Host-pathogen diversity in a wild system: Chondrilla juncea-Puccinia chondrillina

Area of Science:

• Plant pathology
• Evolutionary biology
• Genetics

Background:

• Chondrilla juncea, a clonal composite, coexists with its obligate rust pathogen Puccinia chondrillina.
• Understanding host-pathogen interactions is crucial for managing invasive species and understanding evolutionary dynamics.

Purpose of the Study:

• To determine the resistance structure of a Chondrilla juncea population and the pathotypic structure of its Puccinia chondrillina pathogen population in Turkey.
• To investigate the evidence for a gene-for-gene interaction between this host-pathogen system.

Main Methods:

• Sequential inoculation of 19 Chondrilla juncea host lines with 15 Puccinia chondrillina pathogen isolates.
• Analysis of resistant and susceptible reactions to infer gene-for-gene interactions.
• Detection and characterization of pathogen pathotypes and host resistance phenotypes.

Main Results:

• Seven distinct pathotypes of Puccinia chondrillina were identified, with one dominant type (53%) and a second (13%).
• The Chondrilla juncea population exhibited eight resistance phenotypes, with most represented by single host lines.
• Congruence between host resistance and isozyme phenotypes was moderate (58%), despite clonal host reproduction.
• Pathotypes from other populations differed significantly, with no clear geographic relationship to host attack patterns.

Conclusions:

• The study provides strong circumstantial evidence for a gene-for-gene interaction between Chondrilla juncea and Puccinia chondrillina.
• Despite clonal reproduction in the host, significant diversity exists in both host resistance and pathogen virulence.
• Pathogen populations show considerable variation across different geographic locations, suggesting complex evolutionary trajectories.