Molecular characterization of Platonia insignis Mart. ("bacurizeiro") using inter simple sequence repeat (ISSR) markers.

Platonia insignis Mart. (Clusiaceae) is widespread throughout the Amazon and adjacent areas. The fruits (known locally as "bacuri") have significant commercial potential, but the species is under threat from agro-industrial expansion. The genetic variability within 72 genotypes of P. insignis belonging to ten populations collected in the Brazilian states of Maranhão and Piauí, and maintained in the germplasm collection of Embrapa Meio-Norte, has been determined, and the organization of genetic diversity within populations, between populations and among geographic groups verified. Eighteen selected inter simple sequence repeat primers allowed amplification of 236 loci of which 221 (93.64%) were polymorphic, indicating a high level of genetic diversity. At the population level, the Shannon and Nei diversity indices ranged from 0.082 to 0.323 and from 0.120 to 0.480, respectively. The global coefficient of genetic differentiation (G(ST)) was 0.4730 indicating that differentiation between populations was significant, a finding that was confirmed by analysis of molecular variance (Φ(ST) = 0.28). UPGMA cluster analysis revealed that the genotypes could be stratified into groups that were well defined and consistent with those identified in the dendrogram constructed using pair wise Φ(ST) values. The high genetic diversity established in this study may facilitate the management and conservation of the germplasm of P. insignis.

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 cajá, are an important commercial commodity. We evaluated genetic variability among 32 cajá 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 cajá 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 cajá accessions, which will be useful for genetic improvement programs.

RAPD analysis of the genetic diversity of mango (Mangifera indica) germplasm in Brazil.

We evaluated genetic variability of mango (Mangifera indica) accessions maintained in the Active Germplasm Bank of Embrapa Meio-Norte in Teresina, Piauí, Brazil, using RAPDs. Among these accessions, 35 originated from plantings in Brazil, six from the USA and one from India. Genomic DNA, extracted from leaf material using a commercial purification kit, was subjected to PCR with the primers A01, A09, G03, G10, N05, and M16. Fifty-five polymorphic loci were identified, with mean of 9.16 ± 3.31 bands per primer and 100% polymorphism. Application of unweighted pair group method using arithmetic average cluster analysis demonstrated five genotypic groups among the accessions examined. The genotypes Rosa 41, Rosa 48 and Rosa 49 were highly similar (94% similarity), whereas genotypes Sensation and Rosa 18 were the most divergent (only 7% similarity). The mango accessions were found to have considerable genetic variability, demonstrating the importance of analyzing each genotype in a collection in order to efficiently maintain the germplasm collection.