Population Genetics Coupled Chemical Profiling for Conservation Implications of Decalepis salicifolia (Bedd. ex Hook.f.) Venter, an Endemic and Critically Endangered Species of Western Ghats, India

Estimation of genetic diversity and population genetic structure in Gymnema sylvestre (Retz.) R. Br. ex Schult. populations using DAMD and ISSR markers

BACKGROUND

Gymnema sylvestre (Retz.) R. Br. ex Schult. is a well-known medicinal plant against diabetes in India. There is as such no organized cultivation in India, and the plant is still being collected from the wild for their therapeutic uses. It is, therefore, important to estimate the genetic diversity and population genetic structure of G. sylvestre to ascertain the genetically diverse germplasm. The present study, therefore, was undertaken to analyze the genetic variability in 118 accessions belonging to 11 wild populations of G. sylvestre using directed amplification of minisatellite-region DNA (DAMD) and inter simple sequence repeats (ISSR).

RESULTS

The present genetic analyses of 11 populations with 25 markers (8 DAMD and 17 ISSR) revealed significant genetic diversity (H = 0.26, I = 0.40, PPL = 80.89%) at a species level, while the average genetic diversity at the population level was low. Among the 11 populations studied, PCH and UTK populations showed maximum genetic diversity, followed by KNR and AMB, while TEL population revealed the lowest genetic diversity. AMOVA and G_st values (0.18) revealed that most of the genetic variations are found within populations and very less among populations, and higher gene flow (N_m = 2.29) was found to be responsible for the genetic homogenization of the populations. The clustering pattern resulting from the UPGMA dendrogram was in congruence with STRUCTURE and PCoA, segregating all the 11 populations into two main genetic clusters: cluster I (populations of North and Central India) and cluster II (populations of South India). The clustering patterns obtained from all three statistical methods indicate that the genetic structure in G. sylvestre populations corresponds to the geographical diversity of the populations and represents a strong genetic structure.

CONCLUSION

The genetically diverse populations identified during the present study could be a potential genetic resource for further prospecting and conserving this important plant resource.

Adventitious root cultures of Decalepis salicifolia for the production of 2-hydroxy-4-methoxybenzaldehyde, a vanillin isomer flavor metabolite

Decalepis salicifolia (Bedd. ex. Hook.f.) Venter is a potential natural source of the vanillin isomer, 2-hydroxy-4-methoxybenzaldehyde (2H4MB), an aromatic compound. However, the utilization of the plant is hindered especially due to its critically endangered status and the root-specific accumulation of the compound. The use of in vitro culture techniques offers a sustainable means for the production of valuable metabolites. In this study, an efficient system was established for the production of 2H4MB in the adventitious root cultures of D. salicifolia. Leaf explants of in vitro grown plants produced on an average 4.33 ± 2.07 number of roots with root initiation frequency of 95.69 ± 3.74% in woody plant medium supplemented with 0.5 mg/L α-naphthalene acetic acid (NAA) and 1.0 mg/L kinetin (Kn). The adventitious root biomass accumulation of 10.61 ± 0.89 g fresh weight (FW) was obtained in woody plant liquid media containing 0.5 mg/L NAA and 0.3 mg/L indole-3-butyric acid (IBA) in 60 days of inoculation. Field-grown plants of the same age produced 0.30 ± 0.02 g FW, which was 35-fold lower than the adventitious root culture. The total production of 2H4MB in the same growth period was 4.9-fold higher in adventitious root culture (139.54 μg) as compared to field-grown plants (28.62 μg). Furthermore, sucrose concentration of 2% was favorable for biomass accumulation, whereas 5% was favorable for 2H4MB production. On the other hand, media pH 5.0 was suitable for biomass production and pH 7.0 was best suited for accumulation of 2H4MB. The adventitious roots also showed stable production of biomass and 2H4MB over 2 years. The established adventitious root culture system is suitable for further large-scale production of 2H4MB for flavor and fragrance industrial applications. KEY POINTS: • Biomass accumulation was higher in adventitious root cultures than in field-grown plants. • Manipulation of sucrose concentration and media pH led to increased 2H4MB production. • Adventitious roots showed stable biomass and 2H4MB production over 2 years.