| MRDV is a worldwide disease caused by maize rough dwarf virus. It is one of the most important diseases in maize-growing area in China. Developing and cultivating resistant hybrids is an effective approach to control MRDV. Breeding efforts for resistance to MRDV rely largely on good understanding the resistance and genetic mechanism. This study mainly deals with evaluation and genetic diversity of the germplasm and QTL identification of resistance, both which are of great significance to genetics and breeding for MRDV resistance. The results are as follows:(1) Genetic diversity and resistance to MRDV of 64 maize inbred lines were evaluated under severe MRDV natural stressed enviornments during 2003 and 2004 at Linfen, Shanxi province, China. Of them, 12, 17, 18, 12 and 5 lines were screened out as high resistant, resistant, moderate resistant, susceptible and highly susceptible lines, respectively. Furthermore, 70 SSR markers were implemented to detect genetic diversity of the lines. A total of 276 alleles were found and the mean polymorphism information content is 0.57, which ranged from 0.177 to 0.825. The UPGMA analysis showed that 64 inbred lines could be classified into 6 subgroups (Sipingtou, Luda Red Cob, PA, PB, BSSS and Lancaster), which were generally consistent to their known pedigree and breeder's experiences. According to the percentage of plants infected by MRDV among the six groups, while the lowest level is 1.60% for PB and 4.95% for Sipingtou germplasm, respectively. Both groups were identified as the important sources of resistance to MRDV. 20 SSR markers were identified as significantly correlated with the MRDV resistance. They might be employed for molecular evaluation of maize inbred lines for resistance to MRDV.(2)Two populations [(Huangzao4×Ye107)F2 and (X178×B73) F2] were evaluated for reactions to MRDV under severe natural stressed conditions of MRDV at Linfen, Shanxi province, China during 2000- 2003. Based on constructed genetic maps, 13 QTL conferring resistance to MRDV were identified on chromosome bins 1.03,1.07,2.02,2.04,2.08,3.08,9.06,10.03,10.04 in (Huangzao4×Ye107)F2:3 and F2:4 populations during 2000 and 2001, and 10 QTL conferring resistance to MRDV were identified on chromosome bins 1.03,1.04,3.08,4.09,7.02/3,8.03,8.05/6,10.03 in (X178×B73)F2:3 and F2:4 populations during 2002 and 2003 by using composite interval mapping (CIM).(3) Under BSA strategy, 7 polymorphic SSR markers on chromosome bin 1.07, 3.06, 6.01, 6.05, 10.01/2, 10.03 regions were screened between resistance pool and infectious pool. Combining with their...
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