Genetic diversity of highly productive bacurizeiro (Platonia insignis) mother trees: insights for domestication and genetic improvement of a native Amazonian fruit tree

Platonia insignis Mart. (bacuri) is a fruit tree species native to the Brazilian Amazon that holds considerable ecological and economic importance in the north and northeastern regions. Despite its high commercial potential, fruit production remains limited by self-incompatibility and incipient stage of domestication. In this context, molecular markers represent valuable tools for identifying superior genotypes within natural populations, supporting conservation strategies and genetic improvement programs. We evaluated the genetic diversity of high-yielding P. insignis mother trees from a natural population, from the municipality of Santa Rita, Maranhão State, Brazil. Genomic DNA was extracted from leaf tissue using a modified CTAB protocol. Ten inter-simple sequence repeat (ISSR) primers were used for PCR amplification. Amplified PCR products were separated by electrophoresis on 2% agarose gels, stained with ethidium bromide, and visualized under ultraviolet light. The banding patterns were scored as a binary matrix for subsequent analyses. Genetic diversity parameters, analysis of molecular variance (AMOVA), Mantel test, principal coordinates analysis (PCoA), and unweighted pair-group method with arithmetic mean (UPGMA) clustering were performed using GenAlEx v6.5 and RStudio softwares. Each ISSR primers produced 4-8 reproducible fragments, with 82.14% of the loci being polymorphic. Estimates of the observed number of alleles (Na = 1.82), effective number of alleles (Ne = 1.60), Shannon's information index (I = 0.48), and expected heterozygosity (He = 0.33) indicated high levels of genetic diversity within the population, consistent with those observed in outcrossing species. Nei's genetic distance ranged from 0.09 to 0.90, identifying genotype G13 as the most genetically divergent. PCoA analysis accounted for 33.3% of the total genetic variation, whereas UPGMA clustering grouped the genotypes into four distinct clusters, confirming the high level of genetic variability. The Mantel test revealed a significant positive correlation between genetic and geographic distances (r = 0.319, p < 0.01), providing evidence of isolation by distance within the population. Our results demonstrate that high-yielding mother trees constitute a valuable reservoir of genetic diversity for breeding programs. The highly divergent genotypes represent promising parental candidates for the genetic improvement programs of P. insignis. Furthermore, the significant relationship between genetic and geographic distances suggests that isolation by distance has played an important role in shaping the genetic structure of this natural population. The future integration of these molecular data with fruit morphometric traits will contribute to the identification of elite parental combinations that maximize both genetic divergence and agronomic performance. Overall, this study provides a scientific foundation for accelerate ‘bacurizeiro’ domestication, supporting the conservation of these important genetic resources.