Foliar Sprays of Silver Thiosulfate Produce Male Flowers on Female Hemp Plants

Abstract

<jats:p>Interest in hemp (<jats:italic>Cannabis sativa</jats:italic>) for its medicinal compounds, cannabidiol (CBD), and Δ-9-tetrahydrocannabidiol (THC), continues to increase. Maximizing yield of CBD and/or THC requires female plants because female inflorescences accumulate significantly greater concentrations of these compounds than male inflorescences. Production of all female seed requires induction of female plants to develop male flowers that produce genetically female pollen. Growers would like access to feminized seed to produce all-female crops. We evaluated the efficacy of 0, 0.3, and 3 m<jats:sc>m</jats:sc> silver thiosulfate (STS) applied as a foliar spray (on three occasions 7 days apart) to produce male flowers on four strains of female hemp (having a THC concentration of ≤0.3%), designated CBD hemp A, CBD hemp B, CBD hemp C, and industrial hemp. Silver thiosulfate at 3 m<jats:sc>m</jats:sc> was the most efficacious treatment for all strains. The majority of inflorescences had 100% male flowers at 3 m<jats:sc>m</jats:sc> STS, and terminal inflorescences had ≥95% conversion to male flowers. Silver thiosulfate at 0.3 m<jats:sc>m</jats:sc> produced partial conversion to male flowers, whereas most inflorescences had around 50% male flowers, except for CBD hemp A, which demonstrated greater levels of masculinization. At 0.3 m<jats:sc>m</jats:sc> STS, terminal inflorescences of CBD hemp A had 91% conversion to male flowers. This study demonstrates that male flowers can be produced easily and consistently on female plants through application of foliar sprays of STS under short-day conditions.</jats:p>

Hermaphroditism in Marijuana (Cannabis sativa L.) Inflorescences – Impact on Floral Morphology, Seed Formation, Progeny Sex Ratios, and Genetic Variation

“…Silver nitrate inhibits ethylene action in plants (Kumar et al, 2009) and was reported to increase male sex expression in marijuana, cucumber and gourd plants (Atsmon and Tabbak, 1979;Ram and Sett, 1982;Stankovic and Prodanovic, 2002). In a recent study, applications of silver thiosulfate induced male flower formation on genetically female hemp plants (Lubell and Brand, 2018). These findings demonstrate that changes in growth regulator levels in treated plants can impact hermaphroditic flower formation.…”

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

“…Beginning on 26 Sept. 2019, plants were provided short-day conditions of 12 h using a blackout curtain to initiate the flowering stage. Silver thiosulfate solution at a concentration of 3 mM was prepared according to Lubell and Brand (2018). Female plants were sprayed to runoff (400 mL/plant) on three occasions, 7 d apart, on 26 Sept., 3 Oct., and 10 Oct. 2019.…”

“…Female plants can be masculinized by treatment with silver nitrate or silver thiosulfate (STS). Lubell and Brand (2018) demonstrated that foliar sprays of STS at 0.3 to 3 mM concentrations are effective for inducing male flowers on female plants. They noted that pollen output for masculinized female plants may be reduced compared with pollen output from genetically male plants.…”

Development and validation of genetic markers for sex and cannabinoid chemotype in Cannabis sativa L.

“…Factors such as altered hormones (Lubell & Brand, ; Ram & Jaiswal, ), daylength (Schaffner, ), and autosomal genes (Faux, Berhin, Dauguet, & Bertin, ) have been shown to influence sex expression. Through manipulation of hormones, it is possible to create all‐female progeny using pollen produced by a female (XX) plant induced to produce male flowers and pollen (Lubell & Brand, ). From a commercial perspective, these so‐called ‘feminized’ seeds are generally more expensive to produce than normal dioecious seeds due to the additional work required for their production and the market demand for all‐female seed lots.…”