Analysis of organelle genomes in a somatic hybrid derived from cytoplasmic male-sterile Brassica oleracea and atrazine-resistant B. campestris |
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Authors: | D Robertson J D Palmer E D Earle M A Mutschler |
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Institution: | (1) Department of Plant Breeding, Cornell University, 14853-1902 Ithaca, NY, USA;(2) Department of Biology, University of Michigan, 48109 Ann Arbor, MI, USA;(3) Present address: Department of Zoology, Duke University, 27706 Durham, NC, USA |
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Abstract: | Summary An atrazine-resistant, male-fertile Brassica napus plant was synthesized by fusion of protoplasts from the diploid species B. oleracea and B. campestris. Leaf protoplasts from B. oleracea var. italica carrying the Ogura male-sterile cytoplasm derived from Raphanus sativus were fused with etiolated hypocotyl protoplasts of atrazine-resistant B. campestris. The selection procedure was based on the inability of B. campestris protoplasts to regenerate in the media used, and the reduction of light-induced growth of B. oleracea tissue by atrazine. A somatic hybrid plant that differed in morphology from both B. oleracea and B. campestris was regenerated on medium containing 50 M atrazine. Its chromosome number was 36–38, approximately that of B. napus. Furthermore, nuclear ribosomal DNA from this hybrid was a mixture of both parental rDNAs. Southern blot analyses of chloroplast DNA and an assay involving tetrazolium blue indicated that the hybrid contained atrazine-resistant B. campestris chloroplasts. The hybrid's mitochondrial genome was recombinant, containing fragments unique to each parent, as well as novel fragments carrying putative crossover points. Although the plant was female-sterile, it was successfully used to pollinate B. napus. |
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Keywords: | Somatic hybridization Atrazine resistance Mitochondrial recombinants Brassica Cytoplasmic male sterility |
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