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Two new PCR-based methods were developed to decode prion protein (PrP) gene polymorphisms at codons 136, 154 and 171: a PCR-restriction fragment length polymorphism (RFLP) analysis consisting of two PCR reactions followed by three enzymatic digestions, and a real-time PCR consisting of four reactions with seven fluorogenic probes. Both methods were used to study the distribution of PrP gene polymorphisms in a representative sample (1297 animals) of the populations of the two native breeds of sheep of the Spanish Basque Country, Latxa and Carranzana. Fourteen genotypes were found in the Latxa breed, in which ARQ/ARQ was the genotype most frequently observed (49.3 per cent), followed by ARR/ARQ (32.6 per cent) and ARQ/ARH (5.8 per cent). The genotype associated with the highest resistance to scrapie (ARR/ARR) was present in 5 per cent of the animals analysed. Similar results were observed in the Carranzana sheep.

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In general, plants grown under diffuse light yield higher biomass than those grown under direct light as a result of a more uniform distribution of the light across the plant canopy. We compared the effects of a light-diffusing plastic film and a clear plastic film on growth of Batavia lettuce (Lactuca sativa L.) in two greenhouses during five growth periods. Lettuce grown under the light-diffusing film were smaller (up to 36%) than control plants grown under the clear film, due to the fewer leaves per plant (up to 22%) and lower mean values of individual leaf area (up to 29%). The photosynthetically active radiations use efficiency was sometimes lower (up to 23%) in lettuces grown under the light-diffusing film. The pigment contents tended to be lower in plants grown under the light-diffusing plastic. The total macroelement contents of the lettuces grown under the light-diffusing plastic were up to 10% higher than in the lettuces grown under clear plastic, mainly as a result of higher leaf K contents (up to 19% higher). In addition, use of the light-diffusing plastic tended to increase leaf nitrate contents (by up to 23%). The leaf solid soluble content and acidity values were higher in the lettuces grown under the light-diffusing plastic, while leaf pH values were lower than in the control plants. The findings showed that the light-diffusing plastic was detrimental to production of compact heads of lettuce, and to some quality parameters such as nitrate and pigment contents. Nevertheless, open-leaf cultivars would likely show a different response to the diffuse light Additional key words: diffuse light; Lactuca sativa; light use efficiency; vegetable production.Correspondence should be addressed to Patrick Riga: priga@neiker.eusAbbreviations used: Car (carotenoids); CC (construction cost); dw (dry weight); fw (fresh weight); LUE (light use efficiency); NR (nitrate reductase); PAR (photosynthetically active radiations); PV (photovoltaic solar panel); RH (relative humidity); SLA (specific leaf area); SSC (soluble solids content).