Efficacy and mapping of resistance to Mycosphaerella graminicola in wheat

Wheat is the most important food and feed crop, contributing about 19% of the required human dietary energy. The annual growth rate of the global cereal production -including wheat- is below one per cent. This is due to biotic and biotic constraints – including diseases – such that production falls short of meeting future food demands. Thus more wheat should be produced and the best way to achieve that is to produce and release cultivars with better disease resistance. Septoria tritici blotch (STB) is Europe’s major foliar wheat disease and is caused by the fungus Mycosphaerella graminicola that reduces yields to at least 50% under conducive conditions. STB management relies mostly on chemical control, but the continuously increasing incidence of fungicide resistant strains in fungal populations has resulted in a growing awareness of the importance of host resistance. However, the number of identified resistance genes to STB is very low compared to the number of known resistance genes for other wheat diseases. Moreover, these genes are not very effective and therefore of limited practical value. The aim of this research was to discover new genes for resistance and to develop tools facilitating their deployment in modern breeding programs. Three new resistance genes were detected on chromosomes 3DL, 5AL and 6DS that were designated as Stb16, Stb17 and Stb18, respectively. Stb17 was only expressed in adult plants, which is new for this disease, Stb18 is effective to a limited suite of isolates, but Stb16 has an extremely broad resistance that is of great interest to the commercial breeding industry. However, the impact of an individual gene depends strongly of the genetic make-up of a cultivar. Along with improved testing protocols these results are important for the successful commercial deployment of Stb genes in European wheat breeding programs.</p

Identification of a new resistance gene to septoria tritici blotch in wheat

Door het screenen van lijnen en wilde verwanten van tarwe, is een nieuw resistentiegen tegen STB (Septoria tritici blotch) gevonden

Unraveling and exploitation of diversity for resistance to Mycosphaerella graminicola and Fusarium graminearum in wheat and its progenitors

La fusariose et la septoriose sont deux maladies très dommageables (chute de rendement, toxicité) pour le blé. Il est important d'identifier de nouvelles sources de résistance efficaces contre des isolats de septoriose très virulents et contre la fusariose Fusarium graminearum (majoritairement présente en France). Ainsi, ce projet nous a permis d'identifier de nouvelles sources de résistance à la fusariose et à la septoriose. Parmi celles-ci, les plus intéressantes ont été retenues pour être les parents de nouvelles populations (HD) d'étude. Parallèlement, une population de 235 lignées HD Apache/Balance (ApBa) a été étudiée pour identifier des QTL de résistance à la fusariose qui offrent la possibilité au sélectionneur d'identifier plus efficacement, dans leur matériel, les caractères de résistance issus d'Apach

Finding more resistance sources to septoria tritici blotch of wheat

Bijdrage aan de KNVP-voorjaarsvergaderin

The genetic architecture of seedling resistance to Septoria tritici blotch in the winter wheat doubled-haploid population Solitär × Mazurka

Breeding for resistance to Septoria tritici blotch (STB), caused by Mycosphaerella graminicola (anamorph: Septoria tritici), is an essential component in controlling this important foliar disease of wheat. Inheritance of seedling resistance to seven worldwide pathogen isolates has been studied in a doubled-haploid (DH) population derived from a cross between the field resistant cultivar Solitär and the susceptible cultivar Mazurka. Multiple quantitative trait locus (QTL) mapping revealed major and minor genetic effects on resistance as well as several epistatic relationships in the seedling stage. Solitär conferred resistance to isolate IPO323, governed by Stb6 on chromosome 3A, as well as to IPO99015, IPO92034, Hu1 and Hu2 controlled by a QTL on chromosome arm 1BS, possibly corresponding to Stb11 and minor QTL on chromosomes 1B, 3D, 6B and 7D. Resistance of Mazurka to IPO90015 and BBA22 was caused by a QTL located in a region on 4AL which harbours Stb7 or Stb12. QTL specific to pycnidial coverage on 3B and specific to necrosis on 1A could be discovered for isolate IPO92034. Pairwise epistatic interactions were reliably detected with five isolates. Although their contributions to the total variance are generally low, the genotypic effect of the QTL by QTL interaction of 4AL (Stb7 or Stb12) and 3AS (Stb6) made up almost 15% of disease expression. Altogether, the results suggest a complex inheritance of resistance to STB in the seedling stage in terms of isolate-specificity and resistance mechanisms, which have implications for marker-assisted breeding in an attempt to pyramid STB resistance genes

Association mapping and meta-analysis: two complementary approaches for the detection of reliable Septoria tritici blotch quantitative resistance in bread wheat (Triticum aestivum L.)

Septoria tritici blotch (STB), caused by the ascomycete Mycosphaerella graminicola, is one of the most ubiquitous and important diseases of bread wheat worldwide. The aim of this study was to identify markers linked to loci conferring resistance to STB from seven biparental populations. Linkage analysis, meta-analysis and association mapping were combined to identify robust quantitative trait loci (QTLs) for resistance. Linkage analysis led to the detection of 115 QTLs for resistance to STB and 66 QTLs linked to plant height and/or earliness. Meta-analysis clustered these 115 QTLs into 27 Meta-QTLs (MQTLs) of pathogen resistance, of which 14 were found to be linked to plant height and/or earliness. Both the relationship between dwarfing and susceptibility to STB and the significant negative correlation between earliness and STB symptoms were confirmed. Eleven loci were linked to STB resistance by association mapping using a general linear model and/or a mixed linear model, of which eight co-located with STB MQTLs and two co-located with individual QTLs. Associated markers located in MQTL regions enhanced the relevance of the results and validated the potential of an association mapping approach. With several biparental populations, meta-analysis is the most relevant form of genetic analysis study, but association mapping can be used as a validation method. Regions linked to resistance in both methods should be relevant for use in breeding programs for improving resistance to STB in wheat varieties. The main interest in comparing both approaches is to detect robust loci that will be functional in many genetic backgrounds rather than just in one or a few specific background

FPLC and liquid-chromatography mass spectrometry identify candidate necrosis-inducing proteins from culture filtrates of the fungal wheat pathogen Zymoseptoria tritici

Culture filtrates (CFs) of the fungal wheat pathogen Zymoseptoria tritici were assayed for necrosis-inducing activity after infiltration in leaves of various wheat cultivars. Active fractions were partially purified and characterized. The necrosis-inducing factors in CFs are proteinaceous, heat stable and their necrosis-inducing activity is temperature and light dependent. The in planta activity of CFs was tested by a time series of proteinase K (PK) co-infiltrations, which was unable to affect activity 30min after CF infiltrations. This suggests that the necrosis inducing proteins (NIPs) are either absent from the apoplast and likely actively transported into mesophyll cells or protected from the protease by association with a receptor. Alternatively, plant cell death signaling pathways might be fully engaged during the first 30min and cannot be reversed even after PK treatment. Further fractionation of the CFs with the highest necrosis-inducing activity involved fast performance liquid chromatography, SDS-PAGE and mass spectrometry. This revealed that most of the proteins present in the fractions have not been described before. The two most prominent ZtNIP encoding candidates were heterologously expressed in Pichia pastoris and subsequent infiltration assays showed their differential activity in a range of wheat cultivars