Chiang Mai Journal of Science

Holy basil is a famous Thai culinary herb because of its distinctive aroma combined with great pharmaceutical properties. Essential oil is a key component that influences the aromatic scent as well as the therapeutic properties. Due to the increased demand for holy basil, farmers prefer to grow commercial cultivars, which may result in genetic diversity loss. The purpose of this study was to assess the genetic diversity of holy basil landraces and commercial cultivars in Thailand through morphological, biological, and molecular studies. Genetic analysis of 20 landraces and 5 commercial cultivars based on 70 polymorphic loci using SCoT, SRAP, and PBA markers revealed high level of polymorphism with PIC ranging within 0.25-0.44. The first two axes of PCoA explained 77.54% of observed variation. PCoA and UPGMA dendrogram revealed 2 diverse groups, each containing both landraces and commercial cultivars. The essential oil content of the population ranged from 0.04-0.21%. The genotypes with significantly highest essential oil content were found both in landraces (AN1, CB3, and BR1) and in commercial cultivars (JT2 and TS1). The antioxidant activity, leaf shape index and leaf area ranged within 10.44-21.03%, 1.50-2.23, and 7.11-16.70 cm², respectively. A moderate r=0.515 correlation between essential oil and antioxidant activity was observed. There was no association between marker loci and essential oil content in the evaluated population. These results reveal that the studied population is a valuable germplasm, and the genetic diversity status of holy basil germplasm in Thailand is not yet worrisome. However, a conservation strategy should be pursued to ensure the protection of the valuable germplasm.