New nodule knowledge

Plants are masters of self-defense. They know how to protect themselves from disease. Their internal chemistry has evolved to fight off their most common biological enemies found in nature.

Understanding the process through which plants protect themselves against pathogens gives researchers a tool with which to make the most of these natural defense mechanisms. Recently released research from RWTH Aachen University located in Germany’s Rhine Valley shows that nodulation plays a major role in forming these defense mechanisms.

We have long understood that nodulation is important to plant health. Science has been successful in manipulating nodules for better crop performance, primarily in legumes. The process occurs when nodules on the roots of plants form a symbiotic relationship with nitrogen-fixing bacteria that deliver nutrients to the plant. This process makes legumes an important source of protein for much of the world.

However, Aachen research shows that nodules might have a positive impact on the plant’s microbiome in other ways. The study explored the relationship between nodulation and systemic resistance to disease. Systemic resistance is the process through which plants protect themselves against pathogens.

The study dealt only with pea and Medicago truncatula, a legume native to the Mediterranean. After a powdery mildew attack, nodulation primes these plants to accumulate higher levels of salicylic acid. Salicylic acid is a plant hormone that contributes to defense against biotrophic invaders feeding off the host plants. Biotrophics are parasites that need their host to remain alive.

The research showed that after undergoing nodulation, the plants show a greater resistance to powdery mildew. The scientists hypothesized that this benefit might be directly connected to the increased levels of salicylic acid, said researcher Hannah Kuhn.

“While our work is basic research, it is knowledge that contributes to our understanding of plant defense and plant nutrition, which will be helpful in shaping sustainable agriculture,” says Kuhn.

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