Consumer preference, antibacterial activity and genetic diversity of ginger (Zingiber officinale Roscoe) cultivars grown in Sri Lanka

Abstract

Ginger is a medicinal plant and a valuable spice. The present study was conducted to assess the consumer preference, antibacterial activity and genetic diversity of local ginger in comparison to the Chinese and Rangoon ginger cultivars grown in Sri Lanka. The ginger samples were collected from five districts. The preferred colour, aroma and degree of pungency of rhizomes were recorded by employing a taste panel and the data were subjected to association analysis. The antibacterial activity of the ginger samples were tested against two model pathogens Escherichia coli (JM 109) and Staphylococcus aureus (NCTC 4838) using methanol extract of rhizomes using the paper disc method and measured as diameter of zone of inhibition (DZBI). The DNA extracts of the three cultivars were subjected to PCR, using DNA barcoding primers trnH-psbA, followed by DNA sequencing, alignment and cluster analyses. Two trnH-psbA sequences of Zingiber officinale and Curcuma longa (as out-group) available in GenBank were used for comparison. There were significant associations among ginger cultivars in colour, pungency and aroma. The highest preferred colour was observed in Chinese ginger and the highest degree of pungency and highest preferred aroma were observed in Local and Rangoon gingers. All ginger samples collected exhibited at least 6 mm of DZBI. E. coli was less affected by methanol extract compared to S. aureus. A clear PCR amplicon was obtained for all three gingers. Another second amplicon of lesser intensity was also observed for Chinese and Rangoon gingers. DNA sequencing helped to generate a clear sequence for local ginger but no sequences were obtained for Chinese and Rangoon gingers. This could be due to the presence of second amplicon that would have inhibited DNA sequencing. The DNA sequence based clustering revealed that local ginger is 0.8 % different from the two Z. officinale sequences available in GenBank implying that local ginger in Sri Lanka is genetically different.