Scientists at the U.S. Department of Agriculture Agricultural Research Service (USDA ARS) and Purdue University have discovered a gene in sorghum that could help fortify the crop's defense against anthracnose, a disease that could reduce yields by up to 50 percent. The discovery could lead to the development of disease-resistant sorghum cultivars that are less reliant on fungicides.
Besides being a food crop, sorghum is also used as forage for livestock and materials for bio-based energy. However, anthracnose attacks all parts of a susceptible sorghum cultivar, and genetic-based disease resistance is the most effective and sustainable approach to fighting the disease. According to Matthew Helm, a research molecular biologist at ARS's Crop Production and Pest Control Research Unit in West Lafayette, Indiana, how this resistance actually works in sorghum is poorly understood, and this knowledge gap is worrisome because of the genetic variability among different types of the anthracnose fungus and their potential to overcome a cultivar's resistance genes over time. Anthracnose resistance can also be temperature-dependent, and crops could be vulnerable to infection in high temperatures.
Helm and a team of scientists at Purdue University led by Demeke Mewa have begun to close this gap. They identified a disease resistance gene known as "ANTHRACNOSE RESISTANCE GENE 2" (ARG2) that orchestrates a series of defense responses to early anthracnose infection, preventing its spread to the rest of the plant and grain heads. Sorghum plants carrying ARG2 successfully withstood the fungus even when greenhouse temperatures were increased to 100°F (38°C). The team also determined that ARG2 encodes for a protein in the plasma membrane of resistant sorghum cells, acting like an intruder alert triggered by certain proteins used by the anthracnose fungus to infect the plant. ARG2 does not protect sorghum from all types of anthracnose, but combined with other similar genes could help broaden the protection through convenional or biotechnological breeding methods.

Strengthening Sorghum Against a Worldwide Fungal Threat : USDA ARS