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Cold stress is a major factor limiting the growth of warm-season turfgrass species. Cold tolerance in warm-season turfgrass species could be improved through in vitro selection for somaclonal variations. The objectives of this study were to establish an effective in vitro culture protocol for generating plants from calli using mature seeds of seashore paspalum (Paspalum vaginatum) and to determine whether in vitro cold selection of somaclonal variations would lead to improved cold tolerance in seashore paspalum. The optimal concentrations of supplemental compounds in the culture medium for callus induction, embryogenic callus formation, and plant regeneration were determined. The supplemental compounds included 2,4–dichlorophenoxy acetic acid (2,4-D), 6-benzylaminopurine (6-BA), kinetin (KT), naphthalene-1-acetic acid (NAA), CuSO₄, and acidic hydrolysis casein (AHC). The highest rates of callus induction (97.50%), embryogenic callus formation (66.88%), and regeneration (55.94%) were obtained with the supplemental compounds of 3.0 mg·L⁻¹ 2,4-D and 10.0 mg·L⁻¹ CuSO₄ for callus induction; with 3.0 mg·L⁻¹ 2,4-D, 15 mg·L⁻¹ CuSO₄, and 1.0 g·L⁻¹ AHC for embryogenic callus formation; and with 8.0 mg·L⁻¹ 6-BA, 0.2 mg·L⁻¹ KT, 0.5 mg·L⁻¹ NAA, and 10 mg·L⁻¹ CuSO₄ for plant regeneration. Embryogenic calli were subjected to 2 or 6 °C treatment for 90 days for in vitro cold selection of somaclonal variation. Plants regenerated from calli surviving cold treatment (cold-selected) for 45 or 60 days were then exposed to low temperatures [15/10 or 5/3 °C (day/night)]. Plant variants derived from cold-selected calli exhibited significant improvement in their tolerance to low temperature of either 15/10 or 5/3 °C (day/night), as manifested by higher turf quality, leaf chlorophyll content, and membrane stability as well as lower levels of lipid peroxidation compared with the control plants. This study demonstrated the feasibility of in vitro selection for cold tolerance in seashore paspalum. The cold-tolerant variants could be useful germplasm for breeding programs and further molecular characterization of cold tolerance mechanisms.

Carbohydrate metabolism is important for plant adaptation to drought stress. The objective of this study was to examine major forms of carbohydrates associated with superior drought tolerance and post-drought recovery in kentucky bluegrass (Poa pratensis) by comparing responses of different forms of carbohydrates with drought stress and re-watering in two cultivars contrasting in drought tolerance. Plants of drought-tolerant ‘Midnight’ and drought-sensitive ‘Brilliant’ were maintained well watered or subjected to drought stress for 10 days by withholding irrigation, and drought-stressed plants were re-watered for 3 days. Physiological analysis (turf quality, relative water content, and electrolyte leakage) confirmed the genetic variability of the two cultivars in drought tolerance. The two cultivars exhibited differential responses to drought stress and re-watering for the content of water-soluble sugars (sucrose, fructose, and glucose) and storage carbohydrates (starch and fructan), and ‘Midnight’ maintained higher sucrose content at 10 days of drought stress and more fructan at 3 days of re-watering. The greater accumulation of sucrose in ‘Midnight’ under drought stress corresponded with higher activities of two sucrose-synthesizing enzymes (sucrose phosphate synthase and sucrose synthase) but was not related to the sucrose-degrading enzyme activity (acid invertase). These results suggested that increased sucrose accumulation resulting from the maintenance of active sucrose synthesis could be associated with superior turf performance during drought stress, whereas increased fructan accumulation could contribute to rapid re-growth and post-drought recovery on re-watering in kentucky bluegrass.

Exogenous application of either salicylic acid (SA) or calcium chloride (CaCl₂) to alleviate heat stress has been extensively studied. However, the effects of combined SA and CaCl₂ treatment on the heat tolerance of poinsettia have been poorly studied. This study investigated the role of a foliar spray comprising SA and CaCl₂ in managing heat tolerance of three poinsettia (Euphorbia pulcherrima Willd.) cultivars, Noel, Winter Rose (WR), and Ice Punch’ (IP). Plants were pretreated with SA, CaCl₂, or combined SA and CaCl₂ and then exposed to a temperature of 42 °C for 1 hour. Changes in the relative injury (RI) percentage, malondialdehyde (MDA) content, and antioxidant enzyme activities were determined. All plants were then placed in an environment-controlled greenhouse for 14 days and evaluated. Lateral bud sprouting (%), new leaf numbers, and phenotypic appearance were recorded. Results revealed that the three poinsettia cultivars varied in their appearance, morphological growth patterns, and ability to tolerate high-temperature stress. Plant growth of ‘Noel’ was more robust than that of ‘WR’ and ‘IP’, which were considerably affected by heat stress, resulting in brown, withered leaves and defoliation. In general, the effects of the combined application of SA and CaCl₂ on heat-tolerant ‘Noel’ were superior to those of individual applications and no treatment (for control groups) in terms of the RI percentage, lateral bud sprouting (%), and appearance under heat stress. Application of combined SA and CaCl₂ for ‘Noel’ plants was more beneficial for enhancing catalase activity and resulted in the effective alleviation of decreased malondialdehyde content under heat stress. Treatment including 200 μΜ SA and 10 mm CaCl₂ may alleviate heat stress and may prove useful in breeding programs focused on improving poinsettia cultivars.

Amorphophallus species are one of the main economic crops in the mountainous areas of southwest China. However, soft rot disease (Pectobacterium carotovorum ssp. carotovorum) is devastating for this crop. This study explored the Amorphophallus resistance mechanism against soft rot disease by analyzing transcriptome data using a weighted gene coexpression network analysis. The RNA sequencing of plants infected for 0, 12, 24, and 48 hours produced a total of 52.25 Gb of clean reads. A total of 29,096 genes were divided into 34 modules. Six modules of interest with the highest correlation with the target traits were selected to elucidate the resistance genes and pathways. The selected modules were enriched in the α-linolenic acid metabolism, phenylpropane biosynthesis, plant hormone signal transduction, and plant pathogen interaction pathways. Ultimately, AmBGLU, AmCAML, AmCDPK, AmLOX, and AmRBOHD were identified as genes of interest in the four significantly related metabolic pathways for real-time fluorescence quantitative polymerase chain reaction verification. The determination of salicylic acid (SA) and jasmonic acid (JA) in Amorphophallus muelleri and Amorphophallus konjac that suffered from soft rot disease showed that SA and JA were involved in the A. muelleri and A. konjac defense response against soft rot disease. Methyl jasmonate treatment delayed the onset of A. konjac soft rot disease. This study provides a reference for the interaction between Amorphophallus species and soft rot disease and the breeding of broad-spectrum and specific Amorphophallus cultivars that are resistant to soft rot disease.

Pedicularis rex C. B. Clarke ex Maxim., an endemic species with potential horticultural traits from Himalaya, has a unique cup-like petiole structure and highly infraspecific floral variation among members of the lousewort genus (Orobanchaceae). We developed 13 microsatellite markers from three microsatellite-enriched libraries (AG, AC, and AAG) of P. rex with a modified biotin–streptavidin capture technique. Polymorphism of each locus was assessed in 22 individuals with representation of five populations of P. rex. Number of alleles per locus (A) ranged from two to seven with an average of 4.38. The observed and expected heterozygosities varied from 0.03 to 0.86 and 0.45 to 0.84, respectively. Additionally, among the 13 identified microsatellite markers, 11 of them were successfully amplified in species P. thamnophila, and five of them showed polymorphisms. This study may provide important information for further investigation on the population genetics, introduction, and acclimatization of P. rex and its congeners.

Adequate greenhouse environmental management is very important for improving resource use efficiency and increasing vegetable yield. The objective of this study was to explore suitable climate and cultivation management for cucumber to achieve high yield and build optimal yield models in semi-closed greenhouses. A fruit cucumber cultivar Deltastar was grown over 4 years in greenhouse and weekly data of yields (mean, highest and lowest) and environmental variables, including total radiation, air temperature, relative humidity, and carbon dioxide (CO₂) concentration were collected. Regression analyses were applied to develop the relationships and build best regression models of yields with environmental variables using the first 2 years of data. Data collected in years 3 and 4 were used for model validation. Results showed that total radiation, nutrient, temperature, CO₂ concentration, and average nighttime relative humidity had significant correlations with cucumber yields. The best regression models fit the mean, lowest, and highest yields very well with R ² values of 0.67, 0.66, and 0.64, respectively. Total radiation and air temperature had the most significant contributions to the variations of the yields. Our results of this study provide useful information for improving greenhouse climate management and yield forecast in semi-closed greenhouses.

Tea (Camellia sinensis L.) is an important cash crop. In the context of climate change, analyzing the current distribution of tea trees and climate change environmental variables to predict the potential distribution area of tea trees in the future can help decision-makers make appropriate planting decisions and promote sustainable management. In this study, an optimized MaxEnt model was used to predict the limiting factors of tea tree growth and distribution under current and future climate change scenarios. The climate soil mixing model [area under the curve (AUC) = 0.934] performed excellently. The results showed that precipitation, temperature, slope, and soil factors all affected the distribution of suitable habitats for tea trees. Compared with the current distribution area of tea trees, under three shared socioeconomic pathways (SSP126, SSP245, and SSP585), the area of highly suitable habitats for tea trees will expand, especially in 2061–2080 and 2081–2100 years, and the suitable area will extend overall to the north of China, indicating that future climate change may create more new suitable habitats for tea production, especially in Shandong, Shaanxi, Guizhou, and Yunnan provinces. This study will provide important scientific insights for tea production decision-making, tea garden location selection, and future adaptation methods, and will help in the cultivation and transplantation of tea trees in the future.

Nuclear DNA contents were estimated by flow cytometry in 18 Phalaenopsis Blume species and Doritis pulcherrima Lindl. DNA amounts differed 6.07-fold, from 2.74 pg/diploid nuclear DNA content (2C) in P. sanderiana Rchb.f. to 16.61 pg/2C in P. parishii Rchb.f. Nuclear DNA contents of P. aphrodite Rchb.f. clones, W01-38 (2n = 2x = 38), W01-41 (2n = 3x = 57), and W01-22 (2n = 4x = 76), displayed a linear relationship with their chromosome numbers, indicating the accuracy of flow cytometry. Our results also suggest that the 2C-values of the Phalaenopsis sp. correlate with their chromosome sizes. The comparative analyses of DNA contents may provide information to molecular geneticists and systematists for genome analysis in Phalaenopsis. Endoreduplication was found in various tissues of P. equestris at different levels. The highest degree of endoreduplication in P. equestris was detected in leaves.

Citrus (Citrus sp.) germplasm collections are a valuable resource for citrus genetic breeding studies, and further utilization of the resource requires knowledge of their genotypic and phylogenetic relationships. Diverse citrus accessions, including citron (Citrus medica), mandarin (Citrus reticulata), pummelo (Citrus maxima), papeda (Papeda sp.), trifoliate orange (Poncirus trifoliata), kumquat (Fortunella sp.), and related species, have been housed at the Florida Citrus Arboretum, Winter Haven, FL, but the accessions in the collection have not been genotyped. In this study, a collection of 80 citrus accessions were genotyped using 1536 sweet orange–derived single nucleotide polymorphism (SNP) markers, to determine their SNP fingerprints and to assess genetic diversity, population structure, and phylogenetic relationships, and thereby to test the efficiency of using the single genotype-derived SNP chip with relatively low cost for these analyses. Phylogenetic relationships among the 80 accessions were determined by multivariate analysis. A model-based clustering program detected five basic groups and revealed that C. maxima introgressions varied among mandarin cultivars and segregated in mandarin F₁ progeny. In addition, reciprocal differences in C. maxima contributions were observed among citranges (Citrus sinensis × P. trifoliata vs. P. trifoliata × C. sinensis) and may be caused by the influence of cytoplasmic DNA and its effect on selection of cultivars. Inferred admixture structures of many secondary citrus species and important cultivars were confirmed or revealed, including ‘Bergamot’ sour orange (Citrus aurantium), ‘Kinkoji’ (C. reticulata × Citrus paradisi), ‘Hyuganatsu’ orange (Citrus tamurana), and palestine sweet lime (Citrus aurantifolia). The relatively inexpensive SNP array used in this study generated informative genotyping data and led to good consensus and correlations with previously published observations based on whole genome sequencing (WGS) data. The genotyping data and the phylogenetic results may facilitate further exploitation of interesting genotypes in the collection and additional understanding of phylogenetic relationships in citrus.

The NAC transcription factor is a peculiar kind of transcription factor in plants. Transcription factors are involved in the expression of plant genes under different conditions, and they play a crucial role in plant response to various biotic and abiotic stress. We transferred the ClNAC9 gene into Chrysanthemum grandiflora ‘niu9717’ by Agrobacterium tumefaciens–mediated transformation. The results of kanamycin-resistant screening, polymerase chain reaction (PCR) detection, and Northern blot analysis proved that the target gene had been integrated into the genome of the target plants. Wild-type (WT) plants and transgenic plants were treated with different concentrations of NaCl, NaHCO₃, and drought stress, and physiological indexes, such as antioxidant system activity (superoxide dismutase, peroxidase, catalase), malondialdehyde accumulation, and leaf relative water content, were measured. We also observed changes in plant morphology. The physiological indexes’ changing range and extreme values suggested that transgenic plants’ resistance to salinity, alkali, and drought stress was significantly higher than WT plants. Transgenic plant growth was less inhibited compared with WT plants, indicating that the ClNAC9 gene increased the resistance of transgenic plants under the stress of salinization, alkalization, and drought.