TRANSFER OF CYTOPLASMICALLY-INHERITED TRIAZINE RESISTANCE FROM BIRD'S RAPE TO CULTIVATED OILSEED RAPE (<i>BRASSICA CAMPESTRIS</i> AND <i>B</i>. <i>NAPUS</i>)

Abstract

Atrazine resistant biotypes of bird's rape Brassica campestris L. provided a potential source of cytoplasmically-inherited triazine resistance for cultivated oilseed rape. A back-crossing program was initiated to incorporate the cytoplasm of the triazine resistant bird's rape (2n = 20) into B. napus L. cv. 'Tower' (2n = 38) and B. campestris L. cvs. 'Torch' and 'Candle' (2n = 20). Three 38-chromosome progeny were identified among backcross 1 (BC 1 ) progeny of bird's rape × Tower (recurrent pollen parent). All BC 1 progeny of all crosses between bird's rape (female) and cultivated oilseed rape (recurrent pollen parents) were resistant to post-emergence application of several triazines, including atrazine, cyanazine and metribuzin. In similar crosses using cultivars as the recurrent female parents, BC 1 progeny were susceptible to triazines, which indicated the resistance was cytoplasmically inherited. Selection among BC 2 progeny of all crosses for low erucic acid content in seed was effective. In field trials BC 3 's carrying cytoplasm from bird's rape were not injured by post-emergence applications of triazine herbicides which killed their recurrent cultivar pollen parents. No obvious deleterious effect of the bird's rape cytoplasm has been noted.