Induction and Characterization of Tetraploids from Seeds of Bletilla striata (Thunb.) Reichb.f

In Vitro Polyploidization of Brassolaeliocattleya Hybrid Orchid

The Cattleya (Orchidaceae-Laeliinae subtribe) intergeneric hybrids, such as Brassolaeliocattleya (Blc.), have great ornamental value, due to their compact-size, with large and high color diversity of flowers. Artificial induction of polyploidy brings agronomic, ornamental and genetic benefits to plants. Polyploidization efficiency depends on factors, such as the type of antimitotic, polyploidization method, concentrations, exposure times and type of explant. This study aimed to develop a protocol to polyploidize Blc. orchids, by testing two types of explants (seeds and protocorms), concentrations and exposure times to colchicine. The effects of colchicine on the in vitro development of explants were also investigated. The responses of explants to colchicine depended on the concentrations, exposure time and the interaction of these factors. Flow cytometric analysis evidenced high endopolyploidy and allowed the separation of polyploidized (4C, 8C and 16C peaks) from non-polyploidized (only 2C and 4C peaks) plants. The highest percentage of polyploid plants was regenerated from protocorms (16.4%) treated with colchicine instead of seeds (3.2%). Protocorms treated with colchicine at 500-750 μM for 18 h resulted in the best percentage of polyploidization. Additionally, in vitro natural polyploidization using protocorms was reported (11.5%). Cytological analyses allowed an estimation of the number of chromosomes of the parents (≡70), polyploidized (≡140) and non-polyploidized progeny (≡70).

Soil Microbial Communities Affect the Growth and Secondary Metabolite Accumulation in Bletilla striata (Thunb.) Rchb. f

Bletilla striata (Thunb.) Rchb.f. is a perennial herb belonging to the Orchidaceae family. Its tubers are used in traditional Chinese medicine to treat gastric ulcers, inflammation, silicosis tuberculosis, and pneumogastric hemorrhage. It has been reported that different soil types can affect the growth of B. striata and the accumulation of secondary metabolites in its tubers, but the biological mechanisms underlying these effects remain unclear. In this study, we compared agronomic traits and the accumulation of secondary metabolites (extractum, polysaccharide, total phenol, militarine) in B. striata grown in sandy loam or sandy clay soil. In addition, we compared physicochemical properties and microbial communities between the two soil types. In pot experiments, we tested how irradiating soil or transplanting microbiota from clay or loam into soil affected B. striata growth and accumulation of secondary metabolites. The results showed that sandy loam and sandy clay soils differed significantly in their physicochemical properties as well as in the structure and composition of their microbial communities. Sandy loam soil had higher pH, SOM, SOC, T-Ca, T-N, T-Mg, T-Mn, T-Zn, A-Ca, A-Mn, and A-Cu than sandy clay soil, but significantly lower T-P, T-K, T-Fe, and A-P content. Sandy loam soil showed 7.32% less bacterial diversity based on the Shannon index, 19.59% less based on the Ace index, and 24.55% less based on the Chao index. The first two components of the PCoA explained 74.43% of the variation in the bacterial community (PC1 = 64.92%, PC2 = 9.51%). Similarly, the first two components of the PCoA explained 58.48% of the variation in the fungal community (PC1 = 43.67%, PC2 = 14.81%). The microbiome associated with sandy clay soil can promote the accumulation of militarine in B. striata tubers, but it inhibits the growth of B. striata. The accumulation of secondary metabolites such as militarine in B. striata was significantly higher in sandy clay than in sandy loam soil. Conversely, B. striata grew better in sandy loam soil. The microbiome associated with sandy loam soil can promote the growth of B. striata, but it reduces the accumulation of militarine in B. striata tubers. Pot experiment results further confirmed that the accumulation of secondary metabolites such as militarine was higher in soil transplanted with loam microbiota than in soil transplanted with clay microbiota. These results may help guide efforts to improve B. striata yield and its accumulation of specific secondary metabolites.

Orchid conservation in China from 2000 to 2020: Achievements and perspectives

We review achievements in the conservation of orchid diversity in China over the last 21 years. We provide updated information on orchid biodiversity and suggestions for orchid conservation in China. We outline national policies of biodiversity conservation, especially of orchid conservation, which provide general guidelines for orchid conservation in China. There are now approximately 1708 known species of Orchidaceae in 181 genera in China, including five new genera and 365 new species described over the last 21 years. The assessment of risk of extinction of all 1502 known native orchid species in China in 2013 indicated that 653 species were identified as threatened, 132 species were treated as data-deficient, and four species endemic to China were classified as extinct. Approximately 1100 species (ca. 65%) are protected in national nature reserves, and another ~66 species in provincial nature reserves. About 800 native orchid species have living collections in major botanical gardens. The pollination biology of 74 native orchid species and the genetic diversity and spatial genetic structure of 29 orchid species have been investigated at a local scale and/or across species distributions. The mycorrhizal fungal community composition has been investigated in many genera, such as Bletilla, Coelogyne, Cymbidium, Cypripedium, and Dendrobium. Approximately 292 species will be included in the list of national key protected wild plants this year. Two major tasks for near future include in situ conservation and monitoring population dynamics of endangered species.

Induced autopolyploidy-a promising approach for enhanced biosynthesis of plant secondary metabolites: an insight

Background

Induced polyploidy serves as an efficient approach in extricating genetic potential of cells. During polyploidization, multiple sets of chromosomes are derived from the same organism resulting in the development of an autopolyploid. Alterations owing to artificially induced polyploidy level significantly influence internal homeostatic condition of resultant cells.

Main text

Induced autopolyploidy transpires as a result of an increase in the size of genome without any change in elementary genetic material. Such autopolyploidy, artificially induced via application of antimitotic agents, brings about a lot of beneficial changes in plants, coupled with very few detrimental effects. Induced autopolyploids exhibit superior adaptability, endurance to biotic and abiotic stresses, longer reproductive period and enzyme diversity coupled with enhanced rate of photosynthesis and gene action in comparison to their diploid counterparts. However, reduced rate of transpiration and growth, delay in flowering are some of the demerits of autopolyploids. Inspite of these slight unfavourable outcomes, induced autopolyploidization has been utilized in an array of instances wherein genetic improvement of plant species is concerned, since this technique usually boosts the biomass of concerned economic parts of a plant. In other way, it is also evident that multiplication of genome bestows enhanced production of secondary metabolites, which has contributed to a significant commercial value addition especially for plants with medicinal importance, in particular.

Conclusion

This review makes an attempt to explore the system and success of antimitotic agents vis-à-vis artificial autopolyploidization, interfered with the biosynthesis-cum-production of secondary metabolites having cutting-edge pharmaceutical importance.

Artificial Chromosome Doubling in Allotetraploid Calendula officinalis

Calendula officinalis L. is known as an ornamental plant as well as a source of biochemical compounds used in cosmetics and industry. C. officinalis has a complex karyotype. Published chromosome numbers differ between 2n = 4x = 28 or 32. We have estimated genome sizes in nine commercial cultivars and evaluated the ploidy level by karyotyping and fluorescent in situ hybridization (FISH) using 5S and 45S rDNA loci. The detection of chromosome sets of two rather than four homologues would suggest that C. officinalis has an allotetraploid background. In addition, four signals for 45S but only two for 5S were found by using FISH. Artificial chromosome doubling is a common technique in plant breeding, as polyploidization results in several consequences for plant growth and development. Especially the suggested allotetraploid background in C. officinalis is interesting when examining the effect of chromosome doubling on the plant phenotype. Here we describe chromosome doubling of three allotetraploid cultivars of C. officinalis, 'Nova,' 'WUR 1553-7' and 'Orange Beauty'. Three antimitotic agents - colchicine, oryzalin and trifluralin - were used in different concentrations to find the combination of the best agent and the best dosage to obtain octaploids. For all three cultivars a few octaploids were obtained. A concentration of 200 and 400 ppm of colchicine was most efficient for chromosome doubling in 'Nova' and 'Orange Beauty,' respectively. For 'WUR 1553-7' the treatment with 20 ppm oryzalin was also effective. Cell numbers and first observations of the phenotype in the chromosome doubled plants show thicker leaves and bigger cells, as commonly observed after ploidy doubling. Due to the low number of chromosome doubled plants obtained more elaborate phenotyping will be performed on following generations cultivated under field conditions.