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Physiology and genetics of the kernel color of barley. Faris, Donald George

Abstract

The generally accepted trademark of Canadian malting barley varieties is "blue" aleurone color in the kernel. New Canadian feed barley varieties are preferably marked by a "white" aleurone color. In attempting to meet the color qualifications in new introductions, Canadian barley breeders have often experienced difficulty in separating genetically "blue" from genetically "white" seed. An attempt has been made in this thesis to extend the knowledge on the inheritance, physiology, and separation of "blue" and "white" barley varieties. "Purple" and "black" barley kernel colors were also studied. Crosses were made between twenty barley varieties in an attempt to ascertain the inheritance patterns for kernel color. The study of color inheritance in the kernel acted as a background for physiological, histo-chemical, and chromatographic experiments. The physiological studies of color development in barley plants and caryopses made use of three barley varieties, "Smyrna" (white), "Awnless" (blue), and "Black Hulless" (purple). These three varieties were fed complete, low N, and low P solutions and were divided equally into the five following treatment blocks: "control", "ultra-violet", "infra-red", "dextrose" and "low temperature". The most consistent increase in plant and seed color development was associated with the low N and low P nutrient levels. There was a ""barely significant" difference in color development between the five treatment blocks. Dry and sprouting kernels of "white" and "blue" seeded barley varieties were examined under natural, colored, and ultraviolet lights. The most consistent difference between seed of the two color types was found when dry seed was observed under a dissecting microscope in natural light. Histo-chemical examinations of colored kernels showed that the coloring pigments were localized in the aleurone and pericarp layers. The blue and the purple pigments, located in the aleurone and pericarp layers respectively turned red when placed in cold conditions. Under alkaline conditions the pigments of the two kernel layers generally appeared a green color. These -color changes in the aleurone and pericarp layers of colored barley kernels strongly suggest the presence of anthocyanin pigments. Black pericarp pigments appeared unchanged under alkaline and acid conditions. Barley kernels of many varieties were extracted with alcohol and boiling 2N HCl and the pigment fractions of the extracts separated by paper partition chromatography. Two pigment fractions were obtained from extracts of "blue" seeded barley varieties and at least four from extracts of "purple" seeded varieties. The RF values of the pigment fractions obtained from extracts of "purple" seeded varieties were very similar to the RF values of the pigment fractions separating from extracts of red colored barley plant tissues. All these spots gave the characteristic red to blue color change of anthocyanins in acid and alkaline conditions.

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