Resistance to rice blast disease identified among progeny of a Presidio × Oryza rufipogon advanced backcross population

Abstract

The ancestral species of rice (Oryza sativa L.), collectively identified as the Oryza rufipogon species complex (ORSC), are a potential source of novel resistance (R) genes to control rice blast disease, a major fungal disease worldwide, caused by Magnaporthe oryzae. The objective of this study was to discover novel resistance genes (R genes) in the ORSC accessions and map the gene(s) to chromosome (chr.) position by quantitative trait locus (QTL) mapping. Screening a collection of 94 ORSC accessions for blast disease reaction using three virulent US M. oryzae races and for DNA markers tagging five major R genes identified three potential ORSC donor parents. These accessions were crossed with Presidio, a US long grain cultivar and based on F₁ seed set, blast reaction, and known R gene(s), the Presidio × O. rufipogon (IRGC103404, International Rice Germplasm Collection) cross was selected to develop the advanced backcross mapping population of 244 BC₂F_3:5 backcross inbred lines. QTL mapping of the reaction to six different US blast races identified three QTLs for blast resistance from the wild O. rufipogon donor, qBLAST10 on chr. 10 at 11.92–12.15 Mb, qBLAST11-1 on chr. 11 at 17.29–18.29 Mb, and qBLAST11-2 on chr. 11 at 26.30–27.82 Mb. The QTL qBLAST10 and qBLAST11-2 were resistant to M. oryzae races IB54 and IB45, respectively, whereas qBLAST11-1 was resistant to three races, IB54 and two of the most virulent races, IA1 and IB33. No major R genes mapped to this position; thus, qBLAST11-1 possibly reveals a novel R gene discovered in the wild progenitor.