SELECTION AGAINST SPROUTING DAMAGE IN WHEAT .2. HARVEST RIPENESS, GRAIN MATURITY AND GERMINABILITY

Examination of grain development in two white-grained (non-dormant) and two red-grained (varying dormancy) wheat genotypes has clarified concepts of maturity with respect to grain dehydration, harvest ripeness, embryo maturity, base α-amylase activity and dry weight growth. Each maturity trait had a different pattern of development. The net level of grain maturity at harvest ripeness depended on the relative progress of the maturation traits at the time at which harvest ripeness was defined. Harvest ripeness is defined as the first attainment of 12°% moisture during primary dehydration of the grain, this being closely related to fitness for harvest. The effects of adopting other definitions of harvest ripeness (at 17°% and 20% grain moisture) are discussed. Significant differences amongst genotypes in development patterns, temporal placement, and harvest ripeness level were found in each maturity trait, and the differences were not parallel across traits. Differences in maturation did not coincide with differences in putative dormancy or grain colour. Results indicated that grain maturation was a multi-faceted process, with flexible synchronizations amongst maturation traits at any point in time, such as at harvest ripeness. Germination tests or a-amylase assays on progeny grain samples, at some time after harvest ripeness, measure differences in maturity as well as putative differences in dormancy. Interpretation only in terms of dormancy could be misleading. Adjustment for immaturity is discussed. © 1979 CSIRO.