Polyploidisation is an important process in the evolution of many plant species. An additional set of chromosomes can be derived from intraspecific genome duplication (autopolyploidy) or hybridising divergent genomes and chromosome doubling (allopolyploidy). Special forms of polyploidy are autoallopolyploidy and segmental allopolyploidy. Polyploidy arises from two basic processes: spontaneously occurring disturbances of meiotic division and induced by antimitotic agents’ disruption of mitosis. The first involves the induction and fusion of unreduced gametes, resulting in the formation of triploids and tetraploids. The second process uses antimitotics that disrupt cellular microtubules and prevent chromosome’s sister chromatids motion during anaphase. Colchicine, oryzalin, and trifluralin are the most commonly used antimitotics for inducing polyploids in plants. The exposure time and concentration of the antimitotics and the species, cultivar, genotype, and tissue type affect the efficiency of genome duplication. Polyploids are distinguished from diploids by increased cell size and vegetative parts of plants and increased content of secondary metabolites. Genome duplication generates several changes at the epigenetic level resulting in altered gene expression. Polyploidisation is used in plant breeding to overcome the non-viability and infertility of interspecific hybrids, obtain seedless polyploid cultivars and increase resistance/tolerance to biotic and abiotic factors.

The hemp aphid Phorodon cannabis Passerini is a well- known (Asia, Europe) or newly emerging (North America) insect. It is a monophagous insect pest causing considerable damage in field and glasshouse cultivations. The aim of this work was to study the effects of meteorological (temperature) and agronomical (herbicide) factors on the biology of the hemp aphid. In one experiment, hemp plants were kept at constant temperatures ranging from 20 to 30 °C, and aphid survival and fecundity were measured. In a related experiment conducted at 20 °C, plants were treated with field-appropriate rates of a selective graminicide containing quizalofop-P-tefuryl (40 gL⁻¹, 4.38%, HRAC group 1), commonly used to control weeds in hemp, and aphid enzyme activity was measured in addition to population parameters. We found that hemp aphids could live, feed and reproduce within the whole studied range of temperatures, demonstrating its great evolutionary plasticity. However, the optimal temperature for development was 25 °C, at which the insect lived and reproduced for 25 and 15 days, respectively, with an average fecundity of 7.5 nymphs per reproduction day. The herbicide treatment increased the activity of superoxide dismutase (SOD), catalase (CAT), β-glucosidase, S-glutathione transferase (GST), oxidoreductive peroxidase (POD), and polyphenol oxidase (PPO) in the aphids, but only on certain days after treatment, which indicates a mild stress in aphid tissues, related to a higher reproduction and changed feeding behavior; aphids moved from the actively growing tips compared to untreated plants. The results of these experiments are discussed in terms of the impact on the future management of this pest.

The aim of the study was to determine the breeding value of advanced lines of fibrous flax and oilseed flax (linseed) on the basis of comparative experiments with reference varieties. In field experiments conducted in 2019–2020, the HDH line of fibrous flax and the R26 linseed line were assessed in terms of significant phenotypic traits and also traits affecting the yield structure. Due to the fundamentally different weather conditions in the growing seasons of 2019 and 2020, it was also possible to determine the susceptibility of the studied genotypes of flax to climatic stress factors. The obtained results showed the high breeding value of the HDH line as a potential new variety of fibrous flax. The R26 line did not exceed the reference varieties in terms of the traits essential for the oily form of the cultivated flax cultivars, but it was characterized by a favorable morphological and yield-forming structure for dual purpose varieties. Moreover, both assessed lines showed high resistance to unfavorable climatic conditions.

Summary: Introduction:Many fungal species infect medicinal plants during their cultivation, causing great damage to the yield and decreasing the quality of raw material.Objective:Due to the increase in contamination of raw material and the damage caused by pathogenic fungi, the main species of medicinal plants cultivated in Poland were subject to the investigation.Methods:In 2012–2014, an experiment was conducted on eight medicinal plant species breeding nurseries grown in the field in Plewiska. The following species and cultivars were investigated: lemon balm, peppermint, St. John’s wort cv. ‘Topaz’, lovage cv. ‘Amor’, valerian cv. ‘Polka’, caraway cv. ‘Kończewicki’, sweet basil cv. ‘Wala’, marjoram cv. ‘Miraż’.Results:Fourteen species of eleven genera of pathogenic fungi were isolated from the investigated medicinal plants:Fusarium avenaceum, F. culmorum, F. equiseti, F. oxysporum, Botrytis cinerea, Alternaria alternata, Cladosporiumsp.,Rhizoctonia solani, Septoriasp.,Boeremia exiqua, Golovinomyces cichoracearum, Penicilliumsp.,Ramulariasp., andSclerotinia sclerotiorum.The most severe infection was caused byFusariumsp. andBotrytis cinerea. AlsoCladosporiumsp. (4 species),A. alternataandSeptoriasp. (3 species) infected plant tissue. Leaves and stems were the most infected parts of the tested plants. Lemon balm, lovage and valerian were the most infected species, while marjoram was infected only withFusariumsp.

After many decades when its cultivation was prohibited, hemp is regaining its position as one of the most versatile cultivated crops. Multiplication of monoecious hemp varieties requires manual male plants rouging to keep a high share of monoecious plants in the population. It forces relatively small multiplication fields usually oscillating around 5 ha, where the use of big harvesting machines is not economically feasible. The B-800 mower prototype for hemp panicles proved to be a good alternative to harvest seeds of tall fibrous hemp. The test results of the mower analyzed in this study show that although seed loss on a moderate slope (0.37%) was significantly higher than on a flat slope (0.13%), it was still much lower than in the case of harvesting hemp seed with a combined harvester. Moreover, the field efficiency of 93% is very satisfactory as it is reported for much bigger machines. Finally, the harvesting costs proved to be much lower than most of the machines used for harvesting hemp seed.

Due to the increasing demand for food, the agricultural sector is facing a huge challenge related to its production without having a negative impact on the environment. The above issues are regulated by the current EU policy, indicating the need to conduct plant production by the European Green Deal strategy (2020), based on reducing the use of chemical plant-protection products by 50% and reducing the level of mineral fertilization by 20% by 2030. Using appropriate techniques of applying mineral fertilizers, which have a positive effect on the development and activity of soil microorganisms, the availability of nutrients in the soil can be increased while reducing fertilizer applications. This study aims to show whether the use of foliar nitrogen fertilizers in combination with sulfur in a two-year field experiment with triticale stimulates the multiplication of selected groups of microorganisms and the level of soil enzymatic activity. In addition, effects on the content of available forms of nutrients in the soil, triticale yield, and total nutrient uptake were analyzed. It is shown that the applied foliar fertilizers enriched with sulfur, compared to fertilization with ammonium nitrate, contributed to a 100% increase in the number of analyzed groups of microorganisms, urease, and alkaline phosphatase activity; a 44% increase in dehydrogenase activity; and a 15% increase in acid phosphatase activity. The hybrid application technique, with reduced doses of nitrogen fertilizers enriched with sulfur by 20 and 25%, resulted in grain yields exceeding 8 t/ha. Moreover, compared to conventional fertilization based on ammonium nitrate, an increase in the grain yield of triticale was obtained in the range of 16 to 24%, as well as an increase in the accumulation of nutrients in the plant. It is shown that foliar fertilization is a promising alternative to standard fertilization techniques.