Literature
2020
Barfuss, M.; Mangelsdorff, R.; Tropper, R.
In: EPIG, vol. 83, pp. 5-19, 2020, ISSN: 2364-4486.
Abstract | Links | BibTeX | Tags: microsphaerica
@article{article,
title = {Kreuzungsversuche mit Schlumbergera microsphaerica (K. Schum.) P.V. Heath [Hybridization experiments with Schlumbergera microsphaerica (K. Schum.) P.V. Heath]},
author = {Barfuss, M. and Mangelsdorff, R. and Tropper, R.},
url = {https://www.researchgate.net/publication/340182813_Kreuzungsversuche_mit_Schlumbergera_microsphaerica_K_Schum_PV_Heath_Hybridization_experiments_with_Schlumbergera_microsphaerica_K_Schum_PV_Heath},
issn = {2364-4486},
year = {2020},
date = {2020-03-01},
journal = {EPIG},
volume = {83},
pages = {5-19},
abstract = {Crosses between Schlumbergera species have been known since the 19th century. In almost all crosses, either S. truncata, S. russelliana, S. orssichiana or S. opuntioides are involved. The Schlumbergera species S. kautskyi and S. microsphaerica have rarely, or even not at all, been used in hybridization. The monograph by McMillan & Horobin (1995) on Schlumbergera reports that crossbreeding attempts with these two species were unsuccessful at that time. For S. microsphaerica it is mentioned: ‘It does not appear to cross with other members of the genus.’ Dolly Kölli has shown that it is quite possible to achieve hybrids with S. kautskyi. By means of DNA sequencing methods, crosses can be confirmed at the molecular level by sequence comparisons. As a DNA marker, the nuclear ribosomal ITS region (internal transcribed spacer) is often chosen, which is relatively simple to analyse. The ITS regions have important functions, but do not occur in the finished ribosomes because they are excised and degraded after transcription. Because they do not code, mutations accumulate in these DNA segments, which are frequently used to study close relationships. In this article, crosses with S. microsphaerica are presented and verified with sequence data of the nuclear ribosomal ITS region at the molecular level to exclude the possibility of self- or accidental fertilization with other Schlumbergera pollen. In 2013, Ralph Mangelsdorff pollinated Schlumbergera microsphaerica with a S. truncata cultivar (Fig. 1) and raised some seedlings. In addition, in 2017, Ruud Tropper made further crosses of S. microsphaerica with S. kautskyi, S. opuntioides and S. × buckleyi, and was able to grow several seedlings. Next to these, additional plants were selected for DNA studies (see Fig. 11). All plants are cultivated in the collection of Ruud Tropper either on their own roots or grafted on various stocks (including Pereskiopsis, Schlumbergera, Selenicereus). Specimens were removed from new growth of all plants, freeze-dried and DNA was isolated in aqueous solution with a commercially available DNA extraction kit. The ITS region was amplified and sequenced by PCR with universal angiosperm DNA primers (see section Material und Methoden). To determine the hybrid status, the obtained electronic DNA raw sequence data (electropherograms) of the ITS region were compared (Figs. 4, 6 and 10). 1. Schlumbergera microsphaerica × Schlumbergera truncata. As far as we know, this is the first successful hybridization with Schlumbergera microsphaerica. The result of this cross mostly resembles a small form of S. × exotica and thus corresponds to the image of S. microsphaerica as a smaller sibling of S. opuntioides (Fig. 2). The hybrid looks very different from the mother and father plants. The plant grows slowly on its own roots. It is best grafted, for example, on a strong-growing Schlumbergera stock (Fig. 3). Due to disturbances in pigmentation, the young growth is characterized by a palish colour that makes it sensitive for radiation and can cause dieback. Flowers in anthesis have not yet been observed because the plants are still too young. Figure 4 shows the comparison of a DNA sequence portion of the ribosomal ITS region of S. microsphaerica, S. microsphaerica × S. truncata, and S. truncata. Several DNA-base differences and sequence length differences (gaps) are detectable (Fig. 11). In these positions, the hybrid shows base signals from both parents, and length differences, which cause a shift in parental DNA sequences. These result in superimposed base signals starting from the position of the shift. 2. Schlumbergera kautskyi × Schlumbergera microsphaerica. Schlumbergera kautskyi is highly self-compatible. In the present case, the stamens were removed several days before the flower opened. With the greatest effort, a fruit with six normal-looking seeds could be harvested. Only two of these seeds grew into plants. One was grafted in time to get the best result possible (Fig. 5). Figure 6 shows the comparison of the same DNA sequence portion of the nuclear ribosomal ITS region of S. kautskyi, S. kautskyi × S. microsphaerica, and S. microsphaerica. DNA base differences in multiple positions and sequence length differences are evident (Fig. 11). Again, the hybrid shows in these positions base signals from both parents and shifts in parental DNA sequences. 3. Schlumbergera opuntioides × Schlumbergera microsphaerica. Morphologically, this cross appears as an intermediate form of Schlumbergera opuntioides and S. microsphaerica and less like a dwarf form of S. × exotica (Fig. 7). As with the other two hybrids, the young growth is very pale. Since S. opuntioides and S. microsphaerica presumably are very closely related and show no differences in the DNA sequence of the ITS region, the hybrid S. opuntioides × S. microsphaerica does not exhibit differences either (Fig. 11). 4. Schlumbergera × buckleyi (S. truncata × S. russelliana) × Schlumbergera microsphaerica. Two Schlumbergera cultivars, i.e. S. × buckleyi 'Kolibri', a miniature plant, and S. × buckleyi 'George Gardner' with bright red flowers, raised by Thomas Boyle and presented in previous EPIG journals, were used as mother plants. Fruits were produced easily on both cultivars, each containing about 6-7 seeds. The seeds germinated well and produced seedlings that morphologically look very uniform. The seedlings are similar to the S. microsphaerica × S. truncata cross, but the phylloclades are more rounded (Figs. 8, 9). Again, the striking pale colouration of the young growth recurred in these hybrids. As with the first two crosses, the successful hybridization was confirmed by the DNA sequence section of the ribosomal ITS region (Fig. 10). DNA-base differences and sequence length differences can be detected in several positions (Fig. 11). Like in the other cases the hybrid shows base signals from both parents and a length difference of the parental sequence copies. The present hybridization experiments show that it is possible to use Schlumbergera microsphaerica as a crossing partner for other Schlumbergera species. Successful crossbreeding can be confirmed by DNA sequence data (Fig. 11) and excludes the possibility of self-fertilization. Due to self-fertility of S. microsphaerica, stamens should be removed before anthesis to prevent self-pollination. All hybrids have on average a rather small appearance like that of S. microsphaerica. All crosses with S. microsphaerica involved in this study show disturbances in pigmentation (chlorophyll-forming defects), especially in the young growth. This might indicate that S. microsphaerica is not so closely related to the other species, shows genetic incompatibility, or possesses species-specific metabolic pathways that interfere with those of the other species. Although, according to the present DNA data, S. opuntioides is the sister species to the sympatric S. microsphaerica (there are no differences in the ITS sequence studied here), the hybrids between them show similar disturbances, which is a possible indication of effective reproductive isolation mechanisms. Open flowers have not yet been observed in these new hybrids. The buds of S. × buckleyi 'Kolibri' × S. microsphaerica (Fig. 12) that formed in spring 2019 have fallen off before their anthesis. In order that these new crosses can be addressed by a name, the authors believe that at least for some a description as nothospecies makes perfect sense.},
keywords = {microsphaerica},
pubstate = {published},
tppubtype = {article}
}
Crosses between Schlumbergera species have been known since the 19th century. In almost all crosses, either S. truncata, S. russelliana, S. orssichiana or S. opuntioides are involved. The Schlumbergera species S. kautskyi and S. microsphaerica have rarely, or even not at all, been used in hybridization. The monograph by McMillan & Horobin (1995) on Schlumbergera reports that crossbreeding attempts with these two species were unsuccessful at that time. For S. microsphaerica it is mentioned: ‘It does not appear to cross with other members of the genus.’ Dolly Kölli has shown that it is quite possible to achieve hybrids with S. kautskyi. By means of DNA sequencing methods, crosses can be confirmed at the molecular level by sequence comparisons. As a DNA marker, the nuclear ribosomal ITS region (internal transcribed spacer) is often chosen, which is relatively simple to analyse. The ITS regions have important functions, but do not occur in the finished ribosomes because they are excised and degraded after transcription. Because they do not code, mutations accumulate in these DNA segments, which are frequently used to study close relationships. In this article, crosses with S. microsphaerica are presented and verified with sequence data of the nuclear ribosomal ITS region at the molecular level to exclude the possibility of self- or accidental fertilization with other Schlumbergera pollen. In 2013, Ralph Mangelsdorff pollinated Schlumbergera microsphaerica with a S. truncata cultivar (Fig. 1) and raised some seedlings. In addition, in 2017, Ruud Tropper made further crosses of S. microsphaerica with S. kautskyi, S. opuntioides and S. × buckleyi, and was able to grow several seedlings. Next to these, additional plants were selected for DNA studies (see Fig. 11). All plants are cultivated in the collection of Ruud Tropper either on their own roots or grafted on various stocks (including Pereskiopsis, Schlumbergera, Selenicereus). Specimens were removed from new growth of all plants, freeze-dried and DNA was isolated in aqueous solution with a commercially available DNA extraction kit. The ITS region was amplified and sequenced by PCR with universal angiosperm DNA primers (see section Material und Methoden). To determine the hybrid status, the obtained electronic DNA raw sequence data (electropherograms) of the ITS region were compared (Figs. 4, 6 and 10). 1. Schlumbergera microsphaerica × Schlumbergera truncata. As far as we know, this is the first successful hybridization with Schlumbergera microsphaerica. The result of this cross mostly resembles a small form of S. × exotica and thus corresponds to the image of S. microsphaerica as a smaller sibling of S. opuntioides (Fig. 2). The hybrid looks very different from the mother and father plants. The plant grows slowly on its own roots. It is best grafted, for example, on a strong-growing Schlumbergera stock (Fig. 3). Due to disturbances in pigmentation, the young growth is characterized by a palish colour that makes it sensitive for radiation and can cause dieback. Flowers in anthesis have not yet been observed because the plants are still too young. Figure 4 shows the comparison of a DNA sequence portion of the ribosomal ITS region of S. microsphaerica, S. microsphaerica × S. truncata, and S. truncata. Several DNA-base differences and sequence length differences (gaps) are detectable (Fig. 11). In these positions, the hybrid shows base signals from both parents, and length differences, which cause a shift in parental DNA sequences. These result in superimposed base signals starting from the position of the shift. 2. Schlumbergera kautskyi × Schlumbergera microsphaerica. Schlumbergera kautskyi is highly self-compatible. In the present case, the stamens were removed several days before the flower opened. With the greatest effort, a fruit with six normal-looking seeds could be harvested. Only two of these seeds grew into plants. One was grafted in time to get the best result possible (Fig. 5). Figure 6 shows the comparison of the same DNA sequence portion of the nuclear ribosomal ITS region of S. kautskyi, S. kautskyi × S. microsphaerica, and S. microsphaerica. DNA base differences in multiple positions and sequence length differences are evident (Fig. 11). Again, the hybrid shows in these positions base signals from both parents and shifts in parental DNA sequences. 3. Schlumbergera opuntioides × Schlumbergera microsphaerica. Morphologically, this cross appears as an intermediate form of Schlumbergera opuntioides and S. microsphaerica and less like a dwarf form of S. × exotica (Fig. 7). As with the other two hybrids, the young growth is very pale. Since S. opuntioides and S. microsphaerica presumably are very closely related and show no differences in the DNA sequence of the ITS region, the hybrid S. opuntioides × S. microsphaerica does not exhibit differences either (Fig. 11). 4. Schlumbergera × buckleyi (S. truncata × S. russelliana) × Schlumbergera microsphaerica. Two Schlumbergera cultivars, i.e. S. × buckleyi 'Kolibri', a miniature plant, and S. × buckleyi 'George Gardner' with bright red flowers, raised by Thomas Boyle and presented in previous EPIG journals, were used as mother plants. Fruits were produced easily on both cultivars, each containing about 6-7 seeds. The seeds germinated well and produced seedlings that morphologically look very uniform. The seedlings are similar to the S. microsphaerica × S. truncata cross, but the phylloclades are more rounded (Figs. 8, 9). Again, the striking pale colouration of the young growth recurred in these hybrids. As with the first two crosses, the successful hybridization was confirmed by the DNA sequence section of the ribosomal ITS region (Fig. 10). DNA-base differences and sequence length differences can be detected in several positions (Fig. 11). Like in the other cases the hybrid shows base signals from both parents and a length difference of the parental sequence copies. The present hybridization experiments show that it is possible to use Schlumbergera microsphaerica as a crossing partner for other Schlumbergera species. Successful crossbreeding can be confirmed by DNA sequence data (Fig. 11) and excludes the possibility of self-fertilization. Due to self-fertility of S. microsphaerica, stamens should be removed before anthesis to prevent self-pollination. All hybrids have on average a rather small appearance like that of S. microsphaerica. All crosses with S. microsphaerica involved in this study show disturbances in pigmentation (chlorophyll-forming defects), especially in the young growth. This might indicate that S. microsphaerica is not so closely related to the other species, shows genetic incompatibility, or possesses species-specific metabolic pathways that interfere with those of the other species. Although, according to the present DNA data, S. opuntioides is the sister species to the sympatric S. microsphaerica (there are no differences in the ITS sequence studied here), the hybrids between them show similar disturbances, which is a possible indication of effective reproductive isolation mechanisms. Open flowers have not yet been observed in these new hybrids. The buds of S. × buckleyi 'Kolibri' × S. microsphaerica (Fig. 12) that formed in spring 2019 have fallen off before their anthesis. In order that these new crosses can be addressed by a name, the authors believe that at least for some a description as nothospecies makes perfect sense.