Cannabis ( Cannabis sativa ) grown for flowers containing cannabinoids requires all female plants, which are susceptible to seed set from exposure to pollen. Created triploids demonstrated reduced seed production compared with diploids in field and greenhouse studies in which plants were challenged with pollen from males. In the field, seed production as a percent of floral biomass ranged from 6.7% to 18.0% for triploids and from 52.6% to 57.1% for diploids. The photoperiod-insensitive triploid genotype ‘Purple Star’ × ‘Wilhelmina’ had 98.5% fewer filled (containing a developed embryo) seeds than the photoperiod-insensitive diploid genotype ‘Tsunami’ × ‘Wilhelmina’. In the greenhouse, triploid ‘Wife’ had 99.5% fewer filled seeds than diploid ‘Wife’. Plant growth and flower production were similar with eight triploid and seven diploid genotypes evaluated over three greenhouse studies. There were a few superior triploid and diploid genotypes; however, their performance was more likely attributable to the parental cultivar combination than ploidy level. The optimal cross direction for producing triploid seed in large quantities is tetraploid × diploid because the diploid × tetraploid cross exhibits triploid block caused by endosperm paternal excess. Colchicine-induced tetraploid parent plants should be tested over a prolonged period to eliminate cryptic chimeral mixoploids or tetraploid plants should be derived from seed produced by crossing two colchicine-induced putative tetraploid plants to ensure that seeds from tetraploid × diploid crosses will be triploid. The latter approach is necessary for photoperiod-insensitive cultivars because a prolonged period of ploidy testing is not possible for these plants. These findings indicate that triploid plants have significantly reduced fertility and are a suitable alternative to diploids in situations in which pollen exposure is possible.
Feminized hemp seed producers often use selfing to maintain a strain name; however, selfing may lead to inferior plants for cannabidiol (CBD) production. Using three different hemp strains as parents [Candida (CD-1), Dinamed CBD, and Abacus], two outcrosses [Candida (CD-1) × Abacus and Dinamed CBD × Candida (CD-1)] and one self-cross [Candida (CD-1) × Candida (CD-1)] were conducted to produce feminized seed. Progeny from the self-cross were significantly smaller and had less yield than outcrossed progeny. Selfed progeny were variegated and highly variable for total dry weight and floral dry weight. Discriminant analysis of principal components (DAPC) using amplified fragment length polymorphism (AFLP) separated the three progeny populations and showed that outcrossed populations clustered closer to the maternal parent, possibly the result of a maternal effect. Analysis of molecular variance (AMOVA) indicated that most variation (74.5%) was within populations, because the progeny from all three populations are half-siblings of each other. The selfed progeny population had lower expected heterozygosity (H e = 0.085) than each of the outcrossed progeny populations (H e ≈ 0.10). These results suggest that selfed progeny may demonstrate inbreeding depression resulting from enhanced expression of homozygous recessive traits. It may be beneficial for feminized seed producers to use outcrossing instead of selfing to generate feminized seed for CBD production.
Genetically female seed is sought for cannabidiol (CBD) hemp production because CBD is extracted from the flowers of female hemp plants. The production of all female seed requires masculinization of female plants to produce genetically female pollen that reliably generates female seed. Of the five female hemp genotypes that we masculinized using foliar sprays of silver thiosulfate (Abacus, Cherry Wine, Mountain Mango, Youngsim10, Wife), all genotypes produced fewer large and more irregular or misshapen pollen grains than genetically male plants. The masculinized female genotypes Wife and Cherry Wine produced pollen with germination rates similar to those of the male genotype Kentucky Sunshine. Female hemp genotypes vary in their ability to produce usable pollen that disperses well, is easily collected, and germinates as well as pollen from genetically male hemp plants.
There is demand for micropropagated Cannabis sativa liner plants, because they are uniform, vigorous, and pathogen free; however, availability is limited because of challenges with in vitro culture decline and ex vitro rooting. Ex vitro rooting success of microcuttings was evaluated for ‘Abacus’ and ‘Wife’ when cultures were 6, 9, 12, 15, and 18 weeks old from initiation. Microcuttings of ‘Wife’ harvested from 6, 9, and 12-week-old cultures rooted at or above 80%, but rooting declined to 50% and 30% for 15- and 18-week-old cultures, respectively. Rooting for ‘Abacus’ remained relatively constant between 47% and 70% for microcuttings harvested from 6- to 18-week-old cultures. ‘Wife’ plants grown from microcuttings, stem cuttings, and retip cuttings (cuttings taken from new shoots on recently micropropagated plants) had equivalent total shoot length, number of shoots, and flower dry weight, whereas micropropagated ‘Abacus’ plants had less shoot length and flower dry weight than plants from stem cuttings. However, when micropropagated ‘Abacus’ plants were provided an extra week of vegetative growth to reach an initial size equivalent to stem and retip plants, all plants performed the same. Propagation method did not change cannabinoid content for both ‘Abacus’ and ‘Wife’. Retip cuttings of ‘Abacus’ and ‘Wife’ rooted at 76% to 81% without rooting hormone, which is comparable to rates reported for stem cuttings of C. sativa treated with rooting hormone. Propagators should consider retipping to expand their liner production, because retips root well and possess the same desirable attributes as micropropagated plants.
Myrica gale (sweetgale) is a cold hardy (USDA hardiness zone 2) plant native to the northern latitudes of the northern hemisphere. In North America, the native range is from the northeastern United States west to the Great Lake states, and in the Pacific Northwest north to Alaska (U.S. Department of Agriculture–Natural Resources Conservation Service, 2021). A small population was reported in one county of North Carolina, but its continued existence is questioned beyond 2018 (LeGrand et al., 2021). Myrica gale is also native throughout Canada, Russia, Japan, North Korea, and northern Europe. It
Micropropagation of hemp ( Cannabis sativa ) is constrained by problems with hyperhydricity and culture decline of microshoots. These problems can be reduced by increasing agar and nutrients in the media during micropropagation stages 1 and 2, respectfully. Performance of microshoots of ‘Abacus’ and ‘Wife’ hemp cultured in Driver and Kuniyuki Walnut medium (DKW) for 15 weeks (6 weeks of stage 1 + 9 weeks of stage 2), with subculturing every 3 weeks during both stages 1 and 2, or in Murashige and Skoog with vitamins medium (MS) for 6 weeks (stage 1) followed by Lubell-Brand Cannabis medium (LBC) for 9 weeks (stage 2), with subculturing every 3 weeks during both stages 1 and 2, was evaluated. In a separate study, microshoot performance of ‘Abacus’ and ‘Wife’ in MS for 3 weeks (stage 1) followed by LBC for 6 weeks (stage 2), with subculturing every 3 weeks, using boxes (Magenta GA-7) with lids featuring a vent with a diameter of 10 mm and a pore size of 0.2 µM or using microboxes (Sac O 2 O95/114 + OD95) with lids featuring a filter (Sac O 2 #10) were evaluated. Shoot multiplication rate (SMR) and explant height were greater for ‘Abacus’ in LBC than DKW. For ‘Wife’, SMR at 9 weeks was greater in LBC, as LBC provided more nutrients and water than cultures had received in MS initially during stage 1. Culture medium did not influence ex vitro rooting success, which was 75% for ‘Abacus’ and ≥ 90% for ‘Wife’. Microboxes resulted in greater hyperhydricity of shoots and a lower ex vitro rooting percentage than boxes. For cultivars that are highly prone to developing hyperhydricity, like ‘Abacus’, the microboxes were not adequate to control this condition.
Aroniaberry ( Aronia mitschurinii ) produces small pome fruits that possess health promoting compounds. Management practices for orchards are lacking, since aroniaberry is a relatively new crop. Pruning is an important cultural practice to optimize fruit yield in orchards. The response of an established aroniaberry orchard to pruning was evaluated over three years (2020 to 2022). Pruning treatments were as follows: 1) renewal pruning (removal of shoots to the base) only in year 1; 2) renewal pruning in year 1 + thinning to 18 shoots in year 2; 3) renewal pruning in year 1 + thinning to 9 shoots in year 2; and 4) no-pruning (control). In response to renewal pruning, plants grew uniformly and vigorously, producing 28 new vegetative primary shoots with an average length of 66 cm by the end of the first growing season. Limited flowering and fruiting occurred in the second season for plants receiving pruning treatments. Fruit yield on pruned plants was significantly less than for unpruned controls. In season 2, increased thinning of renewal-pruned plants negatively affected the number of inflorescences per plant, but positively affected individual fruit fresh weight and fruit °Brix:titratable acidity ratios. Fruits from all treatments had similar monomeric anthocyanins, total phenolics and mineral content. In season 3, flower production and predicted fruit yield from pruned plants and unpruned controls were similar, even though pruned plants were substantially smaller. In the third season, there were no longer any differences between renewed + thinned plants and those that received only renewal pruning, making shoot thinning an unnecessary practice. The results of this study demonstrate that renewal pruning can be an effective way to manage and rejuvenate an aging aroniaberry orchard.
There is demand for early-flowering cannabis ( Cannabis sativa ) cultivars to hasten harvest and avoid late-season detrimental weather conditions. A field study and greenhouse studies were conducted to evaluate the effect of gene dosage at the autoflowering locus on flowering timing for diploid and triploid hybrids between autoflowering and photoperiod-sensitive parents. Autoflowering × photoperiod-sensitive hybrids were all photoperiod sensitive, but their critical photoperiods were longer than for homozygous photoperiod-sensitive plants, which resulted in earlier flowering. For triploid genotypes, decreasing dosage of the photoperiod-sensitive allele (A), from AAA to AAa to Aaa, reduced the time to flowering. Flowering timing for the diploid genotype Aa was intermediate between Aaa and AAa. These results provide evidence of incomplete dominance of the A allele at the autoflowering locus. Plants of genotype Aaa flowered 32 to 40 days earlier in the field than genotypes of AA, 15 days earlier than genotype Aa, and were ready for harvest by the second week of August in Connecticut. Plants of Aaa were as tall as other diploid and triploid photoperiod-sensitive genotypes studied, which suggests that they have similar yield potential. The use of tetraploid autoflowering (aaaa) maternal plants in combination with diploid photoperiod-sensitive (AA) pollen parents to produce Aaa genotype seed is a reliable approach for developing early-flowering cultivars of cannabis for flower production purposes.
landscape adaptability, low-maintenance plant Comptonia peregrina is typically 60 to 120 cm tall and produces leaves that are 5 to 12 cm long and 1.2 to 2.5 cm wide (Dirr, 2011).Comptonia peregrina 'Blue Sea' (PP) exhibits a more compact, dense, and uniform habit than is typical for the species.It produces uniformly dark-green foliage with a blue cast (Fig. 1A).The leaves are narrower and finer in texture than the wild C. peregrina (Fig. 1B).'Blue Sea' is like the wild plants in that its foliage produces a sweet fragrance, most noticeably on warm, sunny days.These characteristics make 'Blue Sea' more desirable than the straight species for the nursery industry, which is seeking cultivars of North American native species for the ornamental landscape plant market.C. peregrina is native to eastern North America from Nova Scotia to North Carolina, western South Carolina and northern Georgia, and west to Saskatchewan, Minnesota, Illinois, and Tennessee (Hightshoe, 1988).Plants are cold hardy to the U.S. Department of Agriculture's hardiness zone 4. The shrub is valued for its ability to grow in dry, sandy, and infertile soils with full-sun exposure (Dirr, 2011).In the wild, it occupies dry coniferous woods, exposed gravelly slopes, abandoned pastures, barrens, road cuts, highway embankments, and cut-over forested land (Hightshoe, 1988).C. peregrina can fix nitrogen and form nodules in association with an Actinomycete fungus (Dirr, 2011).
Northern bayberry [ Morella (formerly Myrica ) pensylvanica ] is an attractive, adaptable, semievergreen, northeastern North American native shrub that is sought for landscaping but difficult to propagate clonally. The impact of timing (June, July, or August) and concentration of indole-3-butyric acid [IBA (0, 2000, 4000 or 8000 ppm)] on propagation by stem cuttings was evaluated for genotypes of northern bayberry including the female cultivars Bobzam (Bobbee™) and UConn Compact and an unnamed male. Medium formulation and cytokinin type were evaluated for micropropagation of ‘Bobzam’ and ‘UConn Compact’. Stem cuttings of ‘Bobzam’ and ‘UConn Compact’ rooted poorly (at ≤55% and ≤20%, respectively) at all timings and concentrations of IBA; however, rooting success of ≥85% was achieved for the unnamed male genotype when cuttings were taken in June. Micropropagation of ‘Bobzam’ was successful using Woody Plant medium with 4 mg·L −1 zeatin and explants taken from shoots that had expanded 12 to 18 cm on containerized stock plants. Initiated explants of ‘Bobzam’ required eight subcultures before they began to produce shoots consistently at a 2× multiplication rate and eventually reached a 3× multiplication rate. Micropropagation attempts using Murashige and Skoog medium, the cytokinins 6-benzylaminopurine, meta-topolin, and thidiazuron, or the cultivar ‘UConn Compact’ were unsuccessful. Microshoots of ‘Bobzam’ rooted at ≥80% either by in vitro prerooting or ex vitro rooting directly in trays. Rooted microcuttings easily acclimated to greenhouse conditions and grew rapidly when potted to 1.04-L containers and then into 5.68-L containers. The micropropagation protocol developed for ‘Bobzam’ can be used by propagators to expand production of this popular female cultivar.
