Abstract
BackgroundRice (Oryza sativa) is one of the most important food crops in the world. Rice blast, caused by the fungal pathogen Magnaporthe oryzae, is one of the most destructive rice diseases worldwide. To effectively cope with this problem, the use of rice blast resistance varieties through innovative breeding programs is the best strategy to date. The Thai rice variety Jao Hom Nin (JHN) showed broad-spectrum resistance against Thai rice blast isolates. Two QTLs for blast resistance in JHN were reported on chromosome 1 (QTL1) and 11 (QTL11).ResultsMonogenic lines of QTL1 (QTL1-C) and QTL11 (QTL11-C) in the CO39 genetic background were generated. Cluster analysis based on the disease reaction pattern of QTL1-C and QTL11-C, together with IRBLs, showed that those two monogenic lines were clustered with IRBLsh-S (Pish) and IRBL7-M (Pi7), respectively. Moreover, sequence analysis revealed that Pish and Pi7 were embedded within the QTL1 and QTL11 delimited genomic intervals, respectively. This study thus concluded that QTL1 and QTL11 could encode alleles of Pish and Pi7, designated as Pish-J and Pi7-J, respectively. To validate this hypothesis, the genomic regions of Pish-J and Pi7-J were cloned and sequenced. Protein sequence comparison revealed that Pish-J and Pi7-J were identical to Pish and Pi7, respectively. The holistic disease spectrum of JHN was found to be exactly attributed to the additive ones of both QTL1-C and QTL11-C.ConclusionJHN showed broad spectrum resistance against Thai and Philippine rice blast isolates. As this study demonstrated, the combination of two resistance genes, Pish-J and Pi7-J, in JHN, with each controlling broad-spectrum resistance to rice blast disease, explains the high level of resistance. Thus, the combination of Pish and Pi7 can provide a practical scheme for breeding durable resistance in rice against rice blast disease.
Highlights
Rice (Oryza sativa) is one of the most important food crops in the world
Given the fact that Jao Hom Nin (JHN) contained at least two resistance loci, i.e., QTL1 on chromosome 1 and QTL11 on chromosome 11 (Noenplab et al 2006), we generated two monogenic lines which were designated as QTL1-C and QTL11-C containing individual QTL1 and QTL11, respectively, in the CO39 genetic background via marker aided backcrossing (MABC) (Additional file 2: Figure S1)
12 isolates were avirulent to QTL1-C but virulent to QTL11-C, suggesting that QTL1 rather than QTL11 contributed to the resistance of JHN to these 12 isolates (Table 1)
Summary
Rice (Oryza sativa) is one of the most important food crops in the world. Rice blast, caused by the fungal pathogen Magnaporthe oryzae, is one of the most destructive rice diseases worldwide. Rice blast, caused by an ascomycete Magnaporthe oryzae, is one of the most destructive diseases of rice worldwide (Ahn et al 2000), which leads to economic losses of more than 70 billion dollars (Scheuermann et al 2012). The most powerful tool to control rice blast is to use resistant varieties. These varieties protect rice plants against the pathogens, upon infection, via the induction of hypersensitive response (HR), which occurs via genefor-gene recognition of a pathogen effector (Avr) and a host-encoded resistance (R) protein (Gururani et al 2012).
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