[Analysis of gene loci and epistasis for drought tolerance in seedling stage of rice (Oryza sativa L.)].

Drought tolerance of rice is important because a considerable proportion of the world rice area is not irrigated and is prone to water deficit. In this study, an indica variety, Zhai Ye Qing 8 (ZYQ8), and a japonica variety, Jing Xi 17 (JX17), and their double haploid (DH) population were used for genetic study of drought tolerance. Water supply was stopped in seedling period for 15 days and then drought tolerance of the DH population and their parents were investigated. Mapping quantitative trait loci (QTLs) was undertaken base on the constructed molecular linkage map of this population. Two QTLs (qDR-5 and qDR-12) for drought tolerance were identified, they were in the region of GA41-GA257 on chromosome 5 and RG457-Y12817R on chromosome 12, respectively. The tolerance alleles of both QTLs were from the indica parent, ZYQ8. In the meantime two genes for drought tolerance near GA257 and Y12817R were detected too by using Epistat software, that is in accordance with the result by using Mapmaker/QTL. In addition, three loci (RG541, G318 and G192 on chromosome 1, 4 and 8, respectively) were found interacting with GA257 by Epistat software, while one locus (CT234 on chromosome 3) found interacting with Y12817R were also detected by Epistat software.

[QTL analysis of sheath blight resistance in rice (Oryza sativa L.)].

In this study, an indica variety Zhai Ye Qing 8 (ZYQ8) and a japonica variety Jing Xi 17(JX17) and their double haploid (DH) population were used. Sheath blight resistance of the DH population and their parents was investigated using a syringe inoculation method. Quantitative trait loci (QTL) analysis was undertaken based on a constructed molecular linkage map of this population in Hangzhou and Hainandao respectively. A total of four sheath blight resistant QTLs (qSBR-2, qSBR-3, qSBR-7 and qSBR-11) were identified, and located on chromosome 2, 3, 7 and 11, respectively. Resistant alleles of qSBR-2, qSBR-3, and qSBR-7 were derived from the resistant parent ZYQ8, whereas resistant allele of qSBR-11 from susceptible parent JX17. qSBR-2, qSBR-3 and qSBR-7 were detected both in Hangzhou and Hainandao, whereas qSBR-11 was detected only in Hangzhou. Sheath blight response was significantly correlated with culm length and heading date in Hangzhou's test. Among the QTLs for culm length and heading date, only qCL-3 for culm length, was in the same chromosome region of qSBR-3, the other QTLs were not linked to the QTLs for sheath blight resistance.