Targeted generation of polyploids in Hydrangea macrophylla through cross-based breeding

Polyploidy and aneuploidy by colcemid in Drosophila melanogaster

Immature inflorescence culture and subsequent plant regeneration was practiced for four successive cycles using a Triticum crassum × Hordeum vulgare hybrid cultured on Kao's medium supplemented with 2,4-dichlorophenoxyacetic acid (5 mg/mL). In one line, chromosomal mixoploidy was observed among both mitotic and meiotic cells. Variation in chromosome number of 20 to 98 was observed in mitotic and 14 to 68 among meiocytes in the first cycle regenerants. The range in chromosome number decreased in subsequent regeneration cycles. Fragmented chromosomes were observed at low frequencies in both groups of cells. The high frequency of univalents at meiosis was attributed to possible elimination of chromosomes carrying meiotic pairing control genes.Key words: somaclonal variation, hybrids (intergeneric), tissue culture, chromosomal mixoploidy.

GISH (genomic in situ hybridization) was applied for the analysis of mitotic chromosome constitutions of somatic hybrids and their derivatives between dihaploid clones of cultivated potato (Solanum tuberosum L.) (2n = 2x = 24, AA genome) and the diploid, non-tuberous, wild species Solanum brevidens Phil. (2n = 2x = 24, EE genome). Of the primary somatic hybrids, both tetraploid (2n = 4x) and hexaploid (2n = 6x) plants were found with the genomic constitutions of AAEE and AAEEEE, respectively. Androgenic haploids (somatohaploids) derived from the tetraploid somatic hybrids had the genomic constitutions of AE (2n = 2x = 24) and haploids originating from the hexaploid hybrids were triploid AEE (2n = 3x = 33 and 2n = 3x = 36). As a result of subsequent somatic hybridization from a fusion between dihaploid S. tuberosum (2n = 2x = 24, genome AA) and a triploid somatohaploid (2n = 3x = 33, genome AEE), second-generation somatic hybrids were obtained. These somatic hybrids were pentaploids (2n = 5x, genome AAAEE), but had variable chromosome numbers. GISH analysis revealed that both primary and second-generation somatic hybrids had lost more chromosomes of S. brevidens than of S. tuberosum.

Several crossing series including the hexaploid (2n=6x=42), South American speciesHordeum lechleri and diploid (2n=2x=14) cultivated barley (H. vulgare) were performed. Barley functioned better as the paternal than as the maternal parent in all cases. Viable offspring were only obtained from one hybrid combination when barley was used as the maternal parent. There was an environmental influence on the success of crosses. A high seed set was counteracted by a lower germination frequency. The outcome is that different crossing series give similar results. As a result of chromosome elimination and in a few cases duplication of especially the barley chromosomes, the chromosome numbers of the offspring (239 plants) varied from 2n=21 (trihaploids ofH. lechleri) to 2n=30. Fifty-five % of the plants were euploid with the number expected for a hybrid (2n=28). The frequency of hyperploids, euploids, hypoploids (2n=22–27) and trihaploids varied by year, locality, type (winter/spring) of barley,H. lechleri population, and crossing direction.

Fish sperm cryopreservation is an important technique for optimizing juvenile production in aquaculture stations and laboratories and contributing to the conservation of endangered species. Despite its benefits, the cryopreservation process can cause cellular damage, affecting spermatozoa quality and offspring viability. This study aimed to evaluate the larval development of jundiá Rhamdia quelen originating from cryopreserved sperm. Larvae were obtained from artificial reproduction using oocyte samples from four females combined with fresh (Control) or cryopreserved/thawed sperm. The semen was diluted in the cryoprotective solution (1:3 ratio) consisting of skimmed milk powder (5%), methanol (10%), and fructose (5%), and was packaged into 0.25mL straws. The straws were then stored and cooled in liquid nitrogen vapor for 18h. The straws were individually warmed in a water bath at 25°C for 10s to thaw the samples. The experiments were performed in triplicates. Sperm quality, fertilization, hatching, and larval development were evaluated. After larval hatching, six larval collections were performed (5, 10, 15, 20, and 25days after hatching), and 15 larvae were sampled per collection per treatment. Cryopreservation reduced sperm motility (70.48 ± 7.70 fresh to 41.36 ± 4.80 cryopreserved semen), progressivity (3874 fresh to 2505 cryopreserved semen), and beat cross frequency (55.83 ± 155 fresh to 50.22 ± 190 cryopreserved semen). Increased the percentage of sperm with abnormal morphology and increased most sperm pathologies. Furthermore, the fertilization rate was lower in the cryopreserved group (63.1 ± 18, and 83.72 ± 7.59 for fresh semen), while hatching was not different between groups (65.3 ± 18.05 fresh, 48.89 ± 21.77 cryopreserved semen) Otherwise, the initial larval development morphology showed no difference in the appearance of structures such as the presence of the vitelline structure, pigmentation pattern, development of the anal pore, embryonic membrane, eye, barbells, notochord flexion, and fin rays, for both treatments. There was no significant difference in the frequency of structures between larvae from fresh and cryopreserved/thawed sperm, revealing a similar developmental pattern in both treatments. In conclusion, the cryopreservation protocol affects sperm quality; however, those sperm able to fertilize the oocytes originate normal larvae with regular larval development of R. quelen up to 25days old.

Collectively, populations of Acanthocyclops vernalis, a species complex of freshwater copepods, are remarkably similar as to morphology and DNA content, despite variability in chromosome number. Reproductive isolation had been reported among some populations, but with each new investigation the species boundaries and factors that may influence them appeared less clear. To clarify the pattern of biological species within this group of populations, we adopted a comprehensive approach and examined patterns of reproductive isolation in populations for which morphology, chromosome number, DNA content, and 18S rDNA sequences are known. In this study we established nine isofemale lines from four sites in Wisconsin and performed 266 crosses. Crosses within and among these lines were used to relate the degree of reproductive isolation to chromosome differences and to construct a model to explain the origin and maintenance of chromosome number variability. Different gametic and somatic chromosome numbers were observed among specimens within some isofemale lines. In a few cases, gametes with different haploid numbers were produced by a single female. Matings within isofemale lines always produced at least some reproductively successful replicate crosses (produced viable, fertile offspring). Crosses between lines from the same site showed reduced success relative to within-line crosses. Crosses between populations from distant sites showed limited genetic compatibility, producing viable, fertile F1 offspring but infertile F2 adults. One cross between lines with different chromosome numbers (one with 2n = 8 and one with 2n = 10) produced fertile viable offspring, which reproduced for at least 60 generations. These hybrids had either eight or nine chromosomes in the third generation of inbreeding, and eight chromosomes after 20 generations. These hybrids also had reduced nuclear DNA contents at the third generation, a level that persisted through the 20th generation. Successful backcrosses between some hybrids and their parental lines further demonstrated the potential for genetic compatibility among forms with different chromosome numbers. We propose a model in which alterations due to Robertsonian fusions, translocations, and/or loss of chromosomal fragments generate heritable variation, only some of which leads to reproductive isolation. Hence, some of the criteria traditionally used to recognize species boundaries in animals (morphology, DNA content, chromosome number) may not apply to this species complex.

Karyotypes were determined for six taxa in the genus Sambucus, family Caprifoliaceae. Chromosome number determinations of 2n = 36 agreed with previous findings for S. canadensis and S. nigra of section Eusambucus and for S. ebulus of section Ebulus. Three taxa from the section Botryosambucus were found to have diploid numbers of 38: S. sieboidiana, S. racemosa var. arborescens and S. racemosa var. pubens. A Quebec population of the latter variety had a somatic number of 42. It is suggested that chromosome races in var. pubens came about through aneuploid gamete production in 2n = 36 ancestors and that their persistence may be related to their newly acquired ability to adapt to varying environmental conditions in the formerly glaciated areas.Differences in karotype within sections were small while between sections they were a little greater and rested mainly on variation in chromosome number, presence of satellites and number of telocentrics.

Summary Interspecific crosses between the diploid C. persicum MILL. 'Reinweiss' (2n=2x=48) and C. purpurascens MILL. (2n=2x=34) were carried out in 1993 andhybrids were obtained using ovary culture (EWALD 1996). Sexual plant reproduction of these interspecific hybrids (2n=2x=41 and 2n=4x=82) has been studied. The analysis of the microspores of interspecific hybrids revealed abnormalities in early stages of meiosis. In the anaphase I a high number of univalents wasobserved. Pairing between some chromosomes of C. persicum and C. purpurascens is assumed to be due to homologous regions. The presence of several univalents completely hindered in some cases the separation of chromosomes, so that cell division did not take place. These microspores showed 1n=2x=41 chromosomes, and the resulting pollen grains were viable, normal shaped and of the same size as those of spontaneous occurring amphidiploid hybrid plants (2n=4x=82). Pollen viability ranged after staining with fluorescein diacetate between 0.3% and 34.0% in diploid, and between 9.7% and 54.0% in amphidiploid hybrids. Thegrowth of pollen tubes in the tissue of the pistils was normal in all cross combination. But only in the combination tetraploid C. persicum × amphidiploid hybrid and reciprocal low frequences of micropylar penetration were observed. Sexual reproduction and further cross breeding with C. persicum were only successful when tetraploid plants were used. Spontaneous amphidiploidhybrids developed seeds as well as after selfing and in cross combinations with tetraploid C. persicum . From the seeds of the cross combination tetraploid C. persicum × amphidiploid hybrids plants were grown till flowering which were true to C. persicum or intermediary.

Cytogenetic studies were performed on four male-sterile progenies derived from four different cybrids produced between Brassica napus and B. tournefortii using the donor-recipient protoplast fusion method. The objective of these studies was to characterize the nuclear constitution of the plants. Mitotic investigation revealed that three of the four male-sterile lines had 38 chromosomes, which is equal to that of B. napus. The fourth line, C6, had variable chromosome numbers, ranging from 39 to 42 in different plants. The meiotic behavior in each progeny varied distinctly. Of the plants having 38 chromosomes, fairly high chromosome pairing, on average 18.08 bivalents per cell, was detected at metaphase-I. However, univalents with an average of 1.39 per cell, and very low frequencies of trivalents and/or tetravalents, were also observed in the lines. These results revealed that male-sterile cybrid lines were obtained with 38 chromosomes and a relatively high level of chromosome-pairing ability, indicating their potential for establishing a stable male-sterile rapeseed line.

Two models, Z Dosage and Dominant W, have been proposed to explain sex determination in birds, in which males are characterized by the presence of two Z chromosomes, and females are hemizygous with a Z and a W chromosome. According to the Z Dosage model, high dosage of a Z-linked gene triggers male development, whereas the Dominant W model postulates that a still unknown W-linked gene triggers female development. Using 33 polymorphic microsatellite markers, we describe a female triploid Kentish plover Charadrius alexandrinus identified by characteristic triallelic genotypes at 14 autosomal markers that produced viable diploid offspring. Chromatogram analysis showed that the sex chromosome composition of this female was ZZW. Together with two previously described ZZW female birds, our results suggest a prominent role for a female determining gene on the W chromosome. These results imply that avian sex determination is more dynamic and complex than currently envisioned.

Investigations on radiosensitive and radioresistant populations of Drosophila melanogaster I. Decreased radiosensitivity in stage- 7 oocytes of the irradiated population RÖ I

Callus cultures of two tetraploid plant of Matricaria recutita L. were initiated from leaves and cultured on LINSMAIER‐SKOOG culture medium supplemented with 0.01 mg · 1−1 IAA or 3.00 mg · 1−1 2, 4‐D for three years. The relationship between mitotic activity and growth of calli was studied. The time at which mitotic activity began in both cultures was different. In the callus culture cultivated on the medium with IAA the maximum mitotic activity was observed on the 14th to 17th day of subculture. In the one cultivated on the medium with 2,4‐D, the increase of mitotic activity was observed earlier and corresponded with the beginning of exponential growth. In addition of total mitotic activity individual mitotic phases have also been evaluated. Most mitotically active cells in both cultures were in prophase. Their courses were similar to those of total mitotic activity. Metaphase and telophase stages were present in low frequency. Anaphase occured rarely. The functional dependences of mitotic activity and growth were characterized by appropriate mathematical models.

Editor—Chromosomal rearrangements occur at a low frequency in the general population and chromosomal insertions occur at an estimated frequency of 1 in 5000 newborn infants.1 Adjacent segregation of interchromosomal insertions...

The use of null hypotheses (in a statistical sense) is common in hard sciences but not in theoretical linguistics. Here the null hypothesis that the low frequency of syntactic dependency crossings is expected by an arbitrary ordering of words is rejected. It is shown that this would require star dependency structures, which are both unrealistic and too restrictive. The hypothesis of the limited resources of the human brain is revisited. Stronger null hypotheses taking into account actual dependency lengths for the likelihood of crossings are presented. Those hypotheses suggests that crossings are likely to reduce when dependencies are shortened. A hypothesis based on pressure to reduce dependency lengths is more parsimonious than a principle of minimization of crossings or a grammatical ban that is totally dissociated from the general and non-linguistic principle of economy.

When breeding diploid potatoes, tetraploid progeny can result from the union of 2n eggs and 2n pollen in 2x-2x crosses. Thirty-three crosses were made to examine tetraploid progeny frequency in 2x-2x crosses. All crosses were between S. tuberosum dihaploids and diploid self-compatible donors, M6 and DRH S6-10-4P17. Using chloroplast counting for ploidy determination, the frequency of tetraploid progeny was as high as 45% in one of the 33 crosses. Based upon single nucleotide polymorphism (SNP) genotyping, the tetraploid progeny were attributed to bilateral sexual polyploidization (BSP), which is caused by the union of 2n egg and 2n pollen. Dihaploids were identified that produce lower frequencies of 2n eggs. The results of this study suggest that S. tuberosum dihaploids with a high frequency of 2n eggs should be avoided in 2x - 2x crosses for diploid breeding programs.