Intraspecific competition among Phytophthora infestans genotypes enhances disease severity and shortens incubation periods, revealing a key driver of virulence evolution. 2. Pathogen strains with higher field frequencies exhibit stronger competitive ability but may cause less severe disease, highlighting a fitness-virulence trade-off. 3. Greater genetic distance between co-infecting strains significantly increases pathogenicity, underscoring the role of genetic diversity in disease development. 4. Crop microbe diversification is proposed to mitigate competitive selection of highly virulent strains and promote sustainable disease management. Competition is a fundamental driver of evolution, shaping species’ adaptive trajectories and ecological dynamics, where interspecific competition influences community structure and niche differentiation, while intraspecific competition plays a critical role in functional development and adaptive evolution, particularly in agroecosystems where competition among pathogen genotypes, combined with host-pathogen interactions, significantly impacts the evolution of virulence. Through laboratory experiments involving single and mixed inoculations, this study investigates intraspecific competition in Phytophthora infestans , the causal agent of late blight in potatoes and tomatoes, to understand the impact of genotype frequency, genetic relatedness, and genetic variation on transmission and pathogenicity. Results revealed that strains with higher field frequencies exhibited greater competitive ability, while increased genotypic complexity and genetic distance between coinfecting strains enhanced disease severity and reduced incubation periods, highlighting the role of intraspecific competition in shaping pathogen evolution and virulence, with implications for disease management. Strategies such as crop diversification, biocontrol agents and microbiome applications are proposed to mitigate the evolution of highly virulent strains and promote sustainable agricultural practices. This study bridges theoretical and empirical insights into competitive interactions, offering a deeper understanding of the mechanisms driving pathogen evolution and their ecological consequences.
Wang et al. (Sun,) studied this question.