Host Resistance and Temperature-Dependent Evolution of Aggressiveness in the Plant Pathogen Zymoseptoria tritici

Abstract

Understanding how habitat heterogeneity may affect the evolution of plant pathogens is essential to effectively predict new epidemiological landscapes and manage genetic diversity under changing global climatic conditions. In this study, we explore the effects of habitat heterogeneity, as determined by variation in host resistance and local temperature, on the evolution of Zymoseptoria tritici by comparing the aggressiveness development of five Z. tritici populations originated from different parts of the world on two wheat cultivars varying in resistance to the pathogen. Our results show that host resistance plays an important role in the evolution of Z. tritici. The pathogen was under weak, constraining selection on a host with quantitative resistance but under a stronger, directional selection on a susceptible host. This difference is consistent with theoretical expectations that suggest that quantitative resistance may slow down the evolution of pathogens and therefore be more durable. Our results also show that local temperature interacts with host resistance in influencing the evolution of the pathogen. When infecting a susceptible host, aggressiveness development of Z. tritici was negatively correlated to temperatures of the original collection sites, suggesting a trade-off between the pathogen’s abilities of adapting to higher temperature and causing disease and global warming may have a negative effect on the evolution of pathogens. The finding that no such relationship was detected when the pathogen infected the partially resistant cultivars indicates the evolution of pathogens in quantitatively resistant hosts is less influenced by environments than in susceptible hosts.

In Vitro and In Planta Studies on Temperature Adaptation of Exserohilum turcicum Isolates from Maize in Europe and South America

“…Under controlled conditions, fungal vigor and disease components were most influenced by temperature, which was responsible for the highest variance. In most pathosystems, an increase in temperature is positively associated with aggressiveness [ 32 , 33 ]. As environmental conditions and host genotype usually strongly correlate with disease [ 34 ], the host genotype factor with three levels (reference line B37, susceptible line Sus1, and the hybrid Niklas ® ) was included in the experimental design.…”

Mechanistic models to meet the challenge of climate change in plant–pathogen systems

“…One way that this question has been approached has been to collect pathogens from different climates and compare their genetic variation for infectivity against a common set of host genotypes. At a continental scale, Chen et al [88] compared aggressiveness of Zymoseptoria tritici from five wheat populations spread across three continents on two different cultivars of wheat. They found that pathogen populations from warmer climates had lower lesion growth on a susceptible wheat cultivar than populations from warmer climates, but did not differ in lesion growth on a more resistant wheat cultivar.…”

Climate change and disease in plant communities

“…Less consideration has been given to the eco-evolutionary consequences of climate change for crops and pathogens. In areas where changes favor the pathogen, genetic change in invasive traits such as aggressiveness (and/or infectivity), fungicide sensitivity, and eco-niche breadth and preference [ 5 , 8 , 9 ] can occur rapidly. Equally, there is evidence supporting the possibility of genetically based temperature adaptation [ 10 ] that may make the prospect of expansion of a pathogen’s geographic range more concerning.…”