The influence of the pollination compatibility type on the pistil S-RNase expression in European pear (Pyrus communis).

The S-RNase gene plays an essential role in the gametophytic self-incompatibility (GSI) system of Pyrus. It codes for the stylar-expressed S-RNase protein which inhibits the growth of incompatible pollen tubes through cytotoxicity and the induction of programmed cell death in the pollen tube. While research on the Pyrus GSI system has primarily focused on the S-RNase gene, there is still a lack of insight into its spatiotemporal expression profile and the factors that regulate it. Previous studies have suggested that S-RNase expression in the style is influenced by pollination and is dependent on the compatibility type. We here continue on this basic hypothesis by analyzing the spatiotemporal expression of the S-RNase alleles in Pyrus communis "Conference" styles in response to different types of pollination; namely, upon full- and semi-compatible pollination and upon incompatible selfing. The results revealed that temporal dynamics of S-RNase expression are influenced by the pollen's compatibility type, indicating the presence of a signaling mechanism between pollen and style to control S-RNase production during pollen tube growth. In our experiment, S-RNase expression continuously decreased after cross-pollination and in the unpollinated control. However, after a fully incompatible pollination, S-RNase expression remained constant. Finally, semi-compatible pollination showed a initially constant S-RNase expression for both alleles followed by a strong decrease in expression. Based on these results and previous findings, we propose a regulatory mechanism to explain the effect of pollination and the associated compatibility type on S-RNase expression in the style. This proposed mechanism could be used as a starting point for future research.

Enhancing productivity, modifying biochemical parameters, and regulating the phenylpropanoid pathway in 'Le-Conte' pears through optimal protocatechuic acid treatments.

BACKGROUND: This study aimed to investigate the impact of protocatechuic acid (PRC) treatments on the productivity and fruit quality of 'Le-Conte' pears, with a specific focus on productivity, stone cells content, and antioxidant activity. The research spanned over three consecutive cultivating seasons, with the first season serving as a preliminary study to determine the optimal PRC concentrations and the most effective number of spray applications. During the initial season, response surface methodology (RSM) was employed to optimize PRC concentration and application frequency. PRC was evaluated at concentrations ranging from 50 to 400 ppm, with treatment frequencies of either once or twice. Considering the optimal conditions obtained from RSM results, PRC treatments at 200 ppm and 300 ppm were applied twice, and their respective effects were studied in comparison to the control in the following seasons. RESULTS: RSM results indicated that PRC at 200 and 300 ppm, applied twice, once during full bloom and again three weeks later, yielded the most significant effects. Subsequent studies revealed that PRC treatments had a substantial impact on various aspects of fruit production and quality. Applying 300 ppm PRC once during full bloom and again three weeks later resulted in higher fruit set percentages, lower fruit abscission, and enhanced fruit yield compared to untreated trees. Additionally, the 200 ppm PRC treatment maintained physicochemical characteristics such as fruit color, increased total soluble solids (TSS), and total sugar, and maintained higher ascorbic acid content and antioxidant capacity in the fruits while reducing stone cells content and lignin. Notably, enzyme activities related to phenylpropanoid metabolism and stone cells, including phenylalanine ammonia-lyase (PAL), cinnamate-4-hydroxylase (C4H), 4-Coumarate-CoA Ligase (4CL), cinnamyl alcohol dehydrogenase (CAD), and cinnamoyl-CoA reductase (CCR), as well as peroxidase, polyphenol oxidase, and laccase, were significantly regulated by PRC treatments. CONCLUSION: Overall, this study suggests that PRC treatments are suitable for enhancing pear yield and quality, with PRC at 200 ppm being the more recommended option over 300 ppm. This approach serves as an effective strategy for achieving a balance between enhancing the productivity and fruit quality of 'Le-Conte' pears.

Does Regulated Deficit Irrigation Affect Pear Fruit Texture by Modifying the Stone Cells?

Regulated deficit irrigation (RDI) strategies aim to improve water usage without reducing yield. Generally, irrigation strategy effectiveness is measured as fruit yield, with little consideration of fruit quality. As water deficit and increased plant cell sclerification are often associated, this study explored the effect of RDI on pear fruit stone cells, a crucial trait affecting flesh texture. The presence, distribution, and development of pear fruit stone cells under RDI and full irrigation were compared using Pyrus communis L. cv. Barlett trees, employing recently developed microscope image analysis technology. The control treatment was maintained under non-stress conditions, while the RDI treatment received an average of 15% of the control water during the latter part of Stage I fruit development. Observations at the end of Stage I and at harvest revealed no effect on stone cell presence under the RDI strategy tested. The relative area of stone cells within the flesh was greater at Stage I than at harvest, as stone cell expansion occurred early in development, while the (unsclerified) parenchyma cells, a dominant component of the fruit flesh, expanded until harvest. Stone cell cluster density was higher near the fruit core than in the cortex center and exterior. These initial results suggest that well-planned RDI strategies will generally not affect pear fruit stone cell content and, thus, textural quality. Microscope image analysis supported the results from previously used analytical techniques, mainly chemical, while providing a tool for better understanding the process and factors involved in the timing of stone cell differentiation.

Mass Spectrometric Identification of Metabolites after Magnetic-Pulse Treatment of Infected Pyrus communis L. Microplants.

The major goal of this study is to create a venue for further work on the effect of pulsed magnetic fields on plant metabolism. It deals with metabolite synthesis in the aforementioned conditions in microplants of Pyrus communis L. So far, there have been glimpses into the governing factors of plant biochemistry in vivo, and low-frequency pulsed magnestatic fields have been shown to induce additional electric currents in plant tissues, thus perturbing the value of cell membrane potential and causing the biosynthesis of new metabolites. In this study, sixty-seven metabolites synthesized in microplants within 3-72 h after treatment were identified and annotated. In total, thirty-one metabolites were produced. Magnetic-pulse treatment caused an 8.75-fold increase in the concentration of chlorogenic acid (RT = 8.33 ± 0.0197 min) in tissues and the perturbation of phenolic composition. Aucubin, which has antiviral and antistress biological activity, was identified as well. This study sheds light on the effect of magnetic fields on the biochemistry of low-molecular-weight metabolites of pear plants in vitro, thus providing in-depth metabolite analysis under optimized synthetic conditions. This study utilized high-resolution gas chromatography-mass spectrometry, metabolomics methods, stochastic dynamics mass spectrometry, quantum chemistry, and chemometrics, respectively. Stochastic dynamics uses the relationships between measurands and molecular structures of silylated carbohydrates, showing virtually identical mass spectra and comparable chemometrics parameters.

Efficacy of Iminoctadine Trialbesilate and Trifloxystrobin in Inhibiting and Controlling Pear Powdery Mildew (Phyllactinia pyri) in Hebei Province, China.

Pear powdery mildew (PPM), caused by Phyllactinia pyri, is one of the most serious diseases affecting production in the Hebei pear-growing region of China. Iminoctadine trialbesilate and trifloxystrobin are known to have broad-spectrum activity against a wide range of plant pathogens, including P. pyri. A total of 105 P. pyri strains were isolated from 11 cities in Hebei Province from 2017 to 2019. Iminoctadine trialbesilate and trifloxystrobin significantly inhibited P. pyri growth. Microscopic observation showed that P. pyri mycelia had different degrees of desiccation and that the conidial cell contents had been released. The sensitivities of 60 P. pyri strains to iminoctadine trialbesilate and trifloxystrobin were determined in vitro, and the average EC50 values were 0.5773 ± 0.0014 and 1.2038 ± 0.0010 µg/ml, respectively. The average EC50 values for 85 and 75% of the strains with continuous single peak frequency distributions were 0.4534 ± 0.0012 and 0.8124 ± 0.0039 µg/ml, respectively. These data could be used as the baseline sensitivities of P. pyri to these two fungicides. The maximum difference multiples of the sensitivities of P. pyri strains from the different cities to iminoctadine trialbesilate and trifloxystrobin were 13.5- and 17.2-fold, respectively. Cluster analysis showed that there was no significant correlation between P. pyri sensitivity and geographical origin. The field efficacies in controlling PPM were higher than 85%. These findings can improve how we monitor iminoctadine trialbesilate and trifloxystrobin resistance and improve application efficiency.

Impact of Intron and Retransformation on Transgene Expression in Leaf and Fruit Tissues of Field-Grown Pear Trees.

Stable and high expression of introduced genes is a prerequisite for using transgenic trees. Transgene stacking enables combining several valuable traits, but repeated transformation increases the risk of unintended effects. This work studied the stability and intron-mediated enhancement of uidA gene expression in leaves and different anatomical parts of pear fruits during field trials over 14 years. The stability of reporter and herbicide resistance transgenes in retransformed pear plants, as well as possible unintended effects using high-throughput phenotyping tools, were also investigated. The activity of ß-glucuronidase (GUS) varied depending on the year, but silencing did not occur. The uidA gene was expressed to a maximum in seeds, slightly less in the peel and peduncles, and much less in the pulp of pear fruits. The intron in the uidA gene stably increased expression in leaves and fruits by approximately twofold. Retransformants with the bar gene showed long-term herbicide resistance and exhibited no consistent changes in leaf size and shape. The transgenic pear was used as rootstock and scion, but grafted plants showed no transport of the GUS protein through the graft in the greenhouse and field. This longest field trial of transgenic fruit trees demonstrates stable expression under varying environmental conditions, the expression-enhancing effect of intron and the absence of unintended effects in single- and double-transformed woody plants.

Processing of Enriched Pear Slices with Blueberry Juice: Phenolics, Antioxidant, and Color Characteristics.

This study evaluated the effectiveness of phenolic compound incorporation from blueberry juice into pear slices (PS) using a combination of ohmic heating (OH) and vacuum impregnation (VI), followed by air-drying (AD) or freeze-drying (FD). Our results showed that OH increased the content of bioactive compounds and antioxidant capacity of blueberry juice, with the optimal OH condition set at 50 °C for 20 min under an electric field of 13 V·cm-1. Furthermore, the combination of VI and OH was efficient in enriching PS with bioactive compounds from blueberry juice (such as cyanidin and epigallocatechin), with the optimal VI/OH condition set at 50 °C for 90 min under an electric field of 7.8 V·cm-1. Moreover, anthocyanin pigments from blueberry juice affected the color parameters of PS by increasing the a* parameter and decreasing the b* and L* parameters. However, both FD and AD (at 40, 50, and 60 °C) negatively affected (p ≤ 0.05) the phenolic content and antioxidant capacity. Notably, AD at 60 °C showed the highest levels of phenolic compounds and antioxidant potential for both impregnated and non-impregnated PS.

Pest categorisation of Diplodia bulgarica.

The EFSA Plant Health Panel performed a pest categorisation of Diplodia bulgarica, a clearly defined plant pathogenic fungus of the family Botryosphaeriaceae. The pathogen affects Malus domestica, M. sylvestris and Pyrus communis causing various symptoms such as canker, twig blight, gummosis, pre- and post-harvest fruit rot, dieback and tree decline. The pathogen is present in Asia (India, Iran, Türkiye) and in non-EU Europe (Serbia). Concerning the EU, the pathogen is present in Bulgaria and widespread in Germany. There is a key uncertainty on the geographical distribution of D. bulgarica worldwide and in the EU, because in the past, when molecular tools were not available, the pathogen might have been misidentified as other Diplodia species (e.g. D. intermedia, D. malorum, D. mutila, D. seriata) or other members of the Botryosphaeriaceae family affecting apple and pear based only on morphology and pathogenicity tests. Diplodia bulgarica is not included in Commission Implementing Regulation (EU) 2019/2072. Plants for planting, other than seeds, fresh fruits, and bark and wood of host plants as well as soil and other plant-growing media carrying plant debris are the main pathways for the further entry of the pathogen into the EU. Host availability and climate suitability factors are favourable for the further establishment of the pathogen in the EU. In the areas of its present distribution, including Germany, the pathogen has a direct impact on cultivated hosts. Phytosanitary measures are available to prevent the further introduction and spread of the pathogen into the EU. Diplodia bulgarica satisfies the criteria that are within the remit of EFSA to assess for this species to be regarded as potential Union quarantine pest.

Synergy of 1-MCP and hypobaric treatments prevent fermented flavour and improve consumers' acceptability of 'Shughri' pear.

Development of fermented flavour during storage reduces acceptability of Shughri pear. Therefore, the current study was designed to investigate the combined effect of 1-Methylcyclopropene (1-MCP) and hypobaric treatment on stability of Shughri pear during 120 days of storage. Fruit were treated individually or combinedly with 25, 50, and 75 kilo pascal hypobaric treatments for 4 h and 1-MCP (0.3 µLL-1 and 0.6 µLL-1) for 24 h, whereas control received no treatment. The pears were stored for 120 days at (0 ± 1 °C, 85 ± 5% RH), and were evaluated after every 30 days. After cold storage, pears were shifted to simulated retail conditions (20 ± 3 °C, 65 ± 5% RH). The combination of 25 kPa + 0.6 µLL-1 1-MCP significantly (P ≤ 0.05) delayed fruit ripening, reduced Alcohol dehydrogenase (ADH), and Pyruvate decarboxylase (PDC) activities, maintained the quality, and led to higher consumers' acceptability of the pear followed by 50 kPa + 0.6 µLL-1 and 25 kPa + 0.3 µLL-1. The control fruit were marketable for a week after storage with relatively less acceptability due to fermented flavour compared to treated fruit, marketable for more than two weeks. Among all the treatments, the synergy of 1-MCP and hypobaric treatment 25 kPa + 0.6 µLL-1 1-MCP improved the postharvest storage life and quality parameters, preventing development of fermented flavour in the pears. The experiment was conducted on pilot scale, for commercial application, the results of this study should be validated on large scale.

Pyrus communis L. (Pear) and Malus domestica Borkh. (apple) leaves lipoidal extracts as sources for beta-sitosterol rich formulae and their wound healing evaluation.

Pyrus communis L. (cv. Le-Conte) (pears) and Malus domestica Borkh. (cv. Anna) (apples) are economic fruit crops cultivated in Egypt. Their leaves were assessed for their beta-sitosterol content and found to have 9.4 mg/g dried leaves wt and 5 mg/g dried leaves, respectively. So we used the lipoidal leaves extracts in the formulation of eight beta-sitosterol-rich emulgels from which the most stable formulae were tested for their antimicrobial activity. Finally, the formulae which exerted antimicrobial activity were biologically evaluated for wound healing against well-known wound healing ointment Mebo® which is composed mainly of 0.25% beta-sitosterol in a base of sesame oil and beeswax. Wound contraction was statistically different in both formulae F3 and F8 from both control and Mebo® groups which indicated better wound healing activity of these formulae ensured by further histopathological study of the healed wounds.

Acibenzolar-S-methyl activates phenylpropanoid pathway to enhance resistance against Alternaria alternata in pear fruit.

BACKGROUND: Alternaria alternata is a causal agent of black spot rot of pear fruit after harvest. Acibenzolar-S-methyl (ASM) has been shown to be a potential elicitor of tolerance in several horticultural products. This work was performed to research the influence of ASM on black spot rot of Docteur Jules Guyot pears and vital enzyme activity and gene expression in the phenylpropanoid pathway. RESULTS: ASM remarkably decreased the lesion diameter of A. alternata-inoculated pears. ASM also increased phenylalanine ammonialyase, cinnamate 4-hydroxylase, cinnamyl alcohol dehydrogenase, peroxidase, polyphenol oxidase activities and gene expression, and enhanced 4-coumarate/coenzyme A ligase activity in pears. Moreover, ASM improved the content of phenylalanine, total phenolic compounds, caffeic acid, flavonoids, anthocyanin and lignin in pears. CONCLUSION: ASM could modulate vital enzyme activity and gene expression in the phenylpropanoid pathway to accelerate metabolite synthesis, thereby enhancing resistance against A. alternata in pears. © 2022 Society of Chemical Industry.

Composite coating of chitosan with salicylic acid retards pear fruit softening under cold and supermarket storage.

Fruit softening is enzyme mediated degradation process determined by the action of cell wall modifying enzymes. Present study evaluated the combined effects of chitosan (CH) and salicylic acid (SA) coatings in modulation of fruit softening enzymes in Punjab Beauty pear (Pyrus pyrifolia × Pyrus communis) fruit stored under cold (0-1 °C and 90-95 % RH) and supermarket (20-22 °C and 80-85 % RH) conditions. Composite CH + SA coatings reduced mass loss and retained fruit firmness throughout the 67 and 20 days storage period. In addition, CH + SA prevented membrane damage by suppressing the electrolyte leakage and malondialdehyde (MDA) accumulation as compared to CH or SA alone. CH 2.0 % + SA 2.0 mM coating efficiently delayed the cell wall degrading enzymatic activities including pectin methylesterase (PME), polygalacturonase (PG) and cellulase associated with fruit softening up to 60 and 15 days storage period in cold and supermarket conditions, respectively.

Relationships between trunk radial growth and fruit yield in apple and pear trees on size-controlling rootstocks.

BACKGROUND AND AIMS: Understanding the mutual co-ordination of vegetative and reproductive growth is important in both agricultural and ecological settings. A competitive relationship between vegetative growth and fruiting is often highlighted, resulting in an apparent trade-off between structural growth and fruit production. However, our understanding of factors driving this relationship is limited. METHODS: We used four scions grafted onto a series of size-controlling rootstocks to evaluate the relationships between the annual fruit yield and radial growth of trunks, branches and roots. To assess tree radial growth, we measured ring widths on extracted tree cores, which is an approach not frequently used in a horticultural setting. KEY RESULTS: We found that the yield and radial growth were negatively related when plotted in absolute terms or as detrended and normalized indices. The relationship was stronger in low vigour trees, but only after the age-related trend was removed. In contrast, when trunk radial growth was expressed as basal area increment, the negative relationship disappeared, suggesting that the relationship between trunk radial growth and fruit yield might not be a true trade-off related to the competition between the two sinks. The effect of low yield was associated with increased secondary growth not only in trunks but also in branches and roots. In trunks, we observed that overcropping was associated with reduced secondary growth in a subsequent year, possibly due to the depletion of reserves. CONCLUSIONS: Our results show that variation in annual fruit yield due to tree ageing, weather cueing and inherent alternate bearing behaviour is reflected in the magnitude of secondary growth of fruit trees. We found little support for the competition/architecture theory of rootstock-induced growth vigour control. More broadly, our study aimed at bridging the gap between forest ecology and horticulture.

Enhancement of the Plant Grafting Technique with Dielectric Barrier Discharge Cold Atmospheric Plasma and Plasma-Treated Solution.

A garden plant grafting technique enhanced by cold plasma (CAP) and plasma-treated solutions (PTS) is described for the first time. It has been shown that CAP created by a dielectric barrier discharge (DBD) and PTS makes it possible to increase the growth of Pyrus communis L. by 35-44%, and the diameter of the root collar by 10-28%. In this case, the electrical resistivity of the graft decreased by 20-48%, which indicated the formation of a more developed vascular system at the rootstock-scion interface. The characteristics of DBD CAP and PTS are described in detail.

Stability of Transgene Inheritance in Progeny of Field-Grown Pear Trees over a 7-Year Period.

Breeding woody plants is a very time-consuming process, and genetic engineering tools have been used to shorten the juvenile phase. In addition, transgenic trees for commercial cultivation can also be used in classical breeding, but the segregation of transgenes in the progeny of perennial plants, as well as the possible appearance of unintended changes, have been poorly investigated. We studied the inheritance of the uidA gene in the progeny of field-grown transgenic pear trees for 7 years and the physical and physiological parameters of transgenic seeds. A total of 13 transgenic lines were analyzed, and the uidA gene segregated 1:1 in the progeny of 9 lines and 3:1 in the progeny of 4 lines, which is consistent with Mendelian inheritance for one and two transgene loci, respectively. Rare and random deviations from the Mendelian ratio were observed only for lines with one locus. Transgenic seeds' mass, size, and shape varied slightly, despite significant fluctuations in weather conditions during cultivation. Expression of the uidA gene in the progeny was stable. Our study showed that the transgene inheritance in the progeny of pear trees under field conditions occurs according to Mendelian ratio, does not depend on the environment, and the seed vigor of transgenic seeds does not change.

Acibenzolar-S-methyl activates mitogen-activated protein kinase cascade to mediate chlorophyll and carotenoid metabolisms in the exocarp of Docteur Jules Guyot pears.

BACKGROUND: Acibenzolar-S-methyl (ASM), a well-known plant activator, has been used to protect fruit and vegetable from fungal invasion and maintain quality. However, little is known about the molecular mechanism of ASM in regulating chlorophyll and carotenoid metabolisms. Therefore, Docteur Jules Guyot pears were used as the materials to study the changes of hydrogen peroxide (H2 O2 ) production, mitogen-activated protein kinase (MAPK) cascade, transcription factors, chlorophyll, and carotenoid metabolisms after ASM and PD98059 (a MAPK cascade blocker) treatments. RESULTS: ASM increased NADPH oxidase (NOX) and superoxide dismutase (SOD) activities, and H2 O2 content, promoted PcMAPKKK1, PcMAPKK3, and PcMAPK6 expressions, and down-regulated PcMYC2, PcPIF1, PcPIF3, and PcPIF4 expressions in exocarp of pears. ASM also delayed the decrease of chlorophyll a and b contents, and inhibited the accumulation of ß-carotene, lycopene and lutein, PcNYC1, PcHCAR, PcPPH, PcSGR1/2, PcPAO, PcPSY, PcLCYB, PcCRTZ2, PcCCS1 expressions, and promoted PcLCYE expression. PD98059 + ASM treatments depressed SOD and NOX activities and H2 O2 content, inhibited PcMAPKKK1, PcMAPKK3, PcMAPK6, PcPIF1, and PcPIF3 expressions, and promoted PcMYC2 and PcPIF4 expressions in exocarp of pears. Additionally, PD98059 + ASM accelerated PcNYC1, PcHCAR, PcPPH, PcSGR1/2, PcPAO, PcPSY, PcCYB, PcCRTZ2, and PcCCS1 expressions, thereby reducing chlorophyll a and b contents, and promoting ß-carotene, lycopene and lutein contents. CONCLUSIONS: Postharvest ASM treatment promoted the production of H2 O2 to activate the MAPK cascade, then phosphorylated/dephosphorylated transcription factors expression, and delayed chlorophyll decomposition and carotenoid synthesis in pears. © 2022 Society of Chemical Industry.

Genomic Analysis of the Glutathione S-Transferase Family in Pear (Pyrus communis) and Functional Identification of PcGST57 in Anthocyanin Accumulation.

Anthocyanin accumulation in vacuoles results in red coloration in pear peels. Glutathione S-transferase (GST) proteins have emerged as important regulators of anthocyanin accumulation. Here, a total of 57 PcGST genes were identified in the European pear 'Bartlett' (Pyrus communis) through comprehensive genomic analysis. Phylogenetic analysis showed that PcGST genes were divided into 10 subfamilies. The gene structure, chromosomal localization, collinearity relationship, cis-elements in the promoter region, and conserved motifs of PcGST genes were analyzed. Further research indicated that glutamic acid (Glu) can significantly improve anthocyanin accumulation in pear peels. RNA sequencing (RNA-seq) analysis showed that Glu induced the expression of most PcGST genes, among which PcGST57 was most significantly induced. Further phylogenetic analysis indicated that PcGST57 was closely related to GST genes identified in other species, which were involved in anthocyanin accumulation. Transcript analysis indicated that PcGST57 was expressed in various tissues, other than flesh, and associated with peel coloration at different developmental stages. Silencing of PcGST57 by virus-induced gene silencing (VIGS) inhibited the expression of PcGST57 and reduced the anthocyanin content in pear fruit. In contrast, overexpression of PcGST57 improved anthocyanin accumulation. Collectively, our results demonstrated that PcGST57 was involved in anthocyanin accumulation in pear and provided candidate genes for red pear breeding.

A semi in vivo pollination technique to assess the level of gametophytic self-incompatibility and pollen tube growth in pear (Pyrus communis L.).

KEY MESSAGE: We describe a semi in vivo pollination technique to determine the compatibility relation between different pear cultivars. This assay provides a valuable addition to existing tools in GSI research. The gametophytic self-incompatibility (GSI) system in Pyrus inhibits fertilization by pollen that shares one of the two S-alleles of the style. Depending on their S-locus genotype, two pear cultivars therefore either show a cross-compatible, semi-compatible or incompatible interaction. Because GSI greatly influences seed and fruit set, accurate knowledge of the compatibility type of a cultivar is key for both pear fruit production and breeding. Currently, compatibility relations between different pear cultivars are generally assessed via S-genotyping. However, this approach is restricted to the currently known S-alleles in pear, and does not provide functional assessment of the level of (self-)incompatibility. We here present an optimized semi in vivo pollination assay, that enables quantitative analysis of (self-)incompatibility in pear, and that can also serve useful for more fundamental studies on pollen tube development and pollen-style interactions. This assay involves in vitro incubation of cut pollinated styles followed by microscopic counting of emerging pollen tubes at a specific time interval. The validity and selectivity of this method to determine compatibility interactions in pear is demonstrated in the cultivars "Celina" and "Packham's Triumph." Overall, this technique constitutes a valuable tool for quantitatively determining in vivo pollen tube growth and (cross-)compatibility in pear.

A mutation in the promoter of the arabinogalactan protein 7-like gene PcAGP7-1 affects cell morphogenesis and brassinolide content in pear (Pyrus communis L.) stems.

Dwarfing rootstocks and dwarf cultivars are urgently needed for modern pear cultivation. However, germplasm resources for dwarfing pear are limited, and the underlying mechanisms remain unclear. We previously showed that dwarfism in pear is controlled by the single dominant gene PcDw (Dwarf). We report here that the expression of PcAGP7-1 (ARABINOGALACTAN PROTEIN 7-1), a key candidate gene for PcDw, is significantly higher in dwarf-type pear plants because of a mutation in an E-box in the promoter. Electrophoretic mobility shift assays and transient infiltration showed that the transcription factors PcBZR1 and PcBZR2 could directly bind to the E-box of the PcAGP7-1 promoter and repress transcription. Moreover, transgenic pear lines overexpressing PcAGP7-1 exhibited obvious dwarf phenotypes, whereas RNA interference pear lines for PcAGP7-1 were taller than controls. PcAGP7-1 overexpression also enhanced cell wall thickness, affected cell morphogenesis, and reduced brassinolide (BL) content, which inhibited BR signaling via a negative feedback loop, resulting in further dwarfing. Overall, we identified a dwarfing mechanism in perennial woody plants involving the BL-BZR/BES-AGP-BL regulatory module. Our findings provide insight into the molecular mechanism of plant dwarfism and suggest strategies for the molecular breeding of dwarf pear cultivars.

The features of the fatty acid composition of Pyrus L. total lipids are determined by mountain ecosystem conditions.

The composition of fatty acids (FAs) of total lipids of pericarp, seeds, and leaves of Pyrus caucasica Fed. and Pyrus communis L. growing in mountain ecosystems at different altitudes (300, 700 and 1200 m) was studied. It was found that the greatest differences in the relative content of FAs within a species, depending on the altitudes above sea level, were characteristic of the outer tissues of the pericarp (peel) and leaves, which were in direct contact with the external environment. Pericarp parenchyma to a lesser extent, and seeds practically did not differ in FA composition at different heights. At altitudes with increased UV radiation, conjugated octadecadienoates: rumenic acid (9,11-18:2) and 10,12-18:2 were registered in the pericarp and leaf of Purys L., the functions of which in plants were practically not studied. The wild P. caucasica at all growing altitudes was characterized by more very-long-chain FAs (VLCFAs) than the P. communis cultivar. At 700 m, most likely when exposed to fungal infections, the relative number of VLCFAs increased significantly, and new species of individual odd-chaine FAs appeared in their composition in both representatives. It was especially worth noting the appearance in peel and leaf melissic acid (30:0), which was rarely recorded in the plant. A characteristic feature of only P. communis at an altitude of 700 m was the large number of unsaturated individual VLCFAs. Based on the data obtained, a scheme of possible pathways for VLCFA biosynthesis in P. communis were proposed.