Molecular cloning of the Pi-ta gene has advanced our
understanding of molecular mechanisms of the gene-for-gene
resistance (Jia et al. 2000). This provides a unique opportunity
to study the origin, introduction and distribution of
Pi-ta, and allows research to address the relationship
between Pi-ta and Pi-ta2, another blast R gene that was
mapped at the Pi-ta region (Rybka et al. 1997). Towards this
end, surveys have identified rice cultivars with one Pi-ta
haplotype that confers resistance and three pi-ta haplotypes
that confer susceptibility (Jia et al. 2003). Conserved polymorphisms
between the Pi-ta and pi-ta DNA sequences
allow the development of dominant and codominant markers
from portions of the Pi-ta gene to be used in identification
and incorporation of the Pi-ta gene in MAS (Jia et al. 2002,
2004a,b, Johnson et al. 2003).