A New Resistance Gene in Combination with Rmg8 Confers Strong Resistance Against Triticum Isolates of Pyricularia oryzae in a Common Wheat Landrace

Abstract

The wheat blast fungus (Triticum pathotype of Pyricularia oryzae) first arose in Brazil in 1985 and has recently spread to Asia. Resistance genes against this new pathogen are very rare in common wheat populations. We screened 520 local landraces of common wheat collected worldwide with Br48, a Triticum isolate collected in Brazil, and found a highly resistant, unique accession, GR119. When F seedlings derived from a cross between GR119 and Chinese Spring (CS, susceptible control) were inoculated with Br48, resistant and susceptible seedlings segregated in a 15:1 ratio, suggesting that GR119 carries two resistance genes. When the F seedlings were inoculated with Br48ΔA8 carrying a disrupted allele of AVR-Rmg8 (an avirulence gene corresponding to a previously reported resistance gene, Rmg8), however, the segregation fitted a 3:1 ratio. These results suggest that one of the two genes in GR119 was Rmg8. The other, new gene was tentatively designated as RmgGR119. GR119 was highly resistant to all Triticum isolates tested. Spikes of GR119 were highly resistant to Br48, moderately resistant to Br48ΔA8 and a hybrid culture carrying avr-Rmg8 (nonfunctional allele), and highly resistant to its transformant carrying AVR-Rmg8. The strong resistance of GR119 was attributed to the combined effects of Rmg8 and RmgGR119.

Genome-wide association mapping for wheat blast resistance in CIMMYT’s international screening nurseries evaluated in Bolivia and Bangladesh

“…To understand the frequencies of lines with the 2NS translocation, we obtained their frequencies in eight IBWSNs (45)(46)(47)(48)(49)(50)(51)(52) and SAWSNs (30)(31)(32)(33)(34)(35)(36)(37) distributed internationally between 2012 and 2019 and comprising 4143 lines ( Supplementary Table S9). We observed that in the IBWSNs, the percentage of lines with the 2NS translocation had increased 113.8% in seven years, from 44% in 2012 to 94.1% in 2019.…”

Wheat Blast in Bangladesh: The Current Situation and Future Impacts

“…This is why population genetics for monitoring avirulence genes in the MoT population is important for breeding. Wang et al (2018) found that Avr-Rmg8 gene existed in 15 selected Brazilian isolates and Bangladesh isolate (No. 12), suggesting that introduction of Rmg8 might be effective among most MoT strains ( Wang et al, 2018 ).…”

“…However, there might be hope in the strategy of combining multiple R genes. Wang et al (2018) recently screened 520 wheat cultivars and found that a cultivar, GR119, was highly resistant to the MoT isolate Br47. They identified that the resistance was caused by synergistic effect of two R genes, Rmg8 and RmgGR119 .…”

Wheat blast disease: Bangladesh and global perspectives of blast resistance

“…This "Rmg8" gene is a dominant gene showing high resistance against Triticum isolate Br48 and occupying the long arm of 2B chromosome (Anh et al, 2015). Along with Rmg8, Wang et al (2018) found another wheat blast resistance gene in a local landrace GR119 that gene was designated as RmgGR119. In GR119 the cumulative effect of Rmg8 and RmgGR119 gave a strong blast resistance status (Wang et al, 2018).…”

“…Along with Rmg8, Wang et al (2018) found another wheat blast resistance gene in a local landrace GR119 that gene was designated as RmgGR119. In GR119 the cumulative effect of Rmg8 and RmgGR119 gave a strong blast resistance status (Wang et al, 2018).…”