Comparison of self-pollination and intercrossing for feminized seed production in Thai Hang Kra Rok cannabis (Cannabis sativa L.) landrace

Abstract

Importance of the work: Often, growing 'Hang Kra Rok' cannabis conventional seeds results in unwanted male plants, which substantially reduce cultivation efficiency. Objectives: To compare self-pollination and intercrossing strategies for producing highquality feminized seeds using two distinct Thai landrace accessions. Materials and Methods: Female cuttings from Bangkok and Sakon Nakhon accessions were treated with 30 parts per million colloidal silver to induce male flowers. Selfed (S1) and hybrid (F1) progeny were produced via manual pollination. S1 and F1 progenies were produced and evaluated in a plant factory with artificial lighting (PFAL) system. Results: The S1 progeny (Self-BKK and Self-SKN) and the F1 hybrid (SKN×BKK) produced 100% female plants. In contrast, the F1 hybrid (BKK×SKN) produced a single hermaphroditic plant, accounting for 5.6% of the population. Regarding vegetative growth, the F1 progeny had significantly (p < 0.05) greater plant height than the S1 progeny. Furthermore, flowering onset in the F1 progeny was delayed by approximately 7 d. However, no significant differences were observed in dry inflorescence weights across all treatments. In terms of phytochemical quality, the S1 progeny from the Bangkok source (Self-BKK) had the highest average Δ9-tetrahydrocannabinol (THC) content (6.58%), while the cannabidiol content did not differ significantly among treatments. Main finding: Under controlled PFAL conditions, self-pollination was an effective strategy for maintaining sexual stability and achieving early flowering in these Thai cannabis landraces, without compromising yield or THC quality