| Rice is one of the most important staple food crops in the world, because its genome is small in Gramineae and genes have the characteristic of colinearity with other plants, it has become the model crop for plant genetic and genomic studies. Chilling injury of rice in different developing stages is a common problem which is encountered for global rice cultivated area. It results in root rotting at rice sprout stage and reducing the yield at blooming stage because of low temperature. It is very important to study the characteristic of cold tolerance and make clear the mechanism of cold tolerance in rice. Cold tolerance is controlled by some quantitative trait loci (QTLs) in rice. It makes genetic study and breeding more difficult. Recently, with availability of high density molecular linkage map, QTL mapping of rice has got great achievement for quality, resistance and some other important agronomic traits. However, the study needs to be furthered because of the complexity of QTLs in rice. The results of QTLs can provide very useful academic base for gene map-based cloning and mark assistant selection in plant genetics and breeding.The structure of rice cell membrane is broken under the low temperature stress, dissoluble matter and electrolyte flow to the outside of membrane. We find that leaf osmotic potential, root conductivity and survival percentage are different evidently between the parents, so these index can be used to identify the characteristic of cold tolerance for different rice. We use Dongxiang wild rice with high cold tolerance as the donor parent, and cultivated varieties Nanjing11 to construct segregation population by the method of advanced backcross and detect cold tolerance with the index of leaf osmotic potential, root conductivity and survival percentage. Combining the segregation of SSR markers in the constructed population, we use the QTL mapping software windows QTL cartographer 2.5 to search cold tolerance QTLs in rice. The results were summarized as follows:1. When we use leaf osmotic potential as the index to detect rice cold tolerance, 5 QTLs are found on chromosome 2, 4 and 8, their contribution values are from 7.00% to 14.27%;2. If we use root conductivity as the index, 2 QTLs are found on chromosome 10, their contribution values for the phenotype are 34.13% and 37.02% respectively. They may be the main effect QTLs for cold tolerance in rice. We detect these QTLs located at the side of SSR marker RM171 by developing new SSR markers around qRC-10-2 on chromosome 10;3. No QTL is found for using the index of survival percentage in this research;4. At the same time, we analysis the trait of plant height and spike length in segregation population. 3 QTLs located on chromosome 1, 4 and 8 are detected to control the plant height of rice, qPH-1 is a main effect QTL with 63.79% contribution value for plant height. The qSL-1 for spike length of rice is located between markers RM11650 and RM104 on chromosome 1 with 2.44% contribution value. Another QTL for spike length of rice qSL-8 is located between markers RM339 and RM23613 on chromosome 8 with 5.91% contribution value.These results provide the useful foundation for cold tolerance QTL cloning and marker assistant selection in rice. |
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