Abstract
Understanding how fungi specialize on their plant host is crucial for developing sustainable disease control. A traditional, centuries-old rice agro-system of the Yuanyang terraces was used as a model to show that virulence effectors of the rice blast fungus Magnaporthe oryzaeh play a key role in its specialization on locally grown indica or japonica local rice subspecies. Our results have indicated that major differences in several components of basal immunity and effector-triggered immunity of the japonica and indica rice varieties are associated with specialization of M. oryzae. These differences thus play a key role in determining M. oryzae host specificity and may limit the spread of the pathogen within the Yuanyang agro-system. Specifically, the AVR-Pia effector has been identified as a possible determinant of the specialization of M. oryzae to local japonica rice.
Highlights
Understanding the mechanisms determining host range of plant pathogens is crucial for disease management strategies, phytosanitary regulations and policies
We investigated the molecular basis of M. oryzae specialization to its hosts: rice subspecies japonica and indica
We discovered that specialization of M. oryzae isolates to japonica and indica varieties grown in Yuanyang is correlated with, respectively, the deployment of a large number of Avr-effectors in japonica-borne isolates and a large depletion of Avr-effectors in indica-borne isolates
Summary
Understanding the mechanisms determining host range of plant pathogens is crucial for disease management strategies, phytosanitary regulations and policies. Finding durable methods of controlling the host range of pathogens requires the understanding of the molecular and physiological determinants of pathogen variation in fitness across space and hosts (Williams, 2010; Barrett et al, 2008). Before the advent of molecular genetic methods, classical studies in plant pathology have documented patterns of pathogen fitness on different hosts, including pathogenicity (the capacity to infect) and virulence (the quantity of symptoms) (Johnson, 1961; Nadler, 1995; Brown, 1994). Variations in pathogen fitness have been repeatedly investigated for numerous agricultural pathosystems using controlled cross-inoculation experiments or inoculation on series of differential hosts. Higher pathogen fitness on hosts living in the same habitat is consistent with evolutionary theory, which predicts that parasites should be ahead of
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