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2004
LSU-HHMI Summer Undergraduate Research Program |
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 Jared
Landry Milton Rush, Plant Pathology
In Vitro Screening for Mutants Resistant to Toxic Compounds
in Rice
Blast disease, caused by Pyricularia oryzae, is one
of the most widespread and serious diseases in rice. α-picolinic
acid(C6H5NO2) is a toxin produced by P. oryzae in support
of its penetration and infection activities. Liberty herbicide,
used for weed control, is a toxic compound of microbial origin,
which will be used on rice plants transformed for resistance
to Liberty. This system is being developed commercially and
will be sold under the name “Liberty-Link”. We are
trying to develop an alternative non-transformed Liberty resistance
based on in vitro mutations. In this project, cells
were screened in vitro for mutants resistant to these
toxins. Calli were obtained on solid callus induction medium
using seed-derived callus from Taipei 309 rice. After three
months, these calli were transferred to liquid medium in flasks
to begin in vitro screening. Multiple concentrations of Liberty
herbicide and α-picolinic acid were used to screen calli
for mutants resistant to these toxins. The calli showed resistance
at 10 ppm of Liberty herbicide and 20 ppm of α-picolinic
acid. Mutants at these concentrations were transferred to solid
regeneration medium to obtain plants that will be used for further
testing. Plants are regenerating at this time. Plants resistant
to α-picolinic acid will be tested for resistance to infection
by P. oryzae. Genes for resistance to rice blast can
be transferred to commercial varieties by conventional breeding
procedures. Liberty resistant plants can be crossed with commercial
varieties to replace Liberty resistance based on transgenes
with the resistance based on a mutant gene.
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