Genetic diversity in wild populations of the restinga ecotype of the cashew (Anacardium occidentale) in coastal Piauí, Brazil

• Published in: Plant systematics and evolution Vol. 305; no. 10; pp. 913 - 924
• Main Authors: dos Santos, Juelina O., Mayo, Simon J., Bittencourt, Cleiton B., de Andrade, Ivanilza M.
• Format: Journal Article
• Language: English
• Published: Vienna Springer Science + Business Media 01-12-2019; Springer Vienna; Springer Nature B.V
• Subjects: Anacardiaceae; Anacardium occidentale; Bayesian analysis; Biomedical and Life Sciences; Domestication; Fruit trees; Gene flow; Genetic analysis; Genetic diversity; Heterogeneity; Life Sciences; ORIGINAL ARTICLE; Plant Anatomy/Development; Plant Ecology; Plant Sciences; Plant Systematics/Taxonomy/Biogeography; Population; Population genetics; Population studies; Populations; Primers; Systematics; Brazil; Cerrado Biome; Dune vegetation; Genetic variability; ISSR; Cajuizeiro; Caju; In situ conservation
• ISSN: 0378-2697; 1615-6110; 2199-6881
• DOI: 10.1007/s00606-019-01611-4

The cashew, Anacardium occidentale, is a globally important tropical fruit tree, but little is known about its natural infraspecific systematics. Wild Brazilian populations occur in the cerrado biome and coastal restinga vegetation. We investigated whether wild coastal and domesticated populations could be distinguished genetically using inter-simple repeat molecular markers (ISSRs). In total, 94 polymorphic loci from five primers were used to characterise genetic diversity, structure and differentiation in four wild restinga populations and four domesticated ones from eight localities in Piauí state (30 individuals per population). Genetic diversity was greater overall in wild (% P: 57.2%, I: 0.24, Hₑ: 0.15) than domesticated populations (% P: 49.5%, I: 0.19, H ₑ: 0.12). Significant structure was observed among the eight populations (between-population variance 22%, ΦPT = 0.217, P = 0.001), but only weak distinctions between wild and domesticated groups. Cluster and principal coordinate analyses showed marked genetic disparity in populations. No correlation of genetic and geographical interpopulation distance was found (Mantel test, r = 0.02032, P = 0.4436). Bayesian analysis found an eight-group optimal model (ΔK = 50.2, K = 8), which mostly corresponded to sampled populations. Wild populations show strong genetic heterogeneity within a small geographical area despite probable gene flow between them. Within-population genetic diversity of wild plants varied considerably and was lower where extractive activities by local people are most intense (Labino population). The study underlines the importance of wild populations as in situ genetic reserves and the urgent need for further studies to support their conservation.