Evaluation of genetic similarity between accessions of Pityrocarpa moniliformis (angico-de-bezerro) using RAPD markers.

Pityrocarpa moniliformis (Benth.) Luckow and Jobson, commonly known as angico-de-bezerro, is a forage legume that occurs naturally in the Caatinga of northeastern Brazil. This fast growing, vigorous, melliferous tree is well adapted to arid terrains and its branches and leaves possess high nutritional value. However, the scarcity of information regarding genetic variability within the species limits its possible exploitation as an animal forage. The aim of the study was to evaluate the genetic similarities of ten accessions of P. moniliformis available in the active germplasm collection of Embrapa Meio-Norte, using the RAPD markers to select those most suitable for cultivation and/or plant breeding. Polymerase chain reaction using ten selected RAPD primers generated 110 amplified loci, 106 (96.4%) of which were polymorphic. Primers A10 and M06 produced the largest number of polymorphic loci (18 and 13 bands, respectively), while primers B18 and K15 generated the smallest number (7 bands each). The dendrogram, constructed using the Jaccard coefficients and considering a cut-off point of 0.41 allowed the separation of the ten accessions into four genotypic groups. The highest genetic similarity coefficient (0.56) was observed between group I accessions BGFAB6 and BGFAB9 and BGFAB 7 and BGFAB 8, while the lowest coefficient (0.11) was observed between accessions BGFAB3 (group IV) and BGFAB10 (group III). The results revealed that genetic variability is present in the accessions of P. moniliformis.

RAPD analysis of the genetic diversity among accessions of Fabaceous forages (Poincianella spp) from the Caatinga.

Among members of the Fabaceae family, native to the Brazilian Caatinga, the species Poincianella pyramidalis and P. bracteosa exhibit particular potential as forage for cattle, sheep and goats. With the aim of establishing genetic relationships within Poincianella, random amplified polymorphic DNA analysis was performed on eight accessions of P. pyramidalis and two accessions of P. bracteosa, originating from the semiarid zone of the state of Piauí, northeastern Brazil, and present in the germplasm bank of Embrapa Meio Norte (Teresina, Piauí, Brazil). Amplification reactions using 11 selected arbitrary sequence primers generated 167 fragments with an overall polymorphism of 70.38%. Five monomorphic loci were generated exclusively in P. pyramidalis accessions, while three unique monomorphic loci were associated with P. bracteosa, and these represented potential species-specific markers. The similarity coefficients between Poincianella accessions were low (mean value 0.59) but with a wide variation (range 0.443 to 0.748). The similarity matrix and the dendrogram constructed using the unweighted pair group method allowed the separation of Poincianella accessions into two major clusters represented by the two distinct species, while the accessions of P. pyramidalis could be separated further into three subgroups. The high level of genetic diversity detected in the genus Poincianella could be used in future breeding programs to produce enhanced cultivars, although the variability could be better exploited if more specimens were collected from other locations within the semiarid region of northeastern Brazil.

Determination of the genetic diversity among accessions of Senna spectabilis (canafístula) by using RAPD markers.

Senna spectabilis (DC.) H.S. Irwin & Barneby (Fabaceae; Caesalpinioideae), commonly known as "canafístula" or "cassia", is widely used in the semi-arid region of northeastern Brazil as a source of forage and timber. The plant presents a high nutritional content in comparison with other forage species that are native to the Brazilian Caatinga; thus, it represents a valuable resource during periods of drought. The aim of this study was to evaluate the genetic variability among eight accessions of S. spectabilis available in the forage germplasm collection of Embrapa Meio-Norte using the random-amplified polymorphic DNA technique. The 15 primers selected for use in the analysis produced 107 bands, including 59 (55.14%) that were polymorphic. A similarity matrix was generated on the basis of Jaccard coefficients, and a dendrogram was constructed using the unweighted pair group method with arithmetic mean clustering technique. The mean value of the similarity coefficients was 0.73, and the cophenetic correlation coefficient was 83.76%. Accessions CAN. 4 and CAN. 5 presented the greatest genetic similarity, while CAN. 6 and CAN. 8 were the most divergent. The S. spectabilis accessions were classified into two main groups with group I including accessions CAN. 1, CAN. 2, CAN. 4, CAN. 5, CAN. 7, CAN. 8, and CAN. 9, and group II comprising the single accession CAN. 6. The results presented herein revealed that, although the germplasm collection is presently limited, there is sufficient genetic variability among the accessions to permit future breeding programs.