G. S. C. Buso

Development of microsatellite markers from an enriched genomic library for genetic analysis of melon (Cucumis melo L.)

BackgroundDespite the great advances in genomic technology observed in several crop species, the availability of molecular tools such as microsatellite markers has been limited in melon (Cucumis melo L.) and cucurbit species. The development of microsatellite markers will have a major impact on genetic analysis and breeding of melon, especially on the generation of marker saturated genetic maps and implementation of marker assisted breeding programs. Genomic microsatellite enriched libraries can be an efficient alternative for marker development in such species.ResultsSeven hundred clones containing microsatellite sequences from a Tsp-AG/TC microsatellite enriched library were identified and one-hundred and forty-four primer pairs designed and synthesized. When 67 microsatellite markers were tested on a panel of melon and other cucurbit accessions, 65 revealed DNA polymorphisms among the melon accessions. For some cucurbit species, such as Cucumis sativus, up to 50% of the melon microsatellite markers could be readily used for DNA polymophism assessment, representing a significant reduction of marker development costs. A random sample of 25 microsatellite markers was extracted from the new microsatellite marker set and characterized on 40 accessions of melon, generating an allelic frequency database for the species. The average expected heterozygosity was 0.52, varying from 0.45 to 0.70, indicating that a small set of selected markers should be sufficient to solve questions regarding genotype identity and variety protection. Genetic distances based on microsatellite polymorphism were congruent with data obtained from RAPD marker analysis. Mapping analysis was initiated with 55 newly developed markers and most primers showed segregation according to Mendelian expectations. Linkage analysis detected linkage between 56% of the markers, distributed in nine linkage groups.ConclusionsGenomic library microsatellite enrichment is an efficient procedure for marker development in melon. One-hundred and forty-four new markers were developed from Tsp-AG/TC genomic library. This is the first reported attempt of successfully using enriched library for microsatellite marker development in the species. A sample of the microsatellite markers tested proved efficient for genetic analysis of melon, including genetic distance estimates and identity tests. Linkage analysis indicated that the markers developed are dispersed throughout the genome and should be very useful for genetic analysis of melon.

Analysis of genetic variability of South American wild rice populations (Oryza glumaepatula) with isozymes and RAPD markers

The knowledge of population structure and genetic diversity of wild relatives of rice is needed to investigate their evolutionary history and potential use in breeding programs. Very little is known about the wild rice species (Oryza spp.), particularly those that are native to South America. A study using isozyme and RAPD markers was conducted to estimate the level of genetic diversity of four South American wild rice populations (Oryza glumaepatula) recently collected in the Amazon forest and western Brazil rivers. F‐statistics and genetic diversity parameters calculated from isozyme and RAPD markers indicated high values for inbreeding coefficients and differentiation among the four populations. In agreement with this, a pattern of greater variation between than within populations was observed with both types of markers. These findings were corroborated by an AMOVA analysis, which indicated that a large portion of the total genetic variation was attributed to regional divergence. The partition of the AMOVA analysis among populations showed that most of the genetic diversity was due to differences among populations. This distribution pattern of genetic variation of O. glumaepatula populations is in agreement with the expectation for an autogamous species and provides important baseline data for conservation and collection strategies for this species.

Mating system and fine-scale spatial genetic structure of Solanum lycocarpum St.Hil. (Solanaceae) in the Brazilian Cerrado

Restricted gene dispersion – resulting from both self-pollination and limited capability of pollen migration, as well as seed dispersion at short distances – has been considered the main reason for spatial genetic structuring in plant populations. This study evaluated the intrapopulation genetic structure and the mating system in four populations of Solanum lycocarpum, a woody bush occurring in Brazilian Cerrado vegetation. Two hundred and twenty-four individuals were genotyped through five nuclear SSR loci (30 alleles) and six cpSSR loci (82 haplotypes). The study evidenced that the species mates predominantly by outcrossings

Development, characterization and use of microsatellite markers for genetic analysis of Cashew tree (Anacardium occidentale)

(\hat{t}_{\rm m}\sim1.00)

Análise genética e caracterização molecular de cultivares comerciais de melão utilizando marcadores moleculares SSR.

, that biparental inbreeding is not common, and that there are almost 10 trees participating as pollen donors per mother-tree. The populations were formed by many mother lineages, indicating efficient seed dispersion by the fauna and the occurrence of multiple foundation events. Spatial genetic structure was observed in three populations (average Sp=0.0184 ± 0.0030) and it resulted from both restricted seed dispersion and from vegetative reproduction. During the collection of seeds for ex situ conservation, seeds must be gathered from 150 to 200 mother trees, so that the effective size of 500 individuals is retained. The sampling must comprise the biggest possible number of populations in a wide area to enable the maintenance of the biggest possible haplotypic diversity.

Caracterização e otimização de Primers SSR para B.brizantha, B.humidicola e B.decumbens.

The aim of this work was to analyze the Brazilian and Chinese strains of Ganoderma lucidum with molecular RAPD markers. A similarity matrix was elaborated and the RAPD profiles of G. lucidum strains were also compared to two other Ganoderma spp: G. applanatum and G. lipsiense in order to produce genetic similarity among the species. Based on the primers used, it was possible to determine that the Brazilian strains and Chinese strain CC-22 are alike. The method and the primers selection showed to be appropriate for the genetic identification of G. lucidum strains, enabling them to be improved and used in research, as well as in the world market.

Transferibilidade de Primers Microssatélites Desenhados de Sequências Expressas de Brachiaria brizantha para B. decumbens e B. humidicola.

Background The cashew tree (Anacardium occidentale) is found throughout the Brazilian territory, although it is better adapted to the northeastern coast climate. This fruit crop is essential to the agroindustry of the States of Ceara, Piaui and Rio Grande do Norte, where around 95% of the production is harvested and where the whole processing of the chestnut is done. It currently represents 157 million dollars in exports of nuts. Despite its socio-economic importance it still lags behind in the adoption of breeding technologies. There is very little information about the genetics of this species and no molecular tools yet developed. In this work we developed and characterized a set of microsatellite markers for Anacardium occidentale from the construction of genomic libraries enriched for repetitive sequences.