Abstract:
R1 plants derived from PR3B and IR58025B hybrid parental lines that were transformed
with the Xa21 transgene were evaluated for their reaction to bacterial blight (BB) through
leaf clipping method. Among the total number of PR3B plants 15.9% were resistant, 71.2%
were intermediate and 13% were susceptible. On the contrary, 1.24% of the hybrid
maintainer rice line IR58025B showed intermediate reaction while 98.76% were susceptibile.
None showed resistance. Nineteen selected BB resistant PR3B R1 lines (resistant/
intermediate in Ro screening and resistant in R1 screening) were also subjected to morpho-
agronomic characterization, hygromycin assay and PCR analysis. The lines were comparable
to the untransformed PR3B hybrid line in agronomic traits such as culm number, culm
length, and 100-grain weight but not in panicle length and spikelet sterility. Among the 19
lines tested 17 produced progenies with resistant and susceptible reactions to hygromycin,
while 2 lines resulted into progenies that are all susceptible. The result suggests that only the
17 lines contain the hpt gene coding for hygromycin resistance. PCR results revealed that of
the 19 lines only 11 were positive for the presence of Xa21 gene. Further tests in the
succeeding generations in terms of presence and expression of the Xa21 gene, as well as
morpho-agronomic traits are needed to be performed so that plants that are highly similar to
the original parental lines but exhibiting resistance to BB can be identified.
