Myrciaria dubia, an Amazonian fruit: population structure and its implications for germplasm conservation and genetic improvement.

Myrciaria dubia (camu-camu) is an Amazon tree that produces a tart fruit with high vitamin C content. It is probably the fruit with the highest vitamin C content among all Brazilian fruit crops and it can be used to supplement daily vitamin C dose. This property has attracted the attention of consumers and, consequently, encouraged fruit farmers to produce it. In order to identify and select potential accessions for commercial exploitation and breeding programs, M. dubia has received considerable research attention. The identification and characterization of genetic diversity, as well as identification of the population structure of accessions preserved in germplasm banks are fundamental for the success of any breeding program. The objective of this study was to evaluate the genetic variability of 10 M. dubia populations obtained from the shores of Reis Lake, located in the municipality of Caracaraí, Roraima, Brazil. Fourteen polymorphic inter simple sequence repeat (ISSR) markers were used to study the population genetic diversity, which resulted in 108 identified alleles. Among the 14 primers, GCV, UBC810, and UBC827 produced the highest number of alleles. The study illustrated the suitability and efficiency of ISSR markers to study the genetic diversity of M. dubia accessions. We also revealed the existence of high genetic variability among both accessions and populations that can be exploited in future breeding programs and conservation activities of this species.

Molecular characterization and population structure study of cambuci: strategy for conservation and genetic improvement.

Cambuci (Campomanesia phaea) belongs to the Myrtaceae family and is native to the Atlantic Forest of Brazil. It has ecological and social appeal but is exposed to problems associated with environmental degradation and expansion of agricultural activities in the region. Comprehensive studies on this species are rare, making its conservation and genetic improvement difficult. Thus, it is important to develop research activities to understand the current situation of the species as well as to make recommendations for its conservation and use. This study was performed to characterize the cambuci accessions found in the germplasm bank of Coordenadoria de Assistência Técnica Integral using inter-simple sequence repeat markers, with the goal of understanding the plant's population structure. The results showed the existence of some level of genetic diversity among the cambuci accessions that could be exploited for the genetic improvement of the species. Principal coordinate analysis and discriminant analysis clustered the 80 accessions into three groups, whereas Bayesian model-based clustering analysis clustered them into two groups. The formation of two cluster groups and the high membership coefficients within the groups pointed out the importance of further collection to cover more areas and more genetic variability within the species. The study also showed the lack of conservation activities; therefore, more attention from the appropriate organizations is needed to plan and implement natural and ex situ conservation activities.

Population structure of jatropha and its implication for the breeding program.

Jatropha (Jatropha curcas L.) has potential as an oilseed crop that requires the development of technology for its exploitation. The objective of this study was to assess the population structure and the genetic diversity in jatropha accessions at a global level using simple sequence repeat (SSR) molecular markers. Jatropha accessions (N = 109) from 10 countries were genotyped using 10 SSR markers. The results showed a low level of genetic diversity among 92 accessions originating from India, Mozambique, Ethiopia, Tanzania, Brazil, Honduras, and Indonesia, which were grouped in one cluster. In contrast, accessions from Mexico and Costa Rica showed high level of genetic variability. These accessions may be used to increase the genetic diversity of jatropha in the breeding populations. The study also showed the need of collecting activity from the center of diversity (Mexico and Costa Rica) to aggregate the genetic diversity in the international collections of jatropha.

Evaluation of genetic diversity in fig accessions by using microsatellite markers.

Fig (Ficus carica L.) is a fruit of great importance worldwide. Its propagation is carried out with stem cuttings, a procedure that favors the occurrence of synonymy among specimens. Thus, molecular markers have become an important tool for studies of DNA fingerprinting, germplasm characterization, and genetic diversity evaluation in this plant species. The aim of this study was the analysis of genetic diversity among accessions of fig and the detection of synonyms among samples using molecular markers. Five microsatellite markers previously reported as polymorphic to fig were used to characterize 11 fig cultivars maintained in the germplasm bank located in Lavras, Minas Gerais. A total of 21 polymorphic DNA fragments were amplified, with an average of 4.2 alleles per locus. The average allelic diversity and polymorphic information content were 0.6300 and 0.5644, respectively, whereas the total value for the probability of identity was 1.45 x 10(-4). The study allowed the identification of 10 genotypes and 2 synonymous individuals. The principal coordinate analysis showed no defined clusters despite the formation of groups according to geographical origin. However, neighbor-joining analysis identified the same case of synonymy detected using principal coordinate analysis. The data also indicated that the fig cultivars analyzed constitute a population of individuals with high genetic diversity and a broad range of genetic variation.

Comparison of a retrotransposon-based marker with microsatellite markers for discriminating accessions of Vitis vinifera.

Identification and knowledge concerning genetic diversity are fundamental for efficient management and use of grapevine germplasm. Recently, new types of molecular markers have been developed, such as retrotransposon-based markers. Because of their multilocus pattern, retrotransposon-based markers might be able to differentiate grapevine accessions with just one pair of primers. In order to evaluate the efficiency of this type of marker, we compared retrotransposon marker Tvv1 with seven microsatellite markers frequently used for genotyping of the genus Vitis (VVMD7, VVMD25, VVMD5, VVMD27, VVMD31, VVS2, and VZAG62). The reference population that we used consisted of 26 accessions of Vitis, including seven European varieties of Vitis vinifera, four North American varieties and hybrids of Vitis labrusca, and 15 rootstock hybrids obtained from crosses of several Vitis species. Individually, the Tvv1 and the group of seven SSR markers were capable of distinguishing all accessions except 'White Niagara' compared to 'Red Niagara'. Using the Structure software, the retrotransposon marker Tvv1 generated two clusters: one with V. vinifera plus North American varieties and the other comprising rootstocks. The seven SSR markers generated five clusters: V. vinifera, the North American varieties, and three groups of rootstock hybrids. The percentages of variation explained by the first two components in the principal coordinate analysis were 65.21 (Tvv1) and 50.42 (SSR markers) while the Mantel correlation between the distance matrixes generated by the two types of markers was 42.5%. We conclude that the Tvv1 marker is useful for DNA fingerprinting, but it lacks efficiency for discrimination of structured groups.

Genetic diversity of Brazilian and introduced olive germplasms based on microsatellite markers.

Olive trees have been grown since the beginning of civilization, and the consumption of olives and olive products is increasing worldwide, due to their health benefits and organoleptic qualities. To meet the growing market for olives, commercial cultivation of this species is expanding from traditional areas to new regions. Although the Brazilian olive industry has just begun to be established, breeding programs are already developing cultivars that are more adapted to local conditions. We used 12 microsatellite markers to evaluate 60 olive accessions, including several cultivars that were developed in Brazil. The analyses identified 72 distinct alleles; the largest number of alleles per locus were at the markers GAPU 101 and GAPU 71B, which contained 10 and 9 alleles, respectively. The largest allelic diversity and polymorphic information contents were also found at the GAPU 101 and GAPU 71B markers, with values of 0.8399/0.8203 and 0.8117/0.7863, respectively. Additionally, the 12 microsatellite markers generated a cumulative identity probability of 1.51 x 10(-10), indicating a high level of accuracy of accession identification. The set of markers that we used allowed the identification of 52 of the 60 olive genotypes, in addition to the recognition of several varietal synonyms. The components of a two-dimensional principal coordinate analysis explained 48.6% of the total genetic variation. The results obtained from the microsatellite markers showed a substantial degree of genetic diversity in the olive tree accessions used in Brazil.