Genetic diversity and structure of an active germplasm collection of Annona squamosa L.

Abstract

The fruits of Annona squamosa L. are highly appreciated for their sweet taste and their nutritional and medicinal properties. Since the species is threatened by habitat loss, germplasm conservation is of the utmost importance. The present study aimed to characterize genetic variability among 19 accessions of A. squamosa maintained in the Active Germplasm Bank (AGB) of Embrapa Meio-Norte, Teresina, Piauí, Brazil, and to determine whether the geographical distribution of the genotypes influenced population structure. The accessions were derived from populations originally located in orchards situated some 200 km apart in three municipalities in the northeast of Brazil, namely Timon, Bom Jesus and Canto do Buriti. Leaf DNA was extracted and analyzed by inter simple sequence repeat (ISSR)-polymerase chain reaction. Nine ISSR primers generated 127 scorable bands of which 101 (79.52%) were polymorphic. The within-population diversity was high (Canto do Buriti), intermediary (Timon) and low (Bom Jesus). Unweighted pair-group method with arithmetic averages and Bayesian analysis of polymorphic bands separated the genotypes into two main clusters according to genetic distance and ancestry (vegetative- and seed-propagated groups), indicating that the geographical location of the populations did not influence the genetic diversity of the accessions. While ISSR marker-based DNA fingerprinting of the 19 studied accessions revealed a degree of genetic diversity between populations, the variability detected within each population was somewhat higher. This information will contribute to a better understanding of genetic variation and population structure of the accessions of A. squamosa in the AGB of Embrapa Meio-Norte, and provide crucial information for future conservation and genetic improvement programs of the species.