Genetic characterization of a mutation that enhances paraquat tolerance in the fern Ceratopteris richardii.

Three nuclear mutations that affect tolerance to the herbicide paraquat have been selected in the fern Ceratopteris richardii. Two of the mutations, pq2 and pq45 are allelic and confer low and moderate tolerance, respectively. A third mutation, pqa6, is not linked to the other two and significantly enhances the level of tolerance when in combination with either pq2 or pq45. The pqa6 mutation does not independently confer tolerance in the absence of the other mutations.