt appeared a year later and increased over time, leading to concerns that a Fusarium wilt pandemic could destroy the crop in California.
“The disease has taken off fast and we need to react quickly to address the need,” said Glenn Cole, a breeder and field manager with the Strawberry Breeding Program.
Knapp said the program tries to “encourage people to consider things like disease resistance” and routinely invites growers and other experts to events showcasing research breakthroughs and improved cultivars.
Varieties for the seasons
The new strawberry varieties each have improved flavor and characteristics that allow for near year-round growing around California, where about 1.8 billion pounds of the fruit are harvested each year. Some of the cultivars are adapted for production in the southern part of the state while others do well under the long daylight hours of summer along the coast.
Eclipse, a “summer plant” cultivar, has the potential to increase grower profitability as it produces in the fall and winter, and yields during research testing were 54% higher than similar cultivars. “We expect this cultivar to have wide commercial appeal,” Knapp said. “Eclipse is going to eclipse them all.”
Golden Gate and Keystone are “day neutral.” Those type of cultivars grow throughout the summer on about 60 percent of strawberry farming acres in the state. The “short-day” plants Surfline and Monarch are resistant to Verticillium wilt and Phytophthora crown rot.
Surfline and Eclipse are firmer and promise longer shelf lives. Monarch provides growers with improved fruit qualities relative to other mass-producedcultivars and has characteristics needed for advances in mechanical harvesting, Knapp said.
Genetic tools
Breeding program experts have long been researching ways to improve strawberry cultivars so the crop can withstand pests, disease and other stressors. To find plants that had Fusarium wilt resistance, they obtained the DNA of thousands of plants in field studies. The scientists also developed genetic tools to screen the plants and identify the genes that have resistance to the Fusarium pathogen.
Knowing that information allowed the team to breed resistance into and develop new cultivars, at a faster rate than previous efforts. “These tools have allowed us to sweep out the susceptibility and bring in resistance,” Knapp said.
/h2>Researchers identify genes making strawberries resistant to Fusarium wilt
Resistant varieties to be released later this year to growers
Strawberry losses from Fusarium wilt could become less of a threat after researchers at the University of California, Davis, discovered genes that are resistant to the deadly soilborne disease.
The findings, published in the journal Theoretical and Applied Genetics, are the culmination of several years' work, and the discovery will help protect against disease losses, said Steve Knapp, director of the Strawberry Breeding Program at the college.
“What we've accomplished here is important and it's valuable for the industry and it's going to protect growers,” Knapp said.
Strawberries are a key crop in California, where about 1.8 billion pounds of the nutritious fruit are grown each year, making up roughly 88% of what is harvested in the United States.
Finding the genes could prevent a Fusarium wilt pandemic.
“The disease has started to appear more often up and down the state,” said Glenn Cole, a breeder and field manager with the Strawberry Breeding Program. “Once the wilt gets in, the plant just crashes. You have total die out.”
Searching for resistance
UC Davis scientists screened thousands of strawberry plants in the college nursery and took DNA samples. They then used genetic screening and developed DNA diagnostics to identify genes that are resistant to the primary race of Fusarium wilt.
“The genes have been floating around in the strawberry germplasm for thousands of years,” Cole said, but no one worked to identify them.
This latest development brings “strawberry into the 21st century in terms of solving this problem,” Knapp said.
Protecting future crops
This work means breeders can introduce the resistant gene into future strawberry varieties. This fall the program will release new cultivars that have the Fusarium wilt resistance gene. And the DNA diagnostic tools will help breeders respond to new Fusarium wilt variants that develop.
“There will be new threats and we want to be prepared for them,” Knapp said. “We want to understand how this works in strawberries so that as new threats emerge, we can address them as rapidly as possible.”
“If you don't have fusarium resistance, you're done,” Cole said. “The disease could be around more than you think.”
Fusarium wilt hasn't traditionally been an issue but when the fumigant methyl bromide was phased out in 2005, things changed. The disease was in the soil and without the fumigant, instances of wilt increased, especially in areas where crops weren't rotated.
Breeding new varieties
Knapp and Cole have informed the industry about current strawberry varieties that have the resistance so they can select plants with that added protection. The new resistant varieties coming out later this year will be suitable for several growing seasons.
“It's a big deal,” Cole said. “Everything is incremental in plant breeding, but it's a big deal.”
Plant scientists have been breeding strawberries at UC Davis since the 1930s and they have released more than 60 patented varieties through the public breeding program.
All of the work happened at UC Davis. Dominique Pincot, Mitchell Feldmann, Mishi Vachev, Marta Bjornson, Alan Rodriguez, Randi Famula and Gitta Coaker from the Department of Plant Sciences, and Thomas Gordon from the Department of Plant Pathology contributed to the research, as did Michael Hardigan and Peter Henry who are now at the U.S. Department of Agriculture Agricultural Research Service and Nicholas Cobo who is at University of La Frontera in Chile.
The research was funded by UC Davis and grants from the USDA National Institute of Food and Agriculture Specialty Crop Research Initiative.
/h2>/h2>
Invasive Shothole Borers Threaten California’s Urban Forests
When tiny tree-killing beetles first arrived in Southern California several years ago and began...
Fig 1 Adult female of Polyhagous shot hole borer
Fig 2 Beetle entry hole on an avocado branch
Fig 3 a close up picture of broken branch of red willow tree in OC parks
After shothole borer invasion, UC Irvine becomes ‘perfect testing ground’
Results help inform best practices for managing the disease-causing beetle
The University of California, Irvine campus is home to a vast urban forest consisting of approximately 30,000 trees located in a mix of landscape, riparian and open space settings. In the mid-2010s, that forest came under threat from an invasive species of beetle that arborists and pest researchers were just learning about – the polyphagous shothole borer.
The tiny beetles, which may have arrived in California from their native Southeast Asia via infested shipping materials, tunnel into trees and introduce a fungus that serves as food for adult beetles and their larva.
As the fungus grows, it colonizes the tree's vascular system, blocking transport of water and nutrients. This causes a disease called Fusarium dieback that can kill branches or entire trees.
One reason the beetles were such a threat at UCI was the high number of sycamores on campus, especially in Aldrich Park at the campus center. Hundreds of cottonwoods, native willows, golden rain and coral trees also were affected. In total, the beetles attacked more than 2,000 trees, including 75 different tree species.
A variety of approaches to controlling beetle
To better understand and tackle this problem, UCI's Facilities Management department and Office of Environmental Planning and Sustainability collaborated with researchers affiliated with UC Agriculture and Natural Resources and UC Cooperative Extension. In addition, pesticide-manufacturing companies, pest control advisers and arborists provided materials and labor to help offset the cost of research.
“UCI was the perfect testing ground to determine integrated pest management strategies for this beetle/disease complex,” said John Kabashima, UCCE environmental horticulture advisor emeritus. “Our research was multifaceted, delving into early detection, monitoring and sampling, and cultural and chemical management.”
Kabashima said UCI provided the researchers with “a lot of freedom” to try a variety of approaches and study the results over time.
“We could cut down and sample trees or leave selected infested trees alone; we explored a variety of pesticide/fungicide combinations and application techniques,” he said. “That freedom resulted in many of the management solutions that are used today to effectively control this pest.”
UCI and the researchers also established a full inventory of affected trees on campus, evaluating severity of infestation by the number of entry/exit holes and signs of dieback. One important key to management is getting rid of “amplifiers” – heavily infested trees that are both hazardous and a source of beetles to spread to other trees.
“Typically, shothole borer infestations begin with just a few trees that for some reason are highly attractive to the beetles – perhaps based on tree species, tree spacing, irrigation conditions or other factors,” Kabashima said. “Over time, the beetles and fungus multiply largely undetected in those few trees. When the beetle population reaches a critical point and the trees begin to die, the female beetles fly to adjacent trees in a secondary invasion, eventually infesting many trees over a large area.”
An opportunity to diversify UCI's urban forest
At UCI, that initial invasion took place in landscaped areas containing many large, majestic sycamores that were planted when the campus began operations in the mid-1960s.
Over several years, UCI removed 700 heavily infested trees, including many of those historic sycamores, and replaced them with other tree species.
Today, the forest at UCI is very different than it was in 2015. While shothole borers have not been eliminated completely, their presence is reduced significantly, and UCI now has the tools to manage them effectively. Reforestation efforts resulted in a diverse treescape that is not only more sustainable but also beautiful.
“Managing a 1,500-acre campus with 30,000 trees is a never-ending process,” said Richard Demerjian, UCI's assistant vice chancellor, Campus Physical & Environmental Planning. “Our forest continues to evolve, with an ongoing focus on increasing diversity and plant health.”
Demerjian also noted that UCI is now starting to consider planting new sycamore trees on a limited basis.
A primer on effective shothole borer management
Whether managing a forest of thousands of trees or just a few trees, landscape managers and residents can apply many of the lessons learned at UCI to control invasive shothole borers and other tree pests.
- Avoid monocultures. Tree diversity provides beauty and resiliency.
- Keep trees healthy. Proper irrigation and maintenance will keep trees strong and help protect them from shothole borers and other pests.
- Check trees. Look for the common signs and symptoms of infestation such as beetle entry/exit holes. Regular monitoring ensures that infestations are managed early, before they cause dieback or tree death.
- Confirm suspected infestations. Use the detection tool at www.ishb.org.
- Review management options. For trees with low infestation, prune the infested branches and monitor the tree's health over time. In non-riparian, urban settings, consider treating low and moderately infested trees with pesticides/fungicides demonstrated to be effective against the pest-disease complex (A licensed professional will be needed to apply the treatments). Severely infested trees may require removal.
- Call in a professional. A certified arborist or pest control professional would be able to provide recommendations based on the tree's condition. The local county Agricultural Commissioner's Office and UC Cooperative Extension office may have additional knowledge about current shothole borer monitoring and management programs in your area.
- Take care of green waste. The beetles can survive in cut wood for weeks or even months. Proper disposal of green waste includes chipping infested wood, followed by solarizing or composting the chips.
- Replant wisely. Begin planting new trees only after removing all amplifiers and establishing an ongoing monitoring program. Consider the current concentration of tree species when deciding what type of trees to plant.
Gardening Confusions
By Susanne von Rosenberg, UC Master Gardener of Napa County Some gardening advice...
Not all wilted leaves are caused by lack of water. (gardeningknowhow.com)
Waterlogged soil could be a cause for wilted leaves. (greenmylife.in)
Fusarium wilt in strawberry. Known to affect tomatoes, too. (ucanr.edu)
Verticillium wilt on tomatoes. Caused by a soil fungus. (ucanr.edu)
Vertebrate pests damage roots, leading to loss of water to leaves. (ucanr.edu)
Using tree chips instead of bark chips conserves water. (sonorantreesvc.com)
Read the label. Follow directions exactly. (bgi-usa.com)
Woven landscape fabric is water and air permeable. (flowerarmor.com)
Weeds -do- grow through landscape fabric, and mulch. You might have fewer weeds, but they'll still need to be removed! (homeguides.sfgate.com)
Blog, Linda Chalker-Scott Horticultural Myths (pinterest.com)