Phenotypic and Genetic Characterization of JJ688BL, a Pi40 Introgression Line Conferring Broad-Spectrum Blast Resistance in Rice

Rice blast, caused by the fungal pathogen Magnaporthe oryzae , continues to threaten stable global rice production. Resistance genes at the Piz locus confer broad-spectrum protection against diverse pathogen races, yet their introgression into elite rice cultivars has long been hindered by tight genetic linkage with Heading date 1 ( Hd1 ), a key flowering time regulator. Here, we report JJ688BL, a Pi40 -introgressed mid-late maturing japonica rice line developed by crossing the premium Korean cultivar Hyeonpum with a Pi40 near-isogenic line selected after breaking the Pi40 - Hd1 linkage. JJ688BL retained the heading date of Hyeonpum and showed no yield penalty in preliminary yield trials conducted over two consecutive years, while demonstrating broad-spectrum resistance to all 32 representative Korean blast isolates tested. PacBio HiFi long-read sequencing revealed that Pi40 carries a distinct leucine-rich repeat (LRR) sequence profile compared with other cloned Piz locus resistance genes, suggesting that this divergence may contribute to its broad resistance spectrum. We further evaluated a DpnII -based 9871.T7E marker for differentiating major haplotype groups at the Piz locus during marker-assisted selection. JJ688BL thus serves as a valuable donor for introducing Pi40 -mediated broad-spectrum blast resistance into premium mid-late maturing japonica cultivars.