It Takes a Research Village
Growers like Pete Call and the processors who buy beans are the ultimate beneficiaries of the all-out effort by the Cornell University research team to develop cucumber mosaic virus coping strategies.
Photo by Rocco Laurienzo.
“At the start, we looked at the fields with severe yield loss and had more questions than answers,” Reiners says. “We identified the problem as cucumber mosaic virus and called together the expertise to answer our questions. It was a full effort to respond quickly.”
Julie Kikkert, Cornell Cooperative Extension vegetable specialist, served as the conduit to the processing industry and the growers who periodically met with the research team.
Pete Call was among the growers whose fields were 50 to 100 percent infected with cucumber mosaic virus (CMV) in 2001. Call, who has 2,500 acres of beans, said to the team, “CMV threatens to put us [the New York snap bean industry] out of business.”
The snap bean industry was worth over $30 million, with approximately one-third of that generated from the processing bean side.
Entomologist Brian Nault quickly identified the soybean aphid, a recent invasive pest in the U.S., as the primary vector of CMV, with yellow clover aphid a close second. Epidemiologist Denis Shah identified the specific species most closely linked to CMV transfer.
The virus itself was not a new discovery; rather, the aphid influx raised CMV to critical levels.
“Other critical information early on included the fact that the risk of CMV epidemics was higher in the last half of the growing season, when the aphids were more likely to move in and infect young plants, causing high yield loss,” Nault adds.
“Because an insect was the disease vector, the growers’ response was to kill the insect, but by the time insecticides were applied it was too late,” says Alan Taylor, a seed scientist and professor in the Cornell Department of Horticulture. His focus for solving the problem was on seed treatments.
“One of my roles was to determine if the seed itself could also be transmitting the virus. Our greenhouse screening determined that the virus was not transmitted by the seed; therefore, the virus was coming from the field [environment],” Taylor explains.
The challenge remained to help growers continue to produce a crop.
“We screened dozens of commercially available varieties for CMV resistance to allow growers to continue producing without losing yield. Those determined to have some level of tolerance have increasingly become the industry standards,” Reiners notes.
“Spartacus was identified as the first, best choice. Steve [Reiners] and his technician Jim Ballerstein’s work sought out commercially available varieties that would yield well under CMV pressure and without CMV. That kind of consistency is critical for growers contracting acres for the processing industry,” Nault says.
The snap bean acreage planted with Spartacus increased nearly thirtyfold from 2005 to 2008.
Huntington has since become the preferred late-season variety. Oregon State University developed the parents of Huntington, which is now widely planted by growers and distributed by Syngenta.
Nault received a $50,000 grant from the New York Farm Viability Institute (NYFVI) in 2006 to develop a risk model to help growers adjust acreage and varieties throughout the growing season.
Call, who now grows the Huntington variety, says, “We’ve learned a lot, but CMV is still causing trouble when aphid pressure rises. We do not have all the answers yet. The key lies in Phil Griffiths’ work.”
In 2008, the NYFVI granted Griffiths, a Cornell plant breeder, $325,000 to conduct multiple planting time field trials of snap bean cultivars selectively bred for CMV resistance and to investigate the use of CMV gene fragments to trigger RNA silencing in the snap bean plants as an innate defense mechanism against virus infection.
“The major virus resistance gene combinations that can be bred into cultivars have now been identified. The lines to date are doing what we expect in terms of building CMV resistance, but the gene combinations being assembled will provide additional durability and protection,” says Griffiths.
“Last summer  in Wisconsin, which grows four times the acreage of beans as New York, the virus was as bad as I have ever seen it. The aggressiveness of these strains appears to be caused by satellite RNAs,” he notes.
Griffiths credits the early fieldwork by Reiners’ team with creating a solid foundation for his conventional breeding efforts.
“I am hopeful that in the next couple of years, with good field information on yield and stress tolerance, we will develop an advanced breeding line that can be marketed as a cultivar with the same opportunity for maturity and yield as the currently grown cultivars. However, it will take a couple of seasons to prove its value under various conditions to the point of moving seed into commercial production,” Griffiths says.
Virologist Marc Fuchs is also part of the research effort.
“My initial contribution was to make sure the virus inoculum was robust for evaluating the most promising lines and to characterize their tolerance response,” explains Fuchs. “Longer term, we are using a transgenic engineering approach to activate the plant’s natural defense mechanism – RNA silencing – to fight off the virus. We are searching for a fragment of genetic information in the virus that will act like a vaccination to activate the plant’s immune system.”
Fuchs credits John Sanford with developing pathogen-derived resistance breeding more than 25 years ago at the New York State Agricultural Experiment Station in Geneva, New York. Fuchs is exploring the concept with snap beans, dry beans, grapes and papaya.
The processing industry has been a critical part of the problem-solving effort from the start. Jeff Johnson, agricultural manager with Seneca Foods in Geneva, says, “The Cornell team brought a number of different perspectives to help us get to a point of planting varieties that are more CMV-tolerant to keep the processing industry strong. Now we undertake the longer resistance breeding and gene marker identification process to see what might help in the future.”
Mike Gardinier is vice president of operations with Farm Fresh First, representing 6,500 acres of processing snap beans. Gardinier says, “Every year now we monitor the research reports on all snap bean work. The CMV problem is not resolved yet, but Cornell University, the New York State Vegetable Growers Association Research Council, the processing industry and seed companies have all helped address the short-term impacts. It takes that kind of partnership to raise awareness of the CMV virus complex as an important challenge for attention.”
David Grusenmeyer, NYFVI managing director, notes, “Support for CMV problem-solving has been among the largest grants the institute has ever funded. Our hallmark is responding to grower and industry-identified needs, and the comprehensive approach by the Cornell team addressed the opportunity for both an immediate alternative as well as setting the foundation for longer-term, science-based solutions.”
New York state currently grows approximately 20,000 acres of processing snap beans. CMV also impacts dry beans, melons, cucumbers, some squashes, tomatoes and peppers.
The author is a freelance writer with a 100-acre farm in Mannsville, New York.