Browsing by Subject "Braunrost"

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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.
Wirkung rassenspezifischer Braunrostresistenzen in genetisch diversifizierten Roggenpopulationen
(2004) Wilde, Katinka; Miedaner, Thomas
Leaf rust (Puccinia recondita f.sp. secalis) is the most frequently occuring leaf disease in German winter rye (Secale cereale L.). To test the usefulness and potentially prolong the durability of race-specific resistance genes, we increased host complexity and diversity by producing synthetic (Syn) populations segregating for one to four resistance sources as a model system for hybrid varieties. Thirty synthetics were grown together with three highly susceptible synthetics as checks, two Russian full-sib families (FSF), a leaf-rust-resistant-hybrid variety, a set of 17 differential genotypes and ten parental lines at six locations in three years (17 environments) in Germany under natural infection. The parental lines were only sown in 11 environments. Disease severity of about 120 plants for each synthetic, FSF, hybrid and about 25 plants for each differential genotype and parental line was estimated as percentage of infected leaf area on the leaf below the flag leaf at the mid and the end of the natural epidemic. Susceptible synthetics showed that disease severity was similarly high in all environments. Only two out of 30 synthetics and both FSF were resistant across 17 environments. Low resistance of the synthetic was caused by the low resistance of the parental lines. Nonetheless, some of the synthetics were more resistant than the tested commercial hybrid variety. Even though the resistance was not used in practical breeding programs to date we detected virulence for each resistance gene tested. In conclusion, the German leaf rust population seems to be highly diverse and none of the self-fertile resistance sources used provided full protection. New race-specific resistances or highly effective quantitative resistances are therefore needed and should be combined.