A Model System for Understanding Host–Pathogen Relationships Through In Vitro Host Mimicry

Abstract In vitro host mimicry provides a method to study host–pathogen interactions without constraints of time, space, or host presence. Monilinia fructicola and M. laxa , pathogens causing brown rot disease, have a narrow host range including some pome and stone fruits. Building on previous in vitro mimicry of the peach host and M. fructicola , this paper confirms that various hosts of both fungal species can be mimicked in vitro , offering insights into host preferences. This study developed mimic media for peach, plum, cherry, and apple hosts, evaluating pathogen preferences based on mycelial growth and the expression levels of two effector genes: cutinase 1 ( CUT1 ) and polygalacturonase 1 ( PG1 ). Isolates with different virulence levels were used to assess aggressiveness effects. Effector genes were significantly expressed in host-mimicking media compared to standard potato dextrose agar. Moreover, host preference with the virulence level. The high-virulent M. fructicola isolates favored peach-based medium, while low-virulent isolates preferred plum-based medium. All M. laxa isolates showed the highest growth on peach-based media and the slowest on cherry-based media. This study showed Monilinia host–pathogen relationships in vitro , and the research approach can be used as a model for necrotrophic fungal pathosystems.