Plant & Animal Genome VI Conference Plant & Animal Genome VI Conference
W55
David North Plant Research Centre, Bureau of Sugar Experiment Stations, 50 Meiers Road, Indooroopilly, Brisbane, Australia 4068
Transgenic sugarcane plants containing a sugarcane mosaic potyvirus
coat protein construct are resistant to challenge infection by the
pathogen. These plants were produced by microprojectile transformation
of embryogenic callus derived from immature leaf whorls. The selectable
marker gene was cointroduced with the coat protein gene construct and
transformed cells were selected on geniticin. The sugarcane callus was
left in the dark for 9 weeks on geniticin supplemented medium before
being transferred into light to induce plant regeneration. Regenerated
plants were then established in pots in a containment glasshouse. All
regenerated plants were screened for the presence of the transgenes
using PCR, and positive plants maintained for virus challenge
experiments. Sets from transgenic plants were planted in a
containment glasshouse at the Pathology Farm of BSES and challenged
with SCMV when the plants were approximately six weeks old. Four
phenotypic responses to infection were observed: immune resistance;
recovery resistance; atypical symptoms (apparently resistant), and
typical mosaic symptoms (susceptibility). Of the seventy lines assessed
to date, ten show immunity, ten show recovery resistance and six show
atypical symptoms. The resistance phenotype was 100% correlated with
lack of systemic spread of the virus within the plant (ELISA data), and
inoculum prepared from these plants was not infectious when back-inoculated
on susceptible maize plants. In contrast, inoculum prepared from the
susceptible lines showed 100% correlation with viral titre (ELISA data)
and the development of typical symptoms on back-inoculated maize plants.
Plants with atypical symptoms were negative for virus in the ELISA assay
and symptoms did not develop on back-inoculated maize suggesting that these
plants were indeed resistant. The origin of this resistance is unclear at
this stage. Molecular analysis to elucidate this phenomenon is currently
in progress.