Molecular characterization of cajá, Spondias mombin (Anacardiaceae), by RAPD markers

The arboreal species Spondias mombin L. (Anacardiaceae) is widely distributed in Brazil, where the fruits, known by the common name of caja, are an important commercial commodity. We evaluated genetic variability among 32 caja accessions of the Germplasm Collection of Embrapa Meio-Norte using RAPD technique. Reaction conditions for efficient RAPD amplifications were optimized in preliminary tests, and primers were selected from a set designed by the University of British Columbia on the basis of high levels of polymorphism and adequate band resolution. The 21 primers employed in the final analysis produced 145 fragments, 79% of which were polymorphic. Based on the RAPD data, a dendrogram was constructed using the unweighted pair group method with arithmetic mean clustering technique. The 32 caja accessions were classified into three main groups with a mean genetic similarity of 68.8%. Group I comprised 26 accessions (74.1% similarity), and group II included five accessions (74.0% similarity), while group III consisted of one accession (BGC 06), which exhibited the lowest similarity coefficients. Accessions BGC 06 and BGC 31 were the most unrelated and, hence, most suitable for initial crossings in order to obtain high levels of segregation. We concluded, based on the repeatability and reproducibility tests, that the RAPD technique is reliable and efficient for revealing the genetic diversity of caja accessions, which will be useful for genetic improvement programs.