Resistance to rice blast disease identified in a Presidio x Oryza rufipogon rice advanced backcross population

Authors: Eizenga, Georgia; Grunden, Quynh; Jia, Melissa; Jia, Yulin; Jackson, Aaron

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/26/2026
Publication Date: 5/29/2026
Citation: Eizenga, G.C., Grunden, Q.P., Jia, M.H., Jia, Y., Jackson, A.K. 2026. Resistance to rice blast disease identified in a Presidio x Oryza rufipogon rice advanced backcross population. Crop Science. https://doi.org/10.1002/csc2.70304.
DOI: https://doi.org/10.1002/csc2.70304

Interpretive Summary: Rice is a major cereal crop which feeds more than half of the global population every day. These rice plants are constantly attacked by insect pests and fungal diseases, in fact 10% to 30% of the rice crop is lost to the fungal disease, rice blast, every year. The two main methods of controlling rice blast are fungicides and resistance genes. Unfortunately, the rice blast fungus changes rapidly so it can continue it’s attack on the rice plant, so that the plants that were resistant to rice blast disease become susceptible. This means there is a constant need for new or novel resistance genes. One source of new resistance genes is the rice wild species. These are the plant species that man domesticated in ancient times to select for cultivated rice as we know it today. These rice wild species are a potential source of new blast resistance genes because plants of these wild species have grown for thousands of years and would need resistance genes to survive the attacks of the rice blast fungus. One rice wild species collected in Bangladesh, is classified as Oryza rufipogon, a progenitor species of cultivated rice was identified as resistant to three variants of the blast fungus found in the USA and not have any of the five resistance genes currently in U.S. rice. Through crossing, the O. rufipogon DNA was incorporated into the U.S. rice variety Presidio and three possible novel resistance genes were discovered. Additional evaluations will be conducted to validate these three possible blast resistance genes to add to the arsenal of resistance genes being used to fight the attacks of the rice blast fungus causing rice blast disease.

Technical Abstract: The rice ancestral wild species, 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 main objective of this study was to discover novel R gene(s) in the ORSC accessions and map the gene(s) to chromosome (chr.) position by QTL mapping. Screening a collection of 94 ORSC accessions for blast disease reaction using three virulent U.S. M. oryzae races, and for DNA markers tagging five major R genes identified three potential ORSC donor parents. These accessions were crossed with two U.S. rice cultivars and based on F1 seed set, blast reaction and known R gene(s), the Presidio x O. rufipogon (IRGC103404) cross was selected to develop the advanced backcross mapping population of 244 BC2F3:5 backcross inbred lines (BILs). QTL mapping of the reaction to six different U.S. blast races identified three QTL for blast resistance from the wild O. rufipogon donor, qBLAST10 on chr. 10 at 11.92 to 12.15 Mb, qBLAST11-1 on chr. 11 at 17.29 to18.29 Mb, and qBLAST11-2 on chr. 11 at 26.30 to 27.82 Mb. The QTL qBLAST10 and qBLAST 11-2 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.