Oilseed rape cytoplasm transfer

Beversdorf, W.D., J. Weiss-Lerman, L.R. Erickson, and V. Souza Machado (1980). Transfer of cytoplasmically-inherited triazine resistance from bird s rape to cultivated oilseed rape (Brassica campestris and B. napus). Can. J. Genet. Cytol., 22 167-172. 

Transfer of the tolerant birds rape cytoplasm to B. napus has resulted in stable, highly tolerant genotypes of oilseed rape, one of which has been released as a canola variety, OAC Triton, with another variety, selected in Saskatchewan (tentatively named Tribute) expected for release later this year. 

Figure 1. Transfer of the triazine tolerant cytoplasm from a weed biotype to oilseed rape by backcrossing.

Most of the triazine tolerant weed biotypes Identified to date have economic relatives but few if any are as closely related to economic crops as the birds rape. To date, this cytoplasm has been transfered to oilseed rape, rutabaga and oriental mustard by several breeding groups. Partial cross-compatibi 1 ity with several other Brassica species including the cole crops, and other more distantly related species (eg, Diplotaxis and Raphanus species) may permit transfer by classical methods (perhaps assisted by embryo rescue techniques). Chloroplast or mitochondrial X nuclear Incompatibilities however, may limit this potential. As other triazine tolerant weed biotypes emerge, opportunities for transfer to closely related economic species by classical methods may evolve. 

Combination of atrazine resistance and cytoplasmic male sterility in rapeseed. Transfer of atrazine resistant chloroplasts from bird s rape (B. oapestris) into oilseed rape has been accomplished by back-crossTng (s this volume). The purpose achieved by somatic cell fusion was to combine the atrazine-resistant chloroplasts carried by a B. napus line with cytoplasmic male sterility (CMS), a mitoohondrlal tralt (l9). The CMS trait was carried by a B. napus line with the cytoplasm of radish (Raphanus sativus). Since both traits, atrazine resistance and CMS, are maternally inherited in sexual crosses, the only way to combine the traits was by protoplast fusion. The desired atrazine-resistant cybrids were identified in a randomly regenerated sample of plants by the presence of the CMS flower morphology and their darker green color at low temperature. Somatic hybrids rather than cybrids were obtained in each clone since no irradiation had been used to facilitate the elimination of one of the parental nuclei. 

Barsby, T.L., Yarrow, S.A., Kemble, R.J. and Grant, I. (1987) The transfer of cytoplasmic male sterility to winter-type oilseed rape (Brassica napus L.) by protoplast fusion. Plant Sci. 53, 243-248. 

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