Novel blast resistance genes from a landrace rice variety in Myanmar

Country

Myanmar

Description

The use of broad-spectrum resistance genes is an effective way to achieve durable resistance against rice blast (Pyricularia oryzae Cavara) in rice (Oryza sativa L.).

We previously surveyed the diversity of blast resistance in 948 rice varieties and found Haoru (International Rice Research Institute genebank acc. no. IRGC33090), a Myanmar rice landrace with broad-spectrum resistance against blast.

We examined the genetic basis of Haoru’s broad-spectrum resistance using the standard blast differential system consisting of the standard isolates and differential varieties.

For genetic analysis, we used the BC₁F₁ population and BC₁F₂ lines derived from crosses of Haoru with a susceptible variety, US-2. Co-segregation analysis of the reaction pattern in the BC₁F₁ population against the 20 standard isolates suggested that Haoru harbors three resistance genes.

Using bulk-segregant and linkage analysis, we mapped two of the three resistance genes on chromosomes12 and 6, and designated them as Pi58(t) and Pi59(t), respectively.

Pi58(t) and Pi59(t) were differentiated from other reported resistance genes using the standard differential system. The estimated resistance spectrum of Pi58(t) corresponded with that of Haoru, suggesting that Pi58(t) is primarily responsible for Haoru’s broad-spectrum resistance.

In addition, Pi59(t) and the third gene were also proven to be new and useful genetic resources for studying and improving blast resistance in rice.

Figure, table

Table 1. Reaction patterns of Haoru and segregation lines harboring new resistance genes to standard differential blast isolates

R: Resistant, M: Moderately resistant, S: Susceptible
Fig. 1a. Position of resistance gene, Pi59(t), on chromosome 6.
A: Physical map. Position based on the Nipponabare’s genome sequence.
B: Genetic map. Genetic distances between the gene and markers were estimated using the BC1F2 lines of US-2/Haoru//US-2 (n=55).
Fig. 1b. Position of resistance gene, Pi58(t), on chromosome 12.
A: Physical map. Position based on the Nipponabare’s genome sequence.
B: Genetic map. Genetic distances between the gene and markers were estimated using the BC1F2 lines of US-2/Haoru//US-2 (n=106).