Specific adaptation by Mycosphaerella graminicola to a resistant wheat cultivar

Abstract

Three cultivars of winter bread wheat (Gene, Madsen and Stephens) were each inoculated as seedlings in the greenhouse with seven or eight individual isolates of Mycosphaerella graminicola collected in 1997 from each of the same cultivars in the field. Isolates collected from Gene were virulent to all three cultivars, while isolates obtained from Madsen and Stephens were virulent to those two cultivars and, in all but one case, avirulent to Gene. At its release in 1992, Gene was resistant to M. graminicola, as indicated by both field observations and greenhouse tests, but by 1995 its resistance had substantially deteriorated. This indicated that its resistance was vertical (sensu Vanderplank) or race-specific, and that commercial cultivation of Gene rapidly selected for strains in the local M. graminicola population that were specifically adapted to overcome its resistance.

Chromosomal location of a race-specific resistance gene to Mycosphaerella graminicola in the spring wheat ST6

“…It is unknown whether other Stb genes (Stb1, Stb2, Stb3, Stb4 and Stb5) are involved in gene-for-gene interactions. The breakdown of septoria tritici blotch resistance in Australia, Israel and the USA (Eyal et al 1973;Ballantyne and Thomson 1995;Cowger et al 2000) is also consistent with a gene-for-gene interaction and underlines the need for an improved understanding of this pathosystem.…”

Few Mendelian Genes Underlie the Quantitative Response of a Forest Tree, Eucalyptus globulus, to a Natural Fungal Epidemic

“…The literature abounds with examples from crop plants (e.g., Cowger et al 2000;Talukder et al 2004) and forest trees such as poplar (e.g., Pinon 1995;Frey et al 2005) of breeding programs concentrating on selection for major genes controlling qualitative race-specific resistance, only for the pathogen to evolve new virulent types, resulting in the resistance being overcome. However, although the genetic basis of durable resistance is not fully understood, it is believed that durable host resistance is often conferred by minor genes (Newcombe 1998).…”

The Genomes of Mycosphaerella graminicola and M. fijiensis

“…However, tightly linked molecular markers have not been available until very recently, so relatively few resistance genes have been used in wheat breeding programs. Those that have been used often break down rapidly (Cowger et al 2000) and have a limited efficacy, except for Stb16 (Tabib Ghaffary et al 2012). Thus, deployment of single, major genes for resistance is not likely to be an effective strategy for long-term disease management.…”