Effect of different exogenous sugars on the growth and nutrient uptake of Malus baccata Borkh. under sub-low root zone temperature.

In northern China, soil temperature slowly rises in spring, often subjecting apple roots to sub-low-temperature stress. Sugar acts as both a nutrient and signaling molecule in roots in response to low-temperature stress. To explore the effects of exogenous sugars on the growth and nutrient absorption of Malus baccata Borkh., we analyzed growth parameters, photosynthetic characteristics of leaves, and mineral element content in different tissues of M. baccata seedlings under five treatments, including control (CK), sub-low root zone temperature (L), sub-low root zone temperature + sucrose (LS), sub-low root zone temperature + fructose (LF), and sub-low root zone temperature + glucose (LG). The results showed that compared to CK, plant height, root growth parameters, aboveground biomass, leaf photosynthesis, fluorescence parameters, chlorophyll content, and the contents of nitrogen (N), phosphorus (P), potassium (K), calcium (Ca) and magnesium (Mg) in M. baccata seedlings were significantly decreased under the L treatment, and the content of Ca in roots was significantly increased. Compared to the L treatment without exogenous sugar, photosynthesis, functional parameters, chlorophyll content, and growth parameters increased to different degrees after exogenous sucrose, fructose, and glucose application. The N and P contents in roots were significantly increased. The N, P, and K contents significantly increased in stems while only the Ca content significantly increased in stems treated with sucrose. Leaf N, P, K, Ca, and Mg contents significantly increased after being treated with the three exogenous sugars. In conclusion, exogenous sugars can improve photosynthetic efficiency, promote mineral element absorption, and alleviate the inhibition of growth and development of M. baccata at sub-low root zone temperatures, and the effect of sucrose treatment was better than that of fructose and glucose treatments.

Effects of ground flowering plant traits on the diversity of wild bees in apple orchards during flowering.

Pollination is one of the important ecosystem services related to sustainable development of human society. However, the population diversity and abundance of wild bees, important pollinators, have been significantly reduced by climate change, agricultural intensification, and landscape transformation. Re-establishment of pollinator habitat by planting nectar-producing plants is an important way to maintain pollination service. In this study, we investigated the status of wild bees and the traits of flowering plants in 22 apple orchards during flowering stage in Changping District, Beijing in 2019. We analyzed the response of wild bee diversity to the flowering plant richness, flower color richness, inflorescence type richness, flowering plant coverage, herbaceous layer coverage and different flower color coverage in apple orchards, aiming to provide guidance for the selection of nectar-producing plants to establish the habitat of wild bees. A total of 3517 wild bees were captured during the apple flowering season, representing 49 species, 13 genera, and 5 families. We identified 21 flowering plants species that shared a similar flo-wering period with apple, exhibiting a range of 5 colors and 9 inflorescence types. The Shannon diversity index, evenness index, and social bee richness of wild bee community were positively correlated with flowering plant richness. The total wild bee community richness, social bee richness, underground nesting bee richness were positively correlated with the richness of flowering plant color, but Halictidae bee abundance was negatively correlated with the richness of flowering plant color. The Shannon diversity index and evenness index of wild bee community were positively correlated with the richness of inflorescence types. Megachilidae bee richness was negative correlated with the white flower coverage. Megachilidae bee richness, social bee abundance, and ground nesting bee richness were positively correlated with the purple flower coverage. There was no significant correlation between wild bees and flowering plant richness, flower color richness, inflorescence type richness, flowering plant coverage, herbaceous layer coverage and different flower color coverage in other communities of different families, lifestyles and nesting types. Maintaining diverse ground flowering plants with various traits in orchards is important to improve the diversity of wild bees. In particular, increasing the coverage of purple flower during apple flowering period is helpful to promote the diversity of Megachilidae bee, social bees, and ground nesting bees.

Temporal changes in net ecosystem CO2 exchange and influential factors in an apple orchard in Northeast China.

The apple orchards in Liaoning, one of the four major apple-producing areas in Bohai Bay, Northeast China, play a crucial role in regulating the carbon sink effect. However, there is limited information on the variation in carbon flux and its influential factors in apple orchards in this region. To address this, CO2 flux data were monitored throughout the entire apple growth seasons from April to November in 2017 and 2018 in the apple (Malus pumila Mill. cv Hanfu) orchard in Shenyang, China. The energy closure of the apple orchard was calculated, and variations in net ecosystem exchange (NEE) at different time scales and its response to environmental factors were analyzed. Our results showed that the energy balance ratio of the apple was 0.74 in 2017 and 1.38 in 2018. NEE was generally positive in April and November and negative from May to October, indicating a strong carbon sink throughout the growth season. The daily average NEE ranged from - 0.103 to 0.094 mg m-2 s-1 in 2017 and from - 0.134 to 0.059 mg m-2 s-1 in 2018, with the lowest values observed in June and July. NEE was negatively correlated with net radiation, atmospheric temperature, saturated vapor pressure deficit, and soil temperature. These findings provide valuable insights for predicting carbon flux in orchard ecosystems within the context of global climate change.

Raman spectroscopy as a tool for characterisation of quality parameters in Norwegian grown apples during ripening.

This study shows for the first time the feasibility of Raman spectroscopy as a non-destructive method to follow the ripening process of apple fruits. Two different varieties of apples were studied: 'Aroma' and 'Elstar'. By visual inspection, Raman spectra showed that the starch content was higher in 'Elstar' apples compared to 'Aroma'. The degradation of starch over time could be detected in the Raman spectra, indicating that the method can be used to monitor the ripening process. The ripeness markers starch index, soluble solids content (SSC), and the sugars glucose, fructose and sucrose were determined with traditional destructive methods. Cross validated calibration models based on Raman spectroscopy were obtained for all quality parameters, and test set validation offered good results, with R2 in the range 0.4-0.86 for 'Aroma' and 0.4-0.95 for 'Elstar', respectively. The regression coefficients showed that the calibrations relied on Raman bands associated with starch and different sugars. The results suggest that Raman spectroscopy in the future could be used to determine the optimal time of harvesting and to sort apples into different degrees of ripeness.

Mechanism of Phloretin Accumulation in Malus hupehensis Grown at High Altitudes: Evidence from Quantitative 4D Proteomics.

Phloretin is a natural dihydrochalcone (DHC) that exhibits various pharmacological and therapeutic activities. Malus hupehensis Rehd. (M. hupehensis) is widely planted in the middle of China and its leaves contain an extremely high content of phloridzin, a glycosylated derivative of phloretin. In the present study, we observed a significant increase in phloretin content in the leaves of M. hupehensis planted at high altitudes. To investigate the mechanisms of phloretin accumulation, we explored changes in the proteome profiles of M. hupehensis plants grown at various altitudes. The results showed that at high altitudes, photosynthesis- and DHC biosynthesis-related proteins were downregulated and upregulated, respectively, leading to reduced chlorophyll content and DHC accumulation in the leaves. Moreover, we identified a novel phloridzin-catalyzing glucosidase whose expression level was significantly increased in high-altitude-cultivated plants. This work provided a better understanding of the mechanism of phloretin accumulation and effective and economic strategies for phloretin production.

Identifying indicators of apple bud dormancy status by exposure to artificial forcing conditions.

Dormancy in temperate fruit trees is a mechanism of temporary growth suspension, which is vital for tree survival during winter. Studies on this phenomenon frequently employ scientific methods that aim to detect the timing of dormancy release. Dormancy release occurs when trees have been exposed to sufficient chill, allowing them to resume growth under conducive conditions. This study investigates dormancy dynamics in two apple (Malus × domestica Borkh.) cultivars, 'Nicoter' and 'Topaz', by sampling branches in an orchard over 14 weeks (2019 to 2020) and over 31 weeks (2021 to 2022) and subjecting them to a 42-day budbreak forcing period in a growth chamber. Temporal changes in budbreak percentages demonstrated dormancy progression in the studied apple cultivars and allowed the three main dormancy phases to be distinguished: paradormancy (summer dormancy), endodormancy (deep dormancy) and ecodormancy (spring dormancy), along with transition periods between them. Using these data, we explored the suitability of several alternative methods to determine endodormancy release. Tabuenca's test, which predicts dormancy release based on the differences in dry weights of buds with and without forcing, showed promise for this purpose. However, our data indicated a need for considerable adjustments and validation of this test. Bud weight and water content of buds in the orchard did not align with budbreak percentages under forcing conditions, rendering them unsuitable for determining endodormancy release in 'Nicoter' and 'Topaz'. Shoot growth cessation did not seem to be connected with either dormancy progression or dormancy depth of the studied cultivars, whereas leaf fall coincided with the beginning of the transition from endo- to ecodormancy. This work addresses methodological limitations in dormancy research and suggests considering the mean time to budbreak and budbreak synchrony as additional criteria to assess tree dormancy status.

Magnesium alleviates growth inhibition under low potassium by enhancing photosynthesis and carbon-nitrogen metabolism in apple plants.

Potassium (K) and magnesium (Mg) play analogous roles in regulating plant photosynthesis and carbon and nitrogen (C-N) metabolism. Based on this consensus, we hypothesize that appropriate Mg supplementation may alleviate growth inhibition under low K stress. We monitored morphological, physiological, and molecular changes in G935 apple plants under different K (0.1 and 6 mmol L-1) and Mg supply (3 and 6 mmol L-1) conditions. Low K stress caused changes in root and leaf structure, inhibited photosynthesis, and limited the root growth of the apple rootstock. Further study on Mg supplementation showed that it could promote the uptake of K+ and NO3- by upregulating the expression of K+ transporter proteins such as Arabidopsis K+ transporter 1 (MdAKT1), high-affinity K+ transporter 1 (MdHKT1), and potassium transporter 5 (MdPT5) and nitrate transporters such as nitrate transporter 1.1/1.2/2.1/2.4 (MdNRT 1.1/1.2/2.1/2.4). Mg promoted the translocation of 15N from roots to leaves and enhanced photosynthetic N utilization efficiency (PNUE) by increasing the proportion of photosynthetic N and alleviating photosynthetic restrictions. Furthermore, Mg supplementation improved the synthesis of photosynthates by enhancing the activities of sugar-metabolizing enzymes (Rubisco, SS, SPS, S6PDH). Mg also facilitated the transport of sucrose and sorbitol from leaves to roots by upregulating the expression of sucrose transporter 1.1/1.2/4.1/4.2 (MdSUT 1.1/1.2/4.1/4.2) and sorbitol transporter 1.1/1.2 (MdSOT 1.1/1.2). Overall, Mg effectively alleviated growth inhibition in apple rootstock plants under low K stress by facilitating the uptake of N and K uptake, optimizing nitrogen partitioning, enhancing nitrogen use efficiency (NUE) and PNUE, and promoting the photosynthate synthesis and translocation.

Spatiotemporal patterns of leaf nutrients of wild apples in a wild fruit forest plot in the Ili Valley, China.

Malus sieversii, commonly known as wild apples, represents a Tertiary relict plant species and serves as the progenitor of globally cultivated apple varieties. Unfortunately, wild apple populations are facing significant degradation in localized areas due to a myriad of factors. To gain a comprehensive understanding of the nutrient status and spatiotemporal variations of M. sieversii, green leaves were collected in May and July, and the fallen leaves were collected in October. The concentrations of leaf nitrogen (N), phosphorus (P), and potassium (K) were measured, and the stoichiometric ratios as well as nutrient resorption efficiencies were calculated. The study also explored the relative contributions of soil, topographic, and biotic factors to the variation in nutrient traits. The results indicate that as the growing period progressed, the concentrations of N and P in the leaves significantly decreased (P < 0.05), and the concentration of K in October was significantly lower than in May and July. Throughout plant growth, leaf N-P and N-K exhibited hyperallometric relationships, while P-K showed an isometric relationship. Resorption efficiency followed the order of N < P < K (P < 0.05), with all three ratios being less than 1; this indicates that the order of nutrient limitation is K > P > N. The resorption efficiencies were mainly regulated by nutrient concentrations in fallen leaves. A robust spatial dependence was observed in leaf nutrient concentrations during all periods (70.1-97.9% for structural variation), highlighting that structural variation, rather than random factors, dominated the spatial variation. Nutrient resorption efficiencies (NRE, PRE, and KRE) displayed moderate structural variation (30.2-66.8%). The spatial patterns of nutrient traits varied across growth periods, indicating they are influenced by multifactorial elements (in which, soil property showed the highest influence). In conclusion, wild apples manifested differentiated spatiotemporal variability and influencing factors across various leaf nutrient traits. These results provide crucial insights into the spatiotemporal patterns and influencing factors of leaf nutrient traits of M. sieversii at the permanent plot scale for the first time. This work is of great significance for the ecosystem restoration and sustainable management of degrading wild fruit forests.

Identification of Apple Flower Development-Related Gene Families and Analysis of Transcriptional Regulation.

Apple (Malus domestica Borkh.) stands out as a globally significant fruit tree with considerable economic importance. Nonetheless, the orchard production of 'Fuji' apples faces significant challenges, including delayed flowering in young trees and inconsistent annual yields in mature trees, ultimately resulting in suboptimal fruit yield due to insufficient flower bud formation. Flower development represents a pivotal process influencing plant adaptation to environmental conditions and is a crucial determinant of successful plant reproduction. The three gene or transcription factor (TF) families, C2H2, DELLA, and FKF1, have emerged as key regulators in plant flowering regulation; however, understanding their roles during apple flowering remains limited. Consequently, this study identified 24 MdC2H2, 6 MdDELLA, and 6 MdFKF1 genes in the apple genome with high confidence. Through phylogenetic analyses, the genes within each family were categorized into three distinct subgroups, with all facets of protein physicochemical properties and conserved motifs contingent upon subgroup classification. Repetitive events between these three gene families within the apple genome were elucidated via collinearity analysis. qRT-PCR analysis was conducted and revealed significant expression differences among MdC2H2-18, MdDELLA1, and MdFKF1-4 during apple bud development. Furthermore, yeast two-hybrid analysis unveiled an interaction between MdC2H2-18 and MdDELLA1. The genome-wide identification of the C2H2, DELLA, and FKF1 gene families in apples has shed light on the molecular mechanisms underlying apple flower bud development.

Apple MdZAT5 mediates root development under drought stress.

Root plays an important role in plant drought tolerance, especially in horticultural crops like apples. However, the crucial regulator and molecular mechanism in root development of apple trees under drought are not well unknown. Cys2/His2-type Zinc-finger proteins are essential for plant response to drought, while the members of C2H2 Zinc-finger proteins in apple are largely unknown. In this study, we identified the members of the C1-2i subclass family of C2H2 Zinc-finger proteins in apple (Malus × domestica). Among them, MdZAT5 is significantly induced in apple roots under drought conditions and positively regulates apple root development under drought. Further investigation revealed that MdZAT5 positively regulates root development and root hydraulic conductivity by mediating the transcription level of MdMYB88 under drought stress. Taken together, our results demonstrate the importance of MdZAT5 in root development under drought in apple trees. This finding provides a new candidate direction for apple breeding for drought resistance.

Deep learning with a small dataset predicts chromatin remodelling contribution to winter dormancy of apple axillary buds.

Epigenetic changes serve as a cellular memory for cumulative cold recognition in both herbaceous and tree species, including bud dormancy. However, most studies have discussed predicted chromatin structure with respect to histone marks. In the present study, we investigated the structural dynamics of bona fide chromatin to determine how plants recognize prolonged chilling during the initial stage of bud dormancy. The vegetative axillary buds of the 'Fuji' apple, which shows typical low temperature-dependent, but not photoperiod, dormancy induction, were used for the chromatin structure and transcriptional change analyses. The results were integrated using a deep-learning model and interpreted using statistical models, including Bayesian estimation. Although our model was constructed using a small dataset of two time points, chromatin remodelling due to random changes was excluded. The involvement of most nucleosome structural changes in transcriptional changes and the pivotal contribution of cold-driven circadian rhythm-dependent pathways regulated by the mobility of cis-regulatory elements were predicted. These findings may help to develop potential genetic targets for breeding species with less bud dormancy to overcome the effects of short winters during global warming. Our artificial intelligence concept can improve epigenetic analysis using a small dataset, especially in non-model plants with immature genome databases.

Bacillus B2 promotes root growth and enhances phosphorus absorption in apple rootstocks by affecting MhMYB15.

Due to the chelation of phosphorus in the soil, it becomes unavailable for plant growth and development. The mechanisms by which phosphorus-solubilizing bacteria activate immobilized phosphorus to promote the growth and development of woody plants, as well as the intrinsic molecular mechanisms, are not clear. Through the analysis of microbial communities in the rhizosphere 16S V3-V4 and a homologous gene encoding microbial alkaline phosphomonoesterase (phoD) in phosphate-efficient (PE) and phosphate-inefficient apple rootstocks, it was found that PE significantly enriched beneficial rhizobacteria. The best phosphorus-solubilizing bacteria, Bacillus sp. strain 7DB1 (B2), was isolated, purified, and identified from the rhizosphere soil of PE rootstocks. Incubating with Bacillus B2 into the rhizosphere of apple rootstocks significantly increased the soluble phosphorus and flavonoid content in the rhizosphere soil. Simultaneously, this process stimulates the root development of the rootstocks and enhances plant phosphorus uptake. After root transcriptome sequencing, candidate transcription factor MhMYB15, responsive to Bacillus B2, was identified through heatmap and co-expression network analysis. Yeast one-hybrid, electrophoretic mobility shift assay, and LUC assay confirmed that MhMYB15 can directly bind to the promoter regions of downstream functional genes, including chalcone synthase MhCHS2 and phosphate transporter MhPHT1;15. Transgenic experiments with MhMYB15 revealed that RNAi-MhMYB15 silenced lines failed to induce an increase in flavonoid content and phosphorus levels in the roots under the treatment of Bacillus B2, and plant growth was slower than the control. In conclusion, MhMYB15 actively responds to Bacillus B2, regulating the accumulation of flavonoids and the uptake of phosphorus, thereby influencing plant growth and development.

Movement of ACC oxidase 3 mRNA from seeds to flesh promotes fruit ripening in apple.

Xenia, the phenomenon in which the pollen genotype directly affects the phenotypic characteristics of maternal tissues (i.e., fruit ripening), has applications in crop production and breeding. However, the underlying molecular mechanism has yet to be elucidated. Here, we investigated whether mobile mRNAs from the pollen affect the ripening and quality-related characteristics of the fruit using cross-pollination between distinct Malus domestica (apple) cultivars. We demonstrated that hundreds of mobile mRNAs originating from the seeds are delivered to the fruit. We found that the movement of one of these mRNAs, ACC oxidase 3 (MdACO3), is coordinated with fruit ripening. Salicylic acid treatment, which can cause plasmodesmal closure, blocks MdACO3 movement, indicating that MdACO3 transcripts may move through the plasmodesmata. To assess the role of mobile MdACO3 transcripts in apple fruit, we created MdACO3-GFP-expressing apple seeds using MdACO3-GFP-overexpressing pollen for pollination and showed that MdACO3 transcripts in the transgenic seeds move to the flesh, where they promote fruit ripening. Furthermore, we demonstrated that MdACO3 can be transported from the seeds to fruit in the fleshy-fruited species tomato and strawberry. These results underscore the potential of mobile mRNAs from seeds to influence fruit characteristics, providing an explanation for the xenia phenomenon. Notably, our findings highlight the feasibility of leveraging diverse pollen genomic resources, without resorting to genome editing, to improve fruit quality.

Plant growth promotion and biocontrol properties of a synthetic community in the control of apple disease.

BACKGROUND: Apple Replant Disease (ARD) is common in major apple-growing regions worldwide, but the role of rhizosphere microbiota in conferring ARD resistance and promoting plant growth remains unclear. RESULTS: In this study, a synthetic microbial community (SynCom) was developed to enhance apple plant growth and combat apple pathogens. Eight unique bacteria selected via microbial culture were used to construct the antagonistic synthetic community, which was then inoculated into apple seedlings in greenhouse experiments. Changes in the rhizomicroflora and the growth of aboveground plants were monitored. The eight strains, belonging to the genera Bacillus and Streptomyces, have the ability to antagonize pathogens such as Fusarium oxysporum, Rhizoctonia solani, Botryosphaeria ribis, and Physalospora piricola. Additionally, these eight strains can stably colonize in apple rhizosphere and some of them can produce siderophores, ACC deaminase, and IAA. Greenhouse experiments with Malus hupehensis Rehd indicated that SynCom promotes plant growth (5.23%) and increases the nutrient content of the soil, including soil organic matter (9.25%) and available K (1.99%), P (7.89%), and N (0.19%), and increases bacterial richness and the relative abundance of potentially beneficial bacteria. SynCom also increased the stability of the rhizosphere microbial community, the assembly of which was dominated by deterministic processes (|ß NTI| > 2). CONCLUSIONS: Our results provide insights into the contribution of the microbiome to pathogen inhibition and host growth. The formulation and manipulation of similar SynComs may be a beneficial strategy for promoting plant growth and controlling soil-borne disease.

Tracing the contribution and fate of synthetic nitrogen fertilizer in young apple orchard agrosystems.

Excessive synthetic nitrogen (N) inputs in intensive orchard agrosystems of developing countries are a growing concern regarding their adverse impacts on fruit production and the environment. Quantifying the distribution and contribution of fertilizer N is essential for increasing N use efficiency and minimizing N loss in orchards. A 15N tracer experiment was performed in a young dwarf apple orchard over two growing seasons to determine the fertilizer N transformation and fate. Fertilizer N primarily contributed to 25 % to 75 % of soil nitrate in the top 60 cm, but the contribution to soil microbial biomass N and fixed ammonium was <8 %, with the contribution to plant N ranging from 9 % to 19 %. In most growth periods, soil nitrate and fixed ammonium contents derived from native soil with N fertilization were higher than those not receiving N fertilizer. The N use efficiency of plants was only 2.6 % and 4.9 % in the first and second seasons, respectively, in contrast to 56.6 % and 54.0 % of N recovered in soil. Meanwhile, N assimilated into microbial biomass accounted for 0.8 %, and the proportion fixed by clay minerals was 3.5 %-5.2 %. One season after N fertilization, the nitrate below the 1 m soil layers accounted for 4.6 % of the applied N fertilizer, and the proportion increased to 22.5 % after two seasons. The N loss rate via N2O emission was 0.4 % over two years. The application of N fertilizer facilitated indigenous soil N mineralization, and abiotic ammonium fixation more efficiently retained synthetic N than microbial immobilization. These findings provide new insight into orchard N cycling, and attention should be given to the improvement of soil N retention and turnover capacity regulated by soil microbial and abiotic processes, as well as the potential environmental impacts of additional soil N mineralization resulting from prolonged chemical N fertilization.

Transcriptional landscape and dynamics involved in sugar and acid accumulation during apple fruit development.

In fleshy fruit, sugars and acids are central components of fruit flavor and quality. To date, the mechanisms underlying transcriptional regulation of sugar and acid during fruit development remain largely unknown. Here, we combined ATAC-seq with RNA-seq to investigate the genome-wide chromatin accessibility and to identify putative transcription factors related to sugar and acid accumulation during apple (Malus domestica) fruit development. By integrating the differentially accessible regions and differentially expressed genes, we generated a global data set of promoter-accessibility and expression-increased genes. Using this strategy, we constructed a transcriptional regulatory network enabling screening for key transcription factors and target genes involved in sugar and acid accumulation. Among these transcription factors, 5 fruit-specific DNA binding with one finger genes were selected to confirm their regulatory effects, and our results showed that they could affect sugar or acid concentration by regulating the expression of sugar or acid metabolism-related genes in apple fruits. Our transcriptional regulatory network provides a suitable platform to identify candidate genes that control sugar and acid accumulation. Meanwhile, our data set will aid in analyzing other characteristics of apple fruit that have not been illuminated previously. Overall, these findings support a better understanding of the regulatory dynamics during apple fruit development and lay a foundation for quality improvement of apple.

Effects of water and exogenous glucose on apple seedling growth and soil enzyme activity in semiarid area.

BACKGROUND: Soil water and organic carbon (C) are key factors affecting the growth and development of apple seedlings. The objective of the study was to investigate the effects of different soil moisture and glucose supplies on apple seedling growth and soil enzyme activities. We hypothesized that the growth of apple seedlings was affected by soil water and C content through their effects on root structure, plant physiological properties and soil enzymatic activities. A pot experiment consisting of nine treatments was set up, including three water treatments with soil moisture contents at 75-85% (normal irrigation, CK), 65-75% (light water stress, LS), and 55-65% (mild water stress, MS) of the soil field capacity, in combination with three glucose treatments with carbon/nitrogen (C/N) ratio of 7.5 (C1, no adding glucose), 10 (C2) and 15 (C3), respectively. RESULTS: Results showed that the LSC2 treatment significantly increased plant height by 7%, stem diameter by 5% and leaf area by 17%, as compared with LSC1. Also, LSC2 significantly increased root dry weight, root vitality and soil enzyme activities. Moreover, results of leaf photosynthetic, malondialdehyde (MDA), peroxidase (POD), superoxide dismutase (SOD) and proline contents also proved that adding glucose improved the drought resistance of plants. CONCLUSION: LSC2 treatment is more conducive to the growth of apple seedlings, and application of carbon has a good alleviation effect on plant water stress. The study demonstrated that addition of exogenous glucose alleviated light water deficiency, significantly affected root vitality, and promoted apple seedling growth. © 2024 Society of Chemical Industry.

Phenomics and transcriptomic profiling of fruit development in distinct apple varieties.

Apple is one of the most economically important and popular temperate fruit trees. The domestication of apple has resulted in substantial phenotypic differences, particularly between wild and cultivated varieties. However, the relationship between gene expression and phenotypic variations in apple remains poorly understood. Here, we present a comprehensive dataset featuring five distinct apple varieties, including two wild varieties and three representative cultivated varieties. The dataset comprises of both phenomics data, encompassing twelve fruit quality-related traits continuously measured over two years, and transcriptomic data obtained at different developmental stages with three biological replicates. We performed basic quality control process, gene expression normalization and differential gene expression analysis to demonstrate the utility and reliability of the dataset. Our findings indicate that gene expression strongly related with phenotypic variations in apple. This dataset serves as a valuable resource, encompassing phenomics and transcriptomic data in multiple formats, thereby facilitating further exploration of the relationships between gene expression and phenotypic traits in apple.

Epigenomic mechanism regulating the quality and ripeness of apple fruit with differing harvest maturity.

Harvest maturity significantly affects the quality of apple fruit in post-harvest storage process. Although the regulatory mechanisms underlying fruit ripening have been studied, the associated epigenetic modifications remain unclear. Thus, we compared the DNA methylation changes and the transcriptional responses of mature fruit (MF) and immature fruit (NF). There were significant correlations between DNA methylation and gene expression. Moreover, the sugar contents (sucrose, glucose, and fructose) were higher in MF than in NF, whereas the opposite pattern was detected for the starch content. The expression-level differences were due to DNA methylations and ultimately resulted in diverse fruit textures and ripeness. Furthermore, the higher ethylene, auxin, and abscisic acid levels in MF than in NF, which influenced the fruit texture and ripening, were associated with multiple differentially expressed genes in hormone synthesis, signaling, and response pathways (ACS, ACO, ZEP, NCED, and ABA2) that were regulated by DNA methylations. Multiple transcription factor genes involved in regulating fruit ripening and quality via changes in DNA methylation were identified, including MIKCC-type MADS-box genes and fruit ripening-related genes (NAP, SPL, WRKY, and NAC genes). These findings reflect the diversity in the epigenetic regulation of gene expression and may be relevant for elucidating the epigenetic regulatory mechanism underlying the ripening and quality of apple fruit with differing harvest maturity.

Relationship between skin greasiness and cuticular wax in harvested "Hongro" apples.

We investigated the ripening and skin greasiness of "Hongro" apples during storage at 20 °C. Postharvest treatment using 100 µLL-1 ethylene accelerated ripening and increased greasiness, whereas treatment using 1 µLL-1 1-methylcyclopropene delayed ripening and reduced greasiness. Scanning electron microscopy showed changes in cuticular wax structure linked to greasiness. Metabolic analysis identified specific metabolites related to greasiness, which varied upon postharvest treatment. Greasiness was positively associated with ethylene production and butyl-9,12-octadecadienoate content. Random forest modeling predicted greasiness levels with high accuracy, with root mean square error values of 0.322 and 0.362 for training and validation datasets, respectively. These findings illuminate the complex interplay between postharvest treatment, apple ripening, wax composition, and skin greasiness. The application of predictive models exemplifies the potential for technology-driven approaches in agriculture and aids in the development of postharvest strategies to control greasiness and maintain fruit quality.