Evaluation of Selenium Enrichment Capacity and Screening of Selenium-Rich Varieties in 77 Sweetpotato Germplasm Resources

Selenium is a trace element that acts as a quiet but essential guardian for human health. Found in the soil and passed up through the food chain, it helps the body build specific proteins that fight off damage from everyday stress and keep the immune system functioning properly. Without enough of it, people can face serious health risks, yet many regions around the world have soil that is simply too poor in this mineral to grow crops capable of meeting daily dietary needs. This creates a gap between what people need and what their local environment can provide. One way to bridge this gap is to find plants that are naturally good at pulling selenium from the ground and storing it in their edible parts, turning ordinary food into a source of this vital nutrient. The sweet potato, a staple crop grown in over a hundred countries, is known to have this ability, but not all varieties are equally skilled at it. Some are like efficient sponges, soaking up the mineral, while others are more like sieves, letting most of it pass through.

To solve the puzzle of which sweet potatoes are the best at this, researchers in Guangxi, China, set out to test a large collection of seventy-seven different varieties. They planted these crops in two very different places: one site was a region with soil naturally rich in selenium, and the other was a site with soil that had very little of the mineral. By growing the same plants in these two contrasting environments, the team could see how the soil changed the plants' growth and how much selenium each variety managed to store in its roots. They measured everything from the length of the vines and the number of branches to the weight of the roots and the chemical makeup of the flesh, looking for patterns that would reveal which varieties were the true champions of selenium accumulation.

The results showed that the environment had a profound effect on how the plants grew. In the low-selenium soil, the sweet potatoes grew larger and heavier, producing longer vines and more leafy growth than their counterparts in the selenium-rich soil. It seems that the high-selenium soil, while good for mineral uptake, presented other challenges that kept the plants from reaching their full size. However, the most important discovery was not about size, but about the mineral content itself. The researchers found that the amount of selenium stored in the roots varied wildly from one variety to another, proving that this ability is deeply rooted in the plant's genetics. In the selenium-rich region, the levels of the mineral in the roots ranged from very low to quite high, with some varieties storing nearly ten times more than others.

After carefully comparing the data, the team identified three specific varieties that stood out as the most effective at concentrating selenium. These were named Zhenghong 163, Longzi 9, and Guangzishu 9. When grown in the selenium-rich soil, these three varieties pulled in significantly more of the mineral than the rest of the group. For instance, one of the top performers, Zhenghong 163, contained levels of selenium that were more than three times higher than the lowest-performing variety in the same field. Even more telling was what happened when these top performers were grown in the low-selenium soil. While their selenium levels dropped, as expected, the gap between them and the other varieties remained wide. This confirmed that these three varieties possess a unique genetic trait that allows them to be highly efficient at capturing and holding onto selenium whenever it is available.

The study also revealed a fascinating trade-off between yield and quality. The plants in the selenium-rich soil produced smaller roots and fewer of them compared to the plants in the low-selenium soil, yet they were richer in certain beneficial compounds like antioxidants and dry matter. This suggests that growing sweet potatoes in natural selenium-rich soil might result in a slightly smaller harvest, but one that is nutritionally denser and more valuable for health. The researchers used statistical tools to group the varieties based on their traits, finding that the soil type changed how the plants were classified, further highlighting the complex relationship between the environment and the plant's genetic potential.

Ultimately, this work provides a clear path forward for farmers and breeders. By identifying these specific varieties, the researchers have offered a starting point for developing sweet potatoes that can naturally enrich the human diet with selenium. The top candidates, particularly Zhenghong 163, Longzi 9, and Guangzishu 9, are now ready to be tested in larger fields and potentially introduced to regions where selenium deficiency is a concern. The study confirms that while soil conditions matter, the right variety can make a massive difference, turning a standard crop into a powerful tool for improving public health.