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In the past two decades, the need for a new concept in agriculture has emerged. The new \"Greener revolution\" should rely on the implementation of sustainable practices in crop production and the achievement of increased yields under the conditions of reduction of water, fertilizer, and pesticide use. The utilization of plant secondary metabolites is viewed by many authors as а possible alternative to synthetic chemicals. Bioactive botanical compounds can be obtained from plants in the form of extracts, essential oils (EO), or both. There are four main groups of plant secondary metabolites depending on their chemical structure: terpenes, phenolics, nitrogen-, and sulfur-containing compounds. A growing body of publications is devoted to the pesticidal properties of various secondary metabolites obtained from plants. The botanical families Meliaceae, Rutaceae, Asteraceae, Annonaceae, Labiatae, and Canellaceae include the most valuable species that are rich in secondary metabolites. The strong fumigant properties of the EOs from many plant species make them attractive in different Integrated Post-Harvest Pest Management systems. Suitable carriers for EOs delivery can be designed using nanoencapsulation. On a worldwide scale, the main botanical insecticides that are commercially available at present are Pyrethrum, Azadirachtin from Neem, and EOs from various plant species. Among the botanicals with considerable antimicrobial activity, there are some successfully authorized and developed commercial phenolics, terpenes, and alkaloids. Among the proven active substances are cinnamaldehyde, l-glutamic acid and gamma-aminobutyric acid, Jojoba oil, еssential oils, and others.

We report the development of a procedure for ultrasound-assisted microscale extraction of metabolites from the flowers of Saint John’s wort (Hypericum perforatum L.), designed for comparative metabolite analysis of plants from genetic resource collections and natural and segregating populations. The procedure involves high-throughput methanol extraction of metabolites from ground-frozen flowers at a selected stage of flower development, which is carried out in a standard 2 mL Eppendorf tube. A total of 18 compounds, including chlorogenic acid, catechins, glycosylated flavonoids, hypericins, and hyperforin, were identified based on LC/DAD/QTOF analysis, of which 16 could be detected in the UV-Vis spectrum. Two alternative versions of the procedure were evaluated: the “single-flower” procedure, including repeated collection and analysis of single flowers from the tested plant, and the “bulk-flower” procedure, employing the collection of a bulk flower sample from the tested plant and analysis of a portion of the ground sample. The results showed excellent technical reproducibility of the “single-flower” procedure when used with the suggested combination of the peak areas for the proto- and stable forms of pseudohypericin and hypericin. Application of the developed “single-flower” procedure for comparison of the plants derived from seed progeny of the apomictic line Hp93 revealed significantly lower metabolite variation among the apomictic progeny plants compared to the variation observed among plants belonging to different genotypes.

Temporary immersion systems (TISs) are an advanced biotechnological platform for the large-scale cultivation of medicinal plants and the consistent production of high-value secondary metabolites. In this study, we evaluated three immersion regimes with stand-by periods of 4, 8, or 12 h, each paired with a 15-minute immersion period, to optimise shoot growth and colchicine accumulation in L. and Guss. The 4 h stand-by/15 min immersion regime yielded the highest growth index ( : 0.75 ± 0.08; : 1.25 ± 0.03) and maximum colchicine content ( : 0.19 ± 0.01 mg/g dry biomass; : 0.25 ± 0.02 mg/g dry biomass). Using gas chromatography-mass spectrometry (GC-MS), detailed metabolic profiling of cultures grown under this optimised regime was performed, resulting in the identification of 46 metabolites, including amino acids, organic acids, sugars, sugar alcohols, phenolic, and fatty acids. Volcano plot analysis revealed 11 upregulated and 5 downregulated metabolites in relative to . Significance analysis of metabolomics (SAM) identified 34 metabolites with statistically significant differences between two species. Hierarchical clustering and partial least squares discriminant analysis (PLS-DA) confirmed clear species separation, with Component 1 explaining 68.8% of the total metabolic variance. Glucose-6-phosphate (VIP = 2.01), citric acid (VIP = 1.85), asparagine (VIP = 1.67), and γ-aminobutyric acid (GABA; VIP = 1.52) were the primary biomarkers differentiating the species. These findings confirm that TISs provide an optimised environment for biomass accumulation and stable alkaloid biosynthesis in the Colchicum genus, with emerging as a promising candidate for biotechnological exploitation.

This paper reviews the recent development of the scientific, legislative, economic and environmental aspects of plant organic farming. The impact of organic farming on biodiversity and soil fertility is discussed in comparison with conventional systems. A significant barrier for wide application and future development of organic farming is the existing diversity of national and international policy instruments in this sector. Special attention is paid to up-to-date research techniques that could help solve a number of the problems typically faced in plant organic farming. It is argued that organic farming is still not productive enough to be considered fully sustainable. This underlines the necessity of strong support for more effective implementation of scientific research innovations and improvement of the networking between all stakeholders – organic producers, scientists and corresponding policy makers at the national and international level.

We studied the mode of pollination in Greek oregano (Origanum vulgare ssp. hirtum) under both controlled and open pollination conditions. When grown indoors without the presence of insects, Greek oregano plants did not develop any seeds, indicating a low level of spontaneous self-pollination. Applying manual self-pollination under the same conditions resulted in only 16 seeds, of which only five were able to germinate. At the same time, a clonally propagated Greek oregano plant of the same genotype produced a rich set of over 300 seeds in open field conditions when the flowers were visited by insects in an area where no other Origanum species were observed. Analysis with SSR markers showed that over 70% of the seeds likely resulted from self-pollination, indicating that insect-mediated pollination is essential for the seed development. We further analyzed the cross-pollination of Greek oregano with Common oregano (O. vulgare ssp. vulgare) in open field conditions where the two subspecies were grown in close proximity. Applying SSR markers, we analyzed 83 plants obtained from seeds of three vegetatively propagated Greek oregano mother plants. Surprisingly, the results showed that all analyzed seedlings resulted from cross-pollination of Greek oregano with Common oregano, indicating that cross-pollination between the two subspecies can completely take over the self-pollination or cross-pollination between the Greek oregano plants. The possible impact of the observed high cross-pollination rate on the genetic origin of seeds of selected Greek oregano lines and varieties, as well as on the genetic diversity and structure of natural populations, is discussed.

Main conclusionThe polyploidization of Hippeastrum papilio influences its primary and secondary metabolism including the biosynthesis of bioactive alkaloids.Hippeastrum papilio is an ornamental plant that has advantages in comparison to the currently used plants for the extraction of galanthamine, a natural compound used for the cognitive treatment of Alzheimer’s disease. In the present study, an autotetraploid line of H. papilio was induced for the first time, after treatment with 0.05% colchicine for 48 h. The chromosome number in diploids was found to be 2n = 2x = 22 and for autotetraploids 2n = 4x = 44. The flow cytometric analyses detected a DNA C-value of 14.88 ± 0.03 pg (1C) in diploids and 26.57 ± 0.12 pg in autotetraploids. The morphological, cytological, and phytochemical studies showed significant differences between diploids and autotetraploids. The length and width of stomata in autotetraploids were 22.47% and 17.94%, respectively, larger than those observed in the diploid leaves. The biomass of one-year-old autotetraploid H. papilio plants was reduced by 53.99% for plants’ fresh weight, 56.53% for leaves’ fresh weight, and 21.70% for bulb diameter. The GC–MS analysis of methanol extracts from one-year-old diploid and autotetraploid H. papilio plants revealed over 60 primary and secondary metabolites including alkaloids, phenolic acids, sterols, saccharides, and alcohols, among others. Principal component analysis of the metabolite profiles indicates a divergence of the metabolism between diploid and autotetraploid plants. The content of galanthamine and haemanthamine was found to be 49.73% and 80.10%, respectively, higher in the leaves of autotetraploids, compared to the diploid ones. The biosynthesis of the saccharides shows a tendency to be upregulated in tetraploid plants, while that of phenolic acids was downregulated. Polyploidization of H. papilio creates possibilities for further crop improvement aimed at high-galanthamine-producing genotypes.

Leucojum aestivum (summer snowflake) is a perennial, wild plant species of medical importance. L. aestivum is in danger of extinction and has been thus put under a regulated regime for conservation. However, its natural fields in Bulgaria continue to deteriorate, one of the reasons being contamination of rivers with industrial waste. The plant has been long known not to suffer diseases. In the period 2006-2011, however, diseased bulbs with symptoms of bacteriosis were observed. This paper presents the third of a series of investigations of L. aestivum in Bulgaria with symptoms of bacterial rot. After the pathogenicity tests and on the basis of physiological characteristics, metabolic fingerprints, and PCR with specific primers, bacterial strains-causal agents of bacterial rot of L. aestivum were identified as Burkholderia gladioli and Pseudomonas marginalis. Additional PCR using the RAPD technique differentiated Burkholderia gladioli pv. alliicola. It could be speculated that contamination of rivers may have been the reason for the spread of pathogens which normally infect other bulbous plants and can survive in soil and water, thus contributing to deterioration of the natural L. aestivum fields.

Summer snowflake /Leucojum aestivum L./ is a medical bulbous plant which belongs to family Amarillydaceae. It is wild-spread as natural populations in Bulgaria and a valuable source of galantamine. A few virus and fungal diseases have been described on plants of family Amaryllidaceae but only fungal pathogens on summer snowflake. This paper is the first report of Serratia plymuthica and Stenotrophomonas maltophilia as causal agents of bulb decay of summer snowflake. To our knowledge, this is also the second report of phytopathogenic isolates of the identified two species. The bacteria were isolated from plants in the region of Tutrakan close to the Danube River where pathogenic changes in plant tissues of bulbs of summer snowflake were detected in 2006. Pathogenicity to the natural plant host was confirmed by artificial inoculation. Identification was carried out by biochemical properties and sequence analysis. New hosts upon artificial inoculation of S. maltophilia and S. plymuthica are onion, hyacinth, tulip, narcissus, and crocus. The established bacterial species are known inhabitants of the soil and rhizosphere, contaminants of food and water, human infectious agents, and represent a case, similar to Serratia marcescens, when a species can comprise saprophytic, plant, and human strains simultaneously.