Genetic diversity in a cajuí (Anacardium spp.) germplasm bank as determined by ISSR markers
Some species of Anacardium (Anacardiaceae) produce fruits and pseudofruits that are smaller than those of the common cashew (Anacardium occidentale) and, for this reason, are known collectively in Brazil as “cajuí”. Despite their economic value in the food market and their important environmental and ecological functions, cajuí trees remain underexploited. We employed nine inter-simple sequence repeat (ISSR) markers to characterize two presupposed populations of cajuí comprising 25 accessions maintained in the germplasm bank of Embrapa Meio-Norte (Teresina, PI, Brazil). Population structure and relationships between accessions were determined in order to generate knowledge that could contribute to genetic improvement programs and better management of this germplasm bank. A high degree of polymorphism (91.3%) was observed among the accessions. Analysis of molecular variance and Bayesian analysis demonstrated that the two presupposed populations were not genetically differentiated but constituted a single population containing highly diversified individuals including migrants, migrant descendants and possible hybrids. Nonetheless, genetic variability within the accessions could be organized into two distinct, but linked, groups that had undergone extensive exchange of genetic material, as verified by the high gene flow index ). The substantial genetic variability observed could be attributed to individual differences between accessions rather than to differential spatial distribution. This report enhances our knowledge of the genus Anacardium and should facilitate the future improvement of cajuí culture and fruit quality. In addition, our study highlights the importance of further taxonomic studies on the species of Anacardium that comprise cajuí.