Varietal Variation and Mechanism of Hull-cracked Grains in Two-rowed Barley

Hull-cracked grain which causes low germinability and low malt extract has been observed in malting barley varieties mainly in the western part of Japan. In the first part of this study, more than 600 two-rowed barley varieties were examined for the percentage of hull-cracked grains. A markedly skewed frequency distribution pattern was observed for varietal variation of hull-cracked grain percentage. More than 80% of the varieties developed less than 5% hull-cracked grains, while a few of the varieties frequently developed the hull-cracked grains. The maximum hull-cracked grain percentage was as high as 61% in Yoshikei 16. Improved varieties developed hull-cracked grains more frequently than the local varieties, indicating varietal improvement indirectly caused the hull-cracked grains. In the second part, nine two-rowed varieties were grown in eight different conditions to analyze the mechanism of hull-cracking. Variances due to varieties, environment and their interaction were all statistically significant. Some of the varieties developed almost no hull-cracked grains throughout the environmental conditions examined, while others sharply responded to the environmental conditions. The environmental correlation coefficient between 1,000-kernel weight and hull-cracked grains was as high as 0.918, indicating that hull-cracked grains had developed under favorable ripening conditions.