Chondrostoma polylepis Steindachner X Rutilus lemmingii (Steindachner) (Osteichthyes, Cyprinidae), a new natural hybrid from the Duero River basin, Spain

Hybrids of the Iberian nase, Chondrostoma polylepis, and the pardilla roach, Rutilus lemmingii, were found in the River Yeltes, Salamanca, Spain. Morphological multivariate (PCA) and univariate (ANOVA) analyses of 10 C. polylepis, 33 R. lemmingii and 15 hybrids have shown that the hybrids are intermediate in shape between the parent species, with a stronger resemblance to the nase. A brief discussion of the potential causes of the hybridization is presented.     

The Asplenium aethiopicum complex in South Africa

BRAITHWAITE, A. F., 1986. The Asplenium aethiopicum complex in South Africa . Members of the complex in South Africa form an extensive polyploid series with three sexual and two apomictic cytotypes. The sexual tetraploid ( n = 72), octoploid ( n = 144) and dodecaploid ( n = 216) are described as Asplenium aethiopicum subsp. tripinnatum, A. aethiopicum subsp. aethiopicum and A. aethiopicum subsp. dodecaploideum respectively, and the apomictic octoploids ( 2n = 288) and decaploid ( 2n = 360) as A. aethiopicum subsp. filare , which is subdivided into apomicts pseudqfilare (8X), transvaalense (8 X) and capense (10 X). Comparison of their ecology and distribution suggests there is an increased tolerance to drier and cooler conditions with increase in level of polyploidy among the sexual subspecies and that the apomicts are tolerant of even more extreme conditions. The natural hexaploid hybrid between A. aethiopicum subsp. aethiopicum and A. aethiopicum subsp. tripinnatum is described and its meiotic pairing analysed. The numerical structure of the polyploid series in Africa generally suggests the complex represents a secondary polyploid cycle based on a genome of 72 chromosomes, and the unequivocal antosyndesis between the genomes of A. aethiopicum subsp. aethiopicum shown by the chromosome pairing in the hexaploid hybrids suggests the octoploid is either a segmental allopolyploid or autopolyploid. While it can be concluded from the morphology and cytology of A aethiopicum subsp. filare that the apomicts have arisen more than once, their precise mode of origin is unknown, although there is good evidence in at least one case for suggesting a hybrid origin.     

The constitution of the order centrospermae: rRNA-DNA hybridization studies among betalain- and anthocyanin-producing families

Ribosomal RNA homologies and the thermal stabilities of rRNA/DNA hybrids among ten species of the Centrospermae (including three from the family Caryophyllaceae and seven from five betalain-producing families), three other angiosperms, and one fern, suggest that the betalain-producing families are phylogenetically closer to each other than to the anthocyanin-producing families which are examined.     

Fabrication of DNA/RNA Hybrids Through Sequence-Specific Scission of Both Strands by pcPNA-S1 Nuclease Combination

By combining two strands of pseudo-complementary peptide nucleic acid (pcPNA) with S1 nuclease, a tool for site-selective and dual-strand scission of DNA/RNA hybrids has been developed. Both of the DNA and the RNA strands in the hybrids are hydrolyzed at desired sites to provide unique sticky ends. The scission fragments are directly ligated with other DNA/RNA hybrids by using T4 DNA ligase, resulting in the formation of desired recombinant DNA/RNA hybrids.     

Dual functional cholinesterase and PDE4D inhibitors for the treatment of Alzheimer’s disease: Design,synthesis and evaluation of tacrine-pyrazolo[3,4-b]pyridine hybrids

A series of tacrine-pyrazolo[3,4-b]pyridine hybrids were synthesised and evaluated as dual cholinesterase (ChE) and phosphodiesterase 4D (PDE4D) inhibitors for the treatment of Alzheimer’s disease (AD). Compound 10j, which is tacrine linked with pyrazolo[3,4-b]pyridine moiety by a six-carbon spacer, was the most potent acetylcholinesterase (AChE) with IC₅₀ value of 0.125 μM. Moreover, compound 10j provided a desired balance of AChE and butylcholinesterase (BuChE) and PDE4D inhibition activities, with IC₅₀ value of 0.449 and 0.271 μM, respectively. The above results indicated that this hybrid was a promising dual functional agent for the treatment of AD.     

Wide hybridization between Brazilian soybean cultivars and wild perennial relatives

Employing a different culture strategy, we obtained a greatly improved frequency of embryo rescue in intersubgeneric soybean hybrids. Successful crosses were obtained in 31 different genotype combinations between nine Brazilian soybean lines as the female parents and 12 accessions from Glycine canescens, G. microphylla, G. tabacina and G. tomentella. The hybrid pod retention rate dropped to about 10% during the first 8 days after pollination and stayed largely unchanged up to the 20th day. Immature harvested seeds fell into three size groups: Group 1, smaller than 1.3 mm (mostly empty seed coats); Group 2, 1.9–5.0 mm; Group 3, larger than 5 mm (from selfing). A total of 90 putative hybrid embryos were rescued using a highly enriched B5 medium to nourish the newly dissected embryos. The growing embryos were then placed in a high osmotic, modified B5 medium to induce maturation and dormancy. Schenk and Hildebrandt medium was used to germinate the dormant, partially dehydrated, physiologically mature embryos. Approximately 37% of the rescued embryos developed into plantlets in vitro, and approximately 8% grew into mature plants in the greenhouse. Morphological, cytological and isoenzyme patterns confirmed the hybrid status of all seven mature plants, all of which were generated using G. tomentella G 9943 as the paternal parent. It was observed that all soybean lines crossed with G 9943 were capable of producing mature hybrid plants. There was no correlation between the initial size of Group 2 seeds and plant survival rate. The hybrids were cloned by grafting and treated with colchicine. One of the treated plants displayed chromosome doubling.     

Analysis of pollen proteins of Typha species in relation to identification of hybrids

Hybridization studies have been carried out with Typha angustifolia, T. latifolia, T. shuttleworthii and T. minima. All combinations, except those with T. minima, were successful. The hybrid $\text{T. latifolia (♀) × T. angustifolia (♂)}$ has been obtained after 5 attempts involving hundreds of pollinations. The pollen proteins of the parental as well as the F₁ generation have been examined by isoelectrofocusing (IEF). The proteins from each species and each hybrid form displayed a distinct and constant pattern. The pollen protein profile thus represents a new, quite easily accessible character by which F₁ hybrids between the species studied can be unequivocally identified, whereas the morphological criteria described in the literature to distinguish intermediate forms is insufficient for this purpose.     

Karyotype analysis of regenerated plants from callus cultures of interspecific hybrids of cultivated barley (Hordeum vulgare L.)

Summary The karyotype of 82 regenerated plants from callus cultures of interspecific hybrids between cultivated barley (Hordeum vulgare L.) and seven polyploid wild barley species was examined by C-banding or Feulgen staining. The karyotypic changes observed in 46 plants included aneuploidy, double haploidy, amphidiploidy, deletions, inversions, extra C-bands, and extra euchromatic segments. Apparently, chromosome 5, 6, and 7 of H. vulgare were more frequently exposed to elimination or structural change than the other chromosomes of this species. Irradiation of calli seemed to enhance the occurrence of karyotypic variants.     

Somatic Hybridization of Dihaploid Potato Protoplasts as a Tool for Potato Breeding*

Using electrofusion of protoplasts from different dihaploid potato breeding clones, 308 somatic hybrids, i.e. 16.7% of the totally regenerated plants, were obtained. The results indicate that factors such as ‘combining ability’ strongly influence hybrid formation in these intraspecific fusion experiments. Hybrid identification was predominantly carried out by isoenzyme analysis of the peroxidases and/or esterases in polyacrylamide-gradient gel electrophoresis. Further confirmation of the hybrid character was obtained by scoring phenotypic markers (petal colour, stem anthocyanin production, tuber characteristics, etc.) and, in some combinations, by evaluating tolerance against the herbicide metribuzin and nematode resistance against Globodera rostochiensis (Ro 1). The successful inheritance of metribuzin tolerance and nematode resistance confirm that monogenic dominant inherited traits are combined in the hybrids.