Abstract
Rice blast, caused by Pyricularia oryzae Cavara (Magnaporthe grisea (Hebert) Barr), is one of the most severe global rice diseases. The Philippine rice landrace ‘Ingngoppor-tinawon’ (IT) displays not only high field resistance to rice blast but also high tolerance to lodging, despite its very long culms. These characteristics make IT suitable for use in breeding animal feed varieties as whole-crop silage (WCS). To characterize the blast resistance of IT, quantitative trait locus (QTL) analysis of the resistance using simple sequence repeat (SSR) markers was conducted in F3 progenies derived from crossing IT with a susceptible lowland variety, ‘Koshihikari’. A QTL for blast field resistance (qBFR4) was identified on chromosome 4, and the resistance allele was derived from IT. The QTL explained 73.5% of the phenotypic variation for blast resistance. qBFR4 mapped to almost the same position as that of the blast field-resistance gene Pi39. Inoculation assays revealed that IT (containing qBFR4) showed resistance characteristics that differed from those of Mineharuka (containing Pi39), making it very likely that resistance derived from IT is distinct from Pi39. IT showed broad resistance to Japanese isolates and race-specific resistance to some Philippine isolates.
