Genetic Variation of Rice Blast Resistance Genes inOryza sativaand Its Wild Relatives

Abstract

Rice blast is one of the most serious diseases of cultivated rice. We characterize here the nucleotide variation present at nine blast resistance (R) genes within a collection of 13 indica and 13 japonica rice cultivars, along with 12 accessions of wild rice (Oryza rufipogon). Compared with other functional genes, high genetic diversity has been observed in blast R genes (mean nucleotide diversity of 3.2%), which might be the most important characteristics of blast R genes. Even if the overall diversity in R genes is high, the genes can also be divided into three types according to different degrees of conservation by principal component analysis: relative conservation (Pita, Pit, Pi5-1, and Pid-2), intermediate diversity (Pi37, Pib, and Pi9), and high diversity (Pi36 and Pikm-2), suggesting that these types of R genes might recognize different categories of molecules released by rice blast pathogens. Our data also revealed that a significant regression was observed between the wild and the cultivated accessions with respect to their u a , providing an indication that artificial selection has played an important role during the evolution of these R genes. High correlation between nucleotide diversity and K a /K s or R M in NBSencoding genes might be the clues for possible mechanisms of rapid evolution in these genes.

Exploring Key Blast and Bacterial Blight Resistance Genes in Genetically Diverse Rice Accessions through Molecular and Phenotypic Evaluation

“…The Pib is a blast (fungi) disease resistance gene and it was characterized from an O. sativa indica cultivar (Wang et al, 1999), whereas Xa21 is a BB disease resistance gene and it was identified and characterized from Oryza wild species (Song et al, 1995). However, functional Pib alleles were also reported from different accessions of O. rufipogon (Yang et al, 2007; Liu et al, 2011), while a set of Xa21 alleles were reported from other wild Oryza species ( O. nivara Sharma & Shastry) and O. sativa (Bimolata et al, 2015). Hence, there is a possibility that wild Oryza and/or O. sativa species might possess both of the genes and be segregated together during the domestication process.…”

“…The analysis indicated that Pib and Xa21 genes were grouped in one cluster (Fig. However, functional Pib alleles were also reported from different accessions of O. rufipogon (Yang et al, 2007;Liu et al, 2011), while a set of Xa21 alleles were reported from other wild Oryza species (O. nivara Sharma & Shastry) and O. sativa (Bimolata et al, 2015). They showed high similarity in their presence or distribution among the 211 screened accessions.…”

Rice Blast, A Major Threat to the Rice Production and its Various Management Techniques

“…Due to the high genetic variability of the fungus, resistance to infection by Pyricularia oryzae can be short-lived (Khemmuk, 2017). The breakdown of resistance to Pyricularia oryzae results from evolution of genetic variants (races) in the pathogen populations (Liu et al, 2011).…”

Investigating Rice Blast Resistance Gene Distribution among Landrace Rice Varieties in Lower Northern Thailand for Improving Rice Cultivars

“…More recently, rice blast resistance genes were characterized in landrace rice from various locations such as Bangladesh, China, Japan, Malaysia, Tailand, and Vietnam. From these, more than 30 R genes were identifed in Asian landrace rice, i.e., Pi-36, Pi9, Pib, Pigm(t), Pik-p, Pik-h, Pi-ta, Piz [7,[20][21][22][23]. Of these 30 R genes, the Pi9, Pib, and Pi-ta were commonly found in resistance rice cultivars grown in Malaysia [20] and Tailand [7].…”