Identification and Mapping of the QTL Controlling Resistance to Blast (Magnaporthe grisea) Disease in Rice

The rice blast resistance of one hundred and sixty F(subscript 2)-derived lines from the TNG69 x KHK cross was evaluated in greenhouse inoculation and field tests. Results from both screening methods revealed that the resistance to rice blast was mainly controlled by two major and several minor QTLs (Quantitative trait loci). Broad-sense heritability (H²(subscript B)) was estimated according to the variance of combined analysis. The value was 85.4% in greenhouse inoculation and 73.7% in field test. The blast resistance phenotypes in six environments (2 methods x 3 years) were analyzed using Mapmaker-QTL program. All informative markers distributed within the R165-R750 interval of linkage group A (chromosome 12) were correlated with rice blast resistance. Except for slighter symptom in the field test during 1999, the phenotypic contribution of each detected QTL was ranged from 21.3% to 72.4% with LOD scores from 7.43 to 24.42 in all surveyed environments. Thus, it is suggested that a major resistance gene was located on chromosome 12. Our results not only have proved the efficiency of greenhouse test for rice blast resistance, and have located a major gene with resistance across the different environments. The DNA makers closely linked with QTL affecting blast resistance may provide a useful tool for marker-assistant-selection (MAS) in the near future.