With over 100,000 rice cultivars worldwide, screening for low temperature tolerance at the establishment and the microspore stage in rice has been targeted. Australia's researchers have had success using temperature controlled facilities and serial field trials while Japan's researchers have developed field screening using cool water from bores.
The International Rice Cold Tolerance Nursery (IRCTN) is a selection of cultivars from different origins evaluated at different locations for cold tolerance. Australia has sourced cold tolerant cultivars a result of their performance in the IRCTN, reports in the literature or recommendations by international scientists. One hundred and five international cultivars from 1991 and 1992 (IRCTN) were introduced to Australia and grown in small plots at Yanco Agricultural Institute in 1995. In recent temperature controlled experiments, seven cultivars from this nursery were more cold tolerant than Millin, Australia's most cold tolerant cultivar. Australia has successfully exchanged cold tolerant material and continues to do so with many countries such as Japan. Australia's plant physiologists and breeders are working closely together to improve the level of cold tolerance in commercial rice cultivars.
Rapid screening of genotypes for cold tolerance at the reproductive stage of rice has been a success in experimental stations throughout Japan. Many research stations have established small experimental bays dedicated to screening for cold tolerant cultivars. Rice is transplanted into these bays and then cool bore water (19oC ) is introduced following panicle initiation. Following panicle initiation of the first cultivar to flowering of the last cultivar the water depth is maintained at 20cm for approximately 40 days. The rice breeder from Myagi Prefecture Agriculture Experiment Station, Furukawa, has successfully released cold tolerant cultivars such as Jyoudeki using this deep cold water screening facility (Nagano 1998). The water temperature from a spearhead bore at Yanco, Australia is approximately 20oC, which is approximately 5oC warmer than bore water in Japan and may not be suitable for cool water screening.
