Abstract Detail

Darwins' reversals: What we now know about Feralization and Crop Wild Relatives

Dabney, Clemon [1], Wenger, Jonathan [2], Talmo, Nick [1], Weiblen, George [3].

Insights from feral Cannabis on the history of cultivated fiber hemp.

Cannabis sativa L. was introduced to North America as a cultivated source of durable fiber dating from the 17th Century. Cannabis plants descended from cultivated fiber hemp are extensively naturalized throughout the midwestern United States. Recent legislation defines industrial hemp as different from drug-type Cannabis according to the quantity of tetrahydrocannabinol (THC) present in pistillate inflorescences. We investigated whether feral Cannabis meets the statutory definition of industrial hemp by measuring cannabinoid content and employing a genetic assay.
The cannabinoid profile can be classified according to the ratio of THC to cannabidiol (CBD) observed in three discrete classes, THC-type, intermediate-type, and CBD-type. We used a genetic model associating these three classes with functional and nonfunctional alleles of the cannabidiolic acid synthase gene (CBDAS) to investigate the diversity of cannabinoid profiles in feral populations. It is unknown whether contemporary feral Cannabis may have inherited THC-type genetics from historically cultivated fiber hemp or received THC-type genetics through gene flow from more recent drug cultivation.
Sampling over 1,000 individuals from ten feral populations in Minnesota, North Dakota, and South Dakota, we found each of the three THC:CBD ratio classes present in all populations. Plants exceeding the statutory threshold of 0.3% THC occured in frequencies ranging from one-in-ten to one-in-three plants. Intermediate plants in these feral populations occur in frequencies 10- to 20- times greater than THC-type plants, consistent with an allele for THC-type segregating at low frequency and near Hardy-Weinberg equilibrium. By genotyping 175 offspring of CBD-type pistillate plants, we inferred the frequency of THC-type pollen to match allele frequencies estimated from field genotypes. We genotyped herbarium specimens of feral Cannabis dating from the 1930s to 1990s for possible evidence of THC-type genetics predating contemporary drug cultivation. We found both THC-type and intermediate genotypes in feral Cannabis as far back as 1956.
These results suggest that the original introduction of cultivated fiber hemp to the midwestern United States may have included standing genetic diversity associated with the THC:CBD ratio. A major obstacle to using feral germplasm for industrial hemp breeding is the presence of THC-type alleles. Efforts to redomesticate North American fiber hemp cannot be fully realized until care is taken to identify and exclude THC-type genetics from breeding efforts and germplasm repositories.

1 - University of Minnesota, Plant & Microbial Biology, 140 Gortner Laboratory, 1479 Gortner Avenue, Saint Paul, MN, 55108, USA
2 - University Of Minnesota, Plant & Microbial Biology, 1479 Gortner Ave, 140 Gortner Lab, Saint Paul, MN, 55108, United States
3 - University Of Minnesota, Plant & Microbial Biology, 140 Gortner Laboratory, 1479 Gortner Avenue, St. Paul, MN, 55108, United States

Keywords:
Cannabis
feral
THC
CBD
hemp
allele
CAPS assay
PCR
assay
fiber
herbarium
breeding
germplasm.

Presentation Type: Colloquium Presentations
Session: C03, Darwins' reversals: What we now know about Feralization and Crop Wild Relatives
Location: /
Date: Tuesday, July 20th, 2021
Time: 10:30 AM(EDT)
Number: C03003
Abstract ID:750
Candidate for Awards:Margaret Menzel Award,Emanuel D. Rudolph Award