Managing rice blast through genetic resistance requires continuous monitoring of pathogen evolution to detect genetic and virulence changes. Resistance genes effective against new pathotypes detected in 2002 and 2003 were identified. Gene combinations that effectively resist Colombian blast populations include Pi-1, Pi-2, Pi-33, and Pi-ta2. These resistance genes are now being incorporated into different commercial rice cultivars from Latin America through a backcrossing program, using greenhouse inoculations, field evaluations, and marker-assisted selection.

The most effective resistance genes detected correspond to those avirulence genes found in higher frequencies or with lower rates of mutations in the different genetic lineages of the pathogen. A newly reported resistance gene (Pi-9), derived from the wild rice species (Oryza minuta), was tested and found to be potentially effective against Colombian blast pathogen populations.

Recently detected PCR-based molecular markers, found to be associated with durable blast-resistance genes, are being used to introgress these resistance genes into Colombian rice germplasm, or used to develop more specific markers such as SNPs. Potential donors of durable blast resistance were identified after continuous evaluations since year 2000, and are now included in a blast nursery to be distributed to different Latin American breeding programs for their use as progenitors. Near-isogenic lines with different resistance genes were developed and are also being distributed to Latin American partners to identify those genes that most effectively resist local blast pathogen populations.

Contact: Fernando Correa