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

Abstract

Atrazine resistant biotypes of bird''s rape B. campestris L. provided a potential source of cytoplasmically-inherited triazine resistance for cultivated oilseed rape. A backcrossing program was initiated to incorporate the cytoplasm of the triazine resistant bird''s rape (2n = 20) into B. napus L. Tower (2n = 38) and B. campestris L. ''Torch'' and ''Candle'' (2n = 20). Three 38-chromosome progeny were identified among backcross1 (BC1) progeny of bird''s rape .times. ''Tower'' (recurrent pollen parent). All BC1 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, BC1 progeny were susceptible to triazines, which indicated the resistance was cytoplasmically inherited. Selection among BC2 progeny of all crosses for low erucic acid content in seed was effective. In field trials BC3 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 was noted.