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Cannabis sativa is cultivated for multiple uses including the production of cannabinoids. In developing improved production systems for high‐cannabinoid cultivars, scientists and cultivators must consider the optimization of complex and interacting sets of morphological, phenological, and biochemical traits, which have historically been shaped by natural and anthropogenic selection. Determining factors that modulate cannabinoid variation within and among genotypes is fundamental to developing efficient production systems and understanding the ecological significance of cannabinoids. Thirty‐two high‐cannabinoid hemp cultivars were characterized for traits including flowering date and shoot‐tip cannabinoid concentration. Additionally, a set of plant architecture traits, as well as wet, dry, and stripped inflorescence biomass were measured at harvest. One plant per plot was partitioned post‐harvest to quantify intra‐plant variation in inflorescence biomass production and cannabinoid concentration. Some cultivars showed intra‐plant variation in cannabinoid concentration, while many had a consistent concentration regardless of canopy position. There was both intra‐ and inter‐cultivar variation in architecture that correlated with intra‐plant distribution of inflorescence biomass, and concentration of cannabinoids sampled from various positions within a plant. These relationships among morphological and biochemical traits will inform future decisions by cultivators, regulators, and plant breeders. [ABSTRACT FROM AUTHOR]

Persistence is a critical trait for alfalfa (Medicago sativa L.), yet the genetics of this trait are poorly understood. Herein, we characterize an [F.sub.1] alfalfa population derived from the cross between the two cultivated alfalfa subpecies for persistence in three production seasons at Ames and Nashua, IA, and one production season at Ithaca, NY. Quantitative trait loci (QTLs) underlying persistence were mapped using this population utilizing single-marker analysis and interval mapping procedures. Both parental genomes (Medicago sativa subsp, falcata and M. sativa subsp, sativa) contributed marker alleles associated with persistence, suggesting that alleles from both subspecies have potential for marker-assisted selection. Although, linkage groups 1, 2, and 7 contained putative persistence QTLs, genotype x environment interaction and location-specific QTLs suggest location-specific genetic mechanisms for alfalfa persistence. Nevertheless, in some instances, the same QTLs were identified in different years at the same location. Quantitative trait loci on linkage groups (LGs) 1 and 2 were location-specific for the Ithaca and Ames locations, respectively. The majority of alleles on LG 7 associated with persistence also exhibited association with biomass production and suggest common genetic determinants for both traits. Of particular interest was the identification of simple sequence repeat allele al37288-1a1, which associated positively with persistence in each environment of the study.

Biomass production represents a fundamental biological process of both ecological and agricultural significance. The genetic basis of biomass production is unknown but asssumed to be complex. We developed a full sib, [F.sub.1] mapping population of autotetraploid Medicago sativa (alfalfa) derived from an intersubspecific cross that was known to produce heterosis for biomass production. We evaluated the population for biomass production over several years at three locations (Ames, IA, Nashua, IA, and Ithaca, NY) and concurrently developed a genetic linkage map using restriction fragment length polymorphism (RFLP) and simple sequence repeat (SSR) molecular markers. Transgressive segregants, many of which exhibited high levels of heterosis, were identified in each environment. Despite the complexities of mapping within autotetraploid populations, single-marker analysis of vailance identified 41 marker alleles, many on linkage groups 5 and 7, associated with biomass production in at least one of the sampling periods. Seven alleles were associated with biomass production in more than one of the sampling periods. Favorable alleles were contributed by both parents, one of which is from the M. sativa subsp. falcata germplasm. Thus, increased biomass production alleles can be gleaned from unadapted germplasm. Further, the positive quantitative trait locus (QTL) alleles from the parents are partially complementary, suggesting these loci may play a role in biomass production heterosis.

Genetic improvement of alfalfa (Medicago sativa L.) for increased pectin concentration, estimated by neutral detergent soluble fiber (NDSF), would improve the efficiency of utilization of its high protein and digestibility by ruminants. The objectives of this study were to: (i) estimate the realized direct response from one cycle of phenotypic selection for NDSF concentration; (ii) evaluate association of NDSF concentration with other forage quality traits, and; (iii) determine the impact of selection for NDSF concentration on in vitro dry matter digestibility (IVDMD) of alfalfa. Selection for NDSF was applied to five alfalfa populations from 1996 to 2000 and synthetic generation two seed was produced. Progress from selection for NDSF concentration was evaluated in plot trials for 2 or 3 yr at two locations near Ithaca, NY. Populations divergently selected for NDSF were 1.62 to 5.15 g [kg.sup.-1] of dry matter (DM) higher and 2.26 to 4.20 g [kg.sup.-1] DM lower, respectively, than their respective base populations. Neutral detergent soluble fiber concentration was negatively correlated with total cell wall concentration (CW), and proportions of neutral detergent fiber (NDF), cellulose, and lignin in the CW. A positive correlation existed between NDSF concentration and crude protein (CP) concentration and IVDMD. Populations bred for higher or lower NDSF concentration had 0.20 to 8.82 g [kg.sup.-1] DM higher IVDMD and 0.63 to 15.06 g [kg.sup.-1] DM lower IVDMD than their respective base populations. Selection for NDSF concentration and indirectly for CP, total CW concentration and composition, and IVDMD of alfalfa forage was successful., ALFALFA is the predominant forage source of protein for dairy cattle in temperate regions. High levels of soluble protein typically present in alfalfa exceed the capacity of rumen microbes to [...]

During wilting of alfalfa (Medicago sativa L.) before preservation as silage or hay, proteinases in plant cells hydrolyze soluble protein (SP) into nonprotein N (peptides and amino acids), thus decreasing postharvest quality of alfalfa. Our objectives were to compare (i) expected gain in SP concentration remaining in wilted, lyophilized alfalfa from direct selection with expected and actual gain from indirect selection for N concentration and (ii) phenotypic selection with half-sib (HS) progeny test for gain in both SP and N concentrations in wilted, lyophilized forage. In Exp. 1, heritabilities for SP and N concentrations in wilted, lyophilized alfalfa were estimated by parent-offspring regression and by HS progeny analysis. Samples of alfalfa forage from HS families and individual plants were wilted for 24 h, chopped, frozen, and lyophilized. Near-infrared reflectance spectroscopy (NIRS) was used to predict SP and N concentrations in samples. Heritability estimates for N concentration were moderate in magnitude (0.29 to 0.76), and those for SP concentration were low (-0.03 to 0.46). The expected gain in SP concentration was higher from selection for N concentration than from direct selection. In Exp. 2, two alfalfa populations previously selected for higher N concentration and two unselected cultivars were grown in sward plots. Unwilted forage had 25% (P is less than or equal to 0.01) higher SP concentration in 1987 than forage that had been wilted for 24 h and had 13% (P

Hemp (Cannabis sativa L.) is an emerging dioecious crop grown primarily for grain, fiber, and cannabinoids. There is good evidence for medicinal benefits of the most abundant cannabinoid in hemp, cannabidiol (CBD). For CBD production, female plants producing CBD but not tetrahydrocannabinol (THC) are desired. We developed and validated high‐throughput PACE (PCR Allele Competitive Extension) assays for C. sativa plant sex and cannabinoid chemotype. The sex assay was validated across a wide range of germplasm and resolved male plants from female and monoecious plants. The cannabinoid chemotype assay revealed segregation in hemp populations, and resolved plants producing predominantly THC, predominantly CBD, and roughly equal amounts of THC and CBD. Cultivar populations that were thought to be stabilized for CBD production were found to be segregating phenotypically and genotypically. Many plants predominantly producing CBD accumulated more than the current US legal limit of 0.3% THC by dry weight. These assays and data provide potentially useful tools for breeding and early selection of hemp. [ABSTRACT FROM AUTHOR]