Japonicarice is the fruit of japonica non-waxy rice, which has the characteristics of cold tolerance, weak light tolerance and high temperature avoidance. Mainly distributed in northern China, the middle and lower reaches of the Yangtze River, Yunnan-Guizhou Plateau in low temperature and high altitude areas, South Korea and Japan. Japonica rice grains are generally oval, short in length, 1.4-2.9 times wide, with long and dense villi, long awn, thick rice husk and many horny grains. It is not easy to produce broken rice during processing, with high rice yield, small rice swelling and high viscosity.

Japonica rice can be divided into early japonica rice, middle japonica rice and late japonica rice according to its sowing date, growth period and maturity.

Early japonica rice:

Japonica rice with shorter growth period and earlier harvest period has larger belly white and less horny grains. Most of the early and middle-maturing varieties in the first season of japonica rice in Northeast China and double-cropping rice in Jiangnan rice area belong to early japonica rice type.

The growth period of japonica rice in Northeast China is 90- 180 days, most of them are above 130 days, and only a few of them are 90- 130 days, mainly distributed in the middle of the third accumulated temperature zone, the third accumulated temperature zone and the fourth accumulated temperature zone in Heilongjiang Province. Generally, seedlings are raised in March-April, seedlings are transplanted in May-June, and harvested from north to south in late September, and all harvests are finished at 10.

Medium japonica rice:

The growth period is between early rice and late rice, and the growth period is 125- 150 days, which usually matures in early autumn. Most mid-season japonica rice varieties have moderate photosensitivity, and the days from sowing to heading vary greatly in different regions and different sowing dates. In case of short-term high temperature weather, the growth period will be shortened.

Late japonica rice:

Japonica rice with long growth period and late harvest period has smaller belly white and more horny grains. Late japonica rice is suitable for planting in high altitude areas at high latitudes or low latitudes, and its seeds are not easy to fall off, and it is cold-resistant and weak-light-resistant, but not high-temperature-resistant. Therefore, japonica rice varieties are widely used in late rice in the middle and lower reaches of the Yangtze River and double cropping rice areas north of the Yellow River.

The growth period of late japonica rice is generally 150- 180 days. Sowing begins in April-May, transplanting begins in late May in Northeast China, planting begins in mid-late June in Jiangsu and Zhejiang provinces, and harvesting ends from late June to early October in165438, among which Jiangsu and Zhejiang provinces are representative.