The research, conducted by scientists at the University of Ghana, the CSIR Plant Genetic Resources Research Institute and the Biotechnology and Nuclear Agriculture Research Institute of the Ghana Atomic Energy Commission, was published in Discover Plants. The team took a commercially available, non-genetically modified groundnut variety called Chinese, produced by the International Crops Research Institute for the Semi-Arid Tropics, and exposed both shelled kernels and unshelled pods-in-shell to gamma radiation from a cobalt-60 source at doses of 0, 1, 2, 3, 4 and 5 gray, the standard unit of absorbed radiation dose. For context, these doses are extraordinarily small; food sterilisation treatments typically involve hundreds or thousands of gray, so the researchers were working at the very bottom of the biological dose range.

The experimental design was meticulous. Seeds were packed in hermetic bags and irradiated at the Radiation Technology Centre in Kwabenya, Accra, with dose rates of roughly 70 to 71 gray per hour, calibrated using an ethanol-chlorobenzene dosimeter. Packs were rotated during exposure to ensure uniform dosing. The treated seeds were then stored under ambient conditions for five months, from December 2018 to May 2019, and assessed at eight three-weekly intervals for physiological, sanitary and genetic quality parameters. Laboratory germination tests followed International Seed Testing Association protocols, with measurements of germination percentage, speed and peak of germination, root and shoot length, and a composite vigour index. A parallel field trial using a randomised complete block design checked whether irradiation altered the variety’s distinctive morphological traits.

The headline finding is that irradiated seeds outperformed untreated controls across most physiological measures. Germination percentages during storage were significantly higher in irradiated seeds, peaking at 88 percent for seeds treated with 2 and 4 gray, compared with 84 percent for the untreated controls. The speed and peak value of germination, which capture how quickly and uniformly a seed lot germinates, were also significantly higher in irradiated seeds, with the 2 and 4 gray treatments again leading the pack. Seedling vigour index, calculated as germination percentage multiplied by seedling length, was significantly greater in irradiated seeds than in controls, and the relationship between dose and vigour was positive but non-linear, with a regression fit of R-squared equal to 0.87.

That non-linearity is scientifically telling. At 5 gray, the highest dose tested, some benefits began to erode: root length was significantly shorter in seeds exposed to 5 gray than in those given 2 gray, and germination at 5 gray fell below the levels seen at 2 and 4 gray. This dose-dependent pattern echoes a well-known biological phenomenon called hormesis, in which mild stress triggers beneficial responses while stronger stress causes damage. Low-dose ionising radiation is thought to stimulate antioxidant enzyme activity, enhance metabolic efficiency and prompt cellular repair mechanisms without inflicting irreversible harm. The researchers suggest that these mild physiological nudges may help maintain membrane integrity, reduce oxidative damage from reactive oxygen species, and preserve the enzymatic machinery needed for germination to begin promptly. At higher doses, by contrast, radiation can disrupt membranes, generate excessive free radicals and interfere with DNA synthesis, all of which impair seedling growth.

The study also delivered a clear verdict on seed form. Unshelled seeds, stored in their pods, consistently outperformed shelled kernels. They showed significantly higher germination percentages, faster germination, longer seedlings, greater vigour and, notably, lower moisture content. The pod acts as a natural physical barrier, buffering seeds against mechanical injury, environmental fluctuations and some pest attacks while helping to maintain the moisture balance and food reserves needed for rapid germination. This supports the long-standing practice of storing groundnut in shell, and it also meant that the optimal radiation response differed slightly between forms: the seed coat appears to modify how the seed interacts with the radiation, with the irradiation effect on germination speed being more pronounced in unshelled seeds.

Not everything improved, however. Pathogen infectivity rose dramatically over the storage period, climbing from 22 percent at the start to 79.9 percent by the end, regardless of treatment. Fungi identified during the tests were dominated by Aspergillus species, including A. flavus, A. niger, A. versicolor and A. ochraceous, alongside Botrydiplodia theobromae, Rhizopus and Penicillium. The doses used were simply too low to kill microbes, and the researchers are candid on this point: irradiation at 2 to 4 gray did not improve the sanitary quality of the seeds in either form. The rising fungal load likely reflects latent field infections and handling contamination that flourished as ambient humidity fluctuated with the seasonal shift from dry harmattan winds to the rainy season, which also drove the observed ups and downs in seed moisture content.

The field trial added reassurance on genetic stability. Days to seedling emergence and days to 50 percent flowering, which ranged between 26 and 27 days, were similar across all doses and seed forms. Emergence percentages in the field were actually quite strong, with 100 percent emergence observed for shelled seeds at 3 gray and for unshelled seeds at 2, 4 and 5 gray. Crucially, morphological evaluation showed that leaf shape, leaf colour and petiole colour were unchanged by irradiation, meaning the treatment did not alter the distinctive, uniform and stable characteristics that define the variety. Petiole and leaf colours of both seed forms were unaffected, an important consideration for any seed certification programme.

Why does this matter beyond the laboratory? Groundnut is a lifeline crop for smallholder farmers across West Africa, cultivated for food, fodder and industrial uses, and its rapid seed deterioration undermines seed sufficiency for planting. Existing storage strategies, from hermetic packaging and vacuum sealing to traditional methods using wood ash and sand, have generally failed to extend groundnut seed viability beyond about 20 months. Fungicide and insecticide pre-treatments are one option but carry environmental and cost concerns. Irradiation, by contrast, is eco-friendly, already available in Ghana, and widely used in food processing and agriculture. The findings suggest that a modest pre-storage dose of 2 to 4 gray could become a practical seed-priming step that preserves physiological quality without chemical inputs, though the authors note that further work is needed, particularly on unshelled seeds and on combining radiation with other pathogen-control measures.

The study also fits into a broader scientific conversation about hormesis in crops. Previous research has reported 10 to 25 percent germination increases in irradiated groundnut at low doses, and similar stimulatory effects in sunflower, tomato, maize and lettuce, always with the caveat that benefits reverse as doses climb. The Ghanaian results reinforce the picture of a narrow but real sweet spot: enough radiation to provoke protective stress responses, not enough to cause oxidative trauma. As climate variability intensifies pressure on seed systems in the semi-arid tropics, simple, low-cost physical treatments that squeeze extra months of viability out of precious seed lots could make a genuine difference. For now, the message from Accra is that a whisper of radiation, carefully measured in single gray, may be worth more to a groundnut farmer than a shout.

Subject of Research: Effects of low-dose gamma irradiation on the physiological quality and storability of groundnut seeds

Article Title: Effects of low-dose gamma radiation on quality and storability of groundnut (Arachis hypogaea L.)

Article References: Effects of low-dose gamma radiation on quality and storability of groundnut (Arachis hypogaea L.). (n.d.). https://doi.org/10.1007/s44372-026-00937-x

Image Credits: AI Generated

DOI: 10.1007/s44372-026-00937-x

Keywords: groundnut, gamma radiation, seed storability, seed vigour, germination, hormesis, seed quality, Aspergillus, Ghana, food security, cobalt-60, seed deterioration