Development of Seed Dormancy in Barley, Wheat and Triticale under Controlled Conditions

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Abstract
Different varieties of barley, wheat and triticale were grown in the phytotron at 9°, 15° and 21°C in order to study how the development of seed dormancy in these species depends on the temperature during the ripening period. The seeds were harvested at 70% seed moisture and then at regular intervals until no seed dormancy was left. The germination was performed at 10° and 20°C. The barley material investigated was most sensitive to temperature changes during the ripening period, irrespective of the germination temperature. For germination at 10°C, wheat was more sensitive than triticale, while the converse reaction was found at 20°C. At low temperatures during ripening, wheat was less sensitive to changes in the germination temperature than were barley and triticale; at high temperatures this difference disappeared. Triticale was the most sensitive to changes in the germination temperature. The three species showed different patterns of the development of seed dormancy with the harvest stage. In wheat the rate of reduction of seed dormancy per unit change in the harvest stage was greater than in barley and triticale. In triticale an increased level of seed dormancy was induced shortly after yellow ripeness, which was absent in barley and wheat under the dry air conditions prevailing in the phytotron. In barley as well as in wheat the line variation of seed dormancy was almost independent of the temperature during ripening, but increased with the germination temperature. In barley the ranking of genotypes was more affected by the temperature during the ripening period and germination than in wheat. Genotypic differences were found in the pattern of development with the harvest stage in barley as well as in wheat. Different storage temperatures were applied for phytotron as well as for field grown seeds. In wheat—but not in barley—the sensitivity to differences in the temperature after yellow ripeness was dependent on the conditions for the induction of a secondary dormancy. The variation of seed dormancy between as well as within species is discussed in relation to the origin of the material investigated. The results presented agree closely with experience in the field, and the use of phytotron experiments for the evaluation of seed dormancy of different genotypes of barley and wheat is discussed.