Heat stress is a main threat to current and future global maize production. Adaptation of maize to future warmer conditions requires improving our understanding of crop responses to elevated temperatures. For this purpose, the same short-season (FAO 300) maize hybrid PR37N01 was grown over three years of field experiments on three contrasting Spanish locations in terms of temperature regime. The information complemented three years of greenhouse experiments with the same hybrid, applying heat treatments at various critical moments of the crop cycle. Crop phenology, growth, grain yield, and yield components were monitored. An optimized beta function improved the calculation of thermal time compared to the linear-cutoff estimator with base and optimum temperatures of 8 and 34 °C, respectively. Our results showed that warmer temperatures accelerate development rate resulting in shorter vegetative and reproductive phases (ca. 30 days for the whole cycle). Heat stress did not cause silking delay in relation to anthesis (extended anthesis-silking interval), at least in the range of temperatures (maximum temperature up to 42.9 °C in the field and up to 52.5 °C in the greenhouse) considered in this study. Our results indicated that maize grain yield is reduced under heat stress mainly via pollen viability that in turn determines kernel 2 number, although a smaller but significant effect of the female component has been also detected.

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Comparative performance tests of perennial grasses for biomass yield, quality, and soil nutrient removal are needed to guide decisions toward meeting European Union targets for renewable energy production. We compared hybrid miscanthus (Miscanthus × giganteus Greef and Deuter ex Hodkinson and Renvoize) and switchgrass (Panicum virgatum L.) cultivars Cave-in-Rock, (upland type), Alamo, and Kanlow (lowland types) for biomass yield and changes in soil macronutrient levels and removal rates in a humid Spanish environment. Soil and plant nutrient and C levels were measured aft er each annual biomass harvest for 4 yr. Plant nutrient concentrations were multiplied by biomass yield to express nutrient removal. Yield ranking (4-yr mean) was miscanthus (17.6 Mg ha -1 ) > Kanlow (13.3 Mg ha -1 ) = Alamo (13.0 Mg ha -1 ) > Cave-in-Rock (7.7 Mg ha -1 ). Miscanthus biomass yield peaked in the third year at 27.0 Mg ha -1 . Th e high yield of miscanthus together with its relatively low macronutrient concentrations and intermediate removal rates, indicate its advantages over switchgrass as a biomass crop choice. Alamo and Kanlow usually removed more macronutrients than Cavein-Rock, suggesting a greater long-term fertilizer requirement for the lowland types. Soil C stocks increased by a mean of 2850 kg ha -1 over 4 yr at 0-to 20-cm depth. Phosphorus was the macronutrient most likely to become defi cient aft er repeated harvests. Miscanthus and lowland switchgrass cultivars performed well in the Atlantic maritime region of Spain, therefore the choice of crop would rely on economics of establishment and long-term stand maintenance.

Colonial bentgrass (Agrostis capillaris L.) is a potential source for genetic improvement of resistance to environmental stress and disease for other bentgrass species (Agrostis spp.). To conserve and study the existing genetic resources of colonial bentgrass for use in breeding, genetic diversity was investigated using amplified fragment length polymorphism (AFLP) markers. Included in this study were 22 accessions from US Department of Agriculture germplasm collected from 11 countries, in conjunction with 14 accessions from northern Spain and 3 commercial cultivars. Ten EcoRI-MseI and 6 PstI-MseI AFLP primer combinations produced 181 and 128 informative polymorphic bands, respectively. Cluster analysis of genetic similarity estimates revealed a high level of diversity in colonial bentgrass species with averages of 0.51 (EcoRI-MseI) and 0.63 (PstI-MseI). Greater genetic diversity was detected by the EcoRI-MseI AFLP primer combinations. A low but significant positive correlation (r = 0.44, p = 0.0099) between the 2 Jaccard similarity matrices was obtained by the Mantel test. Commercial cultivars of bentgrass showed a narrow genetic background. The assessment of genetic diversity among colonial bentgrass accessions suggested the potential value of the colonial bentgrass germplasm in turfgrass cultivar improvement.

Fifteen accessions of Festuca group rubra collected in northern Spain were characterized and grouped into four Festuca taxa on the basis of leaf anatomy, morphology and ploidy; seven were identified as F. heteromalla; two as F. trichophylla ssp. asperifolia; two as F. nigrescens ssp. microphylla and four as F. rubra ssp.

Fifty-six half-sib families of perennial ryegrass (Lolium perenne), derived from wild populations in Galicia, were examined for the presence of perennial ryegrass endophytes ; 28 were endophyteinfected (Ej) and 28 were endophyte-free (Ek). All families were established in spaced-plant nurseries and trial plots at two locations in Galicia, in 1992. Ej families had a significantly (P 0n05) higher first cut, spring and total yield than Ek families at one location in the third year after planting. At this location, water deficit was about 75 % higher than at the other location in all three years of study. Endophyte did not affect crown rust susceptibility or forage quality (crude protein, water-soluble carbohydrate and in vitro digestibility). Ergovaline alkaloid concentration in the 28 Ej families varied from 0 to 0n55 µg\g dry matter (DM) (mean 0n15), with 14 families containing levels of ergovaline 0n1 µg\g DM. Thus endophyte infection may benefit the host in drought-prone areas of Galicia, with an increased chance of Ej plants being favoured by either natural or artificial selection.

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