Virus-Resistance Assays.
Since RSV infects plants only
through transmission by planthoppers, the assay for viral
resistance was performed by using viruliferous small brown
planthoppers as vectors.
In our rice culture system, several
plants can be regenerated from each callus line. Therefore,
these plants are assumed to be clones with respect to the
location and the copy number of the CP gene. Three or four
plants (clones) from five independent primary transformants
were examined for resistance to viral infection. Of the four
clones derived from each of the transgenic plants expressing
the RSV CP (lines KI301, KV11514, and NII1801) none
showed symptoms (Table 1).
However, two lines carrying the
CP gene, which did not express the CP (lines NIII606 and
NIII809), demonstrated clear disease symptoms in all the
clones examined. We therefore concluded that virus resistance
is conferred by expression of the CP in primary
transgenic rice plants.
More than 220 plants derived from selfed progeny of six
primary transformants (KV8031, KV113015, KV113016,
KVII5071, KV115072, and KV113092) were examined for
inheritance of the CP gene by Western blot analysis. Results
indicated that the CP gene was stably transmitted to the next
generation in five of six transformants examined.