Efficient isolation of microspores and the production of microspore-derived embryos from Brassica napus

Mechanical isolation of Brassica napus microspores from whole buds with a micro-blender enabled the rapid isolation of large numbers of microspores free from tissue and cellular debris. The procedure resulted in savings of time and labor and could be used independent of the size and number of buds to be examined. Between 700 and 1000 embryos per bud were obtained. Compared to anther removal there was no difference in embryo yields or quality. Microspore isolation under cool conditions and overnight incubation prior to plating improved the frequency of embryogenesis. Over 75% of the embryos developed into normal torpedo-stage structures if the medium was replenished during culture and the embryos placed on a gyratory shaker. Over 80% of the torpedo-shaped embryos would ultimately develop into plants. The implications of these techniques to genetic and physiological studies are discussed.

The combination of polima cms and cytoplasmic triazine resistance in Brassica napus

Protoplast fusion was used to combine cytoplasmic triazine resistance (ctr) and Polima type cytoplasmic male sterility (cms) in Brassica napus. The cybrids produced constitute the major biological input required for the production of commercial single-cross hybrid rapeseed bearing cytoplasmic triazine resistance. The results also indicate that Polima cms is associated with the mitochondrial genome.

The introduction of CMS mitochondria to triazine tolerant Brassica napus L., var. "Regent", by micromanipulation of individual heterokaryons

Cytoplasmic triazine tolerance and cytoplasmic male sterility traits were combined in the nuclear genomic background of the Brassica napus variety 'Regent', following protoplast fusion, selection of fusion products by manual micro-manipulation, and culture in a Nicotiana tabacum nurse system. Whole plant cybrid regenerants were morphologically normal and produced seed on pollination, demonstrating their potential for incorporation into a breeding program.

Mitochondrial DNA rearrangements in somatic hybrids of Solanum tuberosum and Solanum brevidens

Thirty somatic hybrids between Solanum tuberosum and Solanum brevidens were analysed for mitochondrial and chloroplast genome rearrangements. In all cases, the chloroplast genomes were inherited from one of the parental protoplast populations. No chloroplast DNA alterations were evident but a range of mitochondrial DNA alterations, from zero to extensive intra- and inter-molecular recombinations, were found. Such recombinations involved specific 'recombination hot spots' in the mitochondrial genome. Not all hybrids regenerated from a common callus possessed identical mitochondrial genomes, suggesting that sorting out of mitochondrial populations in the callus may have been incomplete at the plant regeneration stage. Sorting out of organelles in planta was not observed.

A rapid and efficient alternative procedure for the regeneration of plants from hypocotyl protoplasts of Brassica napus

Protoplasts of several spring and winter varieties of Brassica napus were isolated from hypocotyl tissue. Protoplasts divided and formed cell colonies at high frequency, without browning when cultured in modified Shepards' medium. This high efficiency of proliferation was sustained through to plant regeneration with all varieties cultured. This has been attributed to the incorporation of a reservoir medium, the presence of 2,4-D in the proliferation medium, and the presence of kinetin in conjunction with lowering of the sucrose concentration in the regeneration medium.

Somatic hybridization in the genus Solanum: S. tuberosum and S. brevidens

Somatic hybrid plants were regenerated from fused mesophyll protoplasts of an albino potato (Solanum tuberosum spp. tuberosum) variant and Solanum brevidens, a non-tuber bearing species which is sexually incompatible with S. tuberosum. These somatic hybrid plants represent the first example of direct hybridization between potato and members of the taxonomic group Etuberosa, and offer the potential for introgressing valuable germplasm from Solanum species outside the sexually compatible range into a worldwide crop species.

Heterokaryon identification through simultaneous fluorescence of tetramethylrhodamine isothiocyanate and fluorescein isothiocyanate labelled protoplasts

Protoplasts were separately stained with the fluorescent dyes fluorescein isothiocyanate (FITC) and tetramethylrhodamine isothiocyanate (TRITC). Following fusion, doubly stained heterokaryons were identified under fluorescence microscopy by using the Zeiss filter set 48 77 05 (excitation filter 450-490 nm, dichroic reflector 510 nm, and barrier filter 520 nm) which allowed simultaneous fluorochrome emissions. Previously, either emission spectrum, but not both, was possible for any single filter set.