Pollen Appearance and In Vitro Germination Varies for Five Strains of Female Hemp Masculinized Using Silver Thiosulfate

Abstract

<jats:p>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.</jats:p>

Characteristics of the Diploid, Triploid, and Tetraploid Versions of a Cannabigerol-Dominant F1 Hybrid Industrial Hemp Cultivar, Cannabis sativa ‘Stem Cell CBG’

“…A final future area of investigation may be into the use of true male pollen in testing the sterility of the triploid C. sativa plants. Previous research has indicated that the pollen from reversed female C. sativa plants is frequently less viable than the pollen from true genetic males [ 38 ]. Since pollen from true males is a contaminant problem from fiber and grain crops, these additional experiments are warranted to ensure that triploid plants will maintain their sterility in field conditions.…”

Production of Feminized Seeds of High CBD Cannabis sativa L. by Manipulation of Sex Expression and Its Application to Breeding

“…Comparison of pollen from naturally male hemp plants and masculinized female ones showed that the latter produce a significantly higher number of irregular or misshapen pollen grains that are inefficient in dispersal from anthers and had a lower germination rate ( DiMatteo et al, 2020 ). In our study, a comparison between pollen from masculinized female plants and male plants was not possible, because the medical breeding populations contained exclusively female plants.…”

“…To the best of our knowledge, this is the first comprehensive scientific report on the induction of fertile male flowers on female plants of medical cannabis ( Cannabis sativa L.). Previous reports on gender manipulation in cannabis were performed on fiber-hemp genotypes ( Ram and Sett, 1982 ; Lubell and Brand, 2018 ; DiMatteo et al, 2020 ), while methods for medical cannabis have been shared among growers for years, but the information was not obtained in a manner based on scientific methodologies.…”

“…There is no quantitative evidence of the success of the method used. More recently, two other studies have also successfully used STS to induce male flowers: DiMatteo et al (2020) sprayed 3 mM of STS until runoff three times at 7-day intervals after exposing the plants to short-day conditions for 12 h. Adal et al (2021) applied 20 ml of STS (2.5 μg/ml) to whole plants on the first and third day after the start of 12-h lighting and fertilization on a foliar basis. However, these studies aimed to investigate some other aspects of male sex induction in cannabis rather than the establishment of the sex induction protocol, so no detailed data on the success of the sex reversal were presented.…”

“…Upon germination, the latter produce entirely female progeny that is used for the production of female flowers. Most cannabis sex manipulation studies are performed on fiber-type hemp ( Ram and Sett, 1982 ; Lubell and Brand, 2018 ; DiMatteo et al, 2020 ), and knowledge about the efficiency of various exogenous factors and application methods for inducing sex conversion in medical cannabis is needed.…”