Jeb S. Fields, Kristopher S. Criscione, and Ashley Edwards
Substrate stratification is an emerging substrate management strategy involving layering multiple substrate materials within a single container to modify physiochemical characteristics of the substrate system. Specifically, stratifying allows growers and researchers to rearrange the air–water balance within a container to modify hydraulic characteristics. Moreover, fertilizer can be incorporated into just the upper strata to reduce leaching. Research to date has shown benefits associated with resource efficiency, production timing, and weed control. With the associated benefits for substrate stratification, interested growers will need pragmatic solutions for onsite trials. Therefore, the objective of this study was to identify a cost-effective solution for growers interested in exploring stratification options. As such, this research was designed to identify a single-screen bark separation to generate fine and coarse bark textures suitable for use as the top and bottom substrate strata. Loblolly pine bark (Pinus taeda) was screened with either a 4.0-mm, 1/4-inch, or 3/8-inch screen, with the particles passing through the screen (unders) separated from retained particles (overs). Stratified substrate systems were engineered with an individual screen wherein the fines were layered atop the coarse particles from the same screen. ‘Natchez’ crepe myrtle (Lagerstroemia indica) liners were planted in either of the three stratified substrate treatments or a nonstratified control. Substrate physical characteristics were assessed for each strata by pre- and postproduction properties to identify changes of substrate. The final growth index of the crop was unaffected by the substrate treatment (P = 0.90); however, stratified substrates did increase dry root weight (P = 0.02), with the smallest screen (4.0 mm) resulting in the greatest root weight. Separation of roots between the two strata indicated the presence of more roots in the upper strata in all substrates. However, the stratified substrates resulted in a greater shift in root location, encouraging increased rooting in the upper strata with fine particles, with the largest screen (3/8 inch) resulting in the greatest differentiation between upper and lower rooting. Each stratified treatment had increase in water-holding capacity in the lower (coarser) strata without changes in the upper strata. Thus, we conclude that single screens can be used to build stratified substrate systems. Moreover, screen aperture size may be used to achieve different outcomes with regard to root growth and development as well as water–air balance. Further research may indicate that screen selection may be used to target specific crop needs.
Young-Sik Park, Je-Chang Lee, Nam-Yong Um, Haet-Nim Jeong, and Jae-Yun Heo
In Korea, ‘Campbell Early’, ‘Shine Muscat’, and ‘Kyoho’ account for more than 90% of the Korean grape cultivation area (
S. Brooks Parrish and Zhanao Deng
Cultivated caladium (Caladium × hortulanum; 2n = 2x = 30) is an important ornamental aroid for the environmental horticulture industry. A better understanding of its genetic diversity is needed for continued improvement of caladium. The caladium germplasm maintained in the University of Florida’s caladium breeding program were surveyed for potential variation in chromosome number and nuclear DNA content to gain a better understanding of caladium genetic diversity at the cytogenetic level. For the first time caladium triploidy was discovered in two breeding lines, UF-15-414 and UF-4407 with 2n = 3x = 45 chromosomes and a nuclear DNA content of 13.86 pg·2C−1. In addition, a new chromosome number (2n = 2x = 34) was found in one cultivar, ‘White Wing’. Compared with their diploid parents or grandparents, the triploids showed a distinct, attractive leaf morphology with rounder and thicker leaves. The pollen stainability of UF-15-414 and UF-4407 was 63% and 73%, respectively, indicating potential male fertility, which was unexpected. Analysis of simple sequence repeat (SSR) marker banding patterns confirmed that UF-15-414 was a direct progeny of UF-4407 through hybridization with the diploid cultivar Aaron, whereas UF-4407 might result from fusion of an unreduced (female or male) gamete with a reduced gamete. Chromosome counting and SSR marker analysis of ‘White Wing’ and its progeny cultivars ‘White Wonder’ and ‘White Delight’ suggested that ‘White Wing’ possibly transmitted its 34 chromosomes to progeny during sexual reproduction. The discovery and characterization of these triploids revealed the occurrence of natural sexual polyploidization in caladium and indicated good potential for creating and selecting new triploids for future caladium breeding. The observed new chromosome number in ‘White Wing’ and its progeny cultivars implies that other chromosome variations may be present among cultivated caladiums. In summary, these results revealed two male-fertile triploid caladiums and a new chromosome number that can enrich the cytogenetic diversity in future caladium cultivar development.
Chia Ting Han, Yu Sung, and Ming-Tung Hsueh
Seeds of some winged bean varieties have low germination due to the presence of water-impermeable hardseeds. Seeds of ‘Taitung No.1’ winged bean had only 31% germination because the remaining 69% of seeds had a water-impermeable seedcoat. Sandpaper abrasion and sulfuric acid immersion for 15 and 25 min effectively removed hardseededness of the seeds, resulting in more than 89% germination. As seed moisture content (MC) decreased from 14.8% to 7%, the percentage of seeds with a water-impermeable seedcoat increased. Seed lots with 14.8%, 11%, 9%, and 7% MC had 7%, 38%, 56%, and 78% of hardseeds, respectively, on day 7 in the germination test. It was found that the hilum was responsible for water loss from the whole seed, and the seedcoats began to become water-impermeable at 12% MC. The lens and micropylar regions were initial water entry sites in the Vaseline-blocking experiment.
Samuel Kwakye, Davie M. Kadyampakeni, Kelly Morgan, Tripti Vashisth, and Alan Wright
Essential nutrients for citrus [‘Bingo’ (Citrus reticulata, Blanco)] production are important for different functions, including photosynthesis, resistance to disease, and productivity. During the past 15 to 20 years, citrus production in Florida has significantly declined as a result of the devastating citrus greening disease also called huanglongbing (HLB). Therefore, a greenhouse study was conducted for 2 years, starting in 2018, at the University of Florida/Institute of Food and Agricultural Sciences Citrus Research and Education Center in Florida to evaluate the effect of varying rates of iron on the growth and development of 2-year-old HLB-affected ‘Bingo’ (Citrus reticulata, Blanco) trees on Kuharske citrange rootstock. Four treatments were used in a randomized complete block (HLB status) design with seven single tree replicates for each treatment. The treatments applied were 0.0 (control), 5.6 (standard fertilization, lx), 11.2 (2x), and 22.4 (4x) kg⋅ha−1 iron on HLB-affected and healthy (non-HLB) citrus trees. Data including trunk diameter, tree height, and leaf samples were collected, processed, and analyzed at 3-month intervals for 2 years. At the end of the second year, trees were destructively sampled and processed as above-ground and below-ground biomass. Tree heights were different among iron rates of HLB-affected trees (P < 0.001); however, they were similar for non-HLB trees for both years. Higher average trunk diameters (P < 0.001) were observed for HLB-affected trees that received the 2x rate compared with the 1x rate and the control. In 2019, non-HLB trees showed 13% to 40% higher iron concentrations in leaves than HLB-affected trees. However, leaf iron concentrations were comparable for HLB-affected and non-HLB trees in 2020. Above-ground biomass for HLB-affected trees had between 33% and 44% more biomass (P < 0.01) than below-ground biomass for the corresponding iron fertilization. Iron accumulation correlated positively with all studied nutrients in the above-ground parts for both HLB-affected and non-HLB trees. A 95% confidence interval at which total biomass was nearly maximum corresponded to an iron rate of 9.6 to 11.8 kg⋅ha−1, which was close to the 2x rate. Therefore, soil iron application using the aforementioned rates may be appropriate for better growth and development of young HLB-affected trees.
Margaret A. Halstead, Andrea R. Garfinkel, Travis C. Marcus, Patrick M. Hayes, and Daniela R. Carrijo
Micropropagation is a valuable production tool for the cultivation of hemp (Cannabis sativa), and development of optimal protocols is ongoing. The goal of this study was to evaluate a novel growing medium combination, consisting of Driver and Kuniyuki Walnut (DKW) medium as the nutrient source and glucose as the carbon source, and to investigate the link between in vitro and in vivo (i.e., greenhouse) plant performance. Among 10 accessions intended to represent a range of heterozygosity levels and various essential oil chemotypes, the DKW–glucose growing medium generally produced the most vigorous plantlets by all parameters evaluated in vitro (height, biomass, canopy area, vegetative growth rate, and regeneration rate). Across four growing media treatments, all of which included meta-topolin as the sole plant growth regulator, poor to no rooting was observed in vitro. Hybrids were more vigorous than nonhybrid selections in vitro, but not in vivo. No correlation was observed between in vitro and in vivo vigor, indicating that, with these media, plant performance in vitro is not predictive of that in vivo.
Rebekah C.I. Maynard and John M. Ruter
Salvia is the largest genus in the Lamiaceae with more than 1000 species. The species S. coccinea used in this study has naturalized in the southeastern United States and is an important plant for pollinators. This project aimed to improve phenotypic characteristics of S. coccinea for use in the landscape by selecting for increased petal size and unique petal color. Two elite accessions were selected for hybridization using the pedigree method. One selection displayed compact habit with bicolored coral and white flowers, while the other was slightly larger with solid red flowers. Selections were made based on improved flower color and larger petal size. The breeding program achieved a 25% increase in petal width and a more vivid petal color for the coral bicolored selections. Additionally, a 60% increase in petal width was achieved for red flowers. These novel selections are attractive plants for the landscape, displaying improved ornamental value and supporting local pollinator populations.
Weiting Huang, Xiaoyan Huang, and Zhongming Fang
Melatonin plays an important role in plant resistance to stress. The role of melatonin in the propagation of plant tissue, such as rhizome proliferation, differentiation, and seedling rooting in Cymbidium species, remains unknown. In this study, we selected C. goeringii and C. faberi as experimental materials and attempted to understand the effect of melatonin on this process. We found that 1.0 μM melatonin was beneficial for rhizome proliferation of C. goeringii, with a proliferation rate of 5.52. In terms of C. faberi, the highest proliferation rate of 8.29 was observed in the medium with 0.5 μM melatonin. In proliferation, the cut rhizome of C. goeringii is more likely to cause browning phenomenon than that of C. faberi. The addition of melatonin can significantly inhibit the browning phenomenon and improve the survival rate of C. goeringii rhizome. The highest number of shoot buds per explant (3.11 after 60 days) was observed in the medium with 1.0 μM melatonin. The number of shoot buds per explant (3.28 after 60 days) was significantly higher for C. faberi in the medium with 5.0 μM melatonin than that for the control. Furthermore, culture medium incorporated with 1.0 μM of melatonin had the best comprehensive effect of seedling height and root number and length of C. goeringii. By contrast, 0.5 μM melatonin significantly promoted root elongation of C. faberi, reaching 1.77 cm, whereas it was 0.28 cm in the control. We demonstrated that melatonin in specific concentrations effectively promote rhizome proliferation, differentiation, and seedlings rooting in the rapid propagation of C. goeringii and C. faberi.