Genetics of resistance to Zymoseptoria tritici and applications to wheat breeding
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This paper reviews current knowledge about genes for resistance to Septoria tritici blotch (STB) of wheat, caused by Zymoseptoria tritici (formerly Mycosphaerella graminicola). These genes can be placed into two classes, although a few may have characteristics of both classes. Qualitative resistance is controlled by genes which control large fractions of genetic variation, 21 of which have been discovered and mapped so far. Most of them have been shown to be genotype-specific, being effective against the minority of Z. tritici isolates which are avirulent, and Stb6 has been shown to control a gene-for-gene relationship. Most qualitative resistances are unlikely to be durable and some formerly effective genes have been overcome by the evolution of pathogen virulence. Quantitative resistance is generally controlled by genes with small-to-moderate effects on STB. They have generally weaker specificity than qualitative genes and have provided more durable resistance. 89 genome regions carrying quantitative trait loci (QTL) or meta-QTL have been identified to date. Some QTL have been mapped at or near loci of qualitative genes, especially Stb6, which is present in several sources of resistance. Another gene of particular interest is Stb16q, which has been effective against all Z. tritici isolates tested so far. In addition to resistance, the susceptibility of wheat cultivars to STB can also be reduced by disease escape traits, some of which may be undesirable in breeding. The fundamental requirements for breeding for STB-resistance are genetic diversity for resistance in wheat germplasm and a field trial site at which STB epidemics occur regularly and effective selection can be conducted for resistance combined with other desirable traits. If these are in place, knowledge of resistance genes can be applied to improving control of STB.Keywords:
Mycosphaerella graminicola
Germ plasm
Pseudothecia of Mycosphaerella graminicola , the teleomorph of Septoria tritici , were observed on wheat debris in France for the first time during autumn 1994. The colonies and conidia, derived from ascospores isolated by micromanipulation, conform to previously published data.
Mycosphaerella graminicola
Mycosphaerella
Graminicola
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Mycosphaerella graminicola
Graminicola
Strobilurin
Mycosphaerella
Fungal pathogen
Host resistance
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The Dothideomycete fungus Zymoseptoria tritici (previously known as Mycosphaerella graminicola and Septoria tritici) is the causative agent of Septoria tritici leaf blotch (STB) disease of wheat (Triticum aestivum L.). In Europe, STB is the most economically damaging disease of wheat, with an estimated ∼€1 billion per year in fungicide expenditure directed toward its control. Here, an overview of our current understanding of the molecular events that occur during Z. tritici infection of wheat leaves is presented. On the host side, this includes the contribution of (1) the pathogen-associated molecular pattern-triggered immunity (PTI) layer of plant defense, and (2) major Stb loci for resistance against Z. tritici. On the pathogen side of the interaction, we consolidate evidence from recent bioinformatic, transcriptomic and proteomic studies that begin to explain the contribution of Z. tritici effector proteins to the biphasic lifestyle of the fungus. This includes the discovery of chitin-binding proteins in the Z. tritici secretome, which contribute to evasion of immune surveillance by this pathogen, and the possible existence of 'necrotrophic' effectors from Z. tritici, which may actively stimulate host recognition in a manner similar to related necrotrophic fungal pathogens. We finish by speculating on how some of these recent fundamental discoveries might be harnessed to help improve resistance to STB in the world's second largest food crop.
Mycosphaerella graminicola
Graminicola
Mycosphaerella
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Mycosphaerella graminicola
Mycosphaerella
Graminicola
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Mycosphaerella graminicola
Mycosphaerella
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Isolate‐specific resistance of 71 cultivars and breeding lines of wheat ( Triticum aestivum ) to septoria tritici blotch was evaluated in six field trials in the Netherlands, Switzerland and the UK between 1995 and 1997. Each plot was inoculated with one of six single‐pycnidium isolates of the pathogen Mycosphaerella graminicola . There were strong interactions between wheat lines and M. graminicola and the line‐by‐isolate interactions were stable over the six trials. Lines with specific resistance or specific susceptibility to each of the isolates were identified. Specific resistance to isolate IPO323 was especially common, being carried by 22 lines from 10 countries. The results confirm that line‐by‐isolate interactions in septoria tritici blotch of wheat are effective in adult plants in field conditions, and are not simply confined to seedlings. Wheat lines with good, quantitative resistance to all or most isolates were identified, including lines from Brazil, the USA and seven European countries. These may be useful as sources of resistance in wheat breeding.
Mycosphaerella graminicola
Graminicola
Mycosphaerella
Common wheat
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Abstract There has been a recent rapid decline in the efficacy of some, but not all, azole fungicides in controlling the Septoria leaf blotch pathogen of wheat, Mycosphaerella graminicola . Hans J. Cools and Bart A. Fraaije ask the question: can widespread resistance to all azoles develop in this pathogen? Copyright © 2008 Society of Chemical Industry
Mycosphaerella graminicola
Mycosphaerella
Azole
Graminicola
Fungal pathogen
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Mycosphaerella graminicola
Mycosphaerella
Graminicola
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