Loss of , Located on a Supernumerary Chromosome, Is Associated with Parasitic Specialization of on Wheat.

, a blast fungus of gramineous plants, is composed of various host genus-specific pathotypes. The avirulence of an isolate on wheat is conditioned by and . We isolated the third avirulence gene from the isolate and designated it as . was effective as an avirulence gene only at the seedling stage or on leaves. homologs were widely distributed in a subpopulation of the pathotype and the pathotype but completely absent in the pathotype (the wheat blast fungus). The homolog found in the pathotype was one of the five genes involved in its avirulence on wheat. A comparative analysis of distribution of and the other two genes previously identified in the pathotype suggested that, in the course of parasitic specialization toward the wheat blast fungus, a common ancestor of the , , , and pathotypes first lost , secondly , and, finally, the function of . or its homologs were located on core chromosomes in and isolates but on supernumerary chromosomes in and isolates. This is an example of interchromosomal translocations of effector genes between core and supernumerary chromosomes. [Formula: see text] Copyright © 2023 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.