Abstract
Knowledge of the natural genetic variation and structure in a species is important for developing appropriate conservation strategies. As genetic diversity analysis among and within populations of Plumbago zeylanica remains unknown, we aimed (i) to examine the patterns and levels of morphological and genetic variability within/among populations and ascertain whether these variations are dependent on geographical conditions; and (ii) to evaluate genetic differentiation and population structure within the species. A total of 130 individuals from 13 populations of P. zeylanica were collected, covering the entire distribution area of species across India. The genetic structure and variation within and among populations were evaluated using inter-simple sequence repeat (ISSR) and randomly amplified DNA polymorphism (RAPD) markers. High levels of genetic diversity and significantly high genetic differentiation were revealed by both the markers among all studied populations. High values of among-population genetic diversity were found, which accounted for 60 % of the total genetic variance. The estimators of genetic diversity were higher in northern and eastern populations than in southern and western populations indicating the possible loss of genetic diversity during the spread of this species to Southern India. Bayesian analysis, unweighted pair group method with arithmetic average cluster analysis and principal coordinates analysis all showed similar results. A significant isolation-by-distance pattern was revealed in P. zeylanica by ISSR (r = 0.413, P = 0.05) and RAPD (r = 0.279, P = 0.05) analysis. The results obtained suggest an urgent need for conservation of existing natural populations along with extensive domestication of this species for commercial purpose.
Highlights
An understanding of the patterns of genetic variation within and among populations of medicinal plants is essential for devising optimum genetic resource management strategies for their conservation, sustainable utilization and genetic improvements
We focused on large-scale population genetic analysis of P. zeylanica using randomly amplified DNA polymorphism (RAPD) and inter-simple sequence repeat (ISSR) markers to (i) evaluate the wide-range genetic structure of 13 populations selected to cover its distribution across India, (ii) infer relationship between latitude and the components of genetic variation in P. zeylanica populations, (iii) compare the population genetic structure in P. zeylanica populations using two dominant markers and (iv) provide necessary information for developing conservation strategies for this endangered medicinal shrub
This study provides a first report of broad survey of genetic variation in P. zeylanica along the latitudinal gradient in India
Summary
An understanding of the patterns of genetic variation within and among populations of medicinal plants is essential for devising optimum genetic resource management strategies for their conservation, sustainable utilization and genetic improvements. Natural populations of medicinal plant species are extensively exploited due to their heavy demands. In such cases, long-term survival as well as semi-domesticated nature of many medicinal plants depends on the maintenance of sufficient genetic variability within and among populations to accommodate new selection pressures exerted by continuous environmental changes (Barrett and Kohn 1991).
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