Low temperature is the greatest concern of rice growers in the temperate regions. Although farmers have tried to deploy varieties with tolerance to low temperature and recommended cultural practices, such as planting date and water depth during panicle development, rice crops still suffer from poor establishment and high grain sterility, due to variable climate every year. In 1993, the average night temperature went down to about 11°C in the summer causing heavy losses in Italy, and particularly in Japan and the Republics of Korea. Japan had a subsequent shortage of rice, and had to import approximately 2 million tons of milled rice in 1994-95.
It is well known that japonica rice is, to some extent, tolerant to cold. However it is less productive if it grows under very low temperature. The critical temperature of rice is around 15°C depending on the varieties. The rice-growing countries in the temperate regions devote their major resource for varietal improvement in this regard. Recent breeding work has focused on cold tolerance, improving seedling vigour, and reducing floret sterility of rice. Date of planting, early-maturing cultivar, and maintaining high water depth during the panicle development could help the rice crops escape from cold.
Farmers, however, still need additional varieties with higher cold tolerance. More strategic research is still required in this field. The biotechnological approach should be more deployed towards identifying high cold tolerance gene from rice or others. Rice growers should be aware of the newly-developed varieties and emerging proven technologies and need to be trained in this area.