Cadmium is a naturally occurring, toxic heavy metal found in many soils across Latin America and the Caribbean, where cacao trees are widely cultivated. It makes its way into cocoa seeds, called beans, that are roasted and made into chocolate, according to the Food and Agriculture Organization of the United Nations (FAO) - but some cacao varieties take up less of the toxic element than others. An international team of researchers, including Penn State scientists, found genetic differences in how two varieties managed cadmium uptake and facilitated the metal's movement throughout the plant.
The findings - published this week (Sept. 8) in Plant and Soil - may be an early step toward breeding cacao that accumulates less cadmium, according to the collaborators from Penn State and Corporación Colombiana de Investigación Agropecuaria-AGROSAVIA (the Colombian Agricultural Research Corporation).
While trace amounts of cadmium in chocolate don't present a serious risk to public health, long-term exposure to too much cadmium can lead to bone fragility as well as kidney and lung damage, explained one of the study's two senior authors, Siela Maximova, research professor of plant biotechnology in Penn State's College of Agricultural Sciences.
"One of the key challenges in cacao farming is managing cadmium levels in the beans, especially in regions where the soil naturally contains cadmium," she said. "If the soil doesn't have cadmium, the plants won't absorb it, and the beans won't contain it. But in areas with contaminated soil, the only solution may be to plant cacao varieties that do not accumulate cadmium. This requires identifying and breeding naturally resistant varieties or using biotechnology to develop new ones, aiming to reduce cadmium uptake while maintaining high yield, disease resistance and good flavor."
