Notched Grains Developed by the Minute Genes of Rice / Unbalanced Growth in Floral Glumes and Caryopsis in Rice VI.

In the previous reports, the author has clarified that unbalanced growth in the floral glumes and caryopsis of rice results in such aberrant grains as notched or hull-cracked grains. Because the grain size of a rice plant is generally conditioned by many minor genes, it should be treated as a quantitatively inherited character. However, if the major genes controlling grain size are available, analysis of their action may offer more simple and precise understanding about the genetic mechanism of grain development. In the present experiment, the effects of minute grain genes on the length of floral glumes and the potential length of caryospsis have been investigated with the nine F2 populations (Table 1). The potential length of the caryopsis (T1) was estimated by the length of "glume-cllpped grains", upper parts of the floral glumes were clipped-off a few days after the anthesis to allow the development of caryopsis without restriction by the size of floral glumes, while the inner length of floral glumes (C1) was indicated by the length of "non-treated gralns" which naturally developed in a state encased in the floral glumes. Without exception, T1 was longer than C1, and the T1/C1 ratio varied from ca. 1.O to larger than 1.7 in the 1, 483 F2 plants examined.