456 CEREAL CHEMISTRY NONWHEAT GRAINS AND PRODUCTS Patterns of Barley Grain Development in Spain and Scotland and Their Implications for Malting Quality J. S. SWANSTON, 1,2 R. P. ELLIS, 1 A. PEREZ-VENDRELL, 3 J. VOLTAS, 4 and J.-L. MOLINA-CANO 4 ABSTRACT Cereal Chem. 74(4):456–461 To determine whether patterns of grain filling were consistent between seasons and different between sites in northern and southern Europe, the cultivar Troubadour and TR49, a mutant derived from it, were grown, over two seasons, at sites in Scotland and northern Spain. Differences in sowing date and climate were reflected in different patterns of grain filling. Ear emergence in Scottish grown barley occurred around the time when daylight hours were maximal; optimal photosynthesis was the likely explanation for the rapid increase in grain size observed at the Scottish site. Differences between the sites in temperature and rainfall were most evident during the last month of the growing season. In Scot- land, where ripening occurred in cooler, more humid conditions, synthe- sis of hordein and β-glucan followed the pattern of grain filling, reaching a peak at ~600 degree days after anthesis (the product of days after anthesis and average temperature). Levels then remained fairly constant until harvest ripeness was reached. In Spain, levels of hordein and β-glucan rose virtually throughout the growing season. Differences observed at maturity, between Scottish and Spanish grown grain, in total nitrogen and β-glucan levels were due to this accumulation in the later stages of growth. This was accompanied by a major change in the ratio of the con- stituent polypeptides of the storage protein and differences in the relative proportions of soluble and insoluble β-glucan. The genotype TR49 was one of several mutants derived from the cultivar Troubadour, by selection for a faster rate of germina- tion (Molina-Cano et al 1989). Although it was shown to be of superior malting quality when compared with its parent, over a range of Spanish sites (Molina-Cano et al 1993), differences between cultivars were much less than those between diverse environments (Molina-Cano et al 1995, Swanston et al 1995). There were differences between Spanish and Scottish grown grain in β-glucan and nitrogen contents, while the relative proportions of the component polypeptides of the main storage protein also varied (Swanston et al 1993b, Molina-Cano et al 1995). Spanish grown grain showed a more rapid and extensive enzyme synthesis during germination (Swanston et al 1995), which may be associ- ated with the higher levels of β-glucanase detected in the mature grain (Ellis et al, in press). Consequently, although β-glucan con- tent of the endosperm cell walls was higher in Spanish as com- pared to Scottish grown grain, there was a greater degree of β- glucan degradation during malting in the Spanish samples. Cell-wall modification was only a limiting factor in malting of these cultivars when grown in Scotland. These data suggested that not only were environmental effects influencing quality, but that different mechanisms to promote malting quality may be operating in the two diverse environments. Molina-Cano et al (1995) suggested that to use parameters to assess quality in a Spanish environment similar to those used in north- western Europe (i.e., low levels of nitrogen and β-glucan) could be misleading. A new definition would require consideration of the rela- tive amounts of components of both storage protein and cell walls. Morgan and Riggs (1981) suggested that levels of β-glucan, especially soluble β-glucan, were increased in hotter, drier envi- ronments, but their work was restricted to sites within the United Kingdom. In addition, MacNicol et al (1993) suggested that the precise timing of a stress factor, rather than the factor itself, may be the critical determinant of the effect. The same authors also demon- strated that the effect on malting performance may not always be predicted from measurements on grain components, as grain stressed by drought in the late grain-filling period showed no change in β- glucan or nitrogen level, but an increase in hot water extract. Recent studies on effects of heat or drought on malting quality (MacNicol et al 1993, Savin and Nicolas 1996) have made use of controlled environments. One potential problem of this approach is that it cannot take into account any variation in conditions prior to the period of stress that could be experienced by a field crop. For example, the root development of barley sown into a damp seed bed may be different from that occurring under drier condi- tions. This may influence the subsequent response of the crop to an extended period of drought. In this article, we consider two widely diverse sites and include data from contrasting seasons. The aim is to determine whether patterns of grain filling are consistent between seasons and whether these patterns clearly differ between sites in northern and southern Europe. As a result, a clearer understanding of the influ- ence of differing environmental conditions on grain texture and composition and how these affect malting performance may be gained. Such information will be of importance in defining the optimal cultivars and husbandry practices (e.g., sowing date) to ensure the production of good malting quality barley across a wider area of the EU than is possible at present. MATERIALS AND METHODS It had been decided to investigate the changes occurring during grain filling, as a possible means of understanding the differences between mature grain of the two genotypes Troubadour and TR49. In 1991, these genotypes, grown in Scotland (Swanston et al 1993a), had shown differences in grain size, nitrogen content, and milling energy, a measure of the mechanical energy required to disrupt the endosperm structure (Allison et al 1979). Differences between the two genotypes in Spain were much less evident (Swanston et al 1993b). In addition, it was possible to determine differences in dor- mancy on grain grown in Scotland (Swanston et al 1993a), so the Scottish site was chosen for a pilot study in 1992. Both genotypes were included in a trial of two replicates, grown at the Scottish Crop Research Institute (SCRI), Dundee. Plots were 2 m long and 1.5 m wide. During the growing season, ears were harvested from the plots, at twice-weekly intervals, and dried as described by Riggs and Gothard (1976). Sampling com- 1 Scottish Crop Research Institute, Invergowrie, Dundee, DD2 5DA, Scotland. 2 Corresponding author, Fax: +44 (0)1382 562426, E-mail: jswans@scri.sari.ac.uk 3 Institut de Reserca i Technologia Agroalimentaries (IRTA), Reus, Spain. 4 Universidad de Lleida /IRTA, Lleida, Spain. Publication no. C-1997-0616-06R. © 1997 by the American Association of Cereal Chemists, Inc.