Effects of genotype and environment on the sprouting propensity and other grain characters of wheat (Triticum aestivum L.): a thesis presented in partial fulfilment of the requirements for the degree of Master of Agricultural Science in Plant Science at Massey University

Sprouting damage nay occur when wet weather initiates germination processes in unharvested grain, with subsequent deterioration in breadmaking quality. It is a potential hazard to wheat growing regions throughout the world, e.g. Europe (Olered, 1967; Belderok, 1968), Australia (Moss, et al., 1972) and New Zealand (Sanders, 1974; McEwan, 1976a). Seed dormancy is usually accepted as being related in some way to resistance to sprouting damage (e.g. Belderok, 1968a); that is, dormancy may be associated with lack of catabolic processes in the endosperm (Ching, 1972; Leshem, 1973; Villiers, 1972). Several enzymes initiated during the germination process are involved in the degradation of the starch and protein of the endosperm. These enzymes include alpha-amylase, which break the branch chain amylopectin starch molecules to dextrins and amylases, and beta-amylase which degrade these smaller compounds to low molecular weight dextrins and maltose (Kent-Jones and Amos, 1967; Pyler, 1969). Beta-amylase is present in the sound grain but its activity is restricted, as there are relatively few exo-groups at which this enzyme is capable of hydrolysing (Kent-Jones and Amos, 1967; Pyler, 1969). Alpha-amylase appears a major factor in starch dextrinisation, and levels of this enzyme relate to the degree of sprout damage (Johansson, 1976; Olered, 1967; Moss et al., 1972). Other enzymes may also be involved in early germination, such as proteolytic enzymes (Gordon, 1975; Kruger, 1976). In sprout damaged wheat, the increased level of starch dextrinisation results in an inferior loaf (Olered, 1967; Pyler, 1967; Moss et al., 1972). The loaf is reduced in volume, has a grey and sticky crumb, and a dark crust colour (Olered, 1967; Kent-Jones and Amos, 1968; Pyler, 1969; McDermott, 1971). Sprout damaged grain may also have a lighter bushel or test weight (Ghaderi and Everson, 1971; Fouler and de la Roche, 1975), and lowered milling yield (Belderok, 1968; McEwan, 1959). [From Introduction