Germination response of South African cannabis landraces to accelerated aging: Implications for seed storage

Abstract

This study investigated the impact of accelerated aging on seed germination in five South African cannabis landraces: Ladysmith Ugwayi wesiZulu (‘L1’) and Iswazi (‘L2’), Bergville Natal (‘B2’) and Ugwayi wesiZulu (‘B1’), and Msinga Ugwayi wesiZulu (M1). Seeds were subjected to aging at 42 °C for 0 (control), 24, 48, 72, 96, and 120 h. Seed viability assessed using a tetrazolium chloride (TTC) test, electrolyte conductivity, pH, and water activity were measured over five days. Germination tests were conducted at 30/25 °C in Petri dishes in the laboratory and validated in a greenhouse, with daily recording of germination percentage (GP), germination rate index (GRI), and coefficient of velocity of germination (CVG). Accelerated aging significantly (p < 0.05) reduced seed viability, GP, GRI, and CVG while increasing electrolyte leakage and water activity. Landrace responses varied with ‘B1’ having maintained the highest viability (100 % unaged, 94.41 % after 120 h), whereas ‘M1’ showed the lowest (70.63 % after aging). Electrolyte conductivity was highest in ‘M1’ (393.2 μS cm⁻¹ g⁻¹ after 120 h), while ‘L2’ exhibited the highest water activity (0.724 after 120 h). Germination declined significantly under prolonged aging, with ‘L2’ and ‘B2’ exhibiting over 50 % reductions in GP. The findings demonstrate that accelerated aging impairs seed quality through electrolyte leakage and moisture uptake demonstrated by water activity, with landrace-dependent sensitivity. These results emphasize the need for controlled storage to preserve cannabis seed viability and germination performance, particularly under conditions of elevated temperature and humidity common to many smallholder farming systems.