Crop load affects apple fruit quality by altering carbon availability for fruit development, yet its metabolic consequences across development are incompletely characterized. We imposed low, medium, and high crop loads at 2.5, 7.5, and 15 fruits/cm 2 trunk cross-sectional area, respectively, on 4-year-old ‘Gala’/‘M.26’ apple trees at 10-mm king fruit size and quantified 57 fruit metabolites, including carbohydrates, organic acids, amino acids, and phenolic compounds, at 38, 78, and 125 days after full bloom (DAB); peel and flesh were analyzed separately at harvest. Crop load effects were limited at 38 DAB but intensified as fruit development progressed. At 78 DAB, fruit with a low crop load had lower levels of starch, γ-aminobutyric acid, and methionine than those of fruit with medium and high crop loads. At harvest, low crop load increased sorbitol by more than three-fold and sucrose by approximately 20% relative to those associated with high crop load, whereas fructose remained unchanged. Low crop load also increased malate, succinate, aspartate, glutamine, and peel cyanidin glycosides, consistent with metabolic shifts toward organic acid, amino acid, and anthocyanin accumulation under high carbon supply per fruit. These results identified crop load-sensitive metabolites, including sorbitol, aspartate, glutamine, malate, and peel anthocyanins, as well as homeostatic metabolites such as fructose and glutamate. The patterns emphasize the sucrose/sorbitol dual carbon supply system as a key link connecting the source–sink status to primary and secondary metabolism in apple.
Pecan is a well-known nut tree native to the United States and Mexico. It is valued as a high-quality source of dried fruit, oil trees, and wood. Seed germination, beginning with imbibition, comprises a series of coordinated physiological and morphogenetic processes that play a key role in the growth of pecan seedlings. Several factors influence the germination of pecan seeds. To explore the mechanisms underlying pecan seed germination, we performed transcriptomic, proteomic, and microRNA (miRNA) analyses on seeds sampled at four different stages to compare changes in messenger RNA (mRNA), protein, and miRNA. Transcriptomic and proteomic analyses highlight pathways associated with plant hormone signal transduction. miRNA profiling identified both conserved and novel miRNAs, with differential expression indicating regulatory roles in germination. A putative miR396–growth regulating factor (GRF) regulatory module was identified and may participate in pecan seed germination, potentially through its association with plant hormone regulation. This multiomics study provides insights into potential molecular regulatory processes underlying pecan seed germination and offers a theoretical basis for future functional studies, seedling cultivation, and breeding improvement.
Cresses are nutrient-dense brassicas. Despite recent studies on their phytonutrient and mineral content, the influence of magnesium fertilization on their mineral and biomass accumulation remains understudied. In this study, five magnesium fertilization rates: 24.3 (control treatment), 100, 150, 200, and 250 mg·L −1 were applied to watercress ( Nasturtium officinale ) and upland cress ( Barbarea verna ) in a controlled greenhouse hydroponic environment. A nutrient film technique hydroponic system was used under a split-plot design. The study aimed to examine the effects of magnesium treatments on mineral nutrient accumulation. Inductively coupled plasma emission spectrometry was used to quantify the mineral nutrients. Results indicate that cress variety significantly influenced nutrient accumulation, whereas magnesium fertilization selectively increased potassium (K) ( P = 0.031) and silicon (Si) ( P = 0.016) at 200 mg·L −1 rate, and copper (Cu) ( P = 0.014) at 24.3 mg·L −1 . The K and Si concentrations were 1.26 and 2.56 times the control value, respectively, while Cu concentration was 1.27 times the lowest treatment value (at 150 mg·L −1 rate). Upland cress had higher nutrient levels than watercress except for sodium (Na) ( P < 0.001), which was 6.3 times higher in watercress. On the other hand, watercress biomass was 2.5 times that of upland cress. These results reveal the importance of optimizing magnesium nutrition and selecting cress varieties for mineral nutrient accumulation in leafy greens.
Phytophthora capsici is a destructive pathogen of pepper ( Capsicum annuum L.), causing severe yield losses worldwide. Although resistance loci derived from the C. annuum landrace CM334 have been widely deployed, durable resistance remains elusive due to complex inheritance and the reported Inhibitor of P. capsici resistance ( Ipcr ) gene that suppresses resistance. We investigated the inheritance and genomic location of Ipcr using an F 2 population derived from a hybridization between CM334 and NMCA10399. Disease evaluations with a virulent P. capsici isolate revealed segregation did not deviate from a 3:13 ratio, consistent with dominant suppression epistasis. Bulk segregant analysis with quantitative trait loci sequencing identified a major susceptibility-associated interval on chromosome 3 (107.6 to 113.4 Mb) significantly associated with susceptibility, in which ΔSNP index values reached –0.62 and G′ statistics exceeded significance thresholds, consistent with dominant suppression of resistance. Candidate gene analysis within this region revealed loci with potential roles in defense regulation, including a CLAVATA3/ESR-related protein, calmodulin-binding protein 60, ASC1-like protein, MLO-like gene, and PBS1-like kinase. These findings refine the genomic position of Ipcr and highlight candidate genes that may condition susceptibility, providing valuable targets for functional validation and breeding strategies to eliminate suppressive alleles and develop durable resistance to P. capsici in pepper.
Among cultivated blueberry types, rabbiteye blueberry ( Vaccinium ashei Reade) is a native hexaploid species valued for its exceptional vigor, adaptability to diverse soils, tolerance to abiotic and biotic stresses, and longevity. Despite these advantages and its continued importance to small-scale and mid-scale growers, rabbiteye breeding has progressed more slowly than southern highbush blueberry breeding. The lack of breeding effort leaves key production challenges in rabbiteye blueberry unaddressed, thus weakening the competitive edge of rabbiteye cultivars and resulting in drastically reduced planting acreage in recent years. These issues, including low fruit quality, late harvest timing, and pollination dependence, highlight important gaps in rabbiteye improvement. Therefore, this review summarizes the origin, biology, commercial history, and global production of rabbiteye blueberry. It also traces the development and status of public and private breeding programs and evaluates the performance of existing cultivars with regard to productivity, stress tolerance, disease resistance, phenology, and fruit quality. We further examined progress made through interspecific hybridization and highlighted persistent challenges, including a narrow genetic base, limited genomic resources, and insufficient breeding investment. Finally, we outlined key priorities for future rabbiteye improvement and emphasized enhanced fruit quality and shelf life, mechanical harvestability, parthenocarpy, optimized phenological development, and the integration of modern genomic and phenomic tools. Renewed and coordinated breeding efforts that leverage both traditional and modern approaches are essential to restoring market confidence in rabbiteye blueberries and supporting a more sustainable and resilient blueberry production system.
Flower color, which is an important ornamental trait, is largely attributed to the accumulation of flavonoids, carotenoids, and betalains in petals. Cyanidin, pelargonidin, and peonidin are the three main anthocyanidins in roses. Although anthocyanins are known to influence pollinator attraction, they are also associated with tolerance to abiotic stressors such as extreme temperatures, reduced precipitation, and ultraviolet (ultraviolet) radiation. Using a comparative study under controlled conditions (growth chambers), we investigated the effect of ultraviolet-B radiation (ultraviolet-B, 280–320 nm) on four anthocyanin pigments (cyanidin-3,5-O-diglucoside, cyanidin-3-O-glucoside, pelargonidin-3,5-O-diglucoside, and pelargonidin-3-O-glucoside) in flower petals of three rose genotypes derived from autotetraploid biparental populations: a transitioning-type rose (a rose with flowers that change color from yellow to dark pink at different stages of flower development because of the accumulation of anthocyanins), a white-type rose (a rose with stable white flowers over different stages of flower development), and a pink-type rose (a rose with stable pink flowers over different stages of flower development). Cyanidin-3,5-O-diglucoside was the most abundant pigment in the pink-type rose. In the white-type rose, only a small amount of pelargonidin-3,5-O-diglucoside was detected. Exposure to ultraviolet-B in addition to visible light did not cause any significant changes in anthocyanin biosynthesis in either the white-type rose or the pink-type rose. In the transitioning-type rose, no pigment was accumulated under white light conditions. However, upon exposure to ultraviolet-B radiation and visible light, the accumulation of cyanidin-3-O-glucoside and pelargonidin-3-O-glucoside increased significantly in freshly open flowers (stage S3) and flowers 1 to 2 days after anthesis (S4 stage). Cyanidin-3-O-glucoside was the most abundant pigment in the transitioning-type rose in these experiments as well as plants grown under field conditions. The pink-type rose mainly synthesized anthocyanidin-3,5-O-diglucoside, whereas petals of the transitioning-type rose were predominantly abundant in anthocyanidin-3-O-glucosides. Thus, our results indicate that the flower color transition phenotype is mediated by the ultraviolet-B-inducible accumulation of cyanidin-3-O-glucoside and pelargonidin-3-O-glucoside.
For alternate bearing mandarin trees (Citrus reticulata), high ON-crop yields alternate almost annually with low OFF-crop yields. In this study, effects of crop load on floral gene expression during the 6 months before full bloom (MBFB) and inflorescence number the following spring in early-maturing ‘Nules Clementine’ and late-maturing ‘Pixie’ mandarin were compared. The OFF-crop trees of both cultivars flowered profusely in April. In these trees, bud FLOWERING LOCUS T (FT) expression was first detected only when the air temperatures decreased to the floral-inductive low temperature (LT) range (4 °C < minimum temperature ≤10 °C) at 4 and 6 MBFB for ‘Nules Clementine’ and ‘Pixie’ mandarin, respectively. Despite occurring on different calendar dates, maximum FT transcript levels corresponded to a similar number of accumulated LT degree-days (56 days at 1 MBFB and 52 days at 3 MBFB) in respective orchards. LEAFY (LFY) and APETALA1 (AP1) were upregulated to maximum levels at a similar number of accumulated warm temperature (WT) degree-days (2 days and 5 days with a maximum temperature ≥24 °C following sufficient LT accumulation) at 1 MBFB for ‘Nules Clementine’ and at 2 MBFB for ‘Pixie’ mandarin. Subsequent maximum expression of downstream APETALA2 (AP2), SEPALLATA1 (SEP1), PISTILLATA (PI), and AGAMOUS (AG) occurred at 1 MBFB for both cultivars, consistent with the initiation of floral organogenesis just before bloom as a result of successful meristem determinacy. The results also provided evidence supporting that the regulation of FT and LFY/AP1 in citrus buds is quantitatively dependent on LT and WT accumulation under the OFF-crop condition. In contrast, ON-crop trees of both cultivars did not produce any inflorescences the following spring. Buds of these trees never expressed FT during the 6 MBFB, LFY expression dropped below the detection limit at 3 MBFB through bloom, and upregulation of AP1 expression did not occur. Consequently, downstream floral organ identity gene expression was significantly lower in ON-crop trees than in OFF-crop trees at 1 MBFB for both cultivars. Early harvest of ON-crop fruit at 3 MBFB or 2 MBFB failed to restore floral gene expression or spring flowering; instead, it increased vegetative shoot number during return bloom, indicating buds were not determined as late as 2 MBFB (February). Collectively, the results suggest that repression of FT during 4 MBFB by the ON crop prevented successful completion of the induction process in floral meristem determinacy by inhibiting LFY and AP1 upregulation, thereby preventing activation of the floral organ identity genes AP2, SEP1, PI, and AG and flower formation.
Dieffenbachia Schott is a widely grown ornamental foliage genus used extensively in interior environments. However, exposure to plant sap can cause skin irritation and inflammation, responses commonly associated with calcium oxalate (CaOx) crystals. Information on the types, densities, and tissue distribution of CaOx crystals in Dieffenbachia remains limited, particularly across leaf and stem developmental stages. The objectives of this study were to characterize the types, densities, and tissue distribution of CaOx crystals in three commercial cultivars, Carina, Rebecca, and Star Bright, and to determine whether crystal occurrence differed among tissues and developmental stages. Tissue-culture liners were grown in an ebb-and-flow system in a shaded greenhouse using the same nutrient solution, and leaves, stems, and spadices were sampled for examination by polarized light microscopy. Three forms of CaOx crystals were identified: raphides, druses, and crystal sand. Raphides and druses were present in leaves, stems, and spadices of all three cultivars, whereas crystal sand occurred only in stems. In leaves, druses greatly outnumbered raphides at all stages, with raphide-to-druse (R/D) ratios ranging from 0.068 to 0.197. Druse density was highest in furled leaves and declined with leaf maturation. In stems, raphides predominated, with R/D ratios ranging from 1.03 to 18.23, whereas druse density increased with internode maturation. Raphide density also increased at sites of axillary bud initiation and in developing male flowers. In spadices, crystals were concentrated primarily in anthers and staminodes. Crystal density differed significantly among cultivars. 'Star Bright' had lower stem druse density, whereas 'Rebecca' had lower raphide densities in the first and third internodes and lower druse densities in leaves than 'Carina'. The higher crystal densities observed in young leaves and actively growing tissues suggest that CaOx crystal formation is closely associated with developing organs and may serve multiple functions during plant growth. The observed cultivar differences further suggest that CaOx crystal traits are genetically variable and may be useful targets in future Dieffenbachia breeding programs.
The study of fruit microbiomes, defined as the microbial community in and on fruit, is a novel frontier that provides the potential for contextualizing pathogen infection and biocontrol in a more holistic and ecological approach. Differences in sample year tend to explain the greatest variation in fruit microbiome studies, with geography, preharvest management regime, and cold storage also resulting in pronounced shifts. However, effects of cultivar and fungicides can be more subtle, with some studies identifying minor or no shifts. This highlights that while agricultural management is important in shaping fruit microbiomes, environmental and spatiotemporal factors are also important to consider. Additionally, there is a need for more studies that delve deeper into the functional roles of the fruit microbiome, which require extension of ‘omics technologies such as shotgun metagenomics and metabolomics to move beyond taxonomic composition and begin to determine what important roles fruit microbial communities can play. Some studies are investigating the role of native microbiota in biocontrol and how native fruit microbiomes influence the fermentation process, and the field must build on these experiments to gain a more complete understanding of how the fruit microbiome is related to pathogen dynamics and modulation of fruit quality.
Heat stress increasingly limits lettuce (Lactuca sativa L.) production in subtropical regions such as Florida, where high temperatures and contrasting soil systems challenge crop establishment and marketable yield. To evaluate the effect of heat stress in Florida conditions, 312 Lactuca accessions (including breeding lines, plant introductions, cultivars, and wild relatives) were first screened for germination under high temperatures. Several accessions maintained high germination (up to 98%) at 30 to 32 °C, indicating genetic variation for thermotolerance at the germination stage. Based on germination performance, up to 102 accessions were initially evaluated in field trials across multiple locations, soil types, and seasons. As a result, 48 accessions were advanced to replicated multienvironment trials. Field experiments revealed significant effects of accession, environment, and their interaction on head weight, bolting, and marketability. While higher yield and marketability were generally observed in muck soils, increased bolting was seen under sandy soil and warmer conditions. Tipburn incidence was minimal across environments. A genotype × environment analysis indicated both crossover and noncrossover interactions in the investigated heat tolerance-related traits and lettuce types, emphasizing the need of multienvironment selection for stable performance. These results demonstrate heritable variation for heat tolerance from germination to mature plants in lettuce and identify germplasm with the potential to improve adaptation and yield stability under warmer subtropical production systems.
Controlled environment agriculture (CEA) refers to the practice of growing crops within regulated, enclosed systems where factors such as light, temperature, humidity, and nutrients can be precisely controlled. These systems generate vast amounts of operational and biological data as sensors continuously monitor plant and environmental conditions. Artificial intelligence (AI), a field focused on creating systems that learn from data and make informed decisions, can then be used to process this huge data set, including environmental adjustments to forecasting crop growth and yield, ultimately improving productivity while reducing waste. Technologies such as machine learning, image processing, robotics, deep learning, Internet of Things (IoT), and neural networks are embedded in AI to address agricultural challenges. AI monitors agricultural parameters such as crop genetics, health and disease, livestock, soil moisture, soil quality and moisture, climate, autonomous machinery, resource efficiency, weed control, genetics, harvest timing and market forecasting to enable real-time monitoring of factors like weather, temperature, water usage, and soil conditions, thus enabling farmers to minimize losses and boost yields. Individual farmers are likely to operate with more than 75 million interconnected devices, with an average farm producing 4.1 million data points on average per day by 2050. This review critically examines the successes and challenges of AI in redefining CEA productivity and sustainability. As AI technologies continue to evolve, their integration into CEA systems will become increasingly vital in building resilient, data-driven, and adaptive agricultural systems for the future. Ultimately, AI-enhanced CEA convergence represents a critical frontier for research and innovation in agri-food systems.
Grape (Vitis spp.) is an economically and culturally significant crop grown in a wide array of climates, including cooler areas that regularly experience freezing temperatures. To better adapt grapes for cultivation in cooler climates, wild grape relatives and hybrids have been and continue to be used in breeding efforts. The US Department of Agriculture, Agricultural Research Service maintains a collection of cultivated and wild cold-hardy grapes in Geneva, NY, USA. This collection contains more than one dozen species, mostly of North American origin, as well as an extensive set of hybrid breeding lines and cultivars. We demonstrate the genetic variation present in the collection using newly developed rhAmpSeq markers to explore phylogenetic relationships. Our findings match those of previous analyses that showed Eurasian species nested within the North American species, suggesting a North American origin of the Vitis genus. In addition, an analysis of ancestry and genetic distance suggested taxonomic identities of 18 previously unidentified accessions and 36 putatively misidentified accessions. The data presented here advance the understanding of the Vitis clade and provide support for ongoing research, conservation, and breeding efforts.
Intraspecific hybridization provides opportunities for trait improvement in scarlet sage (Salvia coccinea), a species with limited cultivar diversity and unknown interspecific compatibility. Previous research established single-gene simple dominance inheritance for red and pink flower colors. However, the inheritance of purple flowers remained unknown. This study investigated flower color inheritance by crossing elite red and pink selections with purple cultivars and assessed flower size improvements across generations. Controlled crosses were conducted between red, pink, and purple parents, producing 300 F1 and 429 F2 individuals. All F1 plants displayed red flowers regardless of parental colors. The F2 generation segregated into red, purple, pink, and a novel white phenotype with variable pink or purple tones. The pink and purple cross progeny fit a 9:3:3:1 phenotypic ratio (P > 0.05), consistent with two-gene recessive epistasis based on observed phenotypic relationships and predicted parental genotypes. Mean flower sizes were 14.6 mm in the F1 and 13.9 mm in the F2, with individual improvements in the F2 of 9.7% for purple, 25.8% for pink, and 22.9% for red compared with parents. Results demonstrate that flower color inheritance in S. coccinea follows a two-gene recessive epistatic pattern rather than single-gene inheritance, explaining previous observations while revealing a new white flower phenotype. This refined genetic understanding facilitates more targeted breeding strategies for ornamental improvement.
Growers implement a variety of strategies to manage soilborne pathogens, plant-parasitic nematodes, arthropod pests, and weeds. These strategies include chemical, cultural, biological, and physical means. One of the physical techniques available is soil solarization, which heats moist soil to high temperatures by trapping solar radiation under transparent plastic tarps. Soil solarization is a chemical-free method that is relatively low-cost compared with other strategies. This technique has been shown to be effective for managing many soilborne pathogens, plant-parasitic nematodes, and weeds, but it has had mixed results for arthropod pests and improving crop yield and quality. This review discusses the basics of soil solarization, its use in vegetable production, the temperatures that can be reached, and the effects on various biotic pressures. The considerations of implementing soil solarization in high tunnels compared with open fields, its influence on temperature, and the economics of soil solarization, are also addressed.
While unmanned aircraft system (UAS)-based photogrammetry and light detection and ranging (LiDAR) are increasingly used for canopy height estimation in forestry and other orchard systems, their application to pecan orchards remains limited. Accurate measurements of tree height and canopy structure are essential in pecan production for assessing tree growth and health, and for supporting precision orchard management. This study provides one of the first systematic evaluations of UAS-based structure-from-motion (SfM) photogrammetry and UASmounted LiDAR for estimating pecan tree height. A rotary-wing UAS equipped with RGB and near-infrared (NIR) cameras collected imagery at 60 and 120 m aboveground over two pecan orchards containing 480 and 308 trees, and LiDAR data were acquired at 70 m. UAS imagery was processed to generate three-dimensional (3D) point clouds, digital surface models (DSMs), digital terrain models (DTMs), and orthomosaics. DTMs were derived using point cloud classification and DSM filtering, and tree heights were calculated relative to these terrain models using canopy height models (CHMs) and point cloud-based approaches. LiDAR data were processed to produce calibrated point clouds, DSMs, and DTMs, from which tree heights were extracted using comparable methods. Image-based tree heights showed strong agreement with manual measurements, with point cloud-derived high percentiles or maxima [R2 = 0.982-0.996; root mean square error (RMSE) = 14 to 25 cm] consistently outperforming CHM-based estimates across ground elevation methods, camera types, and flight altitudes. LiDAR-derived tree heights exhibited similarly high accuracy. Image-based and LiDAR-derived heights were strongly correlated across all trees at 120 m (R2 = 0.982-0.995; RMSE = 18-25 cm), confirming the reliability of SfM photogrammetry. However, incomplete canopy reconstruction in some 60 m datasets led to underestimation, highlighting the importance of sufficient image overlap for accurate 3D canopy modeling. These results demonstrate that UAS image-based point clouds can provide pecan tree heights comparable to LiDAR, offering a cost-effective approach for tree growth monitoring, orchard management, and precision agriculture applications.
Salinity stress can depress tomato yield in diverse environments. Tomato wild relative Solanum sitiens displays notable abiotic stress tolerance, as evidenced by its distribution in the highly arid Atacama Desert of northern Chile and its presence in highly saline soils. We performed a series of greenhouse experiments to characterize sodium chloride salinity tolerance in S. sitiens accession LA4331, tomato fresh-market line LA4354, and 27 introgression lines (ILs) that each contain a chromosomal segment of S. sitiens in the background of LA4354. In response to fertigation with an increasing series of salt doses ranging from 0 mM NaCl (total solution electrical conductivity of 2.5 dS/m) to 150 mM NaCl (17.5 dS/m), LA4354 and processing tomato hybrid SVTM9033 demonstrated significant fruit yield declines and LA4331 demonstrated significant and consistent reductions in vegetative biomass. ILs and their tomato parent largely demonstrated reductions in yield, marketable fruit fraction, and vegetative biomass as well as increases in soluble solids and fruit dry matter content under a 10 dS/m salt treatment compared with a 2.5 dS/m control. However, 21 of 27 ILs displayed smaller relative declines in yield under salt compared with LA4354, suggesting that multiple genes distributed across the S. sitiens genome contribute to yield stability under salt stress in the background of domesticated tomato. Three ILs identified for further characterization in a validation experiment, LA5265, LA5289, and LA5297, displayed relative yield declines of 20% to 45% compared with 54% for LA4354. Furthermore, LA5265 and LA5297 out-yielded LA4354 under salt stress by 92% and 105%, respectively. However, evaluation of crosses between the three ILs and LA4354 indicated that the superior yield stability conferred by introgressions was largely lost in heterozygous state. Future steps required to translate findings to breeding applications include fine-mapping causal genes within introgressions and validating introgression effects in field settings.
. A citizen-science project was conducted in 2024 across four states in the United States (Indiana, Iowa, Tennessee, and North Carolina) to evaluate participant preferences, well-being outcomes, and behavioral changes resulting from container gardening. Two strawberry (Fragaria x ananassa) cultivars-'Berries Galore' (pink flowered) and 'Elan' (white flowered)-and two French marigold (Tagetes patula) types-'Durango Outback' (mixed color) and 'Queen Sophia' (orange/gold)-were distributed to 214 participants along with a plant kit containing all materials required to complete the project. Engagement was maintained using a social media community page, monthly online educational sessions, and frequent e-mail communications. Among the 109 participants who completed pretest and posttest surveys, the demographic skewed toward older, well-educated, female, and experienced gardeners. 'Berries Galore' was preferred over 'Elan', likely because it yielded twice the fruit, was harvested earlier, and provided ornamental value. Marigold cultivar preferences were generally evenly split. Participants were price sensitive, showing similar willingness-to-pay despite performance and preference differences between strawberry cultivars, suggesting that effectively communicating value-added traits is important for consumers. Plant stress (e.g., heat and drought) and critter (e.g., wildlife) damage were reported as common challenges, leading to some plant mortality. Significant improvements in well-being were reported, evidenced by an increase in six positive affects. Participants also showed enhanced confidence in practical skills involving garden pest management and healthy eating habits, a result likely influenced by the online educational sessions. Long-term follow-up revealed sustained behavioral change. For example, 1 year later, 66% of participants had started a home garden, and 77% had purchased more gardening supplies as compared with the previous year. Findings demonstrate that citizen-science gardening programs can effectively generate plant-performance and preference data while enabling assessments of gardening effects on human well-being and lifestyle habits.
. Rheum webbianum Royle is a valuable medicinal herb in China. However, the mitochondrial genome of Rheum webbianum has not yet been reported. In this study, the mitochondrial genome of R. webbianum was assembled by using the reads from the Illumina and Oxford Nanopore sequencing platforms. The R. webbianum mitochondrial genome is circular and 326,286 bp in length. It contains 57 annotated genes, including 35 protein-coding genes, 19 transfer RNA genes, and 3 ribosomal RNA genes. Codon usage, repeated sequences, nonsynonymous to synonymous substitution ratios, RNA editing, synteny, and phylogenetic relationships were all examined. Additionally, 27 homologous segments between the chloroplast and mitochondrial genomes totaling 70,780 bp were found, and their presence was confirmed by polymerase chain reaction. The results of our analyses provide valuable information and a theoretical basis for future research on R. webbianum.
Woody plants have evolved a suite of winter survival traits. Supercooling species are constrained to temperatures above similar to-40 degrees C, whereas non-supercooling species can survive colder temperatures. In midwinter 1986, we observed that starch was present in the xylem of supercooling species but not in non-supercooling species. To explore the relationship between tissue starch and freezing damage in woody plants, we monitored xylem starch and cold hardiness in eight supercooling and three non-supercooling species in Fall/Winter 2023-24. We confirmed that supercooling species retain starch granules within xylem parenchyma (XPC) cells in midwinter whereas non-supercooling species do not. We also observed strong positive correlations between tissue starch content and susceptibility to freezing damage: supercooling species were injured at temperatures ranging from -26 degrees C to -45 degrees C, whereas non-supercooling species survived below -55 degrees C. From Oct through Dec 2023, the percent of starch-filled XPCs in red osier dogwood tissues (non-supercooling) fell from similar to 90% to <3%; during this period, xylem became extremely cold tolerant until March, when starch reserves rapidly recovered. In contrast, the percent of starch-filled XPCs in Red Delicious apple shoots (supercooling) remained high (86% to 98%) through the winter, and xylem suffered freezing damage below -40 degrees C. Based on these observations, we hypothesize that starch granules within XPCs, which can contain freezable water, play an important role in the cold hardiness of woody plants. More work is needed to understand the mechanisms of cold hardiness in supercooling and non-supercooling woody plants and the role of xylem starch reserves.
Papaya ringspot virus (PRSV) is a major threat to papaya production, with no natural resistance identified in Carica papaya L. In several crops, resistance to potyviruses is conferred by mutations in host translation initiation factors, particularly eIF4E and its isoform eIF(iso)4E. In the present study, we used CRISPR/Cas9 technology to edit CpeIF4E and CpeIF(iso)4E using three guide RNAs (gRNAs) per gene, although only CpeIF(iso)4E-edited transform-ants were recovered. Agrobacterium-mediated as well as biolistic methods were used for transformation. Hygromycinresistant callus lines were first screened for Cas9 transgene integration by polymerase chain reaction (PCR) to identify putative transformants, and editing/mutations were confirmed by difference in amplicon size and PacBio HiFi sequencing. Several indels at gRNA5 and gRNA6 target sites were detected in four transformants out of 13, leading to frameshift mutations and loss of functional alleles, whereas no mutations were found within the gRNA4 target region. Successful knockouts were generated for CpeIF(iso)4E, whereas CpeIF4E-edited transformants consistently failed to regenerate, suggesting that CpeIF4E may be essential for papaya viability under tissue culture conditions. Zygosity analysis identified homozygous knockouts in some lines, whereas others were mosaic or hemizygous. This study demonstrates CRISPR-Cas9 as a viable tool for targeted genome editing in papaya and establishes a foundation for the engineering of PRSV resistance and the improvement of economically important traits in this crop.
