Abstract
In Miygai prefecture, the percentage of the first grade rice-grains (%FGG) is lower in the Sennan area than in other areas. Climatic factors during ripening stage were responsible for the inferior quality. We examined the correlation of the number of panicles per m2 (NOP) with %FGG and climatic conditions before heading in the past 28 years in three areas of Miygai; Sennan, Sendai and Osaki. Before 1993, when Sasanishiki was a dominant cultivar, the number of spikelets per m2 (NOS) negatively correlated with %FGG in all areas, and positively correlated with the number of panicles per m2 (NOP) in the years in which a negative correlation was observed between NOS and %FGG. The NOP negatively correlated with accumulated sunshine hours in July in Sennan, daily minimum air temperature from young panicle formation to meiotic stage in Sendai, and daily minimum air temperature in July in Osaki. In the period from 1994 to 2005, when Hitomebore was a dominant cultivar, NOS negatively correlated with %FGG and positively with NOP. NOP positively correlated with accumulated sunshine hours in June in Sennan, and with daily maximum air temperature from transplanting to summer solstice in Sendai. The effect of the weather condition around heading on %FGG in Sasanishiki was different from that in Hitomebore.
