Explore the vast range of titles available.

The conservation of plant genetic resources is essential for breeding programs. Regarding the native species of the Brazilian Cerrado biome, many studies have demonstrated their high potential for use in both medicines and foods. Hymenaea stigonocarpa, a tree with wide occurrence in the Cerrado, has economic importance, and due its extractive use, the establishment of a breeding program is relevant for sustainable use and conservation. Thus, the first germplasm collection of the species was installed at the Federal University of Goiás (UFG). To know the magnitude of genetic variability and how it was distributed in the collection, 353 individuals, distributed in 119 families from 24 subpopulations collected in the Cerrado biome, were genotyped using capillary electrophoresis. Nine pairs of microsatellite markers were genotyped. The UFG germplasm collection showed a high level of genetic diversity (mean \\[\\bar{H}e\\] = 0.554) at the evaluated loci. By Analysis of Molecular Variance (AMOVA), a significant genetic structure was detected (θP = 0.152, p < 0.01), which was expected since the subpopulations that originated the germplasm collection were collected in geographically distant locations. In addition, the germplasm collection had a population effective size of 54.9 and presented an allelic representation of 79.89% compared to 32 natural subpopulations. These results demonstrate that the germplasm collection preserves a high genetic diversity of H. stigonocarpa with a population effective size considered sufficient for the conduction of a breeding program.

Diallel designs are widely used in plant breeding to select parents and to study trait inheritance. The present work aimed to present a method to evaluate two divergent groups of parents, in which one group is used as a tester of the contrasting group. Each parent is crossed with a balanced mixture of seeds from the parents of the other group, and the parents and topcrosses are experimentally evaluated. Two groups of ten inbred maize lines were used to obtain intergroup topcrosses and biparental crosses in a diallel scheme. The data were subjected to analysis of variance and parameter estimation using the two models. The results showed the reliability of the method for the evaluation of lines and prediction of means of hybrid populations and can be recommended when the number of parents to be evaluated is large, making it difficult to evaluate biparental crosses in a diallel scheme.

Hancornia speciosa Gomes is a fruit tree native to Brazil with potential for use in cropping systems. The objective of this study was to characterize accessions of a germplasm collection by evaluating agronomic traits. The collection was planted in 2005, in an experiment with 57 progenies and four replications, totaling 192 individual accessions from 29 natural subpopulations of four botanical varieties, from the Brazilian Cerrado. The components of variance were estimated using the restricted maximum likelihood (REML) procedure. Heritability coefficients show the potential of the collection as base population for selection programs. The trait number of fruits per plant presented the highest estimated selection gain. The accessions of H. speciosa var. cuyabensis are the ones with the greatest potential for selection based on plant size and productivity. Progenies with greater development in the juvenile phase are potentially more productive in the adult phase, allowing the early selection of superior genotypes.

Dipteryx alata Vogel (Leguminosae) is a native Neotropical tree with a wide distribution in the Brazilian Cerrado that is commonly known as the baru tree. The genetic diversity of 150 D. alata progeny from a germplasm collection was characterized using nine microsatellite markers. Genetic diversity analysis detected 50 alleles ranging from 2 to 14 alleles per locus. The genetic differentiation among populations (ϑp = 0.097) suggests moderate genetic structuring and high genetic differentiation among progenies (ϑs = 0.169). The intrapopulation index (f = 0.122) indicates the presence of low endogamy. The effective population size (Ne = 96) shows that the germplasm collection has sufficient representativeness for use as a base population for breeding programmes. These results are useful for the exploitation of the genetic resources of D. alata for future conservation efforts and breeding programmes.

Approaches in population genetics decompose species genetic variation at hierarchical level, understanding the action of microevolutionary processes at spatial scales. We evaluated the taxonomically complex species Hymenaea stigonocarpa, a tree species distributed in central Brazil, presenting three botanical varieties weakly distinguished by morphological traits. We aimed to investigate the spatial genetic structure of populations of H. stigonocarpa along Cerrado biome, assessing genetic differentiation and the existence of hybridization zones in this species. We genotyped 901 plants from 28 local populations using nine nuclear microsatellite loci. Analyses of genetic diversity, Bayesian inference estimated genetic differentiation and migration rate among populations and varieties. Mantel tests and sPCA evaluated spatial pattern of genetic variation. We observed that H. stigonocarpa var. brevipetiolata presented larger genetic differentiation compared to H. stigonocarpa var. stigonocarpa and H. stigonocarpa var. pubescens (FCT = 0.175). Bayesian approaches supported a genetic different cluster and hybridization process in sympatric populations for H. stigonocarpa var. brevipetiolata. Migration rate was high and not significantly higher among varieties, confirming the existence of hybridization. Spatial correlations were relatively low, but with exponential decrease of genetic similarity along of the geographic space. Spatial genetic structure was higher for H. stigonocarpa var. brevipetiolata and local structures were found with sPCA, indicating that neighboring populations are genetically different mainly in populations of eastern Cerrado. The genetic clusters are not congruent with the vegetative characters used to recognize the three botanical varieties, which should be viewed with skepticism. Our genetic analyses strongly support the need for a taxonomic review.

Dipteryx alata is a Neotropical tree widely distributed throughout the Brazilian Cerrado biome and is popularly known as baru. In this study, we evaluated the mating system of D. alata and compared pollen dispersal patterns between the in situ and ex situ conditions. For this, we used 515 genotypes of adults, juveniles, and progeny from a natural population (in situ) in Orizona-GO, Brazil. In addition, we used 488 genotypes of adults and progeny from a germplasm collection (ex situ) located at the Federal University of Goiás. Both locations are situated in central Brazil. The genetic diversity, cross-pollination rates, and pollen dispersal distance under both conditions were estimated. Genetic diversity and polymorphism differed between the in situ and ex situ conditions. The average number of alleles found in situ (5.2) and ex situ (6.2) showed that the germplasm collection stores greater genetic diversity than the in situ condition. Cross-pollination detected among mother trees under both the in situ and ex situ conditions were high (tm = 0.815 and tm = 0.934, respectively), indicating that the species has a mixed reproductive system that was predominantly allogamous. The difference between tm and ts indicated that the in situ condition shows greater biparental inbreeding. Our results showed that, across generations, the ex situ condition preserved a larger number of alleles, confirming that the D. alata germplasm collection plays a role in conserving genetic diversity. The presence of self-fertilization suggests self-compatibility. Paternity correlation and the dispersal distance of the pollen donors were higher in the in situ condition, a maximum distance of 2.9 km of pollen flow. This can be explained by the number of pollinators and tree spatial distribution.

Topcrosses are routinely used in maize-hybrid programs. This study aimed to evaluate heterosis components and combining ability to predict hybrid means between synthetics from two groups of S1 maize lines using the intergroup topcrosses model that includes S2 lines. Two groups, each with 30 S1 maize lines, were crossed using an intergroup topcross system, with a mixture of lines from one group as a tester for the contrasting group. Simultaneously, 30 S2 lines from each group were generated via self-pollination. Lines and topcrosses were experimentally evaluated and the data were analyzed using a model adapted to the study design. The results showed the suitability of the proposed model for studying heterosis components and general combining ability, detailing additive and dominance effects. Prediction of hybrid means between synthetics showed the potential of the lines to generate base populations for an interpopulation breeding program.

Systematic Conservation Planning (SCP) involves a series of steps that should be accomplished to determine the most cost-effective way to invest in conservation action. Although SCP has been usually applied at the species level (or hierarchically higher), it is possible to use alleles from molecular analyses at the population level as basic units for analyses. Here we demonstrate how SCP procedures can be used to establish optimum strategies for in situ and ex situ conservation of a single species, using Dipteryx alata (a Fabaceae tree species widely distributed and endemics to Brazilian Cerrado) as a case study. Data for the analyses consisted in 52 alleles from eight microsatellite loci coded for a total of 644 individual trees sampled in 25 local populations throughout species’ geographic range. We found optimal solutions in which seven local populations are the smallest set of local populations of D. alata that should be conserved to represent the known genetic diversity. Combining these several solutions allowed estimating the relative importance of the local populations for conserving all known alleles, taking into account the current land-use patterns in the region. A germplasm collection for this species already exists, so we also used SCP approach to identify the smallest number of populations that should be further collected in the field to complement the existing collection, showing that only four local populations should be sampled for optimizing the species ex situ representation. The initial application of the SCP methods to genetic data showed here can be a useful starting point for methodological and conceptual improvements and may be a first important step towards a comprehensive and balanced quantitative definition of conservation goals, shedding light to new possibilities for in situ and ex situ designs within species.

This study evaluated the genetic potential of parents used in sugarcane genetic breeding programs based on the performance of previously conducted single crosses. The average selection rate of each family, predicted using Best Linear Unbiased Prediction (BLUP) procedure, was used as a surrogate to the cross performance in the initial evaluation phase. Data analysis was performed using Griffing’s method IV adapted for the available set of crosses to detail the general combining ability (GCA) and specific combining ability (SCA) effects. Significant GCA effects were detected, which demonstrated the possibility of selecting parents based on this parameter. SCA had a higher coefficient of determination than GCA. In conclusion, the selection rate is an effective indicator for evaluation of the combining ability of parents in the first selection stage of a sugarcane breeding program.

Spatial genetic structure (SGS) is the non-random distribution of genotypes in space, which is usually correlated with life history traits and is driven by ecological and demographic processes. This study aimed to use spatial statistical analysis methods to assess genetic diversity and spatial genetic structure in three known disjunct localities where Tibouchina papyrus occurs, varying in aggregation and density of individuals and in landscape characteristics. This small tree species is endemic to the “Cerrado” (savannas) region of Central Brazil and is also restricted to elevation rock fields (“campo rupestre”). Therefore, it can be considered a model species to help guide studies on Cerrado endemic plants that are isolated with geographic distributions restricted to this highland habitat. The analyses were based on the polymorphisms at ten microsatellite loci. Our working hypothesis was that wind-dispersed species, such as T. papyrus, present no or low SGS because of the long distance seed gene flow. The spatial genetic structure was indeed weak for two of the three populations. The intensity and shape of the SGS are related to density and aggregation (defined by Ripley’s K statistic of spatial aggregation) of individuals in the three localities. Low SGS occurs in populations with aggregation patterns, corroborating the overall hypothesis, although in this species, this pattern depends on the landscape characteristics of each local population.