Effect of Triazole and Strobilurin fungicides on seed yield and grain quality of winter rapeseed (Brassica napus L.)
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Field experiments with rapeseed (Brassica napus L.) were carried out from 2007 to 2010 to clarify the effects of triazole and strobilurin fungicides on seed yield and its components as well as on grain quality of the crop under different growing conditions. The field experiments were conducted at the experimental stations in Giessen (silt clay soil) and Rauischholzhausen (loess soil). Three types of field experiments were carried out: 1. fungicides/growth regulator in combination with two cultivars (two experiments), 2. fungicides in combination with nitrogen (four experiments) and 3. sulphur fertilization in combination with fungicides (three experiments). The used triazole and strobilurin fungicides and the trinexapac growth regulator were applied in different combinations at three different growth stages of winter rapeseed. Morphological and physiological data including seeds/pod, pods/plant, pod length, primary and secondary branches per plant, plant height and leaf area index (LAI) were collected. Incidence of diseases and lodging was assessed. Oil content, fatty acid profile, protein content, content of glucosinolates and free fatty acids as well as peroxide values were analyzed as quality parameters. All collected data were statistically analyzed by statistical package PIAF.Results of the experiments revealed that combined application of triazoles and strobilurins had a marked effect on LAI, largely due to a delay in leaf senescence and thus owing to maintenance of a photosynthetically active area over a longer time. Timings of fungicides had clear effect on plant height and LAI of the plant stand. Plant height was reduced significantly by application of fungicides at BBCH 53 compared with autumn application. Growth regulator Moddus (trinexapac) alone as well as in combination with fungicides increased TGW and improved stem stability by reducing intercalary growth. Morphological parameters (seeds/pod, pods/plant, pod length and primary and secondary branches per plant) of rapeseed were not affected by application of fungicides in all experiments. Combined application of Toprex (paclobutrazole&difenoconazole) and Ortiva (azoxystrobin) increased seed yield due to higher LAI and effectively control of diseases. Caramba (metconazole) and Folicur (tebuconazole) application on its own reduced seed yield relative to their combinations with Ortiva. These triazole fungicides provided disease control to some extent, but suppression of LAI and plant height presumably explained much of the seed yield reduction which they caused.Within seed quality parameters of rapeseed, oil content was enhanced by application of Ortiva in combination with other triazole fungicides by prolonging duration for seed filling. The increase of nitrogen fertilization enhanced protein content and decreased the oil content of the seeds. Significant interaction between fungicides and nitrogen was found regarding oil content. Carax (metconazole&mepiqua chloride) included treatments in combination with lower level of nitrogen increased oil content in comparison with other treatments. Fungicides did not alter protein content significantly in most field experiments. Cultivar NK Fair exhibited significantly higher oil, protein and oleic acid contents in comparison with cv. Elektra. Sulphur application enhanced protein percentage but had no effect on oil content. Application of Moddus at BBCH 53 alone as well as in combination with fungicides somehow reduced glucosinolates in all experiments. Fungicides did not exceed the values of free fatty acids and peroxides at such hazardous limits. Wet weather conditions and severe lodging near to maturity also contributed to influence free fatty acids and peroxides in the oil of rapeseed. The proportion of oleic acid was unaffected, while polyunsaturated fatty acids (linoleic and linolenic acid) were affected significantly by the application of fungicides in most experiments. Oleic acid showed a positive correlation with oil content and it was negatively correlated with polyunsaturated fatty acids. Generally it can be concluded that application of triazole and strobilurin fungicides may have various effects on winter rapeseed physiology by increasing leaf area index and modifying the optimal upright canopy. Plants which are applied with these fungicides are less susceptible to lodging, and characterized by delayed leaf senescence which promoted the light interception of plant stand. Triazole and strobilurin fungicide combinations have the potential to improve several growth parameters which limit the yield of winter rapeseed. The use of fungicides prevented a considerable loss in yield, but had no deleterious effect on oil quality.Verknüpfung zu Publikationen oder weiteren Datensätzen
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Giessen : VVB Laufersweiler