Developing New Way to Engineer Less Susceptible Crop Mixtures

A long-standing agricultural practice is to grow multiple plant varieties in the same field to increase disease resistance, but this can produce unpredictable results.

According to a study by Jean-Benoit Morel and coworkers from the Institut National de Recherche pour l'Agriculture, l'Alimentation et l'Environnement in Montpellier, France, plant-to-plant interactions might very well impart disease immunity in both wheat and rice. The study was published on September 12^th, 2023, in the open access journal PLOS Biology.

Neighbor-Modulated Susceptibility (NMS) arises when healthy, neighboring plants of the same species modify pathogen susceptibility and basal immunity. NMS is not well understood, though. Researchers determined disease susceptibility in 200 pairs of rice and durum wheat varieties in order to assess NMS' potential to limit the spread of plant pathogens.

Researchers chose one set of genotypes made up of selectively bred varieties and another from populations that had not been subjected to modern selection. Fungal foliar pathogens were inoculated into pairs of same-species variety mixtures grown in pots under controlled greenhouse conditions, and disease susceptibility was inspected before any possible pathogen dispersal.

By employing a statistical model, the authors were able to quantitatively measure the significance of NMS and determine the proportional influence of neighboring plants on pathogen susceptibility within varietal mixtures.

Scientists found 23 same-species mixtures (11%), where plant-to-plant interactions influenced disease susceptibility, indicating that Neighbor-Modulated Susceptibility is a common phenomenon. They noticed both positive and negative effects from their neighbors, implying that the outcomes of plant-to-plant interactions can vary. The research has several limitations, including the testing of only two crops, rice and wheat.

Future investigations may incorporate field trials, wherein plants are exposed to a diverse array of outdoor environmental conditions, as opposed to being cultivated within a controlled greenhouse setting.

“These findings open new avenues to develop more sustainable agricultural practices by engineering less susceptible crop mixtures thanks to emergent, but now predictable properties of mixtures. Our study suggests that the indirect effects of plant-plant interactions on pathogen susceptibility could be used to design varietal mixtures with embedded crop protection,” the authors stated.

In animals and in particular herds, it is commonly observed that individuals adjust their functioning according to their neighbors, in a way that benefits the group but not necessarily to each individual. This work shows that such a phenomenon exists in plants, suggesting in that case that plants regulate their immunity at the population level, opening new perspectives for crop and ecology research.”

Jean-Benoit Morel, Institut National de Recherche pour l'Agriculture, l'Alimentation et l'Environnement in Montpellier