Durable resistance in agriculture is difficult to achieve, and in fact most resistance factors that are introduced into crops are effective for fewer than five years. In contrast, resistance polymorphisms in nature often persist for thousands, if not millions, of years. Why are these dynamics so different?
In this work, Talia Karasov with recent members of the Bergelson group and in collaboration with Richard Hudson and Roger Innes investigated how polymorphisms in resistance (R) genes are maintained over long time scales.
Through dissecting a resistance polymorphism in nature the authors show that the complexity inherent in ecological communities is key to its longevity. This suggests that the simplicity of agricultural communities may not be conducive to long-term resistance. Our study highlights the value of understanding natural species interactions for resistance management.
Karasov, T. L., Kniskern, J. M., Gao, L., DeYoung, B. J., Ding, J., Dubiella, U., … & Bergelson, J. (2014). The long-term maintenance of a resistance polymorphism through diffuse interactions. Nature, 512(7515), 436-440.
In agriculture, plant resistance to pathogens is typically short-lived, lasting on the order of a few years. In contrast, resistance in natural plant populations seems to persist for millions of years. Why is resistance ephemeral in agriculture, but seemingly indefinite in natural populations? We address this question by studying the coevolution of natural populations of A. thaliana with natural populations of their pathogens using molecular, genomic and ecological techniques.
Our results led us to a hypothesis about what maintains resistance polymorphisms in natural populations: A. thaliana, unlike plants in agriculture, is rarely challenged with one dominant pathogen. Instead, A. thaliana populations are exposed to thousands of microbes, all at low to intermediate abundances, each with different mechanisms of persistence and/or pathogenicity. A. thaliana seems to evolve resistance in response to this diverse microbial community, and not to one pathogen factor. In short, the heterogeneity of the microbial community selects for heterogeneity in resistance traits.