Dioecious Hemp Research Articles

Cannabis Virome Reconstruction and Antiviral RNAi Characterization through Small RNA Sequencing

Viral infections pose an emerging threat to hemp (Cannabis sativa) cultivation. We used Illumina small (s)RNA sequencing for virome reconstruction and characterization of antiviral RNA interference (RNAi) in monoecious and dioecious hemp varieties, which exhibited different virus-like symptoms. Through de novo and reference-based sRNA assembly, we identified and reconstructed Cannabis cryptic virus (family Partitiviridae), Cannabis sativa mitovirus 1 (Mitoviridae) and Grapevine line pattern virus (Bromoviridae) as well as a novel virus tentatively classified into Partitiviridae. Members of both Partitiviridae and Bromoviridae were targeted by antiviral RNAi, generating 21 nt and, less abundant, 22 nt sRNAs from both strands of the entire virus genome, suggesting the involvement of Dicer-like (DCL) 4 and DCL2 in viral sRNA biogenesis, respectively. Mitovirus sRNAs represented predominantly the positive-sense strand and had a wider size range, with the 21 nt class being most abundant on both strands. For all viruses, 21 and 22 nt sRNAs had predominantly 5′-terminal uridine or cytosine, suggesting their binding to antiviral Argonaute (AGO) 1 and AGO5, respectively. As no clear association of any virus with symptoms was observed, further studies should clarify if these viruses individually or in combination can cause hemp diseases.

ЧАСТИЧНАЯ СТЕРИЛЬНОСТЬ МУЖСКОЙ РЕПРОДУКТИВНОЙ СИСТЕМЫ ОДНОДОМНОЙ КОНОПЛИ

In 2018–2020, the authors examined causes of partial sterility of the male reproductive system in monoecious hemp. Male flowers of the dioecious hemp variety Igorkin and the monoecious hemp variety Diana were studied. The buds and open flowers were fixed with aceto-alcohol based on the Krnau method and with chromaceto-formalin according to the Navashin method. The procedure involved staining 5–10 µm thick sections with iron hematoxylin according to Heidenhain’s prescription and with basic fuchsin dye combining a licht-grun tint according to the Modilevsky technique. Many researchers have found that the flowering rate in male monoecious hemp flowers is much lower than in the dioecious variety. Some monoecious hemp plants cannot produce pollen grains as the species can form monoclinous flowers that drop at the bud stage. Studies have also established inherited male sterility and partial male sterility in monoecious hemp. It can be found within a plant, a flower and even an anther. The study aimed to identify the causes of partial sterility of male monoecious hemp flowers. It employed a microscopic analysis of the anther development in monoecious and dioecious hemp varieties. The study has established that the partial sterility of the male reproductive system of monoecious hemp is caused by the tapetum degeneration. Degeneration of the tapetum at any stage brings about sterile and semi-sterile male flowers in monoecious hemp

ASSESSMENT OF STEM PRODUCTION IN SOME VARIETIES OF DIOECIOUS HEMP

Varieties of dioecious hemp (Cannabis sativa L) created at ARDS Lovrin, Lovrin-110, Silvana, Armanca and Teodora, is characterized by the production of strains exceeding 10 t/ha, a fiber content of 25-30 % and can be extended in culture both in our country and in the European Union and not only, due to a low THC content below 0.2%. Dioecious hemp varieties exhibit a high ecological plasicity, when applying appropriate technology they achieve high yields. The researches carried out in the field of cultivation of dioecious hemp in Romania, for stems and seeds, have shown that it can be used in various industries (textile, cellulose, food, etc.) from where to result in high quality products. Following the study undertaken in the period 2021-2022, at ARDS Lovrin, it can be concluded that the variety Armanca has the highest yield of stems per hectare, with an increase of 2373.5 kg/ha, 29.1% more than the yield obtained by the control variety Silvana.

STUDY OF THE CORRELATION OF SOME GROWTH PARAMETERS AT DIOECIOUS HEMP

The present paper deals with the study of the correlation of some growth parameters to 10 bioecotypes of dioecious hemp (Cannabis sativa L) at A.R.D.S. Lovrin. Ten bioecotypes were studied, four of which are established varieties created at A.R.D.S. Lovrin (Lovrin-110, Silvana, Armanca și Teodora) and six perspective lines (Zak-127xLv-110, Lv-428/01, S33/08 R, Lv-434x406CS/04, S354/15, Lv-149 CS/16). From the existing biological material, the dioecious hemp variety Silvana was chosen as a control. A monofactorial experience, having as a factor the existing biological material, was placed in the field of the laboratory for the improvement of dioecious hemp. The four parameters studied and presented are: the total length of the plant, the length of the inflorescence, the technical length and the diameter of the stem of the hemp plants, parameters that were influenced by the climatic conditions of the studied years 2020-2021. Compared to the blank variant, five of the six lines of perspective stand out in terms of the superiority of the technical length of the stem, two of them with very significant positive differences, statistically provided for the probability of transgression 0,1 %.

Fibers development in a dioecious hemp cultivar: the role of plant sex and cultivation conditions

Hemp (Cannabis sativa) is a well-known crop with a great potential to produce fibers without being excessively water and nutrient demanding. Moreover, hemp can be considered a viable and sustainable alternative to reach a cleaner production in the garment industry. Accurate information on fiber traits will enhance the exploitation of hemp in textile and biofuel industry. The aim of this work was to investigate the cyto-histological characteristics of hemp primary and secondary fibers through semi-thin sections and a light microscopy approach. To this purpose, we cultivated in open field a dioecious hemp variety under two different sowing densities and two different fertilization regimes. We confirmed the prominent role of sex in influencing all the analyzed traits; moreover, we found the possibility to mitigate it by changing the sowing density and the fertilization regime. In particular, the cell wall thickening in primary fibers was reduced in female plants by high fertilization. In male plants, combining high fertilization and low density, secondary fibers development is deeply increased. Cell area, in both plant sexes, was reduced by high fertilization. Operating on these simple agronomic aspects could thus result in the desired amount of fibers/lignin, depending on the final purpose of hemp cultivation.

Terpenes and Cannabinoids Yields and Profile from Direct-Seeded and Transplanted CBD-Cannabis sativa.

Following recent legalization, the production of hemp (Cannabis sativa L.) for high-value plant compounds became a major crop in many countries across the world. In this study, we profiled popular plant compounds being extracted for emerging markets, terpenes and cannabinoids, developed in two different planting systems of a single, high-cannabidiol (CBD), low-Δ9-tetrahydrocannabinol (Δ9-THC), dioecious hemp cultivar 'Culver' in central Oregon, U.S.A. One system is the current conventional system of an open, all-female, clonal transplant (OFCT) production system. This is compared to a dioecious, densely seeded (DDS) production system. Overall, the essential oil (EO, chiefly terpenes) and cannabinoid profiles of plants harvested from the two systems were comparable. In comparison to the DDS plots, the EO obtained from colas of the OFCT plots had higher concentrations of α-pinene, myrcene, limonene, β-bisabolene, γ-cadinene, caryophyllene oxide, guaiol, 10-epi-γ-eudesmol, β-eudesmol, bulnesol, epi-α-bisabolol, α-humulene, and CBD, although lower concentrations of 1,8-cineole, (E)-caryophyllene, γ-elemene, α-selinene, selina-4(15),7(11)-diene, selina-3,7(11)-diene, and germacrene B. Of the various plant parts (female leaves and chaff, male flowers) tested in the DDS plots, the highest EO yield was obtained from the chaff. The main EO constituents of female leaves were (E)-caryophyllene (14-21%), caryophyllene oxide (13-16%), α-humulene (5-6%), humulene epoxide II (3.5-3.8%), epi-α-bisabolol (2.7-5.5%), CBD, and α-eudesmol (1.1-2.6%). The principal EO constituents of female chaff from the DDS system were (E)-caryophyllene (∼21%), α-humulene (6.6%), β-selinene (4.5%), α-selinene (3.6%), selina-3,7(11)-diene (9.8%), selina-4(15),7(11)-diene (6.3%), caryophyllene oxide (5.2%), and cannabichromene (3.1%). The major EO constituents of the male flowers were CBD (19.3%), caryophyllene oxide (11%), α-humulene (4.1%), epi-α-bisabolol (3.9%), selina-3,7(11)-diene (3.4%), and β-selinene (3.4%). Cannabinoids were not detected in the EO distilled for 30 min, but they were present in the EO from 240 min of distillation. The EO content of female leaves and male flowers was relatively low, whereas the EO content of the female chaff from the DDS system was significantly greater. Breaking with conventional knowledge, the EO of male flowers may accumulate up to 19% CBD. Distillation of plants from both production systems converted CBD-A to CBD, CBDV-A to CBDV, CBG-A to CBG, and THC-A to THC as a result of the thermal decarboxylation of acidic cannabinoids but otherwise did not affect the total cannabinoid content. Most of the cannabinoids remained in the distilled biomass after the extraction of terpenes (EO). Therefore, the distilled, terpene-free biomass represents a high-value product that could be further extracted for cannabinoids or used as a component in various products.

Dioecious hemp (Cannabis sativa L.) plants do not express significant sexually dimorphic morphology in the seedling stage

Some economically important crop species are dioecious, producing pollen and ovules on distinct, unisexual, individuals. On-the-spot diagnosis of sex is important to breeders and farmers for crop improvement and maximizing yield, yet diagnostic tools at the seedling stage are understudied and lack a scientific basis. Understanding sexual dimorphism in juvenile plants may provide key ecological, evolutionary and economic insights into dioecious plant species in addition to improving the process of crop cultivation. To address this gap in the literature, we asked: can we reliably differentiate males, females, and co-sexual individuals based on seedling morphology in Cannabis sativa, and do the traits used to distinguish sex at this stage vary between genotypes? To answer these questions, we collected data on phenotypic traits of 112 C. sativa plants (50 female, 52 male, 10 co-sexuals) from two hemp cultivars (CFX-1, CFX-2) during the second week of vegetative growth and used ANOVAs to compare morphology among sexes. We found males grew significantly longer hypocotyls than females by week 2, but this difference depended on the cultivar investigated. Preliminary evidence suggests that co-sexual plants may be distinguished from male and female plants using short hypocotyl length and seedling height, although this relationship requires more study since sample sizes of co-sexual plants were small. In one of the cultivars, two-week old male plants tend to produce longer hypocotyls than other plants, which may help to identify these plants prior to anthesis. We call for increased research effort on co-sexual plants, given their heavy economic cost in industrial contexts and rare mention in the literature. Our preliminary data suggests that short hypocotyl length may be an indicator of co-sexuality. These results are the first steps towards developing diagnostic tools for predicting sex using vegetative morphology in dioecious species and understanding how sexual dimorphism influences phenotype preceding sexual maturity.

A Multimethodological Characterization of Cannabis sativa L. Inflorescences from Seven Dioecious Cultivars Grown in Italy: The Effect of Different Harvesting Stages.

The chemical profile of the female inflorescence extracts from seven Cannabis sativa L. dioecious cultivars (Carmagnola, Fibranova, Eletta Campana, Antal, Tiborszallasi, Kompolti, and Tisza) was monitored at three harvesting stages (4, 14, and 30 September), reaching from the beginning of flowering to end of flowering/beginning of seed formation, using untargeted nuclear magnetic resonance (NMR) and targeted (ultra-high-performance liquid chromatography (UHPLC) and spectrophotometry) analyses. The tetrahydrocannabinol content was always below the legal limits (<0.6%) in all the analyzed samples. The NMR metabolite profile (sugars, organic acids, amino acids, and minor compounds) subjected to principal components analysis (PCA) showed a strong variability according to the harvesting stages: samples harvested in stage I were characterized by a high content of sucrose and myo-inositol, whereas the ones harvested in stage II showed high levels of succinic acid, alanine, valine, isoleucine, phenylalanine, and threonine. Samples harvested in stage III were characterized by high levels of glucose, fructose, choline, trigonelline, malic acid, formic acid, and some amino acids. The ratio between chlorophylls and carotenoids content indicated that all plants grew up exposed to the sun, the Eletta Campana cultivar having the highest pigment amount. Tiborszallasi cultivar showed the highest polyphenol content. The highest antioxidant activity was generally observed in stage II. All these results suggested that the Cannabis sativa L. inflorescences of each analyzed dioecious hemp cultivar presented a peculiar chemical profile affected by the harvesting stage. This information could be useful for producers and industries to harvest inflorescences in the appropriate stage to obtain samples with a peculiar chemical profile suitable for proper applications.

THE EVOLUTION OF SEED PRODUCTION IN DIOECIOUS HEMP IN THE PERIOD 2016-2018, IN CLIMATE CONDITIONS FROM S.C.D.A. LOVRIN

Hemp is a multi-purpose crop, being used mainly for the production of stems and fiber, seed, but also for food and medicine. In the western part of the country and not only, dioecious hemp finds favorable conditions for cultivation. One of the research centers in Romania, with a rich tradition in hemp breeding and cultivation is at S.C.D.A. Lovrin. Hemp is a plant with special requirements for temperature, humidity and fertilization. The optimum temperature at which the highest seed and stem productions are obtained is 20-22⁰C together with a good supply of pressing nutrients. During the analyzed period, 2016-2018 the climatic conditions had an atypical evolution, considerably influencing the harvest. The aim of the paper is to evaluate the production of a number of ten varieties, Romanian and foreign, from the S.C.D.A. Lovrin. Climatic conditions had a significant influence on production, the minimum production being recorded in 2017 (240 kg / ha - average experience) and the maximum in 2018 (786 kg / ha seed average experience).

Epigenetic determined sex change of the hemp unisexual hybrids under the influence of pho-toperiod

Hemp (Cannabis sativa L.) is quite sensitive species to photoperiod.The aim and tasks of the study were a comparative analysis of the phenotypic expression of sex in unisexual hybrids of the first generation hemp (dioecious hemp / monoecious) grown in field and under artificial conditions of reduced daylight hours.Material and methods. The studies were conducted on the basis of the Institute of Bast Crops of the NAAS (Glukhov, Sumy region). Hybridization was carried out under conditions of glass house with the use of group isolators according to the scheme of dioecious hemp / monoecious. Local, selection varieties and samples of various ecological and geographical types were parent forms. F1 hybrids were grown in the field and growers from the beginning of budding phase with a shortened daylight duration of 12 hours. The phenological phases were determined on the basis of the BBCH scale. Sex types were determined by N.D. Migal’s (1992) classification and methodology.Results and discussion. In natural (field) conditions, the duration of a light day before the beginning of budding phase was about 15–16.30 hours. Appearance of buds (BBCH 51-59) and mass flowering (BBCH 60-65) were observed with the duration of daylight at 16.30–16 hours. The generative phase occurred in artificially created conditions with a photoperiod of 12 hours too, but the sexual structure of the hybrids was changed. The sex structure of F1 hybrids which were grown in the field, was represented with the female plants and a small number of monoecious plants. The sex structure shifted to the female. Under the influence of the shortened daylight hours, the sexual structure of the hybrids shifted to the male, that is, the content of the female plants decreased (from 36.6 to 92.3 %), the content of monoecious sexual types increased. The emergence of male plants was observed. This regularity expression was more clearly when combined with two exposure factors (photoperiod and the removal of growth points). An epigenetically determined change of the hemp hybrids sexual structure occurs under the influence of a photoperiod. The change of the sexual structure under the influence of the photoperiod is epigenetically deterministic; such as unisexual hybrids (heterozygous for the female and monoecious sex) become almost monoecious in the phenotype and contain male plants.Сonclusions. To establish epigenetically determined changes of sex in hemp hybrids under the influence of photoperiod.

Identification of QTLs for sex expression in dioecious and monoecious hemp (Cannabis sativa L.)

Hemp (Cannabis sativa L.) is a diploid species including both dioecious and monoecious cultivars with hetero- and homomorphic sex chromosomes, respectively. It displays a high plasticity of sex expression, i.e., the ratio of female and male flowers. In this study, we investigated the role of sex chromosomes in the genetic determinism of sex expression in dioecious and monoecious hemp. The experimental materials were three F1 segregating populations, two dioecious (C1 and C2: ‘Carmagnola’ ♀ × ‘Carmagnola’ ♂), and one monoecious (UF: ‘Uso 31’ × ‘Fedora 17’). A ‘sex’ phenotypic marker was mapped in C1 and C2. In total, 23, 42, and 26 AFLP markers (71 markers in total) were mapped to three, nine, and three co-segregation groups putatively located on sex chromosomes in C1, C2, and UF, respectively. Recombination rates with sex ranged from 0 to 0.5. Five sex-linked markers were detected in UF, revealing homologies between the X chromosomes of monoecious hemp and the X and Y chromosomes of dioecious hemp. Five QTLs associated with quantitative variations in sex expression were identified in each map. Four markers associated with variations in sex expression in UF segregated with sex or accounted for a putative QTL in C1 or C2. Two QTLs and three of these markers were mapped in UF in a region homologous to the sex-locus region of the dioecious maps. Given these results, conducting further research on the genetic determinism of sex expression in hemp using a quantitative approach appears relevant.

Influence of Gender on the Mechanical and Physical Properties of Hemp Shiv Fiber Cell Wall in Dioecious Hemp Plant

Hemp (Cannabis sativa L.) shiv has great potential for the production of bio-composites as a reinforcement material. To gain more information about hemp shiv, this research studied the influence of gender on the physical and mechanical properties of the fiber cell wall in the shiv of three dioecious hemp plant varieties by optical microscopy, image analysis software, WXRD, and nanoindentation. The results show that a hemp plant’s gender greatly influences the properties of hemp shiv. While long and thin in female hemp shiv, the fibers are shorter with a larger diameter in male hemp shiv. In addition, the cell walls in female shiv are thinner than those in male shiv. The microfibril angle (MFA), relative degree of crystallinity, elastic modulus, and hardness values of fiber cell walls as well as the lignin content in male hemp plants are higher than those in female hemp plants. Besides, the relationship between mechanical properties and MFA do not align with those observed in previous research, which shows that the gender of an individual plant has a greater effect on the mechanical properties of the fiber cell wall than does its MFA. Thus, when the fiber from this dioecious plant is investigated or used, the sex of the plant should be known and considered.

Sex chromosomes and quantitative sex expression in monoecious hemp (Cannabis sativa L.)

Hemp (Cannabis sativa) has a highly variable sexual phenotype. In dioecious hemp, the sex is controlled by heteromorphic sex chromosomes according to an X-to-autosomes equilibrium. However, in monoecious hemp, the sex determinism remains widely unknown and has never been related to a quantitative approach of sex expression. The present paper aims to contribute to the comprehension of the sex determinism in monoecious hemp by assessing the genotypic variability of its sex expression and establishing its sex chromosomes. Five monoecious and one dioecious cultivars were grown in controlled conditions under several photoperiods. The monoecy degree of 194 monoecious plants was recorded at each node by a figure ranging from 0 (male flowers only) to 6 (female flowers only). The genome size of 55 plants was determined by flow cytometry. The DNA of 115 monoecious plants was screened with the male-associated marker MADC2. The monoecy degree varied significantly among monoecious cultivars from 3.36 ± 2.28 in ‘Uso 31’ to 5.70 ± 0.81 in the most feminised ‘Epsilon 68’. The variation of monoecy degree among cultivars remained consistent across trials despite a significant “cultivar × trial” interaction and partly agreed with their earliness. The genome size of monoecious plants (1.791 ± 0.017 pg) was not different from that of females (1.789 ± 0.019 pg) but significantly lower than that of males (1.835 ± 0.019 pg). MADC2 was absent from all monoecious plants. These results strongly support that cultivars of monoecious hemp have the XX constitution and that their sex expression has a genetic basis.

Nutritive quality of romanian hemp varieties (Cannabis sativa L.) with special focus on oil and metal contents of seeds.

BackgroundThe study aims to determine the nutritional value of hemp seed expressed by the oil content and by the concentration of metals (Ca, Mg, K, Fe, Mn, Zn and Cd), for five varieties of monoecious and dioecious hemp seeds approved in Romania, comparative with the concentration of these metals in the soil.ResultsThe content of oil in hempseed registers a slight decrease in the production records of 2011, losses due to drought and low levels of precipitation during the growth period. The greatest loss is found in Diana monoecious variety (26.54-20.82%) followed by Zenit varieties (27.37-22.97%), Armanca (29.27-25.32%), Silvana (28.89-25.04%) and Denise (26.96-25.30%). Siccative hemp oil has a yellowish green color and an iodine index of 140–156 g I2/100 g oil. Hemp seed are rich in mineral based Ca (144–955 mg/100 g seed), Mg (237–694 mg/100 g seed), K (463–2821 mg/100 g seed), Fe (1133-2400 mg.kg-1), Mn (63–110 mg.kg-1) and Zn (42-94 mg.kg-1). For the soil the following macroelements concentrations were determined: Ca (2100–2520 mg.kg-1), Mg (320–376 mg.kg-1) and K (232–257 mg.kg-1). Mn (156–197 mg.kg-1) and Zn (54–67 mg.kg-1) remain within normal limits for Romania. The soils in the experience area contain large amounts of Fe (19000–20430 mg.kg-1). The presence of K in large quantities determines the accumulation of large quantities of Fe in the soil.ConclusionHempseed belonging to the five Romanian varieties are rich source of nutrients (Ca, Mg, K) and unsaturated oil easily digestible by the body, but the presence of Cd concentrations above the upper limit puts a question mark over the use of seeds in various food products. Hemp extracts easily certain metals from the soil. Significant amounts of Fe (1133–2400 mg.kg-1), Mn (63–110 mg.kg-1), Zn (42–94 mg.kg-1) and Cd (1.3-4.0 mg.kg-1) are found in hemp seeds. Hemp (Cannabis sativa L.) is included among plants suitable for phytoremediation of soil contaminated with cadmium, zinc and iron.

Lignin content and briquette quality of different fibre hemp plant types and energy sunflower

Fibre hemp and energy sunflower are potential energy crops for production of solid biomass as renewable energy. The current study estimated (i) the lignin content of fibre hemp and energy sunflower plants grown on different nitrogen treatments and (ii) the quality of the briquettes made from different plant types of fibre hemp (i.e. monoecious and dioecious), energy sunflower and the combination of fibre hemp and energy sunflower. The monoecious and dioecious fibre hemp cultivars (Chameleon, Finola and Santhica-27, USO-31, respectively) and the energy sunflower cultivar Wielkopolski were grown in the experimental field in 2008–2010 on Stagnic Luvisol soil. The plants were grown on N treatments of N0, mineral nitrogen (100 kg N ha −1), cattle slurry (100 kg N ha −1), sewage sludge (100 kg N ha −1) and vetch (100 kg N ha −1). Calorific values (16.6–17.4 MJ kg −1) of briquettes pressed from different materials did not differ significantly and had relatively low sulphur (<0.05%) and chlorine content (0.03–0.37%). Briquettes with higher compactness were made from the sunflower and the dioecious hemp. Dioecious hemp had significantly higher lignin content. The dioecious hemp needs lower GDD values for maturating, its stems lignin content was higher than of monoecious hemp by harvest time and therefore this plant type is more suitable for briquetting in Nordic climatic conditions. Comparison of the different N treatments indicated that application of sewage sludge decreased the emergence and density of the fibre hemp plants and the lignin content per kg of DM.

Flowering Dynamics in Monoecious and Dioecious Hemp Genotypes

ABSTRACT Flowering is a crucial phase in hemp cultivation. It influences both stem and seed yield. A uniform and short flowering duration in hemp is desirable, because it favors uniform crop development. Moreover, flowering is often taken as a reference point for harvesting, and very long durations of flowering might mislead the operator in judging the proper time for mowing. In this article, a large dataset of flowering time and duration for different monoecious and dioecious varieties was studied and the effect of sowing time and genotype on flowering duration is discussed. Minimal flowering duration was observed when the time from emergence to flowering was short. This, was related however, to low yields. Dynamics of flowering was accurately described by a bi-logistic curve that indicates the presence of two underlying logistic processes.

First Report of Southern Blight Caused by Sclerotium rolfsii on Hemp (Cannabis sativa) in Sicily and Southern Italy.

Hemp (Cannabis sativa L.), family Cannabaceae, is an annual herbaceous plant that is 1.5 to 4.0 m tall and native to the Caucasus Region, northern India, and Iran. It is cultivated in warm to temperate regions worldwide for its fiber, oil, and psychoactive substances. In Europe, commercial plantings have decreased from 52,872 ha in 1989 to 18,716 ha in 2005. Recently however, cultivation of hemp as a natural fiber species has been encouraged by European Union policy (2). During the summer of 2003, patches of dead plants were observed in test plots of 12 monoecious and dioecious hemp cultivars (Beniko, Epsylon 68, Felina 34, Ferimon, Fedora 17, Futura 75, Bialobrzeskie, Dioica 88, Fibranova, Tiborszallasi, Lovrin, and Carmagnola) in an experimental field near Catania (eastern Sicily) previously planted to artichoke (Cynara scolymus L.). Plots were irrigated with a drip irrigation system. Symptoms were first detected in July with day/night temperatures between 35 and 26°C. Infected plants showed a dark brown-to-tan discoloration of the stem near the soil line. As disease progressed, the rot extended down to the crown and taproot, foliage became yellow, and the entire plant eventually collapsed. An extensive white, cottony mycelium and numerous spherical tan-to-dark brown sclerotia (0.5 to 4.0 mm in diameter) developed externally on infected tissues and soil. As much as 60% of the plants were affected in a single plot. Monoecious cultivars that had been planted earlier escaped the disease. Isolations from diseased tissues were performed by plating symptomatic tissues previously disinfected for 1 min in 1% NaOCl and rinsed in sterile water on acidified potato dextrose agar (pH 4.5). Isolations consistently yielded a fungus whose characters corresponded to Sclerotium rolfsii Sacc. (teleomorph Athelia rolfsii (Curzi) Tu & Kimbrough). Pathogenicity of two isolates obtained from infected plants was confirmed by inoculating 120-day-old hemp plants grown in individual pots. Twenty plants for each of the above listed cultivars (10 plants for each isolate) were inoculated by applying toothpick tips (5 mm) colonized by S. rolfsii to the lower part of the stem. Ten noninoculated plants served as controls. Plants were kept in a greenhouse with temperatures between 26 and 32°C and 95% relative humidity. High soil moisture was maintained with frequent watering. All inoculated plants showed blight and basal stem rot after 2 weeks, irrespective of the cultivar. By the third week, plants began to dry up and mycelium and sclerotia developed on the crown. Noninoculated controls remained symptomless. S. rolfsii was reisolated from inoculated plants. Although S. rolfsii has been reported on hemp in India since the 1930s (3), to our knowledge, this is the first report of southern blight caused by this fungus on C. sativa in Sicily and southern Italy. Residues of artichoke, a very susceptible host of S. rolfsii (1), might have been the source of inoculum for this outbreak on hemp. Most likely, high summer temperatures and overirrigation exacerbated the disease severity.

Application of AFLP for the detection of sex‐specific markers in hemp

AbstractTwo dioecious hemp accessions (Can18 and Can17) were tested by bulked segregant analysis for polymorphisms between male and female bulks with amplified fragment length polymorphisms. Thirty‐nine primer combinations were tested and 20 of these yielded one to three male‐specific bands. In contrast, no female‐specific band was detected. Eight of these primer combinations were used for testing 80 progeny plants from a cross between two plants from Can18 and 30 plants from Can17. A total of 16 and 17 male‐specific fragments were obtained for Can 18 and Can 17, respectively. Eleven fragments exhibited the same fragment size in both accessions. All male plants, but not one female plant, showed the respective polymorphic band with each of the eight primer combinations. Problems regarding sex determination under field conditions were successfully overcome by testing plants that had been grown in small pots in a greenhouse. The abundant number of potential markers for the male sex, their complete cosegregation with male plants and the absence of markers for the female sex support the presence of a male sex chromosome in hemp.

Comparison of bast fibre yield and mechanical fibre properties of hemp ( Cannabis sativa L.) cultivars

High stem yield and high bast fibre content in stem are generally accepted as important properties for fibre hemp ( Cannabis sativa L.) Quality demands for fibre used in the new non-woven products have not yet been defined. The Ukrainian monoecious fibre hemp cv. Uso 11 was compared with 13 other fibre hemp cultivars in 1995–1997 in Finland (latitude 60°49′ N). Stem yield, stem length, stem diameter, bast fibre content in stem, bast fibre yield, proportion of primary fibre in the bast fibre and primary fibre yield are reported, as well as breaking tenacity and elongation at break of the fibres. The average stem yield of cv. Uso 11 was 5947 kg dry matter ha −1 and only dioecious cvs. Kompolti Hybrid TC and Novosadski produced significantly higher yields. The bast fibre content in the stem of cv. Uso 11 averaged 21.7%, and four other cultivars, both mono- and dioecious ones, had significantly higher content. The proportion of primary fibre in the bast fibre of cv. Uso 11 averaged 91.0%, and cultivars with significantly lower primary fibre fraction were all dioecious. The average bast fibre and primary fibre yields of cv. Uso 11 were 1301 and 1188 kg dry matter ha −1, respectively. Only cv. Kompolti Hybrid TC produced significantly higher bast fibre and primary fibre yields. The median values for breaking tenacity and elongation at break of the fibres varied, depending on experimental year and cultivar, from 41 to 74 cN/tex and from 3.3 to 5.5%, respectively. The dioecious cultivars showed better or equivalent properties to cv. Uso 11. Because the season was too short for seed production, which is a prerequisite for obtaining the EU subsidy, dioecious hemp cultivars cannot be recommended for cultivation in Finland. However, monoecious Ukrainian cvs. Uso 11 and Uso 31 and Polish cvs. Beniko and Bialobrzeskie are suitable for the long-day growth conditions prevailing in Finland.

Identification of DNA markers linked to the male sex in dioecious hemp (Cannabis sativa L.)

A 400-bp RAPD marker generated by a primer of random decamer sequence has been found associated with the male sex phenotype in 14 dioecious cultivars and accessions of hemp (Cannabis sativa L.). The primer OPA8 generates a set of bands, most of which polymorphic among all the individual plants tested, and 1 of which, named OPA8400, present in all male plants and absent in female plants. A screening of 167 plants belonging to different genotypes for the association of the OPA8400 marker with the sex phenotype revealed that only in 3 cases was the 400-bp band was present in plants phenotypically female; on the contrary, in male plants the band was never missing, while in monoecious plants it was never present. Despite this sex-specific association, the sequences corresponding to OPA8400 were present in both staminate and carpellate plants, as revealed by Southern blotting and hybridization with the cloned RAPD band. The RAPD marker was sequenced, and specific primers were constructed. These primers generated, on the same genotypes used for RAPD analysis, a SCAR marker 390 bp in length and male-specific. This SCAR is suitable for a precise, early and rapid identification of male plants during breeding programs of dioecious and monoecious hemp.