Elizabeth G. Williams

A hybrid between Trifolium repens and T. ambiguum obtained with the aid of embryo culture

Abstract A sterile, stoloniferous hybrid (2n = 32) between Caucasian clover, Trifolium ambiguum (2n = 4x = 32) ♀ and white clover, T. repens ♀ has been produced with the aid of embryo culture using transplanted nurse endosperm. Vegetatively the hybrid strongly resembles T. repens, but several vegetative and floral characters are modified towards T. ambiguum. Hybridity is supported by the presence of heterologous nucleolus-organising chromosomes and by the results of gel electrophoresis of leaf isozymes.

Comparative analysis of fatty acids in pollen and seed of rapeseed

Abstract Lipids accounted for 31.7% of the dry wt of mature, viable pollen of rapeseed ( Brassica napus ). External lipids of the pollen coat, specified by the diploid parental genome, and internal cytoplasmic lipids, presumably specified by the haploid pollen genome, were separated by differential extraction. External lipids and paraffins represented 9.8 % of pollen dry wt, and contained predominantly linolenic (18:3) with significant amounts of palmitic (16:0), stearic (18:0) and myristic (14:0) acids, as well as paraffins. Internal lipids accounted for 21.9% of pollen dry wt and comprised predominantly 18:3 and 16:0. Mature seeds of B. napus comprised 45.0 % lipid, with a fatty acid composition different from that of either pollen fraction. Decanoic (10:0), lauric (12:0) and hexadecatrienoic (16:3) acids were detected in pollen but not in seeds. These data are discussed in relation to pollen biochemistry and the potential for pollen selection in rapeseed breeding.

A partially fertile hybrid between Trifolium repens and T. ambiguum

Abstract A vigorous partially fertile hybrid (2n = 32) between Caucasian clover, Trifolium ambiguum (2n = 4x = 32) ♀,and white clover, T. repens (2n = 32) ♂. has been produced with the aid of embryo culture. Hand polinations with self pollen and pollen from T. repens have yielded F2, F3, and backcross progeny.

Early seed development after crossing of Trifolium ambiguum and T. repens

Abstract Hand pollination of Trifolium ambiguum Bieb. (2n = 4x = 32) with pollen from T. repens L. (2n = 32) resulted in fertilisation and pod enlargement, but no mature viable seed was produced. Hybrid embryos and endosperms were developmentally more advanced than those of T. ambiguum (4x) controls for the first 2 days after pollination. Subsequently hybrid embryo growth slowed, and although an advanced globular or early “heart” stage was attained at 5–6 days after pollination normal differentiation did not proceed beyond this stage and almost all embryos were visibly degenerating by 7–9 days after pollination. Occasional abnormal undifferentiated or partially differentiated embryos were found still showing substantial numbers of cell divisions at 10–13 days after pollination. Hybrid endosperms varied in their development, but never exceeded the 128-nucleate level. By 5 days after pollination all were degenerating. Endosperm failure appears to be a major cause of seed failure in this cross.

Hybrids between Trifolium ambiguum and T. hybridum obtained with the aid of embryo culture

Abstract Two sterile triploid hybrids (2n = 24) between Trifolium ambiguum (2n = 4x = 32) ♀ and T. hybridum (2n = 2x = 16) have been produced with the aid of embryo culture using transplanted nurse endosperm. Vegetative and floral characters are intermediate but tend to resemble those of the T. ambiguum parent more closely. Hybridity is supported by karyotypes, and by the results of gel electrophoresis of leaf isozymes.

Production of tetraploid hybrids between Ornithopus pinnatus and O. sativus using embryo culture

Abstract Four sterile diploid interspecific hybrids were obtained by pollinating precociously exserted stigmas of Ornithopus pinnatus with pollen from O. sativus while buds were still closed, and culturing the resulting hybrid embryos in vitro with nurse endosperm. Doubling the chromosome number of one hybrid by treatment of shoot tips with colchicine gave partial restoration offertility. In vitro embryo culture was necessary to raise naturally selfed F2, F1, and F4 generations as endosperm development was impaired. However, occasional F4 seeds showed almost normal endosperm development, suggesting that in situ maturation of seeds may be achieved in future generations. The project was aimed at combining the high productivity of O. sativus with the prostrate habit, hard-seededness, and foliar tannin production of O. pinnatus. F1 and F4 individuals derived from a single tetraploid F2 plant showed a combination of the leafiness of O. sativus with a trailing habit more like that of O. pinnatus and variation i...

Pollen nuclei after ionising irradiation for egg transformation in Nicotiana.

Abstract Pollen from Nicotiana alata and N. langsdorffii was gamma irradiated at doses previously used to treat donor pollen for egg transformation in these species. Observation with a light microscope of the second pollen mitosis showed that irradiation caused chromatin fragmentation, lack of metaphase orientation, and failure of the generative nucleus to divide.

Glucosinolates in the pollen of rapeseed and indian mustard

Abstract The glucosinolate composition of the pollen from rapeseed (Brassica napus cv Midas) and Indian mustard (B.juncea. cv Early Yellow) was investigated by HPLC. Rapeseed pollen was found to contain significant amounts of 2-hydroxybut-3-enyl-, 2-hydroxypent-4-enyl-, pent-4-enyl-, and 2-phenylethylglucosinolates. Trace amounts of but-3-enyl-, 3-indolylmethyl-, 4-methoxy-3-indolylmethyl-, and 1-methoxy-3-indolylmethylglucosinolates were also observed. Indian mustard pollen contained predominantly prop-2-enylglucosinolate, with minor amounts of 2-hydroxybut-3-enyl-, 2-hydroxypent-4-enyl-, but-3-enyl- and 2-phenylethylglucosinolates. Structural confirmation by GC/MS was obtained for three major rapeseed pollen glucosinolates and four major mustard pollen glucosinolates. Two unidentified glucosinolate-like compounds were also observed in rapeseed pollen. One of these compounds was also found in Indian mustard pollen, but was not observed in seed of either species. Comparison of seed and pollen glucosinolate composition is discussed in relation to the potential of pollen selection for low glucosinolate varieties.

Cytology and fertility of Trifolium repens, T. ambiguum, T. hybridum, and interspecific hybrids

Abstract Meiotic chromosome pairing and pollen fertility data are given for Trifolium repens, T. ambiguum (2x) and (4x), T. hybridum (2x) and (4x), and the hybrids T. ambiguum (4x) × T. repens (FI, F2, F3, and backcross to T. repens) , and T. ambiguum (4x) × T. hybridum (2x). Some autosyndesis of T. repens chromosomes occurs in hybrids with T. ambiguum. This is in keeping with previous evidence for the presence in T. repens of a genetic mechanism to control preferential bivalent pairing, which breaks down after interspecific hybridisation. Pairing of homoeologous T. repens chromosomes in hybrids provides an opportunity for release of new variation by novel recombinational events not possible in the parent species. Variable low fertility in the hybrids is not associated with gross meiotic abnormalities, but may be caused by genetic deficiencies resulting from independent assortment of intraspcific homoeologous chromosomes which normally assort together.

Contributions to a chromosome atlas of the New Zealand flora — 34. Wahlenbergia (Campanulaceae)

Abstract Meiotic and mitotic chromosome counts are documented for 16 taxa and one putative hybrid of Wahlenbergia in New Zealand. Ten taxa, all those with rhizomatous growth form, have 2n = 4x = 36. Of the remaining group, with radicate growth form, five species and one hybrid have 2n = 8x = 72, and an undescribed species has 2n = 6x = 54. Chromosome counts are also provided for two Wahlenbergia species from Australia with 2n = 4x = 36 and 2n = 6x = 54, one from Japan with 2n = 8x = 72, one from New Caledonia with 2n = 8x = 72, and one from West Bengal with 2n = 2x = 18.