Production of new CMS Brassica oleracea by transfer of `Anand' cytoplasm from B. rapa through protoplast fusion |
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Authors: | T Cardi E D Earle |
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Institution: | (1) Department of Plant Breeding and Biometry, Cornell University, Ithaca, NY 14853-1902, USA, US |
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Abstract: | New types of cytoplasmic male sterility (CMS) in Brassica oleracea would be useful for F1 hybrid seed production. The `Anand' cytoplasm derives from the wild species B. tournefortii. Rapid cycling stocks of B. rapa and B. oleracea were used in cybridization experiments as donor and recipient of `Anand' (=`tour') CMS, respectively. Prior to fusion with
PEG, donor protoplasts were inactivated with 30 krad γ-rays and recipient ones with 3 mM iodoacetate, respectively. No calli were obtained from the pre-treated protoplasts. The frequency of shoot regeneration was
21–43% in untreated B. oleracea controls, but only 0–0.5% in `Anand' B. rapa. Putative cybrids were regenerated from about 3% of the calli from fused protoplasts. Regenerated plants were analyzed for
nuclear DNA content, plant and flower morphology, pollen production, female fertility, cold tolerance, and organelle composition.
Eighty-one percent of the regenerated controls and 63% of fusion-derived plants were diploid. The rest showed DNA contents
corresponding to 2x–4x, 4x, or higher ploidy levels, presumably due to somatic doubling in vitro and/or fusions in which the donor nucleus was not completely
eliminated. Sixty-four percent of the cybrids had stamens and petals varying in size and shape and were male-sterile, with
indehiscent anthers. Their phenotype was otherwise similar to that of B. oleracea. The remaining plants had normal flowers and were male-fertile. Data from crosses with fertile pollinators indicated good
female fertility in some of the sterile lines, both after hand and insect pollinations in cages. Mitochondrial (mt) segregation
in the cybrids was slightly biased towards `Anand' mitochondria, and the presence of `Anand' mtDNA fragments was strongly
associated with male sterility. Evidence of mtDNA rearrangements was obtained in some cybrids. Segregation of chloroplasts
was slightly biased towards B. oleracea. The presence of `Anand' chloroplasts with a B. oleracea nucleus did not result in cold temperature chlorosis, as seen in `Ogura' CMS plants.
Received: 22 February 1996 / Accepted: 10 May 1996 |
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Keywords: | Brassica oleracea Brassica tournefortii Anand Cytoplasmic male sterility Protoplast fusion |
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