| Most agronomic characteristics are important in rice such as PH (plant height), HD (heading date), HR (heat-resistance) and yield components or seedling vigor .components. Both DH (doubled haploid) and RIL (recombinant inbred lines) populations were derived. A genetic map was constructed by molecular marker analysis. QTLs associated with these traits above were mapped according to the data for phenotype. At the same time, we transferred gene resistant to bacteria blight into rice on the basis of marker-assisted selection. Following are major contents and results studied.Crosses were produced by using a storable rice variety (Daw Dam) and 2070, Ming Hui 63, Dulur as well as Xie Qing Zao B as parents, among these materials there are abundant polymorphisms of DNA molecular markers. Their Ffs were applied to generate DH lines by an improved method of direct induction of pollen plant. The method of the direct induction of pollen plant was used as check treatment to evaluate the improved method. The results showed that the improved method increased the re-differentiation percentage of pollen callus, the percentage of regeneration plantlets, and the percentage of green regeneration plantlets and produced more vigorous seedlings. The improved method was a competent method of establishing DH population for mapping lox-3 gene. It was also showed that the efficiency of the new method was different among genotypes and out of three experimental crosses Daw Dam/2070 and Daw Dam/Minghui 63 showed more efficient. More than 60 DH lines have been obtained in the present experiment.A RIL population consists of 304 individuals was derived from a cross between Zhongl56, a species sensitive to rice blight but has high yield, and Gumei2, a species resistant to rice blight, which is semi-dwarf. Both parents are selected in China National Rice Research Institute (CNRRI). Applied to RFLP, RAPD, SSLP, RGA and CG, a linkage map consisting of 168 markers was constructed, which covers 1447.9cM of the rice genome and covers all of chromosomes in rice.The parents and a Fg including 304 individuals were grown in the paddy field in China National Rice Research Institute (CNRRI), Hangzhou, China in 2001. The experiments wereIVcarried out in two enviroments followed a randomized complete block design. Recorded the data of HD (heading data), PH (plant height), PL (panicle length), PNPP (panicle number per plant), SNPP (spikelets number per panicle), FGN (filled grain number), GF (grain fertility) and KW (kilo-grain weight). The identification of QTL for PH and HD and yield components and analysis of epistasis and QTL * environment interaction were conducted by using the statistic software of MAPMARKER/QTL. In addition, conditional QTL analysis for PH and PNPP was made.42 QTLs with additive effects covering all chromosomes except 9 chromosome were detected. 6 QTLs have significant QE interaction. 39 QTLs with additive x additive epistatic effects for PH, HD and yield components were detected, including 6 QTLs controlling PH, 2 QTLs controlling HD, 2 QTLs controlling PL, 2 QTLs controlling PNPP, 9 QTLs controlling SNPP, 9 QTLs controlling FGN, 6 QTLs controlling GF, 3 QTLs controlling KW. The phenotypic variances these QTLs explained separately were 12.12%, 1.38%, 3.76%, 5.00%, 10.24%, 20.50%, 16.31% and 4.48%. For all epistatic effects, most effects and variances were lesser. No significant interaction between epistatic effects and environment was detected.In conditional QTL analysis for PH and PNPP, 7 and 3 additive QTLs and 6 and 3 epistatic QTLs for PH and PNPP were detected. For all PH QTLs, qPH7-l and qPHIO showed QE interaction only; qPH7-2 showed both additive effect and QE interaction. No QE interaction for other 4 QTLs was detected. All 3 QTLs controlling PNPP showed additive effects only and no QE interaction was detected. The variances of 6 and 3 epistatic QTLs for PH and PNPP were from 1.9% to 4.2% and from 3.26% to 3.96%. No epistatic QE interaction was detected. Meanwhile conditional QTL analysis showed that HD...
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