A New Era In Peanut Breeding

NCSU peanut breeder Jeff Dunne has brought modern breeding techniques, including the use of marker-assisted and predictive genomic selection capabilities to the already highly successful breeding program.
Using modern techniques, the NCSU program will bring cultivars with improved genetics to the market more quickly and efficiently. 

⋅ BY AMANDA HUBER ⋅

Four years ago, Jeff Dunne took over the helm of peanut breeding at North Carolina State University after the retirement of the well-known and highly respected peanut breeder Tom Isleib, who introduced a number of high-yielding, industry favorite cultivars through conventional breeding methods. While these were big shoes to fill, Dunne’s timing could not have been more perfect in that his goal was to implement the use of genetic markers in peanut breeding. After all, the first phase of the Peanut Genomic Initiative had been completed and the use of this technology was ramping up. 

The goal of any peanut breeding program is to achieve high-yielding, disease-resistant, high-oleic cultivars with good flavor and other marketable characteristics. Conventional peanut breeding emphasizes cultivar pedigree, backcrossing and single-seed descent to include useful genes into elite, agronomic backgrounds to attain the breeding objectives. 

Breeding Efforts For Today And Tomorrow

Today’s more modern breeding programs include the use of marker-assisted breeding techniques with predictive genomic selection capabilities. This approach also offers the opportunity to reduce operating costs, bring cultivars to the market more quickly and improve genetic gain. Making that shift to more modern techniques, changing the way they do things is not as easy as it sounds. Like other peanut breeders, Dunne has spent considerable time simply modernizing and bringing efficiency to their program. 

“Over the past four years, we have worked to make sure this breeding program is running as efficiently as possible so that if we do get some new disease or pest threat, our breeding program is ready to address it quickly and efficiently,” Dunne says. 

For example, he says root-knot nematode has not been a threat in the Virginia-Carolina production area; however, it could become a problem in the future. 

“Is our breeding program ready to quickly and efficiently select for that marker or germplasm line that we know has nematode resistance to produce a cultivar, get it through testing and make it available to producers in a few years? We want our program to be prepared for future and emerging issues.

“The biggest impact we’ve made is getting our program ready to not only address what is here now, such as leaf spot and Tomato Spotted Wilt Virus and improved pod traits for Virginia-type peanuts, but also what’s coming. Can our program adapt quickly enough to respond and get our lines tested quickly enough to cover our growers? These are the questions we’ve been addressing,” Dunne says. 

A Priority List Of Import Traits

As for traits of interest he and others in V-C peanut breeding are evaluating for are regional in nature for the Virginia in-shell roasted market. Traits currently in NCSU phenotyping include: yield (test weight), pod and seed grading, oleic acid content and purity, leaf spot severity, tomato spotted wilt incidence, sclerotinia blight incidence and flavor quality. Dunne says these are the quintessential high-value, high-impact traits for their market and influence the breeding program on a day-to-day basis. 

Drones are used to measure defoliation as part of the visual rating quantification for work with leaf spot resistant traits.

“Three traits we are mainly focused on is work supported by The Peanut Foundation, and the move in this direction fits in with the second phase of The Peanut Genomic Initiative, which puts into practice what was learned in phase one,” he says. “We’re looking at disease quantification methods and better mapping of traits in terms of the marker-selection program. 

“In the case of leaf spot, we do both visual ratings and low throughput quantification separating out lesion counts. We also measure defoliation using a drone, and we are doing more multi-spectral analysis along with cell phone capture to better quantify or correlate the visual leaf spot ratings,” Dunne says. 

“From a Virginia market standpoint, we are very interested in pod characteristics in terms of color and size. Using a QualySense Qsorter Explorer, which is cutting-edge technology for the inspection and fine sorting of seed, we’re able to make better selections in terms of pod size and other characterizations, like maturity.” 

Leaf spot severity is one of the high-value, high-impact traits for the Virginia-Carolina market being studied on a day-to-day basis in the NCSU breeding program.

Lastly, Dunne says they are focused on the high-oleic acid trait, which is valuable in terms of Virginia-type peanuts that are mostly consumed as roasted in-shells or canned. 

“We are 100% high oleic, so keeping seedstock pure is of high importance. To do that, we either screen molecularly for the correct marker early on in the generations to make sure we have that trait incorporated into all our advanced lines and/or we are screening large volumes of seed lots for the high oleic content using the QualySense Qsorter Explorer,” he says. 

Can Flavor Be Addressed Genetically? 

Dunne says they have also put emphasis on flavor and are fortunate to have U.S. Department of Agriculture Agricultural Research Service food technologist Lisa Dean helping work on this trait. 

“She has been helpful in utilizing her resources in the food science lab to help improve the value of the crop by enhancing flavor, as well as nutrition and post-harvest processing. We are also starting to address some non-target quality traits such as pod thickness: What impact does that have from a shelling standpoint? How does it impact the consumer? 

“Quality traits are not always easily addressed. It is hard to narrow down the priority list because we often have other immediate impact-type traits like disease resistance and drought tolerance,” he says.

Speeding Up The Breeding Process

The NC State peanut variety selection tool, go.ncsu.edu/peanut-cultivars, contains more than a decade’s worth of variety trial data.

Conventional peanut breeding often took 10 years to bring a new variety to the market because a program could only have one generation per year. The number of generations could be increased to two per year if the winter nursery in Puerto Rico was used. However, space in the winter nursery has become a premium with a significant price tag to match. 

More recent studies have shown that greenhouses can be used to further increase the number of generations per year by controlling and optimizing the daily light quality and intensity. 

“By using a 20- to 22-hour light cycle, >600 micromole of full spectrum intensity and controlling temperatures and automated irrigation, mature peanut seed can be developed in 75 to 90 days, translating to four generations per year,” Dunne says. “Overall, the efficiency of selection and the rapid cycling in the greenhouse can move high-performing breeding materials to testing faster.

“We’re also using robots to extract DNA from our samples and basically doing everything we can to more efficiently push breeding materials through our greenhouses as quickly as possible to get it into the field and to growers as soon as we can.”

As yet another modernization into using today’s technology, nearly a decade’s worth of data from the NCSU and Peanut Variety and Quality Evaluation testing programs is now available to researchers, Extension specialists, county Extension agents and growers through a web-based application that can be found at go.ncsu.edu/peanut-cultivars. Data such as yield, pod weight, perfect fancy pods, loose-shelled kernels, disease ratings and more are available for multiple areas and years. 

Three new cultivars have been released from the NCSU breeding program since Bailey II. One is Comrade, a joint release with USDA-ARS peanut breeder Kelly Chamberlin that will provide material with Sclerotinia blight resistance and early maturity for the Oklahoma breeding program. 

The other two are NC 20 and NC 21, which will not be available until 2024 or later. Both cultivars have characteristics equivalent to yield, pod and seed size, and disease resistance of Bailey II and Emery, respectively. NC 20 has slightly larger pod and seed sizes than Bailey II but provides similar leaf spot and TSWV resistance. NC 21 has a yield, pod and seed size, and disease package similar to Emery, but is later to mature and holds on to pods under heavy leaf-spot pressure. More information about these releases can be found in 2023 Peanut Information found on the NCSU peanut website at peanut.ces.ncsu.edu.

All of the changes and modernization brought about by Dunne in the NCSU peanut breeding program are being conducted with the Virginia-Carolina peanut growers in mind. No doubt, this storied and successful program is now positioned to develop and deliver cultivars for commercial production in the region well into the future. PG

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