Subfamily Maloideae Research Articles

ROWANS, WHITEBEAMS AND SERVICE TREES

ROWANS, WHITEBEAMS AND SERVICE TREES

Light and scanning electron microscopy observations on morphological diversity of Rosaceae stigma and its taxonomic significance

The stigma morphology can provide a reference for exploring plant systematics and pollination biology. In this study, we observed the stigma morphological characteristics of Rosaceae in Beijing urban area in detail using light microscopy and scanning electron microscopy. The stigma of Rosaceae is entire or bilobed and mostly baculate, crateriform, cristate, discoid, or flattened. The stigma surface may have irregular, strongly raised ridges; or flat without papillae; or composed of densely or loosely arranged papillary cells. Surface ornamentation includes fossulate, psilate, psilate-striate, rugulate, scabrate, striate, and striate-rugulate. There are similarities in stigma morphology among genera and differences in stigma morphology among species within genera. The stigma shape supports the view of molecular systematic classification, that is, the former subfamilies Maloideae, Prunoideae, and Spiraeoideae are grouped into subfamily Amygdaloideae. RESEARCH HIGHLIGHTS: Scanning electron microscopy (SEM) was used to provide high-quality figures for observing stigma morphology. The data on the morphological diversity of stigma were provided to further explore the systematics and pollination biology of Rosaceae.

PM 7/20 (3) Erwinia amylovora

PM 7/20 (3) <i>Erwinia amylovora</i>

Pear genetics: Recent advances, new prospects, and a roadmap for the future.

Pear, belonging to the genus Pyrus, is one of the most economically important temperate fruit crops. Pyrus is an important genus of the Rosaceae family, subfamily Maloideae, and has at least 22 different species with over 5000 accessions maintained or identified worldwide. With the release of draft whole-genome sequences for Pyrus, opportunities for pursuing studies on the evolution, domestication, and molecular breeding of pear, as well as for conducting comparative genomics analyses within the Rosaceae family, have been greatly expanded. In this review, we highlight key advances in pear genetics, genomics, and breeding driven by the availability of whole-genome sequences, including whole-genome resequencing efforts, pear domestication, and evolution. We cover updates on new resources for undertaking gene identification and molecular breeding, as well as for pursuing functional validation of genes associated with desirable economic traits. We also explore future directions for "pear-omics".

The complete chloroplast genome of Crataegus bretschneideri Schneid. (Rosaceae)

Crataegus bretschneideri Schneid., with an unclear phylogenic position, is mainly distributed in northeast and inner mongolia area of China. In this study, the complete chloroplast genome sequence of C. bretschneideri was determined by using Illumina high-throughput sequencing method. The chloroplast genome was 159,607 bp in length and consisted of a large single-copy (LSC) region (87,601 bp), a small single-copy (SSC) region (19,312 bp), separated by a pair of inverted repeat (IRs: 26,347 bp, each) regions. It comprised a total of 114 unique genes, including 80 protein-coding genes, 30 tRNA genes, and 4 rRNA genes. Phylogenetic analysis based on complete chloroplast genomes indicated that C. bretschneideri was closely related to C. marshallii Eggl in the subfamily Maloideae. This complete chloroplast genome will provide valuable insight into evolution, molecular breeding, and phylogenetic analysis of Crataegus species.

Genome-wide survey of G\u03b3 subunit gene family in eight Rosaceae and expression analysis of PbrGGs in pear (Pyrus bretschneideri)

BackgroundHeterotrimeric G-proteins, composed of Gα, Gβ and Gγ subunits, are important signal transmitters, mediating the cellular response to multiple stimuli in animals and plants. The Gγ subunit is an essential component of the G-protein, providing appropriate functional specificity to the heterotrimer complex and has been well studied in many species. However, the evolutionary history, expression pattern and functional characteristics of Gγ subunits has not been explored in the Rosaceae, representing many important fruit crops.ResultsIn this study, 35 Gγ subunit genes were identified from the eight species belonging to the Rosaceae family. Based on the structural gene characteristics, conserved protein motifs and phylogenetic analysis of the Gγ subunit genes, the genes were classified into three clades. Purifying selection was shown to play an important role in the evolution of Gγ subunit genes, while a recent whole-genome duplication event was the principal force determining the expansion of the Gγ subunit gene family in the subfamily Maloideae. Gγ subunit genes exhibited diverse spatiotemporal expression patterns in Chinese white pear, including fruit, root, ovary and bud, and under abiotic stress conditions, the relative expression of Gγ subunit genes were up-regulated or down-regulated. In addition, seven of the Gγ subunit proteins in pear were located on the plasma membrane, in the cytoplasm or nucleus.ConclusionOverall, this study of the Gγ subunit gene family in eight Rosaceae species provided useful information to better understand the evolution and expression of these genes and facilitated further exploration of their functions in these important crop plants.

Monilinia fructicola on loquat: An old pathogen invading a new host

Monilinia fructicola has been widely reported as the causal agent of brown rot disease on many Rosaceae family fruits worldwide. It has been reported on stone fruits, e.g., peach, plum, cherry, apricot and mume; as well as pome fruits, e.g., apple, pear and hawthorn. Loquat is a member of the Eriobotrya genus in subfamily Maloideae along with apple, pear and hawthorn. So far, loquat has not been reported as the host of any Monilia species. In June 2019, brown rot symptoms were observed on loquat fruits in an orchard in Wuhan, Hubei Province, China. Thirty single spore isolates were obtained and identified as M. fructicola based on morphological characteristics and molecular analysis. This is the first report of loquat brown rot disease caused by Monilia species in the world. Furthermore, upon artificial inoculation, all three Monilia species from peach in China, i.e., M. fructicola, M. mumecola and M. yunnanensis, could cause typical brown rot disease on loquat fruits. At the same time, M. fructicola isolates from loquat showed virulence similar to those isolates from peach when the pathogenicity test was conducted on peach fruits. These results suggested that loquat could be infected by other Monilia species and that isolates from loquat also have potential to damage other Rosaceae family fruits in practice.

The complete chloroplast genome of Crataegus hupehensis Sarg. (Rosaceae), a medicinal and edible plant in China

Crataegus hupehensis Sarg. is well-known for its medicinal and nutritive value. In this study, the complete chloroplast genome sequence of C. hupehensis was determined by using Illumina high-throughput sequencing approach. The complete chloroplast genome is 159,766 bp with 36.6% GC content. It contained a pair of inverted repeat regions of 26,385 bp, a large single-copy region of 87,852 bp, and a small single-copy region of 19,144 bp. It contained 112 distinct genes, including 78 protein-coding genes, 4 ribosomal RNA genes, and 30 transfer RNA genes. Phylogenetic analysis based on chloroplast genomes indicated that C. hupehensisis was closely related to C. kansuensis and C. marshallii in the subfamily Maloideae. This complete chloroplast genome will provide valuable insight into evolution, molecular breeding, and phylogenetic analysis of Crataegus species.

The pome fruit (Malinae Rev.) collections of the National dendrological park “Sofiyivka” of NAS of Ukraine

The plant collections of the NDP “Sofiyivka” of NAS of Ukraine including accessions of the subtribe Malinae Rev., formerly the subfamily Maloideae C. Weber (Rosaceae Juss.), are the objects for research in the field of plant introduction and phytodiversity protection. Because of the significant number of park’s holiday-makers, which are not always careful about plants, the posttraumatic regenerative ability of plants is of particular importance for adaptation and periods of the highest regenerative activity could be favourable for vegetative reproduction, including microcloning. Thus, Malinae of the “Sofiyivka” might be useful for germplasm conservation and utilization in the breeding programs.

MORPHOFUNCTIONAL CHARACTERISTICS OF LEAVES AND FRUITS IN MALOIDEAE (ROSACEAE): b. THE ROLE OF SURFACE TISSUES IN THE FORMATION OF RESISTANCE TO FUNGAL DISEASES

Background. Resistance to the effects of plant biotic stressors is determined by a set of factors. Among them, the leading protective role is often assigned to the physiological and biochemical characteristics of the surface tissues. However, one cannot ignore the specificity of the microstructural organization of the plant surface, since the nature of interactions in phytopathogenic organisms is more complex than the chemical impact. Meanwhile, the information accumulated to date about the structure of the surface tissues of the vegetative and reproductive organs of plants, and the interface of mycobiota, is fragmentary.Objective. Mature leaves and fruits taken from representatives of the subfamily Maloideae Werber (Malus domestica Borkh., Pyrus communis L., Cydonia oblonga Mill. and Mespilus germanica L.) were selected for the study.Materials and methods. Samples for the research were taken from the middle part of the crown of model trees in 3 replications. In recent years, scanning electron microscopy (SEM) with cryofixation is considered the most promising technique and is used to analyze the surface of biological organisms and identification of species. It is particularly informative in the case of organisms with complex surface micromorphology and for studying the biodiversity of pathogens. However, in this work we combined the methods of light, electron (SEM, TEM) and confocal microscopy. The samples were also studied using phytopathological and histochemical techniques. Condensed polyphenols were detected using K2Cr2O7 and FeCl3 as well as 4-(Dimethylamino)cinnamaldehyde (DMACA, Sigma-Aldrich).Results. On the basis of the obtained phytopathological materials and published data an overview of fungal diseases afflicting leaves and fruits of M. domestica, P. communis, C. oblonga and M. germanica was made. It has been established that a common feature of the Maloideae fruits is the accumulation of condensed polyphenols, which play an important protective role against biotic stressors, in the cells of the pericarp’s outer tissues. Anatomical and morphological characteristics of passive immunity, or horizontal resistance to fungal pathogens, include the specific nature of waxy and cuticular deposits, features of the formation of cuticular folds and peristomatic rings in the stomata area and microstrands at the base of trichomes, thickness of the cuticle and cork tissue, and the development of lenticels on fruits.Conclusion. The studied model plants suffer from a sufficiently wide range of diseases with different etiologies; among them, the most widespread and harmful are mycoses. In view of this, their resistance to fungal pathogens correlates with the specificity of the leaf and fruit surface microstructure and the content of phenolic substances (polyphenols) in the cells of the pericarp’s surface tissues.

Morphofunctional characteristics of leaves and fruits in Maloideae (Rosaceae): a. Microstructure of surface tissues

Background. The formation of cover tissues (epidermis, cork), providing a connection with the environment, in the evolution of flowering plants was one of the main consequences of the transition to life on earth. The epidermis, which emerged as a device for protecting deeper underlying tissues from drying, subsequently acquired additional functions (participation in gas exchange and transpiration, absorption and isolation of certain substances as well as protection from the penetration of pathogens) and became a multifunctional tissue consisting of several types of cells (basic, stomatal, and trichomes). Features of the fine structure of the epidermis are of interest in representatives of the subfamily Maloideae Werber (Rosaceae Juss.), which grow, inter alia in mountain agrobiocenoses with their rather harsh conditions. They extended their area of distribution to various habitats due to the development of structural adaptations that play an important role in the formation of resistance to stressors of different etiologies.Objective. Representatives of 4 genera were chosen as model objects from subfam. Maloideae for the study: Malus domestica Borkh., Pyrus communis L., Cydonia oblonga Mill., and Mespilus germanica L.Materials and methods. Mature leaves and fruits were selected from the middle part of the crown of three model trees of each species. The samples were studied by scanning electron microscopy (SEM), with a freezing attachment.Results. Leaves of Maloideae were found to be hypostomatic, while the abaxial (lower) epidermis is multifunctional: it performs a barrier function together with the cuticle. Formation of the cuticular nature can be attributed to the surface structures: peristomatic rings and ridges as well as radially extending folds, all forming a specific microrelief. The adaxial (upper) and abaxial surfaces clearly differ not only in the features of the structure, but also in the specificity of the microrelief’s arrangement. Species-specific traits were also found in the structure of the surface tissue of the pericarp. M. germanica, unlike the other species, does not have a continuous cuticular cover and wax deposits: most of a mature fruit’s surface is covered with a peeling cork layer. In the study of the surface of C. oblonga fruits, numerous rather large stomata with peristomatic rings and cuticular cushions were found similar to those in leaves.Conclusion. Surface structures of leaves and fruits in subfam. Maloideae include formations of cuticular nature, with different specificities of microrelief shaping due to the functional load of the epidermal tissue and environmental conditions. They can also be involved in building resistance to biotic stressors. The obtained data on the features of the fine structure of surface tissues are of interest for applied and theoretical studies, especially environmental and botanical, relating to taxonomic issues.

Pollen morphology of subfamily Maloideae (Roseaceae) with special focus on the genus Photinia

Pollen morphology of 27 species of Photinia sensu stricto and five closely related genera of subfamily Maloideae (Rosaceae) were studied in detail. Palynomorphological characteristics were examined using scanning electron microscopy (SEM). Comparative pollen analysis was accomplished based on pollen size, shape, polar and equatorial views, polar and equatorial diameter ratio (P/E ratio), width of aperture, and exine ornamentation. The pollen grains of studied species were found to be monad, tricolporate, small to medium in size (P=17.42–30.45 μm, E=9.26–20.18 μm) and to have shapes oblate-spheroidal (0.88–1.0 μm), prolate-spheroidal (1.01–1.14 μm), sub-prolate (1.15–1.33 μm), prolate (1.34–2 μm), and perprolate (&gt;2 μm). The exine ornamentation was perforated-striate, and two different types were identified. The result of quantitative characters has paltry taxonomic importance. The characters studied here delimit at generic level for some genera but not at species level. The obtained result was partially consistent with that of molecular studies published earlier. The pollen size and shape were found to be different between Asian and American species of Photinia. Especially exine sculpture was found to be an important feature to distinguish species of all genera studied. PCA analysis showed that the pollen shape, pollen sculpture, pollen size, and polarity are the key characters to distinguish the species of Photinia and the closely related genera in subfamily Maloideae. Based on pollen exine, two groups (Type I and Type II) were distinguished. The aim of the present study was to find out the taxonomic significance of palynomorphological characteristics in subfamily Maloideae (Rosaceae).

Characteristics of the world and Russian production of fruits products (apples and pears)

The paper deals with the peculiarities of the biological characteristics of the most important fruit crops of temperate climates apple and pear (Rosaceae family, subfamily Maloideae), taking into account the world, national and regional cultivation. Both cultures are characterized by significant food and commodity value, have some differences in the chemical composition of the fruit, including the leading components of the mass and biologically active substances, which determine the peculiarities of their use in the human diet. In both global and national fruit-growing, pears play a secondary role compared to apple, giving way to the number of varieties, the volume of production and the areas occupied. Based on the analysis of available statistical data of the FAO database, the dynamics of changes from 1990 to 2016 of the world production of apple and pear fruits with visualization on the continents, identifying world leaders and major trends are considered. For the USSR (from 1962 to 1990) and in Russian Federation (from 1992 to 2016) the paper presents a picture of changes in the volume of fruit production, discusses the status of fruit production in the country. The features of the historical development and current state of fruit growing in the Samara Region and prospects are discussed.

Genome Re-Sequencing of Diverse Sweet Cherry (Prunus avium) Individuals Reveals a Modifier Gene Mutation Conferring Pollen-Part Self-Compatibility.

The S-RNase-based gametophytic self-incompatibility (GSI) reproduction barrier is important for maintaining genetic diversity in species of the families Solanaceae, Plantaginaceae and Rosaceae. Among the plant taxa with S-RNase-based GSI, Prunus species in the family Rosaceae exhibit Prunus-specific self-incompatibility (SI). Although pistil S and pollen S determinants have been identified, the mechanism underlying SI remains uncharacterized in Prunus species. A putative pollen-part modifier was identified in this study. Disruption of this modifier supposedly confers self-compatibility (SC) to sweet cherry (Prunus avium) 'Cristobalina'. To identify the modifier, genome re-sequencing experiments were completed involving sweet cherry individuals from 18 cultivars and 43 individuals in two segregating populations. Cataloging of subsequences (35 bp kmers) from the obtained genomic reads, while referring to the mRNA sequencing data, enabled the identification of a candidate gene [M locus-encoded GST (MGST)]. Additionally, the insertion of a transposon-like sequence in the putative MGST promoter region in 'Cristobalina' down-regulated MGST expression levels, probably leading to the SC of this cultivar. Phylogenetic, evolutionary and gene expression analyses revealed that MGST may have undergone lineage-specific evolution, and the encoded protein may function differently from the corresponding proteins encoded by GST orthologs in other species, including members of the subfamily Maloideae (Rosaceae). Thus, MGST may be important for Prunus-specific SI. The identification of this novel modifier will expand our understanding of the Prunus-specific GSI system. We herein discuss the possible functions of MGST in the Prunus-specific GSI system.

Current Status of Knowledge and Research Perspectives in Korean Pear Genomics

The pear (Pyrus spp.) is most important fruit crop in the world. The genus Pyrus belongs to the subfamily Maloideae in the Rosaceae family and contains at least 22 primary species; however, only a few species, including P. pyrifolia, P. ussuriensis, P. bretschneideri, and P. communis have been utilized for fruit production. In Korea, awareness of the importance of the fruit industry and fruit tree breeding is low, and there is little support for genetic and genomic studies of fruit trees. In foreign countries, studies have focused on obtaining genomic information of fruit crops and the development of important agronomic trait-related molecular markers, providing a genomic framework for fruit tree breeding. Although Korea does not actively participate in research on the genomics of fruit trees, it is not far behind other countries in terms of technology and is therefore still competitive in research and development. The resequencing of 'Whangkeumbae' and 'Minibae' pears has been performed using the Illumina Hiseq 2000 platform as a part of the Biogreen 21 project, offering novel, rapid methods for identification of molecular marker, such as single nucleotide polymorphisms, insertion-deletions, and simple sequence repeats, through next-generation sequencing (NGS) technology. These NGS-based molecular markers are useful for genetic studies of Asian pears, e.g., for construction of genetic linkage maps, mapping of quantitative trait loci, and marker-assisted selection.

Newly identified host range of European mountain ash ringspot‐associated virus (EMARaV) and its distribution in the Czech Republic

SummaryIt has been previously shown that European mountain ash ringspot‐associated virus (EMARaV), a multipartite, negative‐strand RNA plant virus, is pathogenic for European mountain ash (Sorbus aucuparia L.). However, its transmissibility to and replication in other host species remains poorly understood. In this work, we performed experimental inoculations of seventeen virus‐tested species and interspecies hybrids of subfamily Maloideae (family: Rosaceae) with buds from EMARaV‐infected S. aucuparia trees. Surprisingly, a majority of the graft‐inoculated tree species, for instance Sorbaronia, Aronia and Amelanchier, developed symptoms typical for EMARaV infection. These symptoms included chlorotic spots of various size and shape and mottling on leaves but not on flowers and fruits. The propagation of EMARaV in graft‐inoculated tree species was subsequently confirmed by molecular detection tools. Based on these results, we carried out a systematic survey throughout the Czech Republic and identified the presence of EMARaV in wild growing trees in all explored regions, with massive disease infestation in several locations. More importantly, EMARaV infection was newly detected in S. aucuparia subsp. moravica, S. aucuparia × Crataegus sanguinea cv. Granatnaja, (Sorbus aria × Aronia arbutifolia) × S. aucuparia cv. Burka, cv. Finskaja (a Sorbus hybrid of unknown origin) and Aronia melanocarpa; all these EMARaV‐infested trees were grown in production orchards. The sequencing of the nucleocapsid (NC)‐coding gene from several of these EMARaV isolates provided insight into the population structure and phylogenetic relationships of the EMARaV variants occurring in the Czech Republic. Together, our biological and molecular findings extend our knowledge on the host range of EMARaV and provide the first evidence of its natural occurrence in hosts dissimilar to S. aucuparia.

Characterization of Erwinia amylovora Strains from Bulgaria by Pulsed-Field Gel Electrophoresis

The aim of this study was to characterize genetically Bulgarian Erwinia amylovora strains using pulsed-field gel electrophoresis (PFGE) analysis. Fifty E. amylovora strains isolated from different hosts, locations, as well as in different years were analysed by PFGE after XbaI, SpeI, and XhoI digestion of the genomic DNA. The strains were distributed into four groups according to their XbaI-generated profile. About 82% of the strains displayed a PFGE profile identical to that of type Pt2. Three strains belonged to the Central Europe Pt1 type. Two new PFGE profiles, not reported so far, were established--one for a strain isolated from Malus domestica and another for all Fragaria spp. strains. The same grouping of the strains was obtained after analysis of the SpeI digestion patterns. On the basis of PFGE profiles, after XbaI and SpeI digestion, a genetic differentiation between the strains associated with subfamily Maloideae and subfamily Rosoideae was revealed. The presence of more than one PFGE profile in the population of E. amylovora in Bulgaria suggests a multiple source of inoculum.

Comparison of fatty acid profiles and contents of seed oils recovered from dessert and cider apples and further Rosaceous plants

To get a more comprehensive knowledge of oil contents and fatty acid pattern, seed oils from various Rosaceous plants belonging to the subfamilies Maloideae and Rosoideae, respectively, were investigated. For this purpose, isolated seeds of 18 dessert and cider apple (Malus domestica BORKH.) cultivars of different provenances, pear (Pyrus communis L.), rose hip (Rosa canina L.), quince (Cydonia oblonga Mill.), and red chokeberry (Aronia arbutifolia L.) were analyzed for their oil content and fatty acid composition. Oil contents varied significantly, not only among the different genera, but also among cultivars of one species, ranging from 0.8 to 29.4 g/100 g dry matter. Qualitatively, the fatty acid profiles of the investigated seed oils showed good agreement in all representatives of the Rosaceae. Their triacylglycerols were uniformly composed of linoleic, oleic, palmitic, stearic, palmitoleic, α-linolenic, arachidic, gondoic, and behenic acids. Quantitation of individual fatty acids revealed the oils to be rich in mono- and diunsaturated oleic acid and linoleic acid, ranging from 15.1 to 33.3 g/100 g and from 32.5 to 49.7 g/100 g, respectively. As expected, contents of saturated fatty acids were 6–10 times lower. Moreover, apple cultivars showed pronounced differences in yields, numbers, and weights of their seeds. As demonstrated by the data obtained from this study, seeds resulting from the processing of apple, pear, quince, chokeberry (Maloideae), and rose hip (Rosoideae) into juices, jellies, and jams may serve as a promising source for the recovery of nutritionally valuable edible oils.

Formation of biphenyl and dibenzofuran phytoalexins in the transition zones of fire blight-infected stems of Malus domestica cv. ‘Holsteiner Cox’ and Pyrus communis cv. ‘Conference’

In the rosaceous subtribe Pyrinae (formerly subfamily Maloideae), pathogen attack leads to formation of biphenyls and dibenzofurans. Accumulation of these phytoalexins was studied in greenhouse-grown grafted shoots of Malus domestica cv. ‘Holsteiner Cox’ and Pyrus communis cv. ‘Conference’ after inoculation with the fire blight bacterium, Erwinia amylovora. No phytoalexins were found in leaves. However, both classes of defence compounds were detected in the transition zone of stems. The flanking stem segments above and below this zone, which were necrotic and healthy, respectively, were devoid of detectable phytoalexins. The transition zone of apple stems contained the biphenyls 3-hydroxy-5-methoxyaucuparin, aucuparin, noraucuparin and 2′-hydroxyaucuparin and the dibenzofurans eriobofuran and noreriobofuran. In pear, aucuparin, 2′-hydroxyaucuparin, noreriobofuran and in addition 3,4,5-trimethoxybiphenyl were detected. The total phytoalexin content in the transition zone of pear was 25 times lower than that in apple. Leaves and stems of mock-inoculated apple and pear shoots lacked phytoalexins. A number of biphenyls and dibenzofurans were tested for their in vitro antibacterial activity against some Erwinia amylovora strains. The most efficient compound was 3,5-dihydroxybiphenyl (MIC=115μg/ml), the immediate product of biphenyl synthase which initiates phytoalexin biosynthesis.

Floral traits affecting fire blight infection and management

Erwinia amylovora, the causative agent of fire blight, colonizes primarily the flowers of the sub-family Maloideae. Commercially important fruit tree species such as apple (Malus domestica) and pear (Pyrus communis) are also affected by the disease. Epiphytic bacterial populations develop on the stigma, from where the pathogen colonizes the hypanthium, aided by moisture. Under favorable conditions, nectar provides a rich medium for growth, which allows bacterial invasion of tissues through the stomata of the nectary. The paper reviews various floral traits that may play a role in the onset and progression of the infection. Flower age, stigma morphology and longevity, the size of epiphytic bacterial population, morphology of the hypanthium, anatomy of the nectary, dynamics of nectar secretion, as well as the volume, concentration and composition of the nectar are discussed in detail, comparing traits of susceptible versus tolerant apple and pear cultivars. Management programs, aiming at the suppression of E. amylovora on floral parts by antibiotics, chemical compounds, natural substances or biological control agents, are also discussed.