Unsinkable Icebergs

Unsinkable Icebergs

Researchers at USDA’s Agricultural Research Service  (ARS) in Salinas, CA, are on a roll this year, as they’ve developed several new parent iceberg lettuces with the ability to ward off such destructive disorders as Verticillium wilt, corky root, and mosaic virus. Here’s a closer look at these promising developments, which should prove quite a boon to growers in the coming years.

Verticillium Wilt Resistance

Iceberg lettuce is renowned for its big, firm, round heads, so it was with no small measure of dismay when a dozen years ago growers in Coastal California started seeing their beauties collapsing like deflated balls. The cause was determined to be a soil-dwelling, root-rotting fungus called Verticillium dahlie, which causes the disease Verticillium wilt.

Symptoms of the disease first appear on the basal leaves as areas of chlorosis and angular necrotic lesions along the leaf margins prior to wilting, says Ryan Hayes, an ARS research geneticist. Other key foliar symptoms include stunting and defoliation.

The disease symptoms appear first on the older leaves, progressing inward and eventually leading to the plant’s death. What makes the disease even more insidious is that plants that succumb to Verticillium dahlie produce large quantities of microsclereotia that can persist in the soil for 10 to 15 years. The fungus can also infect and kill hundreds of other kinds of plants, including strawberries and tomatoes.

Hayes teamed up with Krishna Subbarao of the University of California-Davis to develop three parent lettuces with Verticillium wilt resistance. They crossed the Pacific variety with La Brillante, a Batavia-type lettuce cultivar with resistance to race 1 of Verticillium dahlie. Batavia-type is a primitive version of iceberg, says Hayes, a predecessor to today’s iceberg. They have had requests for seed from more than a half-dozen seed companies, who he expects will cross the parent lines with consumer-friendly lettuces. “It will be nice to get Vert resistance in commercial varieties,” says Hayes. “And we’ll get there, I have no doubt about that.”

Corky Root And Mosaic Virus

These two microbial enemies are not as devastating as Verticillium wilt in that they don’t kill the lettuce plants, but they cause plenty of damage nonetheless. For example, in California and Florida fields severely infested with corky root, yield losses from reduced head size can reach 30% to 70%, says Hayes. Corky root has been observed in all the major lettuce-producing regions in the world, including Western Europe, Australia, and New Zealand, as well as North America. Its name derives from the fact that the lettuce roots develop ugly, yellow-to-brown lesions that harden to a cork-like texture. It is caused by the bacterium Sphingomonas suberifaciens.

Lettuce mosaic is generally not nearly such a problem as corky root, as it is generally controlled in California and Arizona through seed indexing, i.e. planting virus-free seed. But there is only one cultivar with resistance to both mosaic virus and corky root, and it is protected by patent, which greatly restricts breeding research. Like corky root, mosaic results in stunted growth. In addition, the leaves develop an unattractive mottling, hence its name. The virus is generally spread by green peach aphids.

Hayes worked with fellow ARS plant geneticists Edward J. Ryder, who is now retired, and Beiquan Mou, who was the project leader, to develop a total of seven kinds of parent iceberg lettuces that shrug off attack by the two microbial enemies. The parent plants are the first publicly available iceberg lettuce parents with resistance to both corky root and lettuce mosaic. The lettuces were developed specifically for California climates and soils, and the sooner they are crossed with consumer-friendly icebergs, the better. “I know growers are really interested in resistant varieties,” says Hayes.

Leave a Reply

Featured Stories
Farm ManagementAn Excellent Industry Education [Opinion]
July 31, 2015
The end of one era, and the ushering in of another. Read More
Stone FruitThe Strong Staying Power Of The Redhaven Name In Peaches
July 31, 2015
People tend to be nostalgic about peach varieties, but the switch of varieties grown by a region happens for a Read More
Crop ProtectionResources For Knowing Your Soil
July 30, 2015
Getting to know your soil and learning other environmental and natural resources data can be downloaded and is available for use with many computer software platforms for general resource analysis and farm management. Read More
money
CitrusBankrupt Florida Farm To Yield Plenty Of Land, Equipment In Upcoming Auction
July 30, 2015
As many as seven different buyers could be part of this Chapter 11 proceeding. Read More
Sanjay Shukla
ProductionGeometrically Speaking, Thinking Smaller Might Produce Big Savings For Vegetable Growers
July 30, 2015
University of Florida scientist develops compact planting bed formula that cuts water, fertilizer, and pesticide use in half. Read More
GrapesDrought’s Impact On California Winegrapes
July 30, 2015
The impact is minimal this year, but the future is uncertain if the drought continues. Read More
Apples & PearsEPA Approves New 1-MCP Technology
July 30, 2015
EPA approved Fysium, a new 1-MCP product from Pace International LLC. Considered new technology, this product is produced on-site by Read More
Crop ProtectionNew Fungicide Targets Key Diseases
July 30, 2015
This disease control tool hits two different parts of the fungal life cycle. Read More
CitrusWestern Growers Praises Introduction Of California Emergency Drought Relief Act
July 30, 2015
Legislation contains short- and long-term provisions to deal with the historic drought. Read More
Farm ManagementFour Great Pricing Tips From U-Pick Experts
July 30, 2015
Although each of the growers I talked to has his or her own take on a pricing structure, they all Read More
The Latest
Farm ManagementAn Excellent Industry Education [Opinion]
July 31, 2015
The end of one era, and the ushering in of another. Read More
Stone FruitThe Strong Staying Power Of The Redhaven Name In Peache…
July 31, 2015
People tend to be nostalgic about peach varieties, but the switch of varieties grown by a region happens for a Read More
Crop ProtectionResources For Knowing Your Soil
July 30, 2015
Getting to know your soil and learning other environmental and natural resources data can be downloaded and is available for use with many computer software platforms for general resource analysis and farm management. Read More
money
CitrusBankrupt Florida Farm To Yield Plenty Of Land, Equipmen…
July 30, 2015
As many as seven different buyers could be part of this Chapter 11 proceeding. Read More
Sanjay Shukla
ProductionGeometrically Speaking, Thinking Smaller Might Produce …
July 30, 2015
University of Florida scientist develops compact planting bed formula that cuts water, fertilizer, and pesticide use in half. Read More
GrapesDrought’s Impact On California Winegrapes
July 30, 2015
The impact is minimal this year, but the future is uncertain if the drought continues. Read More
Apples & PearsEPA Approves New 1-MCP Technology
July 30, 2015
EPA approved Fysium, a new 1-MCP product from Pace International LLC. Considered new technology, this product is produced on-site by Read More
Crop ProtectionNew Fungicide Targets Key Diseases
July 30, 2015
This disease control tool hits two different parts of the fungal life cycle. Read More
CitrusWestern Growers Praises Introduction Of California Emer…
July 30, 2015
Legislation contains short- and long-term provisions to deal with the historic drought. Read More
Farm ManagementFour Great Pricing Tips From U-Pick Experts
July 30, 2015
Although each of the growers I talked to has his or her own take on a pricing structure, they all Read More
BerriesUC-Davis Responds To California Auditor’s Recomme…
July 30, 2015
Following a six-month review of the University of California (UC)-Davis Strawberry breeding program, the California state auditor’s office has released Read More
Farm ManagementHow To Find Your Perfect U-Pick Pricing Structure
July 30, 2015
If there’s one mission impossible for pick-your-own operations, it might just be how to set a pricing structure. Odds are you’ve Read More
CitrusGroup Food Safety Audits May Help Prepare You For The P…
July 29, 2015
Group food safety audits, slated to be available next spring, may save small- to mid-size growers time and money. Read More
PotatoesPotato Production And The Environmental Component Of Pl…
July 29, 2015
Part of being prepared for unusual weather patterns means being on the lookout for problematic pathogens and other pests. Read More
Farm ManagementUnited Farm Workers Turns Up Heat On California Growers
July 29, 2015
With temperatures soaring into the triple digits, union organizers are focusing on heat illness regulations. Read More
Apples & PearsResearch Is Vital To Keep Asian Apple Export Markets Op…
July 29, 2015
With the large domestic production of U.S. apples in recent years, Asian export markets (China, etc.) are vital. This is Read More
Disease ControlNew Disease Control Tools For Fruit And Nut Growers
July 29, 2015
Apple scab is a big problem for growers in the Midwest and East. But, a new fungicide boasts efficacy against Read More
IrrigationRiver Point Farms Sets Standard For Water Application, …
July 28, 2015
Efficient systems help the Oregon farm, one of the largest onion growers in the U.S., achieve high yields while minimizing water inputs. Read More