In vitro propagation, lactucin quantification, and antibacterial activity of Indian lettuce (Lactuca indica L.)

Bal Kumari Oliya,Moon Young Kim,Suk-Ha Lee

doi:10.1007/s11627-021-10234-9

Abstract

Lactuca indica L. (Asteraceae), a wild lettuce, is used as a vegetable and in traditional medicine. This study aims to establish in vitro propagation protocol and evaluate lactucin and antibacterial property from in vitro and natural plant tissues. Leaf blades and petioles were cultured in vitro on Murashige and Skoog (MS) medium supplemented with various concentrations of 6-benzylaminopurine (BAP) and 1.2 mg L–1 indoleacetic acid (IAA). Leaf petioles and a lower BAP concentration (0.5 mg L–1) were optimal for direct shoot induction, while the leaf blade and a higher BAP (4 mg L–1) concentration performed best for callus induction. When the callus was subcultured, 98.7% of samples regenerated plants on MS medium supplemented with 1.5 mg L–1 BAP and 0.5 mg L–1 IAA. MS medium containing 1 mg L–1 IAA was best for in vitro rooting. A high-performance liquid chromatography analysis of the in vitro samples revealed a higher amount of lactucin (sesquiterpene lactones) in the root than the callus and the leaf, whereas in naturally grown plants, higher lactucin amounts were obtained from the juvenile root followed by the root of the flowering plant and juvenile leaf as the lowest concentration. All tissue extracts showed antibacterial activity against Pseudomonas fuscovaginae (a rice pathogen) and Escherichia coli, which was directly proportional to amount of lactucin produced. This in vitro regeneration and phytochemical investigation will facilitate the further exploitation of this useful wild plant.

Highlights

Lactuca indica L., popularly known as Indian lettuce, is a lactiferous medicinal herb in the Asteraceae
Investigation of the in vitro cultivation of Lactuca indica is still lacking; the objectives of this study are (1) to develop a protocol for in vitro propagation via direct and indirect organogenesis using leaf-blade and leaf-petiole explants; (2) to quantify the lactucin concentrations of in vitro–developed leaves, callus, and roots, and compare them with the quantities found in the roots, leaves, and stems of field-grown plants at the juvenile and flowering stages using high-performance liquid chromatography (HPLC); and (3) to compare the antibacterial performance of in vitro–grown tissue extracts with that of field-grown plant tissues collected at the juvenile and flowering stages
Among the various concentrations of BAP used in the Murashige and Skoog (MS) media, in combination with a constant concentration (1.2 mg L –1) of indoleacetic acid (IAA), 4.0 mg L–1 BAP was significantly more able to generate calluses on 72.0% explants of the total petiole cultured, followed by 2.0 mg L–1 BAP (55.0%), 1.0 mg L–1 BAP (25.0%), and 0.5 mg L–1 BAP (10.7%), respectively

Summary

Introduction

Lactuca indica L., popularly known as Indian lettuce, is a lactiferous medicinal herb in the Asteraceae. It is widely distributed across Asian countries, including the Republic of Korea, Indonesia, China, Japan, India, and Malaysia (Jeffrey 1966; Oliya et al 2018). The leaves of this plant have long been used in salads, soups, and fermented. In addition to its medicinal and therapeutic properties, Lactuca indica has a strong potential for breeding as a crop in its own right or as a possible candidate for improving the traits of cultivated lettuce (Lactuca sativa L.) (Kim et al 2012; van Treuren et al 2013; Lebeda et al 2014; Ha et al 2017; Oliya et al 2018)

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