Jared Landry and M.C. Rush, Plant Pathology and Crop Physiology, LSU Agricultural Center

In Vitro Selection 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. Another toxic compound, 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 to avoid the complications of using GMO rice crops. In this project, cells were screened in vitro for mutants resistant to these toxins. Calli were obtained on solid callus induction medium using seed of 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 a-picolinic acid were each 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. Plants resistant to a-picolinic acid were regenerated and are currently being tested for their resistance to the toxin. Plants resistant to a-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. When developed, Liberty resistant plants can be crossed with commercial varieties to replace Liberty resistance based on transgenes with the resistance based on a mutant gene.