A recent study conducted by an international team of researchers has identified the “sweetness gene” responsible for low levels of bitter alkaloids in lupin beans. Lupins, a legume that has been consumed in various regions for thousands of years, are known for their high protein and fiber content, low carbohydrate levels, and low glycemic index. However, some varieties also contain high levels of bitter alkaloids.
The researchers discovered that around 100 years ago, plant breeders in Germany found natural mutations that produced “sweet lupins” with significantly lower levels of bitter alkaloids. These sweet varieties of lupin, including white lupin, narrow-leafed lupin, and yellow lupin, have become increasingly popular as food for both animals and humans.
To uncover the genetic basis for sweetness in lupins, the researchers used a combination of biochemical and genetic approaches. They studied the biochemistry of alkaloids in bitter and sweet varieties and analyzed the alkaloid levels in 227 varieties of white lupin. By examining markers across the lupin genome, they were able to identify a strong link between a specific gene sequence variation and changes in alkaloid levels.
To confirm their findings, the researchers tested whether the variation in this gene would also produce sweetness in other types of lupin. They collaborated with a company called Traitomic, which screened a large number of narrow-leafed lupin seeds until they found one with the desired mutation. When tested, this plant exhibited low alkaloid levels, confirming the discovery of the “sweetness gene.”
The research provides plant breeders with a reliable genetic marker to identify strains of lupin with low alkaloid levels. This will make it easier to consistently grow sweet lupins and may lead to increased cultivation of these high-protein legumes for human consumption.
Currently, narrow-leafed lupin is the most commonly grown variety in Australia due to difficulties in maintaining the sweetness of white lupin and the presence of a fungal disease called lupin anthracnose. However, with the identification of the sweetness gene, there is potential for white lupin to make a comeback in the future.
