From farmer to consumer, whatever questions arise, the National Peanut Research Lab uses cutting-edge research techniques to find the answer.
⋅ BY AMANDA HUBER ⋅
The National Peanut Research Lab, in Dawson, Georgia, was a stop on this year’s Georgia Peanut Tour. Researchers gave brief explanations of their work on everything from planting to post-harvest and processing. Many researchers are working together to solve the problem of aflatoxin in the U.S. peanut industry. Although the number of projects and scope of work is too great to put into a few pages, a brief look at some of their projects follows.
Reducing Aflatoxin With Seed Coatings, Late-Season MoistureOr Decoys
Photo by Georgia Peanut Commission
Aflatoxin contamination is a recurring problem in the U.S. peanut industry, and mitigating it costs all segments of the industry millions of dollars. This one topic dominates multiple researchers’ time and efforts. Ron Sorenson, NPRL research agronomist, is approaching the problem in multiple ways from seed coatings, to mowing peanut plants to providing “decoys” in the field, all in an effort to reduce aflatoxin.
One project involves Syngenta’s Afla-Guard, a biological control agent for displacing the strains of Aspergillus flavus with a nontoxigenic strain of A. flavus, that has had varying amounts of success in reducing aflatoxin over the years. It is labeled for use on almonds, peanuts, pistachios and corn, but not as a seed coating.
Sorenson says they asked their cohort to put the Afla-Guard and bioplastic coating on peanut seed, which were then planted. He was looking at germination rates initially and will follow the crop to harvest to see if aflatoxin is reduced in any meaningful amount.
“We are trying different types of non-toxogenic forms of aspergillus as well as some other agronomic practices to reduce aflatoxin,” he says. “Working with another USDA lab who was testing seed coatings on corn and soybeans, we asked about putting it on peanuts.”
One of the agronomic practices he is testing involves keeping soil moisture higher later in the season. Drought often brings on the presence of aflatoxin.
“The way we went about doing that is to cut or mow the peanut plants so that it would stop transpiration. Then, we were also looking at historical rainfall data to time the cutting,” he says.
“If we cut the peanut off, we know we lose about 10% to 12% of yield on one cut. But would you rather lose 12% of yield or have the whole field go Seg. 2? That’s a choice and we don’t know how viable it would be. It’s just the beginning of testing.”
Yet another avenue of study involves knowing the purpose of the fungi in the first place.
“Aspergillus is out there to decompose organic matter, and it just happens to secrete aflatoxin,” Sorenson says. “We have no real knowledge of when or why that happens.
“However, since aspergillus is out there to decompose organic material, we thought, ‘let’s put something out there for it to work on.’ So, we put out peanut hulls to see if aspergillus would work on the decoy rather than the good peanuts.”
As novel as these projects seem, Sorenson says they are looking for anything a farmer could do to reduce aflatoxin.
Aflatoxin Detection, Drought-Tolerant Varieties And Discovery Of Resistant Genes
As a costly problem to the industry, aflatoxin is also a tricky one to mitigate and research. Although aspergillus fungi is present in the soil and, as mentioned previously, serves the purpose of breaking down organic materials, it does not always produce aflatoxin. Being able to detect when aspergillus-produced aflatoxin is present in the field is the subject of a research focus as NPRL.
With the overall goal of improving peanut quality, specific projects include developing a remote-sensing-based approach for in-field aflatoxin hotspot prediction and management. Another project will evaluate a deep learning-assisted hyperspectral fluorescence imaging system for post-harvest aflatoxin detection at the shelling plant so that contaminated peanut kernels may be identified and segregated rapidly and reliably.
Phat Dang, NPRL research chemist, works to discover drought-tolerant peanut varieties and to understand the underlying physiological mechanisms of water spender and water saver cultivars.
He has found that some peanuts are “water savers,” which can shutdown physiological response to minimize water loss. “Water spenders” are those varieties that keep growing under short-term drought stress.
“We want to know if there’s a yield difference in the different types of physiological responses that we find in these two groups of cultivars,” Dang says. “Using rooting tubes, which is a hollow tube reaching deep into the soil, we’ll take pictures of the root structure and see if root development changes with drought tolerance.”
Dang and his research collaborators will also measure physiological traits, such as high water-use efficiency, effective use of water, nitrogen fixation and root characteristics using semi- and high-throughput phenotyping techniques. RNA sequencing will be performed to correlate gene expression with physiological traits to identify molecular and genetic controls.
Because drought is a factor in increased aflatoxin in peanuts, it is hoped that drought-tolerant varieties could reduce this costly problem.
Another scientist at NPRL, research chemist Victor Sobolev, is working to identify and integrate beneficial genes from disease-resistant peanut and wild peanut sources into genetically stable peanut germplasm.
“Peanut seeds are often invaded by fungi that produce highly carcinogenic aflatoxins,” Sobolev says. “We will work to manage this in peanuts by exploring the natural, phytoalexin-based defense mechanism of the peanut. This requires the analysis of thousands of single small, scarce seeds for aflatoxin and phytoalexin content.”
Because current commercial peanut cultivars often demonstrate limited resistance to fungal pathogens, he says, wild peanut species are likely the source of needed disease resistance.
To reduce disease pressure and aflatoxin contamination, they are working to develop resistant peanut cultivars through introgression of beneficial genes and alleles from wild peanut species into elite cultivars.
Reducing Post-Harvest Moisture, Foreign Material
Another NPRL agricultural engineer, Chris Butts, who is semi-retired but still working on a few projects, also researches post-harvest storage of peanuts.
“This is a study to determine the ventilation rates for peanut and the head space needed over peanuts in the warehouse,” Butts says. Essentially, how much air and when to run the fans.
“When to run the fans is still a major question,” he says. “The industry typically runs fans 24/7. The questions are, ‘If it’s raining, do I turn on the fans and pull in moist air? If it’s foggy, do I run the fans? If I’ve had a hurricane and the power goes out, which warehouse do I put the generator on? Is it last year’s crop or this year’s peanuts? Which set of fans do I run?’
“Questions like that are what we are still trying to answer,” Butts says.
In an industry change, he says conventional tall warehouses for peanut storage are likely to change to a flat-type warehouse for storage.
Based on their research, Butts says, “I think you’ll see fewer problems in terms of moisture migration and foreign material distribution in the flat storage. Those warehouses are loaded with conveyors from the ground as opposed to the conveyor running up high, down the center of the warehouse, which puts all your foreign material right under the belt.”
Although in the flat warehouse, foreign material still ends up under the belt. With the belt continuously moving, the material is more spread out, which is preferred.
Reducing foreign material in peanuts is always a point of study for post-harvest storage.
These are only a fraction of the many projects in progress at the National Peanut Research Lab, a truly important part of the peanut industry. PG