“Our objective is to increase the resiliency and food security of sorghum farmers and consumers in Ethiopia and West Africa. Dr. Mengiste’s novel proposal to improve host-plant resistance against crippling diseases endemic to sorghum in humid lowland areas of western Ethiopia will serve the broader sorghum development community and is a flagship global public good characteristic of the U.S. land grant mission. Apart from planting new seeds, the farm cost to this innovation is negligible," says Dr. Timothy Dalton, director of SMIL.

“This new variety, the Merera variety, has multiple benefits including resistance to pathogens, birds and, above all, better yields than the current varieties Ethiopian farmers have. With these improved traits and yield potential, it can mean a better livelihood for them,” says Dr. Mengiste.

One of the most significant of these pathogens, Anthracnose, attacks all parts of the plant – leaves, stalk and head. It leaves nothing that can be used for food, the primary sorghum use in Africa; or biofuels and animal feed, the primary sorghum use in the United States. The research focused on a genomics approach to mapping genes and exploring more than 2,000 Ethiopian sorghum germplasm through multiple location field trials over many years.

The newly discovered gene, named Anthracnose Resistance Gene1, or ARG1, is unique, according to Dr. Mengiste.

“Although some natural resistance to fungal disease was known in sorghum, genes that confer widespread resistance have not been identified,” he said. “It is remarkable that a single gene leads to resistance across a broad spectrum of fungi and multiple strains of the Anthracnose fungus.”

The regulation of the gene also is unusual. It is embedded in a second gene, and both genes appear to have been altered by small stretches of mobile DNA called transposable elements. “The gene in which ARG1 is embedded is an antisense RNA. Its expression is opposite to ARG1, which results in a situation where the two could interfere with each other,” said Damon Lisch, associate professor of botany and plant pathology at Purdue University who was involved in the research.

“All sorghum plants have some version of these two genes, but susceptible varieties of sorghum express a lot of the antisense RNA and very little of ARG1, which also appears to encode a nonfunctional protein,” he said. The disease-resistant version of ARG1 is expressed at a much higher level, encodes a functional protein, and is associated with an antisense RNA gene that is turned down, resulting in less interference.

“Insertion of transposable elements is often harmful,” he said. “However, in this case, it appears that the transposable elements have been beneficial by ‘reprogramming’ both genes to optimize resistance to fungal pathogens. In a way, it has fixed a broken system in the plants.”

“Transposable elements are known to be involved in some human and plant diseases, but their involvement in disease resistance is considered uncommon – for now,” he said. “With technological advancements, we are able to spot these parasitic strands of DNA within a gene sequence, and we are finding them everywhere. The genome is really an exciting ecosystem, and there is much more to discover within it.”