BLAST RESISTANCE GENES IN WILD RICE

BLAST RESISTANCE GENES IN WILD RICE Oryza rufipogon
AND RICE CULTIVAR IR64

ABSTRACT
Rice improvement for durable resistance to blast is difficult due to
the complexity in inheritance of the resistance. A study was
conducted to analyze blast resistance in rice using two different
approaches, i.e. blast QTL mapping and comparison of resistance
spectrum and genetic control. The blast QTL mapping was done
using an interspecific population originated from backcrossing
between wild rice Oryza rufipogon and cultivated rice IR64.
Comparison of the resistance spectrum and the genetic control
was based on phenotypic reactions. Results of the experiment
showed that based on the blast QTL mapping, two resistance
genes, Pirf2-1(t) and Pir2-3(t), were mapped on chromosome 2.
The Pirf2-1(t) gene was isolated from the chromosome 2 of O.
rufipogon and encoding resistance to Pyricularia grisea race 001,
while the Pir2-3(t) gene that was isolated from rice cultivar IR64
was encoding for resistance to P. grisea race 173. Based on the
resistance spectrum, O. rufipogon has a non-race specific
resistance to P. grisea races. The Pirf2-1(t) gene in O. rufipogon
that contributed to a dominant mode of resistance to rice blast
was affected by a duplicate epistasis. The Pir2-3(t) gene in IR64
that contributed to an additive mode of resistance was affected by
a complementary epistasis.