Effects of Heat and Water Stress on Malt Quality and Grain Parameters of Schooner Barley Grown in Cabinets

In growth-cabinet experiments heat and water stresses were separately applied to populations of barley plants, cv. Schooner, 17 or 27 days post-anthesis (DPA), after which the mature grain was micromalted and a number of malt quality parameters measured. Water stress at 17 DPA (mid grain-fill) led to decreased grain (1 → 3),(1 → 4)-β-glucan and increased malt extract, (1 → 3),(1 → 4)-β-glucanase, α-amylase and β-amylase, while at 27 DPA (late grain-fill) only extract was increased. Heat stress with maintenance of soil moisture level had no effect on these parameters. Both types of stress reduced yield and grain size. Neither stressed nor unstressed grain showed any dormancy. These findings indicate that the malting performance of Schooner barley is more related to water stress than heat stress. They also suggest that a limited episode of water stress during grain-fill may be beneficial for malting quality.