Seasonal climate effects on root colour and compounds of red radish

‘Nevadar’ radishes were grown throughout the year. Climate parameters (mean temperature, mean irradiation) and quality characteristics of radishes fulfilling consumer quality requirements, such as root colour, glucosinolates, monosaccharides and pectic substances, were determined. The quality characteristics strongly differed depending on the seasonal climate conditions. The seasonal dependence ranged from a slight climate influence (alkenyl glucosinolates r2 = 0.23), over a moderate climate effect (indolyl glucosinolates r2 = 0.40, glucose r2 = 0.50) up to a strongly distinctive climate influence (hue angle r2 = 0.77, chroma r2 = 0.72, fructose r2 = 0.81, pectic substances r2 = 0.99). Therefore, according to consumer-oriented quality production of radish, the temperature and irradiation influence should be taken into account in the production process. Recommendations for quality production of radish will be the selection of bright red cultivars marked by a high photosynthetic capacity (yield > 0.80 mV) at relatively low mean irradiation intensities (50–100 µmol m2 s−1) and lower mean temperatures (11–13 °C). Thus sufficient photochemical energy can be provided for the synthesis of quality-determining compounds. For the production of bioactive radishes showing particularly relatively high contents of indolyl glucosinolates, cultivation should be carried out in spring and autumn. In summer cultivation, consumer preferences in taste can particularly be satisfied with the desired contents of alkenyl glucosinolates and monosaccharides.