Recalcitrance of Cannabis sativa to de novo regeneration; a multi-genotype replication study

Cannabis sativa is relatively  recalcitrant to regeneration from somatic tissues, but several reports have been published demonstrating a response. Most reports show low levels of regeneration from somatic tissues, but a landmark publication by Lata et al. in 2010 reported regeneration from leaf explants with a 96% response rate, producing an average of 12.3 shoots per explant in a single, high-THC genotype.  Despite the importance regeneration plays in plant biotechnology this protocol has not been used in subsequent papers in the decade since it was published, raising the concern that it is not reproducible. Many researchers are looking to build research programmes in this growing field, and it is important that the reproducibility and robustness of single-genotype C. sativa regeneration protocols undergo multi-lab validations to ensure they are reproducible across the species.  Replication studies in this burgeoning field will help research groups avoid lost time and resources which arise from pursuing protocols that are not reproducible.  Here we test the replicability of this protocol across 10 drug-type C. sativa genotypes.   This protocol successfully induced callus in all 10 genotypes.  Callus size and appearance substantially differed among cultivars, with the most responsive genotype producing 6-fold more callus than the least responsive genotype.  However, the most successful shoot induction medium developed in the 2010 paper failed to induce regeneration in any of the cultivars tested, resulting in the eventual necrosis of the calli.    Based on this replication study, it is evident that the existing regeneration protocol is not robust and could not be replicated in any of the 10 genotypes tested.