Abstract
Key messageWe identified allelic variation at two major loci, QSnb.nmbu-2A.1 and QSnb.nmbu-5A.1, showing consistent and additive effects on SNB field resistance. Validation of QSnb.nmbu-2A.1 across genetic backgrounds further highlights its usefulness for marker-assisted selection.Septoria nodorum blotch (SNB) is a disease of wheat (Triticum aestivum and T. durum) caused by the necrotrophic fungal pathogen Parastagonospora nodorum. SNB resistance is a typical quantitative trait, controlled by multiple quantitative trait loci (QTL) of minor effect. To achieve increased plant resistance, selection for resistance alleles and/or selection against susceptibility alleles must be undertaken. Here, we performed genetic analysis of SNB resistance using an eight-founder German Multiparent Advanced Generation Inter-Cross (MAGIC) population, termed BMWpop. Field trials and greenhouse testing were conducted over three seasons in Norway, with genetic analysis identifying ten SNB resistance QTL. Of these, two QTL were identified over two seasons: QSnb.nmbu-2A.1 on chromosome 2A and QSnb.nmbu-5A.1 on chromosome 5A. The chromosome 2A BMWpop QTL co-located with a robust SNB resistance QTL recently identified in an independent eight-founder MAGIC population constructed using varieties released in the United Kingdom (UK). The validation of this SNB resistance QTL in two independent multi-founder mapping populations, regardless of the differences in genetic background and agricultural environment, highlights the value of this locus in SNB resistance breeding. The second robust QTL identified in the BMWpop, QSnb.nmbu-5A.1, was not identified in the UK MAGIC population. Combining resistance alleles at both loci resulted in additive effects on SNB resistance. Therefore, using marker assisted selection to combine resistance alleles is a promising strategy for improving SNB resistance in wheat breeding. Indeed, the multi-locus haplotypes determined in this study provide markers for efficient tracking of these beneficial alleles in future wheat genetics and breeding activities.
Highlights
Wheat is one of the most important staple food sources worldwide, with gross production valued at around 168 billion US dollars (Food and Agriculture Organization of the1 3 Vol.:(0123456789)Theoretical and Applied Genetics (2021) 134:125–142United Nations 2016)
The objectives of this study were to (1) identify Septoria nodorum blotch (SNB) quantitative trait loci (QTL) in the German BMWpop Multiparent Advanced Generation Inter-Cross (MAGIC) population by both seedling infiltration and field testing and compare these with QTL identified in the United Kingdom (UK) ‘NIAB Elite MAGIC’ population, (2) where phenotypic differences between the BMWpop founders for sensitivity to known P. nodorum effectors or culture filtrate (CF) are identified, phenotypically screen the population to investigate whether sensitivity QTL co-locate with adult plant SNB QTL, and (3) identify haplotypes and determine additive effects at the prioritized QTL that might help future breeding efforts to combine multiple sources of SNB resistance
As neither Plant height (PH) nor days to heading (DH) was significantly correlated with disease severity in 2016, the mean disease severities from 2016 were used directly for both QTL and haplotype analysis, while disease severity data from both 2017 and 2018 were corrected for Genotypes possessing either only the susceptible haplotype 4 at QSnb.nmbu-2A.1/2018 or only the susceptible allele for marker wsnp_Ex_c898_1738424 at QSnb.nmbu-5A.1, were grouped together as carrying one resistant allele
Summary
Wheat is one of the most important staple food sources worldwide, with gross production valued at around 168 billion US dollars (Food and Agriculture Organization of the1 3 Vol.:(0123456789)Theoretical and Applied Genetics (2021) 134:125–142United Nations 2016). Wheat production is threatened by various bacterial, fungal and viral diseases. Parastagonospora nodorum is a devastating fungal pathogen of both bread wheat (Triticum aestivum) and durum wheat (T. durum) with disease epidemics reported in most wheat producing regions with warm and humid growing conditions (Oliver et al 2012; Francki 2013; Ficke et al 2018). Regardless of resistance breeding efforts, no cultivar has shown complete resistance to P. nodorum in the field, and control of SNB still largely depends on fungicide application (Duba et al 2018). Intensive use of fungicides increases the risk of fungicide resistance, and the resulting reduction in available modes of action challenges the effectiveness of future chemical control (Holloman 2015). Research on host genetic resistance is needed in parallel with efforts to find new modes of action for chemical control
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