Classification of Cannabis Plants Grown in Northern Thailand using Physico-Chemical Properties

Abstract

The Thai government has recognized that hemp may make useful contributions to the economy as an alternative crop.  This study was conducted to provide information in both chemical and physical characters of Thai-grown cannabis for breeders to discriminate their phenotypes and accessions in order to select the low intoxicant with high fiber producing cultivars.  The cannabinoids on the basis of THC, CBD and CBN content of 750 plants from eight accessions derived from five local cannabis cultivars were analyzed individually and their morphological features were also determined.  According to the individual plants belonging to the same accessions showing distinct THC/CBD ratios were classified into different phenotypes, it is impossible to classify only single plant for defining the phenotype or determine cannabinoids content on the single analysis.  THC content is found to correlate negatively to their physical characters such as plant height, stem diameter and fiber weight.  Principal component analysis showed that the fiber weight, cork weight and stem diameter of the plant as well as chemical features such a THC content, CBD content, THC/CBD ratio and log10(THC/CBD ratio) explained most of the total variation which could distinguish accession and phenotype of the cannabis plants.  Stepwise discriminant analysis confirmed that cannabinoids and some physical properties could be used to classify the phenotype of cannabis plants into drug, intermediate and fiber types as well, whereas the accessions of cannabis could not be discriminated clearly by using only their physico-chemical parameters.  The genetic characteristics which affect the chemical patterns and morphological traits among cannabis accessions grown in northern Thailand should be considerable to investigate in further study.

Keywords: classification, cannabis plant, northern Thailand, physico-chemical properties, discriminant analysis, principal component analysis