Abstract
An X-ray induced mutant of 4-rowed lvinter barley produced awn of diverse types in a spike (Table 1). This was more variable in the intensity of expression than the analogous mutant subcalcaroides described by BANDLOW (1954), as shown in Fig. 1. That is, this mutant makes partly the same structural pattern, but gives different end product of development, as corrupared with subcalcaroides. As the mutant's spikes were divided into three kinds : n-, n→a-and a-types (Table 2), X3 progenies were classifled as given in Table 3. However, no plant having spikes of n- and a-types was found in X3-and X4-generations. Although the seeds were selected from the plant having spikes of each type in X3 generation, no of Tokyo) change was observed in the appearance of abnormal plants in X4. (Table 4). The expression of mutated character intensified at the early differentiated part, such as early heading spikes or the upper portion in a spike. Thus. it is probable that the spikelets of lateral row differentiate later in comparison with those of middle row at the same position (Fig. 2). In the cross with mother-type or hooded, the inheritance of mutant character is completely recessive. From these results, it is concluded that the mutant character is induced by point-mutation and its gene-expression is affected by some environmental factors, probably temperature etc
