Diversity and genetic structure in a mini-garden of Dalbergia nigra: A tree threatened with extinction in the Atlantic Forest

Abstract

Maintaining genetic variability within rare or threatened species is essential for the development of conservation and restoration strategies. Therefore, the objective of this study was to characterize the diversity and genetic structure in Dalbergia nigra mini-garden. DNA samples from 90 individuals of D. nigra originated from seeds collected in Linhares-ES and Viçosa-MG were analyzed using Inter Simple Squence Repeat (ISSR) markers. For this, eleven primers were selected, which generated 180 fragments (70.76% polymorphism). The polymorphic information content (PIC) for the markers used averaged 0.38, considering them as moderately informative. The number of ISSR fragments to obtain desired precision in genetic diversity analyses was shown to be 122 polymorphic fragments, which was attained by examining 11 ISSR markers with clear amplification patterns. It was observed that for the origin of Linhares the number of alleles observed (Ao) was 1.99 and the number of effective alleles (Ae) was 1.60. For the origin of Viçosa, the values of Ao and Ae were 1.92 and 1.57, respectively. High genetic diversity was found with parameters Shannon index (I* = 0.5538) and genetic diversity of Nei (H* = 0.3742) for all populations sampled; from Viçosa, these parameters were 0.4963 and 0.3334, respectively, and from Linhares, they were 0.5328 and 0.3563. In the graphic representation of genetic distances, 10 groups were formed, three of them with only one genotype in each group. Among the individuals from Viçosa, the presence of five groups was revealed, one of which was isolated. For comparisons between individuals from Linhares, grouping by the Unweighted Pair Group Method with Arithmetic mean (UPGMA) method revealed seven groups, two of which contained only one individual. Molecular variance analysis (AMOVA) for D. nigra populations indicated moderate genetic differentiation (ΦST = 0.118). The ΔK statistic corroborates the analysis of the structure, indicating the convergence of two Bayesian groups (K = 2). The ISSR markers were efficient in detecting genetic diversity in D. nigra. The populations of D. nigra present moderate genetic differentiation, with the highest proportion of genetic diversity within the populations. Mini-stumps have high diversity and, therefore, have the potential to be used as matrices for the collection of propagules in the production of seedlings for conservation purposes.