This work aims to characterize the genetic diversity of species, early hybrids, and cultivars using microsatellite simple sequence repeat (SSR) markers, as well as analyze and identify the origin of Hemerocallis spp. early hybrids. For this research, samples were collected from different types of daylily species, early hybrids (known or hypothetically first-generation hybrids from Hemerocallis species), foreign, and Lithuanian varieties. An initial screening of SSR primers developed for Hemerocallis citrina was performed, and their suitability for testing other daylily species and hybrids was evaluated. The genetic diversity was assessed with the selected eight-primer set, and molecular SSR profiles were created. Primer SAU00097 is the most informative according to heterozygosity (0.95) and polymorphism information content (PIC) (0.17). The highest heterozygosity was observed in Lithuanian cultivars (0.713), the lowest in species (0.583). Genetic relationships between species show that only fulvous daylilies are separated into a different cluster. The highest variation among genotypes was observed in the species group (18%), while modern cultivars had the slightest variation among genotypes (1%). The putative origin of early hybrids was analyzed using a likelihood heatmap of all genotypes. Results show what species might be used in breeding for early hybrids. Several modern diploid and tetraploid daylily cultivars have triploid species as ancestors.

The apple tree (Malus × domestica Borkh.) belongs to the Rosaceae. Due to its adaptability and tolerance to different soil and climatic conditions, it is cultivated worldwide for fresh consumption. The priorities of apple growers are high-quality fruits and stable yield for high production. About 90 to 95 percent of fruits should fall or be eliminated from apple trees to avoid overcropping and poor-quality fruits. Apple trees engage in a complex biological process known as yield self-regulation, which is influenced by several internal and external factors. Apple buds develop in different stages along the branches, and they can potentially give rise to new shoots, leaves, flowers, or fruit clusters. The apple genotype determines how many buds will develop into fruit-bearing structures and the capacity for yield self-regulation. Plant hormones such as ethylene, cytokinins, auxins, and gibberellins play a crucial role in regulating the fruit set, growth, and development, and the balance of these hormones influences the flowering intensity, fruit size, and fruit number on the apple tree. Apple growers often interfere in the self-regulation process by manually thinning fruit clusters. Different thinning methods, such as by hand, mechanical thinning, or applying chemical substances, are used for flower and fruit thinning. The most profitable in commercial orchards is the use of chemicals for elimination, but more environmentally sustainable solutions are required due to the European Green Deal. This review focuses on the biological factors and genetic mechanisms in apple yield self-regulation for a better understanding of the regulatory mechanism of fruitlet abscission for future breeding programs targeted at self-regulating yield apple varieties.

This study aimed to understand the differences in the performance of diploid and tetraploid daylily cultivars under water deficit conditions, which are essential indicators of drought tolerance. This research revealed that tetraploid daylilies performed better than diploid varieties in arid conditions due to their enhanced adaptability and resilience to water deficit conditions. The analysis of the results highlighted the need to clarify the specific physiological and molecular mechanisms underlying the enhanced drought tolerance observed in tetraploid plants compared to diploids. This research offers valuable knowledge for improving crop resilience and sustainable floricultural practices in changing environmental conditions. The morphological and physiological parameters were analyzed in 19 diploid and 21 tetraploid daylily cultivars under controlled water deficit conditions, and three drought resistance groups were formed based on the clustering of these parameters. In a high drought resistance cluster, 93.3% tetraploid cultivars were exhibited. This study demonstrates the significance of ploidy in shaping plant responses to drought stress. It emphasizes the importance of studying plant responses to water deficit in landscape horticulture to develop drought-tolerant plants and ensure aspects of climate change.

Daylily (Hemerocallis L.) is a popular herbaceous perennial ornamental plant. The American Hemerocallis Society (AHS) currently has over 96,000 cultivars registered. Of these, half are tetraploids (4x), and the other half are diploids (2x). To enrich the breeding lines of tetraploid daylilies, colchicine is the most widely used. During the experiment, oryzalin (ORZ) and colchicine (CLC) were used for the polyploidisation of daylilies. Germinating seeds derived from diploid and tetraploid daylily cultivars as maternal plants were exposed to solutions of ORZ and CLC at different concentrations. Ploidy of seedlings was determined after six months by flow cytometry, and the obtained results were related to the size of the stomata. Chimerism of the young side shoots developing on treated plants was assessed three years after polyploidisation by checking the ploidy using a flow cytometer. It has been found that whole-genome duplication is not common in daylilies during polyploidisation of germinating seeds - triploids (3x), pentaploids (5x), hexaploids (6x), and heptaploids (7x) were obtained. The optimal concentration of CLC for induction higher ploidy was 125-250 mu mol when exposed to seeds of the diploid maternal plant (DMP) and 250-500 mu mol when exposed to the tetraploid maternal plant (TMP) one. In the case of ORZ, optimal treatments were 10 mu mol for germinating DMP seeds and 40 mu mol for TMP seeds, respectively. Stomata size can preliminarily determine daylily ploidy. A flow cytometry should be used for a more accurate determination of ploidy. Individuals treated with antimitotic agents are prone to chimerism. The most extensive ploidy variation observed in individuals with uneven ploidy is usually in the direction of even ploidy. Therefore, the ploidy of clones used for breeding should be checked regularly.

The aim of this study was to evaluate phenotypic traits and genetic diversity of the 13 tomato (Solanum lycopersicum L.) varieties and 6 hybrids developed at the Institute of Horticulture Lithuanian Research Centre for Agriculture and Forestry (LRCAF IH). For the molecular characterisation, seven previously published microsatellite markers (SSR) were used. A24 and 26 alleles were detected in tomato varieties and hybrids, respectively. Based on the polymorphism information content (PIC) value, the most informative SSR primers for varieties were TMS52, TGS0007, LEMDDNa and Tom236-237, and the most informative SSR primers for hybrids were SSR248 and TMS52. In UPGMA cluster analysis, tomato varieties are grouped in some cases due to genetic relationships, as the same cluster cultivars ‘Viltis’ (the parent of cv. ‘Laukiai’) and ‘Aušriai’ (the progeny of cv. ‘Jurgiai’) are present. The grouping of all hybrids in the dendrogram is related to the parental forms, and it shows the usefulness of molecular markers for tomato breeding, as they can be used to trace the origin of hybrids and, eventually, varieties accurately. The knowledge about the genetic background of Lithuanian tomato cultivars will help plan targeted crosses in tomato breeding programs.

Chromosome doubling in ornamental plants, as shown by our study in daylilies (Hemerocallis spp.), has great potential to increase tolerance to abiotic stress. Drought is the most critical growth-limiting factor in a changing climate. Drought tolerance is one of the decisive factors for the survival, productivity, and appearance of perennial ornamental plants. Understanding and elucidating the molecular mechanisms that determine plant response to abiotic stress is essential. De novo transcriptome assembly of diploid and autotetraploid Hemerocallis spp. cv. Trahlyta was performed under artificially induced stress to elucidate the molecular mechanisms related to plant response to drought. In daylily mRNA, 237,886 transcripts were detected, and 42.4% of them were identified as annotated unigenes. In the experiment, diploid plants were more stressed, with 2871 upregulated or downregulated DEGs (differentially expressed genes) responding to drought, while tetraploid plants had 1599 DEGs. The proportion of upregulated DEGs differed by 1.3 times between diploid and autotetraploid genotypes, whereas the proportion of downregulated DEGs was 1.8 times greater in diploid plants. Signaling pathways related to the drought response were activated in daylilies, and key candidate genes were identified in both ploidy genotypes. In autotetraploid plants, more drought-related pathways were activated than in diploids—43 and 19, respectively. The most abundant DEGs in both cases were KEGG (Kyoto Encyclopedia of Genes and Genomes), metabolic (ko01100), and biosynthesis of secondary metabolites (ko01110) pathways. Summarizing the data, it was found that autotetraploid plants of the daylily have a wider potential for adaptation to drought stress. Therefore, they adapt faster and better to adverse drought conditions by activating alternative signaling pathways. The comparative transcriptome analysis of diploid and autotetraploid plants allows us to understand the molecular mechanisms of drought resistance and it is also essential for daylily breeding programs to develop drought-resistant genotypes in the future.