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Open access

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.

Open access

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.

Open access

Nicholas Meier, Mark V. Coggeshall, J. Bryan Webber, Elias Bunting, and Ronald S. Revord

Eastern black walnut (Juglans nigra) is a large tree endemic to the eastern United States and is highly sought after for its timber products and uniquely flavored nuts. The University of Missouri Center for Agroforestry in New Franklin, MO, USA, hosts an eastern black walnut cultivar repository. This collection supports an ongoing breeding program to improve economic performance for nut production (kernel weight, nut quality, precocity, and yield). In 1996, 54 cultivars were grafted and planted in a series of experimental orchards for evaluation. From 2001 until 2015, trees were evaluated for 12 phenological and eight nut quality/yield traits. Economically relevant traits including kernel weight, kernel percentage, and precocity (total nuts produced age 6 to 10 years) ranged from 1.1 to 8.6 g, 5.3% to 39.3%, and 16 to 1522 total nuts per tree, respectively. Kernel percentage was positively correlated with kernel weight (r = 0.51) and precocity (r = 0.38). Precocity was negatively correlated with the first (r = −0.39) and last (r = −0.30) female bloom. Principal component analysis and biplot analyses revealed high levels of variation among the cultivars. The first two components explain 43.4% of the total variation. Nut dimensions (nut length and nut thickness), nut and kernel weight, and kernel percentage are the largest drivers of variation in the collection. Eigenvectors for precocity and kernel percentage load together and are orthogonal to kernel weight, suggesting these three important traits can be improved simultaneously. Also, nut length loads with kernel weight, providing a candidate indirect selection parameter to increase kernel weight. These data inform strategies for crossing scheme design, expectations for multitrait genetic gain, complementary hybridization, and identifying unique recombinants.

Open access

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.

Open access

Bing Li, Jingjing Zhang, Xiurui Gao, Xiuqing Pan, Rong Zhou, and Yanrong Wu

Thermosensitive genic male sterile (TGMS) lines are the core of two-line hybrid systems. MicroRNAs (miRNAs) play critical roles in plant growth and development. However, knowledge of regulation of anther development by miRNAs in TGMS eggplant (Solanum melongena) is largely unexplored. To investigate the mechanism underlying miRNA regulation of male sterility, we employed high-throughput small RNA sequencing in anther samples from the reverse TGMS line 05ms and the temperature-insensitive line S63 in eggplant, under high temperature and low temperature conditions. The 05ms line is sterile at low temperature and fertile at high temperature. A total of 166,273,427 raw reads were obtained, 143 known miRNAs from 42 miRNA families and 104 novel miRNAs were detected. Further, six differentially expressed miRNAs (DEMs) were identified, including three known (miR168b-3p, miR397–5p, and miR408) and three novel miRNAs (Novel_116, Novel_119, and Novel_97), which might be related to anther development. Moreover, the six DEMs were validated by quantitative real-time polymerase chain reaction and 892 target genes of which were predicted. Gene Ontology analysis of target genes revealed significant enrichment in the “copper ion binding,” “oxidation-reduction process,” and “oxidoreductase activity” terms. Kyoto Encyclopedia of Genes and Genomes analysis revealed that “plant hormone signal transduction” and “other glycan degradation” were enriched. In addition, we constructed regulatory networks comprising miRNAs, target genes, and important terms/pathways and found the miR397-5p was the most linked miRNA, down-regulated under low temperature. Our findings contribute to understanding of the roles of miRNA during anther development and provide the theoretical foundation for two-line hybrid breeding of eggplant.

Open access

Jinzhu Zhang, Yu Mo, Shuai Chen, Caihua Li, Qingxi Fang, Jie Dong, Zhongsheng Mou, Zheyu Zhang, Daidi Che, and Qingshan Chen

The DNA binding with one finger (Dof), as an important transcription factor, plays an important role in growth and development, primary and secondary metabolism, stress resistance, and plant hormone signal transduction. However, the identification and analysis of the Dof transcription factor family in Rosa is rarely reported. In this study, 28 Rosa chinensis Dof (RcDof) members were identified, which were located on seven chromosomes. The RcDofs were divided into 12 subfamilies according to evolutionary analysis. Through motif, gene structure, and cis-acting element analyses of the 12 subfamilies, the functions of RcDofs were analyzed and predicted. Furthermore, the Dof members in R. chinensis ‘Old Blush’ and another three species (Arabidopsis thaliana, Oryza sativa, and Zea mays) were systematically analyzed. Twelve subfamilies were found in these four species and the motifs and gene structures of Dof members in each subfamily were similar, which further proves that the RcDofs analysis is accurate. Through an intra- and interspecies collinearity analysis, it was found that the collinearity between A. thaliana and R. chinensis is closer in comparison. Tissue expression analysis of RcDofs was by quantitative reverse-transcription polymerase chain reaction (PCR). Quantitative real-time PCR analysis showed expressions of the RcDofs are tissue specific. The RcDofs had higher expression in leaves, roots, and flowers than other tissues. Taken together, this study provides valuable information for future research on functional exploration of RcDof genes and molecular breeding in Rosa.

Open access

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.