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Polyploidization is an important source of variability for plant breeding. Polyploids are often characterised by increased resistance to biotic and abiotic stresses. Since drought and pathogen attack are the main threats to apple cultivation, obtaining new sources of resistance is an important issue for apple breeding. The newly obtained autotetraploid clones of apple cv. ‘Redchief’ showed superior resistance to fire blight. The aim of the presented research was the in-depth phenotypic characterisation of ‘Redchief’ tetraploids and assessment of their response to drought at the physiological and genetic level. The growth of own-rooted five-year-old trees of ‘Redchief’ tetraploids was poor compared with diploids; all growth parameters—the number and length of current season shoots, the total length of current season shoots per tree and the cross-section area of the trunk—were reduced in tetraploid clones. Grafting on M9 rootstock improved the growth characteristics of ‘Redchief’ tetraploids. Compared with diploid plants, the leaves of tetraploids were thicker, with altered shape, higher chlorophyll content, and larger stomata, but the stomatal density decreased. The leaf anatomical structure of tetraploids was changed, the adaxial and abaxial epidermis and both types of mesophyll were significantly thicker than in diploids. Moreover, the pollen grains of tetraploids were larger, but their viability and germination were reduced. Under conditions of limited water supply, the reduction in growth parameters was smaller and the physiological parameters were higher in the ‘Redchief’ tetraploid clone 4x-25 than in diploid plants. The expression of APX gene was higher in tetraploids than in diploids 15 days after drought stress induction. The results suggest the enhanced drought tolerance of the studied ‘Redchief’ autotetraploid clone compared with its diploid counterpart.

Plants can react to environmental stresses through the abscission of infected, damaged, or senescent organs. A possible mode of action of methyl jasmonate (JA-Me) to induce the formation of the secondary abscission zone (SAZ) in the stems of Bryophyllum calycinum was investigated concerning plant hormone dynamics. Internode segments were prepared mainly from the second or third internode from the top of plants with active elongation. JA-Me applied to the middle of internode segments induced the SAZ formation above and below the treatment after 5–7 days. At 6 to 7 days after JA-Me treatment, the above and below internode pieces adjacent to the SAZ were excised and subjected to comprehensive analyses of plant hormones. The endogenous levels of auxin-related compounds between both sides adjacent to the SAZ were quite different. No differences were observed in the level of jasmonic acid (JA), but the contents of 12-oxo-phytodienoic acid (OPDA), a precursor of JA, and N-jasmonyl-leucine (JA-Leu) substantially decreased on the JA-Me side. Almost no effects of JA-Me on the dynamics of other plant hormones (cytokinins, abscisic acid, and gibberellins) were observed. Similar JA-Me effects on plant hormones and morphology were observed in the last internode of the decapitated growing plants. These suggest that the application of JA-Me induces the SAZ in the internode of B. calycinum by affecting endogenous levels of auxin- and jasmonate-related compounds.

To expand the gene pool and introduce new traits to the tetraploid cultivars of Vaccinium corymbosum from wild diploid species V. myrtillus, it is necessary to double the chromosome number in diploid species in order to overcome a post zygotic crossing barrier and a strong triploid block, existing within the genus Vaccinium. Five genetically diverse bilberry genotypes were selected from 21 accessions taken from the breeding collection of the National Institute of Horticultural Research (Skierniewice, Poland) for this study. The bilberry genotypes were derived from the Polish locations of Bolimów Landscape Park, Budy Grabskie and forest complex Zwierzyniec (Łódź Province), and habitats in Norway. The selection of genotypes was made based on the analysis of amplified fragment length polymorphism (AFLP-PCR). Analysis of the Jaccard similarity indexes and the UPGMA method revealed that the examined accessions formed two main groups on the dendrogram. The first group consisted of accessions from Norway, while the second group agglomerated Polish accessions. A further two classes were distinguished in the Polish group: the first included accessions from Budy Grabskie and the second from Zwierzyniec, located ca. 9 km from Budy Grabskie. In order to obtain plant material for in vitro polyploidisation, in vitro shoot cultures of the selected accessions were initiated and multiplied. Both antimitotics used, colchicine and APM, induced tetraploids for all of the accessions. The obtained tetraploids were multiplied, rooted ex vitro and grown in a greenhouse and then in a field. The first flowering was observed in 1.5-year-old plants, either diploid or tetraploid. Diploids bloomed slightly earlier and more profusely than tetraploid plants. Compared to diploids, autotetraploids had significantly larger flowers by ca. 64% and larger pollen tetrads by ca. 35%. The germination capacity of pollen tetrads was high in tetraploids (87.8%), although slightly lower than in diploids (94.3%). After pollinating the flowers of three highbush blueberry cultivars with pollen from the bilberry tetraploid accession, J-4-4x, the plants formed fruits, some of which contained properly formed seeds. The effectiveness of interspecific crossing between V. corymbosum and tetraploid V. myrtillus, defined as the percentage of obtained seedlings in relation to the number of pollinated flowers, was highest (53.3%) in the blueberry ‘Liberty’, and lower in ‘Bluecrop’ and ‘Northland’, 14.8% and 10.0%, respectively. Before using the seedlings for further breeding, their hybridity will be confirmed by molecular markers and the phenotype will be evaluated.

In Brassica, interspecific hybridisation plays an important role in the formation of allopolyploid cultivars. In this study, the ploidy of F1 and F2 generations resulting from interspecific hybridisation between B. oleracea inbred lines of head cabbage (B. oleracea L. var. capitata) (2n = 18) and kale (B. oleracea L. var. acephala) (2n = 18) with inbred lines of rapeseed (B. napus L.) (2n = 38) was examined by flow cytometry analysis and chromosome observation. Furthermore, the effect of meiotic polyploidisation on selected phenotypic and anatomical traits was assessed. The F1 hybrids of head cabbage × rapeseed (S3) and kale × rapeseed crosses (S20) were allotriploids with 2n = 28 chromosomes, and nuclear DNA amounts of 1.97 (S3) and 1.99 pg (S20). These values were intermediate between B. oleracea and B. napus. In interspecific hybrids of the F2 generation, which were derived after self-pollination of F1 hybrids (FS3, FS20) or by open crosses between F1 generation hybrids (FC320, FC230), the chromosome numbers were similar 2n = 56 or 2n = 55, whereas the genome sizes varied between 3.81 (FS20) and 3.95 pg 2C (FC230). Allohexaploid F2 hybrids had many superior agronomic traits compared to parental B. napus and B. oleracea lines and triploid F1 hybrids. In the generative stage, they were characterised by larger flowers and flower elements, such as anthers and lateral nectaries. F2 hybrids were male and female fertile. The pollen viability of F2 hybrids was comparable to parental genotypes and varied from 75.38% (FS3) to 88.24% (FC320), whereas in triploids of F1 hybrids only 6.76% (S3) and 13.46% (S20) of pollen grains were fertile. Interspecific hybrids of the F2 generation derived by open crosses between plants of the F1 generation (FC320, FC230) had a better ability to set seed than F2 hybrids generated from the self-pollination of F1 hybrids. In the vegetative stage, F2 plants had bigger and thicker leaves, larger stomata, and significantly thicker layers of palisade and spongy mesophyll than triploids of the F1 generation and parental lines of B. oleracea and B. napus. The allohexaploid F2 hybrids analysed in this study can be used as innovative germplasm resources for further breeding new vegetable Brassica crops at the hexaploid level.

The structure and ultrastructure of two developmental stages of the spangle gall induced by Neuroterus quercusbaccarum (Hymenoptera, Cynipidae) were investigated using light microscopy (LM), fluorescence microscopy (FM), and transmission (TEM) and scanning (SEM) electron microscopy. The general design of the gall structure was typical of Cynipidae, but some structural features distinguished the spangle gall. Previously undescribed, characteristic multicellular epidermal protuberances with large openings were observed in autumn on the surface of galls. These may facilitate the gas exchange between the atmosphere and the inside of the gall, thus assisting larval respiration. The larval chamber is surrounded by both a sclerenchymatous capsule and numerous cells containing calcium oxalate crystals that may both serve as protective barriers. In young galls, the nutritive tissue is a wall-less protoplasmic mass, potentially easily accessible to young larvae with delicate mandibles. Cell walls only develop at a later stage. The nutritive tissue was found to be rich in proteins and lipids, but starch grains were not observed. Cellular topology suggests that spangle galls grow by anticlinal division of marginal epidermal cells and periclinal division of subepidermal cells. Cellular proliferation (hyperplasia) also occurs in the leaf tissue near the connection with the gall peduncle, which eventually lignifies.

This article provides an overview of the origin, genetic diversity and methods and trends in breeding of selected ornamental geophytes (Lilium, Tulipa, Narcissus and Hippeastrum). The role of interspecific hybridisation and polyploidisation in assortment development is reviewed. A great variety of cultivars with traits of interest have been generated over the last century by using classical breeding. Geophyte breeders have been interested in a diversity of traits, including resistance to diseases, flower colour and shape, long lasting flowering and a long vase life. Shortening the long breeding process of many geophytes by reducing the juvenile phase and using in vitro techniques are reviewed. Currently, the breeding process has been enhanced by using modern molecular cytogenetic techniques. Genomic in situ hybridisation is frequently used, among other techniques, for genome differentiation in interspecific hybrids, and for assessment of the extent of intergenomic recombination in backcross progenies. Furthermore, several molecular marker techniques are used for verification of hybrid status, identification of genetic diversity, confirmation of the genetic fidelity of in vitro propagated plants and construction of high-density linkage maps. Recently, a myriad of new plant breeding technologies, such as cisgenetics and genome editing technologies have been used to improve the traits of ornamental geophytes, an endeavour that is discussed here. Breeding trends, cultivar novelties as well a new cultivars registered by international authorities during the last five years are presented in detail.

The mode of action of 1-naphthylphthalamic acid (NPA) to induce conspicuous local stem swelling in the area of its application to the growing internode in intact Bryophyllum calycinum was studied based on the aspects of histological observation and comprehensive analyses of plant hormones. Histological analyses revealed that NPA induced an increase in cell size and numerous cell divisions in the cortex and pith, respectively, compared to untreated stem. In the area of NPA application, vascular tissues had significantly wider cambial zones consisting of 5–6 cell layers, whereas phloem and xylem seemed not to be affected. This indicates that stem swelling in the area of NPA application is caused by stimulation of cell division and cell enlargement mainly in the cambial zone, cortex, and pith. Comprehensive analyses of plant hormones revealed that NPA substantially increased endogenous levels of indole-3-acetic acid (IAA) in the swelling area. NPA also increased endogenous levels of cytokinins, jasmonic acid, and its precursor, 12-oxo-phytodienoic acid, but did not increase abscisic acid and gibberellin levels. It was shown, using radiolabeled 14C-IAA, that NPA applied to the middle of internode segments had little effect on polar auxin transport, while 2,3,5-triiodobenzoic acid substantially inhibited it. These results strongly suggest that NPA induces changes in endogenous levels of plant hormones, such as IAA, cytokinins, and jasmonic acid, and their hormonal crosstalk results in a conspicuous local stem swelling. The possible different mode of action of NPA from other polar auxin transport inhibitors in succulent plants is extensively discussed.

The cabbage whitefly (CW), Aleyrodes proletella (L.) (Hemiptera: Aleyrodidae), is an important pest in Brassica oleracea L. crops. Little is known about the mechanisms of resistance to CW of savoy cabbage and kale cultivars. Light microscopy (LM) and scanning electron microscopy (SEM) analysis were used to determine the relationship between the morphological and anatomical features of savoy cabbage (Brassica oleracea L. convar. capitata (L.) Alef. var. sabauda L.) and kale (Brassica oleracea L. convar. acephala (DC.) Alef. var. sabellica L.) leaves and host suitability to colonization by CW. Two kale cultivars, “Redbor” and “Starbor”, and two savoy cabbage cultivars, “Gloriosa” and “Alcosa”, that differed in the degree of infestation by A. proletella were taken for histological analysis. The lowest infestation by all forms of A. proletella was observed on savoy cabbage cultivar “Alcosa” and kale cultivar “Starbor”. The reduced colonization by cabbage whitefly may be related to the structure of the epidermis and the anatomical features of the leaf. The leaves of “Starbor” and “Alcosa” had more folds in the epidermis, less numerous but larger stomata, and a more compact mesophyll structure compared to “Redbor” and “Gloriosa”. In both analysed species, there was no clear relationship between the thickness of the abaxial epidermal layer, thickness of the lamina, number of vascular bundles, and degree of infestation by the cabbage whitefly. This study identified promising sources of resistance to A. proletella among cultivars of savoy cabbage and kale. Varying infestation by CW was associated with morphological and anatomical characteristics of leaves. Further study is needed to confirm the relationship between insect resistance and leaf surface and morphological characteristics of leaves in a broader range of Brassica spp.

Among the fungal diseases of apple trees, serious yield losses are due to an apple scab caused by Venturia inaequalis. Protection against this disease is based mainly on chemical treatments, which are currently very limited. Therefore, it is extremely important to introduce cultivars with reduced susceptibility to this pathogen. One of the important sources of variability for breeding is the process of polyploidization. Newly obtained polyploids may acquire new features, including increased resistance to diseases. In our earlier studies, numerous tetraploids have been obtained for several apple cultivars with ‘Free Redstar’ tetraploids manifesting enhanced resistance to apple scab. In the present study, tetraploids of ‘Free Redstar’ were assessed in terms of phenotype and genotype with particular emphasis on the genetic background of their increased resistance to apple scab. Compared to diploid plants, tetraploids (own-rooted plants) were characterized with poor growth, especially during first growing season. They had considerably shorter shoots, fewer branches, smaller stem diameter, and reshaped leaves. In contrast to own-rooted plants, in M9-grafted three-year old trees, no significant differences between diplo- and tetraploids were observed, either in morphological or physiological parameters, with the exceptions of the increased leaf thickness and chlorophyll content recorded in tetraploids. Significant differences between sibling tetraploid clones were recorded, particularly in leaf shape and some physiological parameters. The amplified fragment length polymorphism (AFLP) analysis confirmed genetic polymorphism of tetraploid clones. Methylation-sensitive amplification polymorphism (MSAP) analysis showed that the level of DNA methylation was twice as high in young tetraploid plants as in a diploid donor tree, which may explain the weaker vigour of neotetraploids in the early period of their growth in the juvenile phase. Molecular analysis showed that ‘Free Redstar’ cultivar and their tetraploids bear six Rvi genes (Rvi5, Rvi6, Rvi8, Rvi11, Rvi14 and Rvi17). Transcriptome analysis confirmed enhanced resistance to apple scab of ‘Free Redstar’ tetraploids since the expression levels of genes related to resistance were strongly enhanced in tetraploids compared to their diploid counterparts.

An effective method of tulip regeneration via somatic embryogenesis (SE) was developed. Explants, flower stem slices excised from cooled bulbs were incubated in darkness on MS modified media containing auxins alone (2,4-dichlorophenoxyacetic acid—2,4-D, 1-naphthalene acetic acid—NAA and 4-amino-3,5,6-trichloro-2-pyridine carboxylic acid—picloram) or combined with thidiazuron (TDZ) at 0.1 and 0.5 mg L−1. Yellowish-white callus with a granular structure was developed in the presence of all auxins on the cut surface from the tissues of the vascular bundles. From this, lines of embryogenic calli were derived. The addition of TDZ to the medium with auxins significantly stimulated somatic embryo formation. Cyclic and the most intensive proliferation of embryogenic callus as well as embryo formation was obtained in the presence of 2,4-D at 0.1 mg L−1 combined with TDZ at 0.5 mg L−1. Addition of proline enhanced either callus proliferation rate or frequency of embryo formation. The best quality embryos with cotyledons longer than 10 mm able to form bulbs were recorded when TDZ was replaced with 6-benzylaminopurine (BAP) at the concentration of 0.1 mg L−1. Histomorphology showed that the development of somatic embryos could have either external or internal origins. Embryos of external origin were initiated by cell division on the edge of embryogenic calli. Embryos of internal origin resulted from the division of parenchyma cells inside the tissue. Embryonic cells were characterized by their small volume, regular shape, dense cytoplasm and large nuclei. The globular embryos were covered by a distinct layer of periderm. Then, the embryos developed into structures having leaf-shaped cotyledons with a procambial strand and a sideward-orientated meristem of the vegetative apex (stolon). Cotyledon embryos did not show vascular connections with the parent tissue, and they did not develop embryonic roots.