Selection against sprouting damage in wheat. III.* Dormancy, germinative alpha-amylase, grain redness and flavanols

Abstract

Grain development of embryo dormancy, germinative α-amylase, pigmentation and flavanols was examined in the wheats Timgalen and Gamut (white-grained, non-dormant), and Pembina and Sonora (red-grained with different levels of dormancy). It was found that each trait had distinctive patterns of development. The net result at harvest ripeness depended on the synchronizations amongst the traits.

Dormancy, as judged by embryo response (i.e. embryo dormancy), was restricted to the red wheats. Three ways of expressing it were noted: (1) in terms of development patterns, (2) as levels at harvest ripeness or at harvest, and (3) by the length of the period of embryo dormancy after harvest ripeness. Two hypotheses linking embryo dormancy and grain redness appeared plausible from the results. One was that the polyphenol oxidase complex, which polymerizes flavanols to the putative pigment phlobaphene, contributes towards embryo dormancy, probably through enhancement of hypo-oxia. The other was that the pigment itself and its tanning complexes cause the hypo-oxia. Flavanols did not appear to be in vivo germination inhibitors.

Dormancy, as judged by α-amylase response (i.e. amylase dormancy), was not always present together with embryo dormancy. A long period of amylase dormancy was found in the more embryo-dormant red wheat, but not in the other. Conversely, a short period of amylase dormancy was found in one white wheat, but it was not embryo-dormant.

Possible relationships between these physiological traits and the classical genes for red grain-coat were discussed. Implications concerning selection against sprouting damage were considered.

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*Part II, Aust. J. Agric. Res 30: 1-17 (1979).