Blast, caused by Pyricularia grisea Cav., is one of the major fungal diseases infected rice (Oryza sativa L.) in Vietnam. This disease occurs in Vietnam which cause the yield loss of up to 20% particularly in a year with long wet season. Local varieties have been considered as genetic sources of disease resistance among crops. The breeding program was aimed at improvement of blast resistant varieties. Six crosses of plants, OM 24/IR 64, IR 24/OM 2514, C 53/IR 64, C53/OM 2514, OM 1308/TeTep and IR 36/C 53 were obtained. Four crosses were mapped using molecular marker. The resistance genes are inherited dominant and located on chromosomes 6, 8 and 11. A simple sequence repeat (SSR) marker (RM 483) was used to detect 100 local varieties to find resistance with some race at Mekong delta. Phenotypic selection was used to compare with genotype in order to check how accurate the polymorphisms in varieties show that marker assisted selection (MAS) reached an accuracy of 100% in SSR marker with RM 483. These methods can be applied in practice to select varieties that have blast resistance genes for breeding rice, because of their high precision levels. Polymorphisms also show that MAS reached an accuracy of 100% in sequence tagged site (STS) marker with RG64 and 99.49% in SSR marker with RM21. Several blast resistant rice varieties [P(OM 1), OMP 2, OM P4, OMP 5, and OMP 6] have been reported by many researchers. These are considered as valuable material for pyramiding resistance genes to create durable resistant varieties.
Keys words: Oryza sativa, blast resistance, polymerase chain reaction, simple sequence repeat, sequence tagged site (STS) marker
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