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Spelt products are popular with consumers achieving higher market prizes, making them susceptible to food adulteration with less valuable cereals. To facilitate product control, a recently developed duplex droplet digital PCR method enables the detection and quantification of common wheat (Triticum aestivum) contaminations in food products made from spelt (Triticum spelta). The duplex droplet digital PCR assay targets the γ-gliadin gene and the Q-locus of both subspecies. In this study, the method was validated in an interlaboratory ring trial involving 11 participating laboratories. Test materials containing defined proportions of spelt and common wheat were prepared and tested. The ring trial procedure included DNA extraction of the test samples and determination of subspecies proportions using droplet digital PCR. Results from the ring trial confirmed the method's capability for specific detection and quantification of common wheat in spelt, with acceptable relative measurement uncertainties, and without requiring reference material for calibration. To our knowledge, this is the first interlaboratory validation of a digital PCR method for species differentiation in food.

Thermal reaction norms for growth rates of six Emiliania huxleyiisolates originating from the central Atlantic (Azores, Portugal) and five isolates from the coastal North Atlantic (Bergen, Norway) were assessed. We used the template mode of variation model to decompose variations in growth rates into modes of biological interest: vertical shift, horizontal shift, and generalist—specialist variation. In line with the actual habitat conditions, isolates from Bergen (Bergen population) grew well at lower temperatures, and isolates from the Azores (Azores population) performed better at higher temperatures. The optimum growth temperature of the Azores population was significantly higher than that of the Bergen population. Neutral genetic differentiation was found between populations by microsatellite analysis. These findings indicate that E. huxleyipopulations are adapted to local temperature regimes. Next to between‐population variation, we also found variation within populations. Genotype‐by‐environment interactions resulted in the most pronounced phenotypic differences when isolates were exposed to temperatures outside the range they naturally encounter. Variation in thermal reaction norms between and within populations emphasizes the importance of using more than one isolate when studying the consequences of global change on marine phytoplankton. Phenotypic plasticity and standing genetic variation will be important in determining the potential of natural E. huxleyipopulations to cope with global climate change.