Without shattering,immature seeds would all fully mature,increasing yield by up to 15%.Thus,further domestication of non-shattering cultivars could greatly improve yield via a multifold mechanism,preventing harvesting loss and permitting all seeds to reach maturity.Seed traits that expand market options will also be valuable.For example,there has been little research investigating the differences in hemp seed flavors.Taste tests in our lab identified varieties with weak to strong flavors of hazelnut or walnut ,as well as one with a mild flavor.More work has been done on altering seed oil composition,although hemp seeds already possess valuable v-3 characteristics.Hemp seed oil is 85% polyunsaturated fatty acids with 60% and 24% being v-6 and v-3 fats,respectively.Further increases in v-3 fatty acid levels might foster the favorability of hemp seed for human and animal dietary needs.Overall,different tastes and oil compositions would expand the use of hemp seed in human and animal food products.Hemp stalks contain two key fractions,the bast fiber and hurd.To separate bast fibers from the inner hurd,the stalks must undergo a process called ‘retting’.Retting relies on the diverse microbial populations in the environment to break down pectin and other components that bind the fibers to the hurd tissue.Crop maturity at harvest,retting method,environmental conditions,as well as the nature of the bacterial and fungal populations,are factors that impact retting.Harvesting the crop at initiation of flowering improves fiber yield,strength,and quality.Continuing studies on the biodiversity,relationships,and functions of microbial communities will improve our understanding of the retting process and augment the consistency of obtaining high quality products.Retting methods,ebb and flow primarily dew- and water-retting,pose drawbacks,including inconsistent fiber strength and quality,and polluted wastewater,respectively.

Development of varieties having bast fiber with higher cellulose content as well as lower pectin and lignin cross-linkages may decrease the retting requirements,thus improving fiber strength and quality while saving time and labor.Hemp produces a diverse array of nonintoxicating phytocannabinoids,terpenes,and phenolic compounds with potential pharmaceutical values as drugs or supplements.The biosynthesis of terpenophenolic phytocannabinoids in Cannabis is well understood,albeit,several early steps in the pathway remain to be characterized.Understanding the regulation of phytocannabinoid biosynthesis is vital to development of varieties that are optimized for production of desirable metabolites while maintaining low levels of THC.Little is known about the endogenous and environmental regulation of phytocannabinoids.Abscisic acid,ethylene,and gibberellic acid modulate the production of phytocannabinoids.However;at present,factors controlling the epigenetic,transcriptional,and post-transcriptional regulation of phytocannabinoid biosynthesis remain uncharacterized.Hemp trichomes are classified into bulbous,capitate-sessile,capitate-stalked,and nonglandular types.Phytocannabinoid production and accumulation are localized to the capitate-stalked glandular trichomes.Increased production of phytocannabinoids in marijuana is,at least partially,due to the presence of larger glandular trichomes.Elucidating hormonal and other signaling cascades that regulate the development and size of specific types of hemp trichomes will also be important in maximizing phytocannabinoid production in hemp.The effects of agronomic practices and nutrients on phytocannabinoid production also need to be investigated.Anecdotal claims from marijuana growers suggest that pollination of Cannabis flowers lowers phytocannabinoid yield,consistent with decreases in essential oil levels.Further studies to evaluate this concern are essential to maximize the production of CBD and other desired phytocannabinoids.Germplasm collections are a fundamental source of genetic and phenotypic diversity for plant breeding and research.Currently,access to and utility of accession collections remain limited due to the lack of a core Cannabis germplasm collection.

As THC levels may limit germplasm utility in many regions,accessions with <0.3% THC should be used to form a hemp-only germplasm core collection.Establishment of a core collection encompassing the range of hemp genetic and phenotypic diversity would increase the utility of germplasm resources and be invaluable for breeding and genetic analyses.Comparisons of accessions present in existing collections are needed to help establish such a core collection.Similarly,centralized and curated collections of hemp mutants are not available.The development of mutant germplasm collections will provide a rich source of genetic variation for studying gene function and improved traits for breeding.Hemp is a dioecious plant with female and male hemp plants being valued differently depending upon the products.For phytocannabinoid production,a pure female population is most desirable.As a seed crop,a female predominant population,with a limited number of male plants for pollination,or a monoecious variety,is most desirable to maximize yield.For fiber production,males and females are both utilized,although males are preferred.Therefore,a major goal of hemp growers and breeders is to quickly and easily determine or manipulate the sex of plants,preferably prior to planting.Sex in hemp is genetically determined by a pair of heteromorphic sex chromosomes; females have an XX chromosome pair whereas males have XY.However,environmental conditions and phytohormones can affect sexual phenotype,suggesting other overriding regulatory mechanisms are involved in determining sex in hemp.Monoecious cultivars possess XX sex chromosomes,but they produce flower clusters with male flowers at the bottom and females towards the top of each inflorescence.Notably,male flowers occur as the plant transitions from rapid growth to flowering.In hemp,gibberellins are associated with plant masculinity and greater fiber number,length,and diameter.Thus,a concentration gradient of gibberellin and other hormones may dictate inflorescence sex.Genetic markers have been developed to differentiate sex in hemp plants; however,such a method is not viable for commercial plantings.Recently,quantitative trait loci were identified for sex expression in dioecious and monoecious hemp.

Cloning of the responsible genes from these QTLs will greatly improve our understanding of genetic control of sex in hemp.Identification of genes present on the sex chromosomes,especially outside the pseudoautosomal recombinant region,will be critical for understanding sex-linked traits.Continued development of molecular markers is needed to improve QTL mapping resolution and for marker-assisted selection of desirable traits in breeding programs.The organic food market is a key player in promoting hemp food and CBD products.As such,widespread public acceptance of transgenic hemp is unlikely.It also remains unknown whether the public will welcome hemp modified using gene-editing techniques,which lack non-plant or plant-pest DNA sequences.Thus,many improvements to hemp will probably be accomplished using traditional breeding methods.However; for research purposes,the development of applicable molecular biology techniques is imperative to further study the molecular mechanisms that determine important traits in hemp.Publication of a draft-quality Cannabis genome and other genetic studies have shed some light into the difference between marijuana and hemp.The Cannabis draft genomeAppendix Aiii has been compared with draft genome sequences of its closest relative common hop as well as more distant species including bread nut and mulberry.Recently,low coverage whole-genome sequencing and genotyping-by-sequencing have been performed on 54 and 325 distinct cultivars,respectively.However; with only raw data files available,the lack of websites with easy to-use graphical user interfaces for data analyses limits the utility of these draft-level genome sequences.Transcriptome assemblies are also available ,but are primarily targeted toward understanding phytocannabinoid metabolism.Comparison of marijuana and hemp indicates that the expression of phytocannabinoid biosynthetic genes is higher in marijuana,suggesting that transcriptional regulation of the pathway may be one factor controlling cannabinoid production.Recently,a transcriptome was generated for hemp bast fibers at different growth stages,providing insight into fiber development.The evolution of genetic differences between seed/oil,fiber,and dual-purpose cultivars is less studied.In-depth genetic comparisons of diverse seed/oil,fiber,and phytocannabinoid cultivars are needed to identify the specific genes and mechanisms controlling important yield traits.

To attain the full benefit of these and other studies across species,the genome sequence needs to be improved beyond draft quality,and websites with user-friendly graphical user interfaces must be developed.To characterize hemp gene functions,methods to manipulate gene expression are urgently needed.Protocols for developing transformed hairy roots and cell suspension cultures are available,but the utility of both methods is limited since neither tissue produces seed,fiber,or phytocannabinoids.A whole-plant regeneration protocol has been developed for marijuana,suggesting that the development of transgenic hemp plants is feasible.Virus-induced gene silencing methods would also prove useful for studying gene function,but thus far have been unsuccessful.Alternatively,isolation of mutants from chemical mutagenesis screens is possible,but extremely difficult due to the anemophilous and dioecious nature of hemp.Currently,exploitation of the natural genetic diversity present within hemp may be the most straightforward way to study gene functions.In the present study,salivary biomarkers for gastric ulceration in pigs were explored,and significant differences in oxylipin levels were observed between healthy pigs and pigs with gastric ulcers.The results suggest that reduced levels of oxylipins deriving from linoleic acid might function as biomarkers for gastric ulcers in pigs.The potential of oxylipins as biomarkers for early diagnosis of gastric ulceration and thereby as a tool to prevent severe gastric ulcer development would be relevant investigating.Moreover,hemp seed hulls might reduce the incidence of severe gastric ulcers in pigs.Ulceration of the stomach is a common disease in pig production worldwide and is associated with economic losses as well as animal health and welfare issues.Severe ulcers often lead to weight loss,and bleeding ulcers may lead to spontaneous death.Thus,prevention of gastric ulcers is important to improve animal production as well as animal health and welfare.The structure of the feed is known as a major risk factor for the development of gastric ulcers.Several studies have observed an association between fine-pelleted feed and incidences of gastric ulcers,presumably due to a more fluid stomach content,dry racks which increases the risk of the acidic chyme of the more distal regions coming in contact with the non-glandular part of the stomach.Thus,feeding ingredients with a high swelling capacity is expected to result in a more solid stomach content and thereby reduce the risk of developing gastric ulcers; however,there is a gap in knowledge regarding potential dietary treatments.Hemp is an old culture plant which is easy to cultivate and manage and is known as an important source of fibre as well as a medical product due to its high content of bio-active compounds with antioxidant properties.Different hemp feed products exist,including hemp seed cake and hemp seed hulls.Hemp seed cake is a by-product after oil extraction and has a high protein content as well as some fibre,whereas hemp seed hulls are the outer shell of the seed with a high fibre content.Studies indicate that hemp might protect the gastric mucosa by inhibition of gastric acid secretion through cannabinoid receptors in the gastrointestinal tract including the stomach.In addition,the potential swelling capacity of hemp seed hulls may result in a more solid stomach content.

Clinical diagnostics of gastric ulceration in pigs is difficult since gastric ulcers are often sub-clinical with only the most severe ulcers resulting in the development of clinical signs,such as anorexia,anaemia or sudden death.Therefore,an efficient non-invasive method is required to be able to detect early stages of gastric ulceration in pigs,allowing intervention with preventive measures,e.g.by regulating the particle size of the feed,to reduce the economic losses as well as animal health and welfare issues.Saliva is a bio-specimen that has received attention for detection of disease biomarkers,as it has shown to contain compounds that are associated with certain diseases.In addition,collection of saliva is simple and noninvasive.Salivary glands with high permeability are surrounded by capillaries allowing exchange of molecules.Hence,saliva contains a variety of locally synthesised compounds as well as systemic compounds that might act as biomarkers.Studies have indicated that several factors present in saliva protect the oesophagus,including epithelial growth factors,mucins and prostaglandins.The maintenance of oesophageal health is to a large degree dependent on saliva ,indicating that saliva might be a potential biospecimen for identifying possible biomarkers that reflect the health status of the upper part of the gastrointestinal tract,including pars oesophagea.Since gastric ulcers in pigs are mostly located in the region of pars oesophagea,saliva might contain metabolites that indicate the presence of gastric ulcers.Non-targeted metabolomics is an analytical technique used to study a wide range of small molecules in biospecimens,making it possible to discover metabolites that discriminate across phenotypes,including health status.In this study,the saliva metabolome was explored for potential biomarkers associated with the presence of gastric ulceration in pigs.In addition,the effect of hemp on the incidence of gastric ulcers was examined.It is hypothesised that saliva contains metabolites that can be used as biomarkers for gastric ulceration.Furthermore,it is hypothesised that hemp seed cake and hemp seed hulls reduce the incidence of gastric ulcers via anti-inflammatory effects and by conferring more solidness to the gastric content,respectively.The pigs were provided dry feed ad libitum in single-space feeders and were offered the experimental diets from approximately 30 kg BW and until slaughter weight.One dry-feed dispenser with water supply and one drinking trough were available per pen.All pigs had permanent free access to water.Four experimental diets were formulated: meal feed without addition of hemp seed products ; pelleted feed without addition of hemp seed products ; pelleted feed added 4% hemp seed cake ; pelleted feed added 4% hemp seed hulls.Ingredient composition of the experimental diets is shown in Table 1.