A mysterious virus has been identified as the culprit behind a devastating plant disease that blights the lives of many of the world's poorest farmers.
The microbe, carried by tiny mites, is thought to cause pigeonpea sterility mosaic disease (PSMD), which annually destroys millions of hectares of a crop that provides India with a vital source of protein.
It had managed to evade detection despite 70 years of work to pinpoint the root of the problem.
Teifion Jones, who led the work at the Scottish Crop Research Institute near Dundee, said: "We have discovered that the diseased pigeonpea plants contain an unusual type of virus, and we are now working to characterise the virus and to develop diagnostic tools for its rapid detection."
The research by the Scottish team, working with colleagues at the International Crop Research Institute for the Semi-Arid Tropics in India, is seeking to characterise the virus.
Their work could lead to the creation of disease-resistant varieties of the plant and improve the lives of the farmers who rely on it.
More than 1 billion people worldwide depend on the pigeonpea for much of the protein in their diet, making it one of the most important legumes under cultivation.
Indian subsistence farmers in particular choose to grow the crop because it can withstand drought and high temperature while helping to improve the soil.
However, productivity levels are very low, with 2.6 million tonnes from 3.5 million hectares of land in India, in part because of PSMD.
Dr Jones said: "Our aim is to achieve sustainable pigeonpea production in the Indian subcontinent and improve the working and living conditions and incomes of some of the world's most poor and needy farmers."