2005 Volume 7 Issue 1 Pages 1-7
The amylose content of the endosperm is a major factor affecting the stickiness of boiled rice. The response of the amylose content of low-amylose lines derived from several mutants to temperature during the ripening period was investigated. The amylose content decreased from the low temperature treatment to the high temperature treatment in each line or cultivar examined. The amylose content of the nonwaxy cultivar “Tsugaru-roman” ranged from 12% (high temperature treatment) to 23% (low temperature treatment). The ratio of the decrease of the amylose content to the increase of the temperature during the ripening period (Δ AM/ °C) ranged from 0.8%/°C to 1.1%/°C in “Tsugaru-roman”. The progeny lines of “Milky-queen” (harboring the wx-mq gene) and “Yamagata 84” (harboring the wx-y gene) showed lower values of Δ AM/°C, whereas the progeny lines of “74wx2N-1” displayed remarkable changes in the amylose content, compared to the nonwaxy cultivars. “Fukei 191”, from “NM391” (harboring the du(t) gene), showed a smaller decrease in the amylose content in 2001 and remarkable changes in the amylose content similar to those observed in the “74wx2N-1” progenies in 2002. The amylose content of “Tankei 2031” (low-amylose gene has not yet been identified) was about 3% lower than that of the nonwaxy cultivar in each treatment. The value was comparatively higher than that of other low-amylose lines. These varietal differences in the response of the amylose content to the temperature during the ripening period are considered to be controlled by the low-amylose genes harbored by each line.
