NOXious gases and the unpredictability of emerging plant pathogens under climate change

Abstract

Emerging pathogens of crops threaten food security and are increasingly problematic due to intensive agriculture and high volumes of trade and transport in plants and plant products. The ability to predict pathogen risk to agricultural regions would therefore be valuable. However, predictions are complicated by multi-faceted relationships between crops, their pathogens, and climate change. Climate change is related to industrialization, which has brought not only a rise in greenhouse gas emissions but also an increase in other atmospheric pollutants. Here, we consider the implications of rising levels of reactive nitrogen gases and their manifold interactions with crops and crop diseases.

Fig. 1.

Examples of species affected by EPPs. Clockwise from left: English Elm (Ulmus minor) (photograph by Ptelea [136]), decimated by the “Dutch Elm disease” pathogen, Ophiostoma novo-ulmi; European Ash (Fraxinus excelsior; photograph by Botaurus stellaris [137]), under threat from “Ash dieback” caused by Hymenoscyphus fraxineus; ‘Ōhi’a (Metrosideros polymorpha; photograph by Forest & Kim Starr [138]), threatened by “Rapid ‘Ōhi’a death” due to Cerasystis frimbriata and barley (Hordeum vulgare; photograph by raul.dupagne [139]), the host of Ramularia collo-cygni

Fig. 2.

Schematic representation of some of the interactions between plant nitrogen status and defense signaling. In concert with reactive oxygen species (ROS), NO acts to mediate plant hormone signaling and anti-pathogen defenses. Atmospheric NO₂ can enter leaves and stimulate the production of NO, while abiotic stress interacts with biotic stress signaling via both ROS and NO. In addition, plant nitrogen status can impose restraints on defense signaling when low and promote NO production if high. Factors including root features, soils, and soil ecology that may affect plant nitrogen status are not represented in this figure

Fig. 3.

Schematic representation of the various factors that may impact plant–pathogen interactions via anthropogenic changes in atmospheric composition