Linear Correlation Analysis of Zymoseptoria tritici Aggressiveness with In Vitro Growth Rate.

Zymoseptoria tritici is a globally distributed plant-pathogenic fungus causing Septoria tritici blotch of wheat. In this study, the in vitro growth rates and aggressiveness of 141 genetically distinct isolates sampled from four wheat fields on three continents were assessed to determine the association of these two ecological parameters. Aggressiveness was assessed on two spring wheat cultivars ('Toronit' and 'Greina') in a greenhouse using percentages of leaf area covered by lesions and pycnidia. We found a positive correlation between aggressiveness of pathogen strains on the two cultivars, consistent with a quantitative and host-nonspecific interaction in this pathosystem. We also found a positive correlation between aggressiveness and average growth rate at two temperatures, suggesting that in vitro pathogen growth rate may make a significant contribution to pathogen aggressiveness.