Malus Hupehensis Research Articles

Nine New Glycosylated Compounds from the Leaves of the Medicinal Plant Malus hupehensis

Nine New Glycosylated Compounds from the Leaves of the Medicinal Plant Malus hupehensis

Mixed application of raw amino acid powder and Trichoderma harzianum fertilizer for the prevention and management of apple replant disease

Apple replant disease (ARD) is mainly caused by biological factors, and it severely restricts the development of the apple industry. The use of biological control measures to alleviate ARD is critically important for the sustainable development of the apple industry. The effects of raw amino acid powder and Trichoderma harzianum fertilizer on plant biomass, leaf and root indexes, soil physical and chemical properties, soil enzyme activity, and the soil fungal community were studied under pot and field conditions using Malus hupehensis Rehd. seedlings and grafted trees (Fuji New 2001/M9T337) as experimental materials. We found that the application of the materials significantly promoted plant growth, increased the leaf photosynthesis and chlorophyll content, root respiration rate, root antioxidant enzyme activity, and soil enzyme activity, significantly decreased the number of Fusarium sp. in soil, and significantly increased the abundance of beneficial bacteria. In conclusion, the mixed application of raw amino acid powder and Trichoderma harzianum fertilizer can is an effective method for the prevention and management of ARD.

Screening and identification of Paenibacillus polymyxa GRY-11 and its biological control potential against apple replant disease.

Apple replant disease (ARD) is a significant factor restricting the healthy development of the apple industry. Biological control is an important and sustainable method for mitigating ARD. In this study, a strain of Paenibacillus polymyxa GRY-11 was isolated and screened from the rhizosphere soil of healthy apple trees in old apple orchards in Shandong Province, China, and the effects of strain GRY-11 on soil microbial community and ARD were studied. The result showed that P. polymyxa GRY-11 could effectively inhibit the growth of the main pathogenic fungi that caused ARD, and the inhibition rates of the strain against Fusarium moniliforme, Fusarium proliferatum, Fusarium solani, and Fusarium oxysporum were 80.00%, 71.60%, 75.00%, and 70.00%, respectively. In addition, the fermentation supernatant played an active role in suppressing the growth of pathogenic fungi. The results of the pot experiment showed that the bacterial fertilizer of the GRY-11 promoted the growth of Malus hupehensis seedlings, improved the activity of protective enzymes in plant roots, enhanced the soil enzyme content, and optimized the soil microbial environment. In general, the GRY-11 can be used as an effective microbial preparation to alleviate ARD. Our study offers novel perspectives for the prevention of ARD.

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.

Abscisic acid regulates Cl- efflux via the ABI5-ZAT10-SLAH3 module in chloride-stressed Malus hupehensis.

The overload of Cl- typically causes cell damage and death in plants, especially in Cl--sensitive crops. Abscisic acid (ABA) is a stress-induced phytohormone that can alleviate chloride stress by reducing Cl- accumulation; however, the mechanism is not clear. Here, we found that the application of ABA elevated Cl- efflux from roots and reduced membrane damage and cell death in chloride-stressed Malus hupehensis. MhSLAH3, a homolog of the slow anion channel from M. hupehensis, encoded a channel controlling Cl- efflux and was induced by both chloride and ABA. MhSLAH3 overexpression accelerated Cl- efflux, which enhanced the tolerance of M. hupehensis to chloride stress, and retarded chloride-induced cell death. However, the suppression of MhSLAH3 partially offset the acceleration effect of ABA on Cl- efflux. MhZAT10L was then identified as a C2H2-type transcription factor upstream of MhSLAH3, repressing MhSLAH3 transcription under chloride stress. The suppression of MhZAT10L accelerated Cl- efflux by releasing suppressed MhSLAH3, but MhZAT10L overexpression counteracted the effects of ABA on Cl- efflux. MhABI5 promoted Cl- efflux mediated by MhSLAH3 due to induction by ABA and transcriptional repression of MhZAT10L, but this function of MhABI5 was reversed by MhZAT10L overexpression. The suppression of MhABI5 diminished the positive effects of ABA on Cl- efflux and retarding cell death. Thus, ABA repressed MhZAT10L transcription by activating MhABI5, further releasing MhSLAH3 to accelerate Cl- efflux. These findings provide a new evidence of ABA regulation of Cl- efflux.

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

BackgroundApple 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.ResultsIn 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 (|β NTI| > 2).ConclusionsOur 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.

Leaf Fermentation Products of Allium sativum L. Can Alleviate Apple Replant Disease (ARD)

Apple replant disease (ARD) is a serious threat to newly replanted apple seedlings. The alleviation of ARD is of great significance for the healthy development of the apple industry. In this study, we investigated the effects of leaf fermentation products (LFP) of Allium sativum L. on the replanted soil environment and Malus hupehensis Rehd. seedlings. The results showed that LFP increased biomass accumulation, changed root architecture, increased root anti-oxidant enzyme activity, and decreased root MDA content under replanted conditions. In addition, the application of LFP increased soil nutrients and soil enzyme activity and reduced phenolic acid content. Furthermore, the LFP enriched the number of beneficial bacteria and reduced the number of harmful fungi, which positively affected the soil microbial community structure. Overall, our results demonstrated that LFP of A. sativum L. could alleviate the occurrence of ARD and provide new insights for the reuse of the leaves of A. sativum L. and the prevention of ARD.

MhZAT10L positively modulates NaCl-induced cell death by triggering MhVPEγ transcription in Malus hupehensis

Excess sodium chloride (NaCl) in soil causes several secondary stresses for plants. The plant-specific vacuolar processing enzyme (VPE) plays a positive role in regulating stress-induced cell death. Here, we observed that NaCl treatment leads to a significant increase in cell death and upregulation of MhVPEγ expression in Malus hupehensis roots. Meanwhile, we also identified a C2H2-type transcription factor upstream of MhVPEγ, MhZAT10L, which positively regulated MhVPEγ transcription. The transcription of MhZAT10L was induced by NaCl. And genetic experiments using transgenic Malus hupehensis roots and apple calli showed that the suppression of MhZAT10L decreased their sensitivity to NaCl, as well as mitigated the generation of reactive oxygen species (ROS), cell death, and MhVPEγ expression induced by NaCl. Conversely, the overexpression of MhZAT10L enhanced their sensitivity to NaCl, accelerated ROS generation, and promoted cell death by directly activating MhVPEγ transcription. Overall, our findings indicate that MhZAT10L positively regulates NaCl-induced cell death by activating MhVPEγ transcription.

Analysis of drought resistance of Malus hupehensis plants irradiated with 12C6+ heavy ion

Heavy ion radiation is widely used in radiation mutation breeding because it usually leads to a high mutation rate of irradiated materials. However, there is a scarcity of reports on heavy ion radiation's effects on apples. In this study, the seeds of Malus hupehensis irradiated by 12C6+ heavy ions were used as materials. Subsequently, the germinated plants underwent two brief drought treatments. The results revealed enhanced drought resistance in the irradiated plants, leading to the selection of four mutants (DR-1, DR-2, DR-3, and DR-27). Under prolonged drought treatment, these four mutant lines exhibited significantly lower stomatal density and higher POD activity than the control. Consequently, they suffered less damage while maintaining consistent growth and development, showcasing substantial drought resistance. Transcriptome analysis indicated higher expression levels of stress-responsive genes and pathways in DR-1 and DR-27 plants under prolonged drought stress compared to the control. Notably, within the starch and sucrose metabolic pathway, mutant plants displayed elevated sucrose synthase expression and significantly higher sucrose content than the control, indicating enhanced osmoregulation of mutants. Therefore, these results demonstrate that, under prolonged drought stress, mutant plants sustain growth and development by reducing stomatal density and boosting antioxidant enzyme activity and osmoregulation. We found that 12C6+ heavy ion radiation could enhance the drought resistance of Malus hupehensis plants, and the drought resistant plants which had been verified by long-term drought were selected from the irradiated plants, which provided a new theoretical and technical basis for 12C6+ heavy ion radiation breeding and was of great significance to the development of apple industry in arid areas.

Optimization of Microwave Assisted Aqueous Two‐Phase Extraction of Polysaccharides from Malus hupehensis and Evaluation Its Antioxidant Activity

AbstractThe two models of microwave assisted aqueous two‐phase extraction (MATPE) of polysaccharides from Malus hupehensis are established by response surface methodology (RSM) and back propagation neural network (BP‐NN), compared their prediction ability, and comparatively optimized extraction process by using RSM and BP‐NN coupled genetic algorithm (GA), and the antioxidant activity of M. hupehensis polysaccharides (MHPs) is evaluated by the scavenging ability of free radicals. The results show that the predictive ability of BP‐NN is significantly better than that of RSM. The optimal extraction parameters to achieve the highest MHPs yield (4.71 ± 0.04)% by MATPE are obtained through BP‐NN coupled GA method under the microwave power of 337 W, mass fraction of ammonium sulfate of 23%, ethanol concentration of 29%, and liquid‐to‐solid ratio of 22 mL g−1. The IC50 values of 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) and hydroxyl radicals (OH) scavenging capacities for MHPs achieve 5.13 and 3.29 mg mL−1, respectively. The findings provide important references for the development and utilization of M. hupehensis.

Nitrogen Application Timing and Levels Affect the Fate and Budget of Fertilizer Nitrogen in the Apple-Soil System.

This study aimed to determine the effects of the nitrogen (N) application period and level on the fate of fertilizer N and the contribution of N absorption and translocation to apple organ N. Two N application periods (labeled by the 15N tracer technique in spring and summer, represented by SP and SU, respectively) and three N levels (N0, MN, and HN) were used to determine the physiological indexes and aboveground, root, and soil 15N content of 4-year-old dwarf ('Red Fuji'/M9T337) and arborized ('Red Fuji'/Malus hupehensis Rehd.) apple trees. The results showed that HN led to shoot overgrowth, which was not conducive to the growth of the apple root system (root length, root tips, root surface area, and root volume) or the improvement of root activity. The contribution of soil N to apple organ N accounted for more than 50%, and the contribution of N application in summer to fruit N was higher than that in spring. Under HN treatment, the proportion of soil N absorbed by trees decreased, while that of fertilizer N increased; however, the highest proportion was still less than 50%, so apple trees were highly dependent on soil N. Under MN treatment, fertilizer N residue was similar to soil N consumption, and soil N fertility maintained a basic balance. Under HN treatment, fertilizer N residue was significantly higher than soil N consumption, indicating that excessive N application increased fertilizer N residue in the soil. Overall, the 15N utilization rate of arborized trees (17.33-22.38%) was higher than that of dwarf trees (12.89-16.91%). A total of 12.89-22.38% of fertilizer 15N was absorbed by trees, 30.37-35.41% of fertilizer 15N remained in the soil, and 44.65-54.46% of fertilizer 15N was lost. The 15N utilization rate and 15N residual rate of summer N application were higher than those of spring N application, and the 15N loss rate was lower than that of spring N application. High microbial biomass N (MBN) may be one of the reasons for the high N utilization rate and the low loss rate of N application in summer.

Host-induced gene silencing in wild apple germplasm Malus hupehensis confers resistance to the fungal pathogen Botryosphaeria dothidea.

Host-induced gene silencing (HIGS) is an inherent mechanism of plant resistance to fungal pathogens, resulting from cross-kingdom RNA interference (RNAi) mediated by small RNAs (sRNAs) delivered from plants into invading fungi. Introducing artificial sRNA precursors into crops can trigger HIGS of selected fungal genes, and thus has potential applications in agricultural disease control. To investigate the HIGS of apple (Malus sp.) during the interaction with Botryosphaeria dothidea, the pathogenic fungus causing apple ring rot disease, we evaluated whether apple miRNAs can be transported into and target genes in B. dothidea. Indeed, miR159a from Malus hupehensis, a wild apple germplasm with B. dothidea resistance, silenced the fungal sugar transporter gene BdSTP. The accumulation of miR159a in extracellular vesicles (EVs) of both infected M. hupehensis and invading B. dothidea suggests that this miRNA of the host is transported into the fungus via the EV pathway. Knockout of BdSTP caused defects in fungal growth and proliferation, whereas knockin of a miR159a-insensitive version of BdSTP resulted in increased pathogenicity. Inhibition of miR159a in M. hupehensis substantially enhanced plant sensitivity to B. dothidea, indicating miR159a-mediated HIGS against BdSTP being integral to apple immunity. Introducing artificial sRNA precursors targeting BdSTP and BdALS, an acetolactate synthase gene, into M. hupehensis revealed that double-stranded RNAs were more potent than engineered MIRNAs in triggering HIGS alternative to those natural of apple and inhibiting infection. These results provide preliminary evidence for cross-kingdom RNAi in the apple-B. dothidea interaction and establish HIGS as a potential disease control strategy in apple.

Bacterial community structure and co-occurrence networks in the rhizosphere and root endosphere of the grafted apple

BackgroundCompared with aerial plant tissues (such as leaf, stem, and flower), root-associated microbiomes play an indisputable role in promoting plant health and productivity. We thus explored the similarities and differences between rhizosphere and root endosphere bacterial community in the grafted apple system.ResultsUsing pot experiments, three microhabitats (bulk soil, rhizosphere and root endosphere) samples were obtained from two-year-old apple trees grafted on the four different rootstocks. We then investigated the bacterial community composition, diversity, and co-occurrence network in three microhabitats using the Illumina sequencing methods. Only 63 amplicon sequence variants (ASVs) out of a total of 24,485 were shared in the rhizosphere and root endosphere of apple grafted on the four different rootstocks (M9T337, Malus hupehensis Rehd., Malus robusta Rehd., and Malus baccata Borkh.). The core microbiome contained 8 phyla and 25 families. From the bulk soil to the rhizosphere to the root endosphere, the members of the phylum and class levels demonstrated a significant enrichment and depletion pattern. Co-occurrence network analysis showed the network complexity of the rhizosphere was higher than the root endosphere. Most of the keystone nodes in both networks were classified as Proteobacteria, Actinobacteriota and Bacteroidetes and were low abundance species.ConclusionThe hierarchical filtration pattern existed not only in the assembly of root endosphere bacteria, but also in the core microbiome. Moreover, most of the core ASVs were high-abundance species, while the keystone ASVs of the network were low-abundance species.

Complete chloroplast genome of the Malus baccata var. gracilis provides insights into the evolution and phylogeny of Malus species.

Malus baccata (L.) var. gracilis (Rehd.) has high ornamental value and breeding significance, andcomparative chloroplast genome analysis was applied to facilitate genetic breeding for desired traits andresistance and provide insight into the phylogeny of this genus. Using data from whole-genomesequencing, a tetrameric chloroplast genome with a length of 159,992 bp and a total GC content of36.56% was constructed. The M. baccata var. gracilis chloroplast genome consists of a large single-copy sequence (88,100 bp), a short single-copy region (19,186 bp), and two inverted repeat regions, IRa(26,353 bp) and IRb (26,353 bp). This chloroplast genome contains 112 annotated genes, including 79protein-coding genes (nine multicopy), 29 tRNA genes (eight multicopy), and four rRNA genes (allmulticopy). Calculating the relative synonymous codon usage revealed a total of 32 high-frequencycodons, and the codons exhibited a biased usage pattern towards A/U as the ending nucleotide.Interspecific sequence comparison and boundary analysis revealed significant sequence variation in thevast single-copy region, as well as generally similar expansion and contraction of the SSC and IRregions for 10 analyzed Malus species. M. baccata var. gracilis and Malus hupehensis were groupedtogether into one branch based on phylogenetic analysis of chloroplast genome sequences. Thechloroplast genome of Malus species provides an important foundation for species identification, geneticdiversity analysis, and Malus chloroplast genetic engineering. Additionally, the results can facilitate theuse of pendant traits to improve apple tree shape.

Improving apple orchard health: The role of arbuscular mycorrhizal fungi in alleviating replant disease and strengthening soil microbial communities

The occurrence of apple replant disease (ARD) is inevitable during the renewal and transformation of aging orchards. This disease seriously threatens the healthy and sustainable development of the apple industry. Arbuscular mycorrhizal fungi (AMF) have shown great potential in promoting plant growth, resisting soil-pathogen infection and improving soil quality. However, there is relatively little information available about the application of AMF in the prevention and control of ARD. In this study, we conducted a pot and field experiment were conducted with inoculation of AMF (Paraglomus sp. SW1) on apple rootstock (Malus hupehensis Rehd. in the pot experiment and M9T337 in the field experiment) to explore the biocontrol effect of AMF on ARD by comparing the changes in fungal and AMF communities after AMF inoculation on apples under replanting conditions. AMF-inoculated apple was used as the treatment, while non-inoculated apple was used as the control. The results showed that AMF-inoculated plants not only promoted the growth of M. hupehensis Rehd., but also stimulated the branch elongation growth of young apple trees, compared to the control. After inoculation with AMF, the community structure of soil fungi and arbuscular mycorrhizal fungi changed significantly, with an increase in the abundance of fungi and AMF in soil, and a significant reduction in the abundance of Fusarium spp., especially Fusarium moniliforme, Fusarium solani, and Fusarium proliferatum. Additionally, the soil enzyme activity increased significantly. Furthermore, the levels of ammonium nitrogen (NH4+), nitrate nitrogen (NO3−), available phosphorus (AP), available potassium (AK), organic matter (SOM), and pH in the rhizosphere soil were significantly related to the changes in the community structure of fungi and AMF. The AP, NH4+ and NO3− was found to drive the fungal communities, while NH4+ and NO3− drove the AM fungal communities in replanting soil. In conclusion, apple-arbuscular mycorrhizal symbionts can effectively alleviate ARD by promoting plant growth and optimizing the structure of soil microbial communities. Future research, should test other gardening plants following AMF inoculation to prepare for a wider application in controlling replant disease.

A Study on the Causes of Apomixis in Malus shizongensis

Apomixis is a unique reproductive process that produces fertile offspring without the combination of sperm and egg cells. This process perfectly reproduces maternal DNA, making it possible to fix heterosis during reproduction. Malus shizongensis is a newly discovered species that is closely related to Malus hupehensis Rehd. After de-male bagging, it was found that the fruit set rate reached 78.7%. Preliminary analysis indicated that M. shizongensis have apomictic reproductive characteristics. In this work, we employed paraffin sectioning and electron scanning microscopy to explore apomixis in M. shizongensis during the development of male–female gametes and embryo sacs. Stigma fluorescence assays showed that pollen germination was normal, but less pollen entered the ovaries. Additionally, analysis of anthers indicated the presence of dysplasia and paraffin sectioning revealed that the pollen mother cells were aborted due to abnormal disintegration of the tapetum layer. Taken together, our results indicate that the primary causes of apomixis in M. shizongensis are anther dysplasia and male gamete development failure, resulting in reduced pollen tube entry into ovaries and reduced reproduction of female gametes. In conclusion, this study provide a theoretical basis and technical supports for apple stock breeding and apple industry development.

Effects of Crystal Lime Sulfur Fumigation and Application of Root-Growth-Promoting Agents on the Control of Apple Replant Disease

Apple replant disease (ARD) is seriously hindering the development of the apple industry. This experiment assessed the effects of two different root-growth-promoting agents (Indoleacetic acid and nutrient elements) on the microbial environment of apple-replanted soil and the growth of apple rootstock Malus hupehensis Rehd. seedlings after fumigation with crystal lime sulfur. The results showed that the simultaneous application of crystal lime sulfur, indoleacetic acid, and nutrient elements (T4) improved the biomass of Malus hupehensis Rehd. seedlings. It also enhanced the activities of soil enzymes and root antioxidant enzymes (SOD, POD, CAT). Their activities were significantly higher than in the individual treatments and resulted in a decrease in malondialdehyde (MDA) content. The T4 treatment significantly increased the net photosynthetic rate and chlorophyll content of the plant, thus effectively increasing the plant growth status. After fumigation, the amount of soil microorganisms was reduced, and the amount of bacteria and actinomycetes was increased after mixed application with the root-growth-promoting agent. The abundance of different species such as Pseudallescheria, Guehomyces, Trichoderma, Bacillus, Gaiella, and Sphingomonas was effectively increased, and the amount of Fusarium oxysporum was reduced. Through correlation analysis between different species and plant and soil enzymes, we found that the different species were positively correlated with root respiration rate and SOD activity and negatively correlated with MDA content. The differentially accumulated microbial species may be the key microorganism that promotes plant growth. Therefore, the simultaneous application of crystal lime sulfur, indoleacetic acid, and nutrient elements can optimize the apple replant soil environment and promote the growth of Malus hupehensis Rehd. seedlings, and can be used to control apple replant disease.

Melatonin enhances KCl salinity tolerance by maintaining K+ homeostasis in Malus hupehensis.

Large amounts of potash fertilizer are often applied to apple (Malus domestica) orchards to enhance fruit quality and yields, but this treatment aggravates KCl-based salinity stress. Melatonin (MT) is involved in a variety of abiotic stress responses in plants. However, its role in KCl stress tolerance is still unknown. In the present study, we determined that an appropriate concentration (100 μm) of MT significantly alleviated KCl stress in Malus hupehensis by enhancing K+ efflux out of cells and compartmentalizing K+ in vacuoles. Transcriptome deep-sequencing analysis identified the core transcription factor gene MdWRKY53, whose expression responded to both KCl and MT treatment. Overexpressing MdWRKY53 enhanced KCl tolerance in transgenic apple plants by increasing K+ efflux and K+ compartmentalization. Subsequently, we characterized the transporter genes MdGORK1 and MdNHX2 as downstream targets of MdWRKY53 by ChIP-seq. MdGORK1 localized to the plasma membrane and enhanced K+ efflux to increase KCl tolerance in transgenic apple plants. Moreover, overexpressing MdNHX2 enhanced the KCl tolerance of transgenic apple plants/callus by compartmentalizing K+ into the vacuole. RT-qPCR and LUC activity analyses indicated that MdWRKY53 binds to the promoters of MdGORK1 and MdNHX2 and induces their transcription. Taken together, our findings reveal that the MT-WRKY53-GORK1/NHX2-K+ module regulates K+ homeostasis to enhance KCl stress tolerance in apple. These findings shed light on the molecular mechanism of apple response to KCl-based salinity stress and lay the foundation for the practical application of MT in salt stress.

Effects of 10 Dwarfing Interstocks on Cold Resistance of ‘Tianhong 2’ Apple

The lack of dwarf stock with good cold resistance has affected the production of apples in northern China. Annual dormant branches of ‘Tianhong 2’ apple were grafted on 10 different dwarf interstocks (the rootstocks were the seedlings of Malus hupehensis var. Pingyiensis) as test materials. Among these 10 interstocks, Huang 6, 244, NO.1, 53, 24-5, ZC9-3, Jizhen 1 were newly developed by us (Apple Research Group of Hebei Agricultural University), and three interstocks with different degrees of cold resistance (GM256–with strongest cold resistance, SH40–with stronger cold resistance, M9–with poor cold resistance) were used as controls. The semi-lethal temperature (LT50) and related physiological indexes of the branches in the overwintering process were studied. Based on the comprehensive physiological indexes, the effects of 10 interstocks on cold resistance of the ‘Tianhong 2’ apple were analyzed. The results showed that the effects of 10 kinds of interstocks on the cold resistance of ‘Tianhong 2’ apple were quite different. The order of effects on cold resistance from strong to weak was as follow: GM256 > Huang 6 > 244 >NO.1> 53 > 24-5 > ZC9-3 >Jizhen 1 > SH40 > M9. The purpose of this study was to screen out the interstocks with strong cold resistance, in order to provide some basis for the selection and utilization of interstocks with strong cold resistance in apple cultivation to further promote the development of the apple industry in China.

Waterlogging-responsive Genes Revealed by Transcriptome Sequencing in Leaves of Two Crabapple Species with Contrasting Waterlogging Tolerance

Crabapples (Malus sp.) are ornamental woody plants that belong to the Rosaceae family. Flooding has severely hampered the growth and development of crabapple, and little is known about the molecular responses of crabapple to waterlogging tolerance. Cuttings of waterlogging-tolerant Malus hupehensis and waterlogging-intolerant Malus halliana received flooding treatment of 30 days and regular planting, respectively. Using transcriptome sequencing, we isolated 5703 and 2735 waterlogging-responsive genes from waterlogging-treated M. hupehensis and M. halliana leaves. Among these differentially expressed genes (DEGs), only 746 were shared by both. Several variables may explain the greater waterlogging tolerance of M. hupehensis: there were more waterlogging response genes related to carbohydrate and energy metabolism; signal transduction; antioxidation; lipid metabolism; protein and amino acid metabolism; and polysaccharide, cell wall, and cytoskeleton metabolism pathway in the waterlogged leaves of M. hupehensis than in M. halliana. In particular, the number of DEGs related to anaerobic metabolism, fatty acid metabolism, protein phosphorylation and dephosphorylation, γ-aminobutyric acid metabolism and cellulase, pectinase metabolism pathway in the flooded leaves of M. hupehensis was more than that in M. halliana. The alterations in gene expression patterns of the two crabapple species induced by waterlogging varied substantially. These outcomes pave the way for further studies into the functions of genes that may be involved in waterlogging tolerance in crabapples.