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Rice ( Oryza sativa L) is an important cereal crop and staple food crop of the world, whose yield could be influenced by biotic and abiotic conditions, resulting in 1-100% yield losses depending on the incidences of diseases or severity of stress condition. The research was basically to identify the polymorphic markers at the target region (parental survey) and screened for selection of improved lines with multiple traits of resistance/tolerance to two or three of blast, bacterial leaf blight and drought tolerance. Three varieties were used; two high yielding varieties of Putra-1 and MR219-PL-137 resistant to blast and tolerant to drought respectively, and an IRBB60 bacterial leaf blight resistance variety. They were crossed to a common recipient parent (Putra-1) to produce two categories of F 1 hybrid as baseline for development of improved lines in three crossing methods which produced five populations (PB, PD, PBD, PDB, DPB) through marker-assisted pedigree selection. The populations were screened by genotyping using SSR markers to select lines polymorphic to parental cultivars and carrying the linked markers/QTLs for diseases resistance and drought tolerance: Blast resistance (RM6836 and RM8225), IRBB60 (RM224, RG136, RM122, RM21), MR219-PL-137 drought tolerance QTLs (RM236, RM520, RM511, RM1261). The results of gel electrophoresis agreed with the phenotyping results of the improved lines F 4 , F 3 (2), F 3 for single, double and three-way (and reciprocal) crosses respectively and also susceptible parent cultivars. |
