Studies On Cold Tolerance Of Yunnan Rice (Oryza Sativa L.) Genetic Resources

It is one of world wide damages caused by low temperature weather in rice(Oryza sativa L.) production. Yunnan province is located in high plateau with low latitude. Low temperature weather and blast disease are both the most serious problems in rice production of this province. Studies showed that there are rich germplasms with cold tolerance in Yunnan rice genetic resources.We have been studying on cold tolerance by using Yunnan rice genetic resources since 1990. The studies were carried out in Yunnan Academy of Agricultural Sciences based in Kunming, National Key Laboratory of Crop Genetic Improvement based in Huazhong Agricultural University, Hokkaido National Agricultural Experiment Station based in Sapporo, Japan. This papers were comprised of three following sections, i.e. Screening for resources with cold tolerance, genetic analysis of cold tolerant resources, QTL mapping for cold tolerance in Yunnan landrace Kunmingxiaobaigu(KMXBG). Major results were as below.1. Seventy-nine Yunnan rice accessions were identified to be tolerant to cold at budding stage in the total of 2763 ones. Five rice resources with cold tolerance at seedling stage were found from 475 ones.2. Evaluations of cold tolerance were undertaken on 15 rice accessions at booting stage and on 64 ones at flowering stage under controlled conditions. A lot of rice genetic resources were confirmed to be cold tolerant, such as Kunmingxiaobaigu, Banjiemang, Lijing No.2 and Jingdiao No.3, etc.3. Three effective factors were estimated to control cold tolerance of KMXBG at booting stage through the program designed by Ishige(1979) when F2 and BCF1 populations related to Nipponbare were used. One or two major genes were supposed to control cold tolerance of KMXBG at booting stage under controlled condition through the software supplied kindly by Wang Jiankang(1998) when the segregation population involved by Towada (TW) was applied. Both above supported that a few of major genes involved the cold tolerance of KMXBG at booting stage.4. A linkage map was constructed by using 156 DNA markers wife 250 F2 plants of cross between KMXBG and TW. The map contains 18 linkage groups covering 1535 cM.5. Spikelet fertility was used as indicator for cold tolerance at reproductive stage in the F2, F3 and F4 populations of cross between KMXBG and TW. 11, 10 and 9 loci for cold toleance were detected by ANOVA, while 7 QTLs, 4 QTLs and 3 QTLs for cold tolerance were detected by Mapmaker and MapQTL in F2) F3 and F4 populations, respectively. 95.9%, 52.7% and 17% phenotypic variances could be explained by the QTLs in F2, F3 and F4 population, respectively. Eleven QTLs were considered to relate to cold tolerance of KMXBG based on comparing both results above. The eleven QTLs distributed over eight chromosomes, i.e. chromosome 1,2,3,6, 7,8,10 and 12. It was not reported about QTL mapping for cold tolerance at reproductive stage using directly rice landrace with cold tolerance.6. Eleven QTLs for cold tolerance were tentatively nominated here, i.e. qrct-1 (t)-qrct -11 (t).The loci of qrct-1 (t), qrct-2 (t), qrct-4 (t), qrct-6 (t), qrct-9 (t) and qrct-11 (t). were first reported for cold tolerance at reproductive stage.7. The DNA markers related to the special spikelet fertility showed almost similar to these related to the total spikelet fertility, too. The fact leads to think that the investigation of the total spikelet fertility can be replaced by that of the special spikelet fertility. The regenerated culm weight (RCW) was in correlation with the amount of bleeding water under low temperature. It is proposed to use RCW under low temperature as an indicator for cold tolerance.