二条オオムギにおける裂皮粒歩合の品種変異と発生機構

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.

二条カワムギ615品種を供試して裂皮粒（外頴が裂けて頴果が外から見えるもの）の発生歩合を調査した。全体の83％にあたる513品種では裂皮粒歩合が5％以下であったが、最高の品種は61％と高い値を示し、裂皮粒歩合の頻度分布は極めて歪んでいた。在来品種に比べて育成品種の中には裂皮粒歩合の高いものが多く、品種改善、特にビール麦としての品種改善の方向と裂皮粒の発生には関係があるとみられた。次に裂皮粒歩合の異なる二条オオムギ9品種を様々な条件で栽培し、裂皮粒歩合と1,000粒重を調査したところ、両者の環境相関係数は0.918と密接で、登熟の良い環境条件で裂皮粒が多発すること、すなわち、穀皮の大きさに比べて穀粒が大きくなり過ぎるような条件で裂皮粒が発生することが明らかにされた。