Adenium obesum (Forssk.), Roem. & Schult., commonly known as desert rose, is a high-value, container-grown ornamental plant produced worldwide for its bright floral display and striking sculptural caudex. Little scientific-based information exists regarding the effect of light intensity and nutritional levels on Adenium growth and flowering. In this study, A. obesum ‘Red’ and ‘Ice Pink’ were grown under full sun [with a measured maximum photosynthetically active radiation (PAR) of 1850 μmol·m−2·s−1], 30% shade (1255 μmol·m−2·s−1), or 50% shade (943 μmol·m−2·s−1) in 1.25-L pots top-dressed with controlled-release fertilizer Nutricote® Plus (18N–2.6P–6.6K) at rates to provide 0.4, 0.9, or 1.4 g of nitrogen (N) per pot. Canopy height and width, flower number, and visual quality ratings (based on plant size and form, foliage color, and flowering) were highest after 16 weeks of growth for both cultivars when fertilized with 1.4 g of N per pot. A 30% shade level resulted in plants with the highest flower numbers and quality ratings. Plants grown at 50% shade had the greatest canopy heights and widths, but flower numbers and quality ratings were low. In full sun, plants were smaller overall. In a second experiment, A. obesum ‘Red’ produced the highest shoot dry weight when grown 20 weeks at 30% or 50% shade with 1.4 g of N per pot. Root formation is an important measure of aesthetic value for this crop. As plants mature, roots enlarge dramatically and are often washed to expose sculptural forms. The highest root dry weights were measured at 1.4 g of N under both full sun and 30% shade.
Kaitlyn McBride, Richard J. Henny, Jianjun Chen, and Terri A. Mellich
Peng Li, Weifeng Wu, Faxing Chen, Xinghui Liu, Yongan Lin, and Jianjun Chen
Juan Chen, Nianhe Xia, Xiaoming Wang, Richard C. Beeson Jr., and Jianjun Chen
Ploidy levels and genome sizes have significant implications in plant evolution and crop improvement. Species of Lonicera L. have long been cultivated as medicinal, ornamental crops, or both. However, chromosome numbers, karyotypes, and DNA contents have only been documented in a few species, of which some controversies regarding basic chromosome numbers and karyotypes remain. This study analyzed the chromosome numbers and karyomorphology of 11 cultivars across four species and also the DNA content of 10 cultivars representing six species of Lonicera. Among them, the chromosome numbers of nine cultivars are reported for the first time. Results showed that the basic chromosome number of x = 9 was constant, and chromosome numbers of 2n = 18, 27, 36, or 54 were observed, suggesting that polyploidy exists in the genus. Five cultivars are diploid with 2n = 18; one cultivar is triploid, four are tetraploid, and one is hexaploid. The karyotypes of all studied cultivars are 3B or 3A, except Lonicera sempervirens ‘Crimson Cascade’ that is 2B based on the Stebbins’ asymmetry classification of karyotypes. The asymmetry index (A1) values vary from 0.47 to 0.60. The chromosome lengths range from 0.77 to 4.09 μm. Total karyotype lengths differ from 33.55 to 78.71 μm. The 1C-value of 10 cultivars varies 3-fold, ranging from 1.158 to 3.664 pg. Information gathered from this study could be valuable for improving breeding efficiency in the development of new cultivars of Lonicera with enhanced medicinal, ornamental value, or both.
Juan Chen, Nianhe Xia, Jietang Zhao, Jianjun Chen, and Richard J. Henny
Curcuma L. is an economically important genus in the family Zingiberaceae. Many species are grown as medicinal, culinary, and ornamental crops. As a result of their high morphological diversity and small chromosome sizes, chromosome numbers and species relationships of Chinese Curcumas remain debated. This study examined chromosome numbers of 15 populations representing 11 species of Curcuma from China. Results showed that only Curcuma flaviflora S. Q. Tong was diploid with 2n = 2x = 42 and C. kwangsiensis S. G. Lee & C. F. Liang was tetraploid with 2n = 4x = 84. The other species were triploid (2n = 3x = 63). The study indicated that the basic chromosome number of Curcuma from China could be x = 21. The diploid C. flaviflora produced viable seeds, which was the main means for propagation. The tetraploid and the triploids produced no seeds and relied on rhizomes for propagation. Chromosome sizes of all species were small, ranging from 0.5 to 2.1 μm, which prevented karyotype analysis. The fact that nine of 11 species studied were triploid indicates that triploidy may have some type of competitive advantage over the diploid and tetraploid. In addition, the triploids are popular commercially because of abundant rhizome production and this may contribute to their wide distributions.
Pachanoor S. Devanand, Jianjun Chen, Richard J. Henny, and Chih-Cheng T. Chao
Philodendrons (Philodendron Schott) are among the most popular tropical ornamental foliage plants used for interior decoration. However, limited information is available on the genetic relationships among popular Philodendron species and cultivars. This study analyzed genetic similarity of 43 cultivars across 15 species using amplified fragment length polymorphism (AFLP) markers with near infrared fluorescence labeled primers. Forty-eight EcoR I + 2/Mse I + 3 primer set combinations were screened, from which six primer sets were selected and used in this investigation. Each selected primer set generated 96 to 130 scorable fragments. A total of 664 AFLP fragments were detected, of which 424 (64%) were polymorphic. All cultivars were clearly differentiated by their AFLP fingerprints, and the relationships were analyzed using the unweighted pair-group method of arithmetic average cluster analysis (UPGMA) and principal coordinated analysis (PCA). The 43 cultivars were divided into five clusters. Cluster I comprises eight cultivars with arborescent growth style. Cluster II has only one cultivar, `Goeldii'. There are 16 cultivars in cluster III, and most of them are self-heading interspecific hybrids originated from R.H. McColley's breeding program in Apopka, Fla. Cluster IV contains 13 cultivars that exhibit semi-vining growth style. Cluster V has five cultivars that are true vining in morphology, and they have lowest genetic similarity with philodendrons in other clusters. Cultivated philodendrons are generally genetically diverse except the self-heading hybrids in cluster III that were mainly developed using self-heading and semi-vining species as parents. Seven hybrid cultivars have Jaccard's similarity coefficients of 0.88 or higher, suggesting that future hybrid development needs to select parents with diverse genetic backgrounds.
Jinggui Fang, Jianjun Chen, Richard J. Henny, and Chih-Cheng T. Chao
Ornamental Ficus L. is a group of lactiferous trees, shrubs, and woody root-climbing vines that are cultivated either as landscape plants in the tropics and subtropics or as foliage plants used worldwide for interiorscaping. With the recent rapid expansion of the ornamental plant industry, more new Ficus species and cultivars have been introduced. However, no study has thus far addressed the genetic relationships of cultivated ornamental Ficus. Using amplified fragment length polymorphism (AFLP) markers with near-infrared fluorescence-labeled primers, this study analyzed the genetic relatedness of 56 commercial cultivars across 12 species. Forty-eight EcoRI + 2/MseI + 3 primer set combinations were initially screened, from which six primer sets were selected and used in this investigation. Most cultivars were differentiated by their AFLP fingerprints, and their relationships were determined using the unweighted pair-group method of arithmetic average cluster analysis. The 56 cultivars were divided into 12 clusters that correspond to 12 species, indicating that no interspecific hybrids of ornamental Ficus are in commercial production. The 12 species are genetically diverse, with Jaccard's similarity coefficients ranging from 0.21 to 0.43. However, cultivars within three species—Ficus benjamina L., Ficus elastica Roxb. Ex Hornem., and Ficus pumila L.—are genetically close. Twenty-seven of the 29 cultivars of F. benjamina and five cultivars of F. pumila had Jaccard's similarity coefficients of 0.98 or higher respectively. Nine cultivars of F. elastica shared Jaccard's coefficients higher than 0.96. These results indicate potential genetic vulnerability of these cultivars within the three species. Because there are increasing reports of invasive pests in the ornamental plant industry, strategies for conserving genetic resources and broadening genetic diversity of cultivated Ficus are discussed.
Huijie Zeng, Yun Li, Jianjun Chen, Xiaoming Wang, Zhongquan Qiao, Yongxin Li, Neng Cai, and Sisi Liu
Xiaoming Wang, Yongxin Li, Huijie Zeng, Neng Cai, Zhongquan Qiao, Xiangying Wang, and Jianjun Chen
Weigela florida (Bunge) A. DC. is a popular flowering shrub adapted to a wide range of environmental conditions. Efficient methods for micropropagation of this species have not been well developed. The present study established a protocol for in vitro shoot culture of W. florida ‘Tango’ after a systematic evaluation of different culture media, cytokinins, and auxins on axillary shoot induction. Single-node stems were cultured on Driver and Kuniyuki Walnut (DKW) medium for initial production of axillary shoots. The shoots were used as explants and cultured on DKW medium supplemented with 8.88 μm 6-benzylaminopurine (BA) and 0.27 μm naphthaleneacetic acid (NAA), resulting in the production of more than six axillary shoots per explant. The axillary shoots could either be used as explants for additional shoot production or be cultured on ½ DKW medium supplemented with 0.25 μm indole-3-butyric acid (IBA) for rooting. Plantlets were transplanted into a substrate with 99% survival rate in a shaded greenhouse. This established method could be used for rapid propagation of W. florida to speed the introduction of new hybrids or cultivars for commercial production.
Yuncong Li, Edward Hanlon, George O'Connor, Jianjun Chen, and Maria Silveira
Compost is the product resulting from the controlled biological decomposition of organic material that has been sanitized through the generation of heat and processed to further reduce pathogens as defined by the U.S. Environmental Protection Agency and stabilized to the point that the compost is beneficial to plant growth. Organic materials used for composting in Florida are mainly yard wastes (trash) and food wastes. More than 5.7 million tons of composts could be produced from yard trash and food waste in the state. Animal manure and biosolids (treated sludge) can also be composted, but are not discussed in this article. “Other wastes” as discussed herein [food processing wastes, coal ash, wood ash, drinking water treatment residuals (WTRs), and phosphogypsum] are by-products of leading Florida industries and are available in large quantities for reuse. About 5 million tons of food processing waste [citrus (Citrus spp.) and vegetables alone], 1.85 million tons of coal ash (from 28 coal-burning power plants), 0.05 million tons of wood ash, 1000 million tons of phosphogypsum (from the state's phosphate fertilizer industry), and significant, but unknown, amounts of WTRs are available. Due to the growing interest in sustainable agriculture practices, this article is intended to discuss the current regulations and guidelines for composting and the use of composts and other wastes in Florida, the characteristics, benefits, and concerns of Florida compost and other wastes, and current research and needs of research and extension for incorporating compost and other waste materials in Florida's sustainable agriculture. Our literature search was largely limited to studies conducted in Florida.
Jianjun Chen, Dennis B. McConnell, Cynthia A. Robinson, Russell D. Caldwell, and Yingfeng Huang
Three composts, derived from municipal solid waste with biosolids, yard trimmings, and yard trimmings with biosolids, were mixed by volume with sphagnum peat and pine bark to formulate 12 substrates. After characterizing physical and chemical properties, the substrates, along with a control, were used for rooting single eye cuttings of pothos (Epipremnum aureum) and terminal cuttings of maranta (Maranta leuconeura) and schefflera (Schefflera arboricola) in enclosed polyethylene tents. All cuttings initiated roots with no significant difference in root numbers per cutting 14 days after sticking, but root lengths 21 days and root-ball coverage ratings 45 days after sticking were significantly affected by substrates. Five of 12 compost-formulated substrates resulted in root lengths of cuttings equal to or longer than the control. In addition to desirable physical properties such as bulk density, total porosity, and air space, common chemical characteristics of the five substrates included low concentration of mineral elements, initial electrical conductivity ≤3.0 dS·m-1 based on the pour through extraction method, and pH between 3.8 to 5.0. The five substrates were formulated by combining composted municipal solid waste with biosolids or yard trimmings with biosolids volumetrically at 20% or less or composted yard trimmings at 50% or less with equal volumes of sphagnum peat and pine bark.