Characterization and germination dynamics of cannabis landraces across diverse environmental conditions.

Abstract

Cannabis sativa L. is globally esteemed for its diverse applications, yet historical legal barriers impeded research and industrial advancement. The pharmaceutical relevance of its cannabinoids drives recent regulatory relaxations. Nevertheless, delineating cultivars remains pivotal for optimizing cannabis products. Understanding the physiological intricacies of cannabis germination and seedling establishment, particularly for South African genotypes, remains limited. Therefore, this study aims to differentiate cannabis genotypes and explore seed germination and seedling development to enhance sustainable farming practices across diverse environmental conditions. Eleven cannabis genotypes were used, including landraces Ladysmith Ugwayi wesiZulu (‘L1’) and Iswazi (‘L2’), Durban Poison (‘H1’), Bergville Ugwayi wesiZulu (‘B1’), Natal (‘B2’) and Iswazi (‘B3’), and Msinga Ugwayi wesiZulu (‘M1’) and Iswazi (‘M2’), and the commercially available ‘Hemp’, ‘Cherry bubble gum’ (‘Highcannabidiol (CBD)’) and ‘White Rhino’ (‘High-9-tetrahydrocannabinol (THC)’) genotypes. Characterizing cannabis landraces involved assessing physical traits, mineral element composition and Short Tandem Repeats (STR) markers of the seeds. Pre-treatment effects on seed dormancy and germination were also evaluated, alongside the effect of temperature regimes, polyethylene glycol (PEG)-induced drought stress, accelerated aging, and sodium chloride (NaCl) salinity stress. The study revealed a strong positive correlation (p<0.001) among cannabis accessions based on STR markers, physical traits, and mineral profiling. However, clustering based on mineral composition varied from clustering based on physical traits, and STR markers produced different groupings, highlighting a complex relationship among these characteristics. As a result, the genotypes, especially the landraces, could not be classified as ‘High-CBD’, ‘High-THC’, or ‘Hemp’ based on the measured parameters. On the other hand, landraces and environment interactions generally exhibited significant differences (p<0.05) in germination characteristics, with sodium chloride (NaCl), and polyethylene glycol (PEG) levels generally impeding germination; however, tolerance varied among genotypes. ‘H1’, ‘L2’, and ‘B2’ are ideal for saline conditions, while ‘L2’, ‘B1’, ‘H1’, and ‘B3’ are recommended for farmers with limited water resources. Accelerated aging also significantly reduced germination performance in cannabis landraces, highlighting the importance of optimal storage for seed viability. Gibberellic acid (GA3), potassium nitrate (KNO3), and prechilling proved effective in enhancing germination and breaking physiological dormancy. Temperature also played a crucial role in cannabis germination percentage and germination rate, as well as biochemical composition. Genotypes ‘L1’, ‘B1’, ‘H1’, ‘B2’, and ‘M1’ demonstrated higher germination at cooler temperatures of 20/15 °C, while ‘B3’, ‘M2’, and ‘L2’ performed better under warmer conditions of 30/25 °C. However, higher temperatures were generally detrimental to the germination of cannabis landraces. Our findings reveal that genotype selection and optimal planting dates are sensitive to temperature variations and depend on genotype-specific traits and biochemical factors. These results highlight the importance of carefully considering these variables in cannabis cultivation practices. In summary, the study provides crucial information for genotype classification, helping licensed producers and plant breeders optimize genotype selection for medicinal cannabis and hemp, ensure regulatory compliance, and maximize yields. It details the physiological and biochemical processes in cannabis germination and seedling development, laying a foundation for future research, clinical studies, and production strategy optimization.