Abstract
In recent years, consumers in Hokkaido complain of the occurrence of notched-belly rice kernels in rice variety “Nanatsuboshi”. In order to investigate the factors that caused notched-belly rice kernels, we conducted experiments in an air-conditioned room. The results are summarized as follows. 1) The rate of the occurrence of notched-belly rice kernels increased by exposing the plants to a temperature lower than 19°C for two weeks from heading time. The most temperature sensitive period was three to four days after heading time. 2) The ratio of notched-belly rice kernels was higher in secondary tillers than in primary tillers, and in secondary than in primary rachis-branches. 3) Shading before heading time shortened the rice hull and increased the number of notched-belly rice kernels. 4) Sieving with a grader with larger than 2.0mm mesh clearly removed notched-belly rice kernels rate. Therefore, it is necessary to predict the occurrence of the notched-belly rice kernel by the weather condition during the sensitive period and to sieve brown rice carefully to remove notched-belly rice kernels.
