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  • Author or Editor: Ying Wang x
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Abstract

Photosynthetic photon flux (PPF) at 290 μmol·s-1·m-2 and warm propagation medium (28°C) enhanced both shoot and root growth of golden pothos (Epipremnum aureum) from single-node leaf-bud cuttings compared to PPF at 60 μmol·s-1·m-2 and unheated medium (10° to 16°). Heated cuttings accumulated much more dry matter in new growth, but parent leaves had smaller area leaf weight than unheated cuttings. Soaking cuttings in 500 or 750 ppm BA before planting caused slower initial growth of the axillary shoot, and stem length was reduced to 75% of the control. Leaf number and total leaf area was unaffected by BA. Leaf-bud cuttings needed 10 more days to unfold the first leaf compared to stem cuttings without parent leaves. Shoots developed from leaf-bud cuttings had longer stems, more leaves and total leaf area, and heavier dry weight than shoots from stem cuttings. Chemical name used: N-(phenylmethyl)-1H-purin-6-amine (BA).

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Five Wave™ petunias, i.e., `Purple Wave™', `Pink Wave™', `Misty Lilac Wave™', and `Rose Wave™', and two hedgaflora petunias, i.e., `Dramatica Cherry™', and `Dramatica Hot Pink™', were investigated to determine the effects of plant growth regulators on plant size, branching, and flowering. Plant regulator treatments consisted of daminozide (B-Nine) spray two times at 7500 ppm, Paclobutrazol (Bonzi) spray two times at 30 ppm, paclobutrazol drench at 5 ppm, paclobutrazol drench at 5 ppm plus spray at 30 ppm, and ethephone (Florel) spray two times at 500 ppm. Plant diameter and central stem height were controlled effectively through daminozide spray and paclobutrazol drench. Plant branching was promoted by ethephone and daminozide. However, time to flowering was delayed significantly in the ethephone treatment. The size of the first flower responded to plant growth regulators negatively. The different responses to growth regulators among different types of petunias and different varieties in the same petunia type will be discussed based on the current trial and other separated experiments.

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Epimedium species are traditional Chinese medicinal plants as well as potential groundcover and ornamental plants. In this study, genome size and genome structures of Epimedium species were investigated using flow cytometric and fluorescence in situ hybridization (FISH). The nuclear DNA content of Epimedium species ranged from 8.42 pg/2C (8230.7 Mbp) to 9.97 pg/2C (9752.8 Mbp). The pairwise nucleotide diversity (π) of the fragments of the genes for reverse transcriptase (rt) of Ty1-copia retrotransposon within a species of rt fragments ranged from 0.251 to 0.428 in 10 Epimedium species. Phylogenetic analysis of the sequences revealed four major clades with the largest subclade containing 72 sequences of relatively low nucleotide diversity. FISH indicated that Ty1-copia retrotransposons are distributed unevenly along the pachytene chromosomes of E. wushanense and E. sagittatum, mostly associated with the pericentromeric and terminal heterochromatin. The relatively low sequence heterogeneity of Ty1-copia rt sequences implies that the Epimedium genomes have experienced a few relatively large-scale proliferation events of copia elements, which could be one of the major forces resulting in the large genome size of Epimedium species.

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Cross-species amplification of 55 microsatellite loci developed in european chestnut (Castanea sativa Mill.) and japanese chestnut (C. crenata Sieb & Zucc.) was tested in three chestnut species from China [C. mollissima Blume, C. seguinii Dode, and C. henryi (Skan.) Rehder & Wilson]. Among all the tested loci, 47 (85.5%), 47 (85.5%), and 44 (80%) were successfully amplified in each of the three Chinese species, respectively. All microsatellite loci tested from C. crenata successfully amplified in the Chinese species, while only 80.5%, 80.5%, and 73.2% of the loci originating from C. sativa amplified in the three Chinese species. The level of polymorphism and mean number of alleles was 58.2% and 4.12 for C. mollissima, 60% and 4.64 for C. seguinii, and 60% and 4.76 for C. henryi, with mean observed heterozygosity ranging from 0.440 to 0.549 and mean expected heterozygosity ranging from 0.506 to 0.615. Transferability of Castanea Mill. microsatellites provides a powerful tool for chestnut breeding programs and conservation genetic studies of Castanea species.

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Perennial ryegrass (Lolium perenne L.) is a widely used cool-season turfgrass species. The exact ploidy levels of the worldwide perennial ryegrass accessions in the USDA National Plant Germplasm System (NPGS) are unknown, which could complicate future use and breeding efforts. The objective of this study was to determine the ploidy level and DNA content of the 194 USDA NPGS perennial ryegrass accessions and six commercial cultivars (Brightstar SLT, Catalina II, Divine, Inspire, Manhattan 4, Silver Dollar) using flow cytometry. Among the 200 accessions, 194 diploids and six tetraploids were identified. Three tetraploids originated from Canada with the remaining from Ireland, Japan, and The Netherlands. The average DNA content was 5.60 pg/2C for the diploid and 11.45 pg/2C for the tetraploid. The 2C DNA content was positively correlated (r = 0.23, P < 0.01) with seedling plant height but not seedling leaf width. This ploidy data provide important information for future marker trait analysis and cultivar improvement.

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Fritillaria crassicaulis S. C. Chen is a precious traditional Chinese medicine, but the number of populations has declined rapidly due to overexploitation. An artificial rapid propagation system was established to screen the suitable plant regeneration method and to explore the efficient propagation method, useful for propagation technology or for further research and development of F. crassicaulis. This study selected scale as the experimental material, set Murashige and Skoog (MS) medium as the basic medium, and optimized the types and proportions of plant growth regulator (PGR) suitable for callus induction, bulblet differentiation and proliferation, and plant regeneration by means of single-factor, full-factorial, and L9 (3)4 orthogonal experiments. Results demonstrate that in the experiment with single exogenous PGR, the high concentration of 6-benzylaminopurine (6-BA) was significantly better than kinetin (KT) to induce bulblets, 2, 4-dichloroacetic acid (2, 4-D) had a significant effect on callus induction, and a higher concentration of naphthaleneacetic acid (NAA) was beneficial to the occurrence and growth of bulbs, but the rooting effect promoted by indole butyric acid (IBA) was preferable to that by NAA. In MS medium with 0.5 mg/L 2, 4-D and 1.5 mg/L 6-BA, a large number of yellowish-green compact calli could be induced from the scales with the calli induction frequency at 93.3%, and about 11.4% materials directly differentiated bulblets. In the subsequent orthogonal experiment, after the scales were cultured in MS medium with 2.0 mg/L 6-BA, 0.5 mg/L 2, 4-D, and 0.1 mg/L NAA for 20 days, the small yellow and white globular protuberances formed near the incision, but no callus appeared, and many protuberances appeared on the surface of the scales. After 60 days, the protuberances at the incision developed into bulblets directly, while protuberances on the surface of the scales developed into few bulblets but crowded “leaf spines,” which gradually died and disappeared in the later culture; the proliferation coefficient was ∼6.30 then. Experimental results indicate that the optimal rooting medium for bulblets was 1/2MS medium with 2.0 mg/L IBA and 1.0 mg/L activated carbon (AC), with the rooting rate at 95.6%. This study identifies bulblet regeneration of F. crassicaulis, and an efficient direct organogenesis method was established: regenerated bulblets could be induced from scales in one step, so a large number of regenerated plants with the same genotype could be obtained in a short time.

Open Access

Forty-eight kiwifruit cultivars and selections, representing more than 90% of total world kiwifruit production, were investigated using nine SSR markers to establish genetic identities, and evaluate genetic diversity and relatedness. These nine SSRs were polymorphic and a total of 213 alleles were detected, resulting in a mean number of 23.7 alleles per locus, ranging from nine to 38 alleles. One hundred and thirty-three alleles were found to be common to both A. chinensis and A. deliciosa, while 33 and 36 were specific to A. chinensis and A. deliciosa, respectively. In addition, 34 alleles were specific to one single genotype and provided a set of valuable alleles for cultivar identification. A single SSR locus UDK 96-414 could differentiate all 48 genotypes except two presumable clones. Mean number of alleles per locus (A), percentage of polymorphic loci (P), and direct count heterozygosity (Ho) assessed for each genotype over all loci revealed considerable differences among these 48 genotypes. On average, A = 2.6, P = 89.4% and Ho = 0.546 were found in A. chinensis cultivars, while A = 3.5, P = 97.0% and Ho = 0.671 in A. deliciosa cultivars. Consensus fingerprint profiling using SSR markers is a useful and reliable method for establishing genetic identities of kiwifruit cultivars and selections. It also improves evaluation effectiveness of genetic diversity and relatedness compared to RAPD markers.

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Argeranthemum frutescens `Butterfly' and `Sugar Baby', Brachycome hybrid `Ultra', Helichrysum bracteatum `Golden Beauty', Scaevola aemula `New Wonder',Supertunia axillaris hybrids `Kilkenny Bells' and `Pink Victory', Sutera cordata `Mauve Mist' and `Snowflake', and Verbena hybrid `Blue' were grown in a glass greenhouse maintained at 20°C under seven different photoperiods (10-, 12-, 13-, 14-, 16-, 24-hr, and 4-hr night interruption). Black cloth was pulled at 1700 and opened at 0800 HR; incandescent lamps provided 2 μmol·m–2·s–1 to extend light hours to the designed photoperiods. Seedlings were pinched 3 days after transplant. Responses to photoperiod were clearly species-dependent. The tested species can be classified into three groups: 1) stem elongation and flowering were promoted in the long-day treatment (A. frutescens and S. axillaris hybrids), 2) only stem elongation was promoted in the long-day treatment (S. aemula, H. bracteatum, and B. hybrid), and 3) neither flowering nor stem elongation were affected by photoperiod (S. cordata and V. hybrid).

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