Water use efficiency of sugar beet cultivars (Beta vulgaris L.) susceptible, tolerant or resistant to Heterodera schachtii (Schmidt) in environments with contrasting infestation levels

Heterodera schachtii is an important pest in many European sugar beet growing regions. Yield response to H. schachtii can be highly variable depending on the infestation level, soil properties, weather conditions and the cultivar. This study aimed at evaluating the effects of nematode infestation on sugar and dry matter yield, crop evapotranspiration (ETc) and water use efficiency (WUE) of cultivars being susceptible, tolerant or resistant to H. schachtii. Field experiments were conducted in seven environments (site x year) with contrasting infestation levels located in Northern Germany from 2013 to 2014. Total ETc was estimated using the FAO dual crop coefficient approach. Crop coefficients were calculated for each cultivar and environment and were adjusted to nematode induced variation in crop canopy and soil cover. Differences in ETc between cultivars within environments were considerably smaller than effects among environments. There was no significant correlation between nematode infestation and ETc valid for all environments. Yield of all cultivars decreased linearly with increasing initial nematode infestation with the strongest response in the susceptible cultivar. Yield of the tolerant and the resistant cultivar under nematode infestation was higher than of the susceptible cultivar. Differences in WUE were primarily associated with yield differences and not due to ETc variability. Higher biomass production of the tolerant and the resistant cultivar under nematode infestation was not associated with higher water use. We concluded that differences in ETc between cultivars were negligibly small and do not affect yield formation. (C) 2015 Elsevier B.V. All rights reserved.