Browsing by Person "Miedaner, T."

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Breeding progress of disease resistance and impact of disease severity under natural infections in winter wheat variety trials
(2021) Laidig, F.; Feike, T.; Hadasch, S.; Rentel, D.; Klocke, B.; Miedaner, T.; Piepho, H. P.
Key message: Breeding progress of resistance to fungal wheat diseases and impact of disease severity on yield reduction in long-term variety trials under natural infection were estimated by mixed linear regression models. Abstract: This study aimed at quantifying breeding progress achieved in resistance breeding towards varieties with higher yield and lower susceptibility for 6 major diseases, as well as estimating decreasing yields and increasing disease susceptibility of varieties due to ageing effects during the period 1983–2019. A further aim was the prediction of disease-related yield reductions during 2005–2019 by mixed linear regression models using disease severity scores as covariates. For yield and all diseases, overall progress of the fully treated intensity (I2) was considerably higher than for the intensity without fungicides and growth regulators (I1). The disease severity level was considerably reduced during the study period for mildew (MLD), tan spot (DTR) and Septoria nodorum blotch (ear) (SNB) and to a lesser extent for brown (leaf) rust (BNR) and Septoria tritici blotch (STB), however, not for yellow/stripe rust (YLR). Ageing effects increased susceptibility of varieties strongly for BNR and MLD, but were comparatively weak for SNB and DTR. Considerable yield reductions under high disease severity were predicted for STB (−6.6%), BNR (−6.5%) and yellow rust (YLR, −5.8%), but lower reductions for the other diseases. The reduction for resistant vs. highly susceptible varieties under high severity conditions was about halved for BNR and YLR, providing evidence of resistance breeding progress. The empirical evidence on the functional relations between disease severity, variety susceptibility and yield reductions based on a large-scale multiple-disease field trial data set in German winter wheat is an important contribution to the ongoing discussion on fungicide use and its environmental impact.
Genome-wide association study for resistances to yellow rust, powdery mildew, and Septoria tritici blotch in cultivated emmer
(2024) Miedaner, T.; Afzal, M.; Longin, C. F.
Emmer is a progenitor of bread wheat and evolved in the Levant together with the yellow rust (YR), powdery mildew (PM) fungi, and a precursor of Zymoseptoria tritici causing Septoria tritici blotch (STB). We performed a genome-wide association mapping for the three disease resistances with 143 cultivated emmer accessions in multi-environmental trials. Significant (P < 0.001) genotypic variation was found with high heritabilities for the resistances to the two biotrophs and a moderate heritability for STB resistance. For YR, PM, and STB severity nine, three, and seven marker-trait associations, respectively, were detected that were significant across all environments. Most of them were of low to moderate effect, but for PM resistance a potentially new major gene was found on chromosome 7AS. Genomic prediction abilities were high throughout for all three resistances (≥ 0.8) and decreased only slightly for YR and PM resistances when the prediction was done for the second year with the first year as training set (≥ 0.7). For STB resistance prediction ability was much lower in this scenario (0.4). Despite this, genomic selection should be advantageous given the large number of small QTLs responsible for quantitative disease resistances. A challenge for the future is to combine these multiple disease resistances with better lodging tolerance and higher grain yield.