| Rice is one of the most important grain crops in China. Most of the important agronomic traits in crops are quantitative such as plant type, yield component, rice quality, and resistance to diseases and insect etc. Improvement of these quantitative traits is one of the major objectives in crop genetic breeding program. Lodging resistance has been a key target trait for raising yield potential and is associated with many component traits such as height, stem strength and thickness, etc. While phenotypic selection for lodging resistance selection has been effective, its genetic basis remains poorly understood. Bacterial blight (BB) caused by Xanthomonas Oryzae pv. oryzae (Xoo) is one of the most destructive diseases of rice throughout the world. DNA markers and derived molecular linkage maps have provided powerful tools for molecular dissection of monogenic traits and Mendelian components of quantitative traits. A complete and well-distributed molecular linkage map with 256 markers was constructed using a set of recombinant (RI) lines (F14) obtained from an inter-subspecific cross between an Oryza saliva L. ssp. Indica cultivar (Teqing) and ajaponica cultivar (Lemont). It is consisted of 115 simple sequence repeat (SSR) markers, 84 random amplified polymorphic DNA (RAPD), 47 restriction fragment length polymorphism (RFLP) markers, 7 isozymes, and 3 morphological markers. The genetic map spanned 1938.8cM and covered all of 12 rice chromosomes with an average distance of 7.6 cM between adjacent markers. Segregation of 70% of the markers fit the 1:1 Mendelian expectation, whereas the remaining 30% of markers showing segregation distortion largely clustered in the end regions of chromosome 6, 7, 8, and 11. On average, Lemont alleles accounted for 46.1% of the genome of the RI population. Almost all SSR and RFLP markers were mapped to their reported chromosomes and had the linear orders matching perfectly with the previous genetic map. This map have been used for mapping genes and quantitative loci (QTLs) affecting traits segregating in the population. Three groups of component traits, which may potentially contribute to lodging resistance x in rice, included stem thickness related traits, plant height related traits and vegetative growth traits. For all the tested traits, except LUTN, PH, and NEI, there were significant difference between Lemont and Teqing. Transgressive segregation was observed for all the traits examined. QTLMapper version 1.0 was used to detect main-effect and epistatic QTLs associated with the 15 lodging resistance traits in the RI population. A total of 65 significant main-effect QTLs distributing 19 genomic regions of all the 12 rice chromosomes and 68 pairs of significant (NO.001) digenic epistatic loci, were detected for all the tested traits. The number of significant QTLs affecting each trait ranged from 3 to 7. The percentage of genotypic variation explained by each QTL ranged from 5.0% to 34.3%. For those traits for which two or more QTLs were detected, alleles for increased trait values were from both parents. Only one significant interaction occurred between main-effect QTLs (for HD), and 11 interactions occurred between main-effect QTL5 and æ…´ackground?loci. All of the other interactions occurred between unlinked æ…´ackground?loci. These QTLs and epistasis provided useful information for marker- assisted selection (MAS) for these traits, and for improvement of rice lodging resistance. GenesIQTLs affect...
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