Eder Jorge de Oliveira

Correlações genéticas e análise de trilha para número de frutos comerciais por planta em mamoeiro

The objective of this work was to determine how the number of commercial fruit per plant (CFrP) is related to 16 morphological and agronomical traits in papaya (Carica papaya L.). The experiment was carried out in the 2008/2009-crop season, using an augmented randomized block design. Nineteen non-common (germplasm accessions) and three common genotypes (varieties and hybrids) were evaluated with ten repetitions. Correlations between CFrP and morpho-agronomic traits were outspread in direct and indirect effects. High variability was found for the evaluated traits. The estimates of genetic correlations were higher than phenotypic correlations for all characters. CFrP was positively and significantly correlated with number of fruits per axil (NFAx) and negatively with the internal diameter of the cavity of the fruit, pulp thickness, fruit weight, fruit length (FrL) and fruit diameter. However, path analysis showed that, among this traits, NFAx and FrL have more direct effect on CFrP. Furthermore, plant height, number of flowers per peduncle and leaf width are more easily measured and are expressed before fruit production, making them more suitable for indirect selection in breeding programs of this crop.

ISSR Markers as a Tool for the Assessment of Genetic Diversity in Passiflora

Genetic variation among sweet, purple, and yellow passion fruit accessions was assessed using inter-simple sequence repeat (ISSR) markers. Eighteen ISSR primers were used to evaluate 45 accessions. The number of polymorphic bands per primer varied from 4 to 22, with 12.4 bands per primer on average. Nei’s genetic distance between accessions ranged from 0.04 to 0.35. Clustering using the neighbor-joining method resulted in the formation of 11 major clusters. It was not possible to classify the accessions according to their geographic origin, showing that there is no structure in the gene bank. The overall mean Shannon–Weaver diversity index was 0.32, indicating good resolution of genetic diversity in passion fruit germplasm using ISSR markers. Our results indicate that ISSR can be useful for genetic diversity studies, to provide practical information for parental selection and to assist breeding and conservation strategies.

Polymorphism of Microsatellite Markers in Papaya (Carica papaya L.)

A set of 81 new microsatellite markers for Carica papaya L. previously identified by data mining using freely available sequence information from Genbank were tested for polymorphism using 30 germplasm accessions from the Papaya Germplasm Bank (PGM) at Embrapa Mandioca e Fruticultura Tropical (CNPMF) and 18 landraces. The data were used to estimate pairwise genetic distances between the genotypes. A neighbor-joining based dendrogram was used to define clusters and infer possible genetic structuring of the collection. Most microsatellites were polymorphic (73%), with an observed number of alleles per locus ranging from one to eleven. The levels of observed and expected heterozygosity for 51 polymorphic loci varied from 0.00 to 0.85 and from 0.08 to 0.82, averaging 0.19 and 0.59, respectively. Forty-four percent of microsatellites showed polymorphism information content (PIC) higher than 0.50. The compound microsatellites seem to be more informative than dinucleotide and trinucleotide repeats in average alleles per locus and PIC. Among dinucleotides, AG/TC or GA/CT repeat motifs exhibited more informativeness than TA/AT, GT/CA and TG/AC repeat motifs. The neighbor-joining analysis based on shared allele distance could differentiate all the papaya accessions and landraces as well as differences in their genetic structure. This set of markers will be useful for examining parentage, inbreeding and population structure in papaya.

Severidade de doenças em maracujazeiro para identificação de fontes de resistência em condições de campo

O objetivo deste trabalho foi utilizar uma escala de severidade para algumas doencas do maracujazeiro, visando a identificacao de fontes de resistencia. Foram avaliados 75 acessos de Passiflora spp. em condicoes de campo, sob alta infeccao natural dos patogenos, para a severidade da virose, nas folhas (VIFO), frutos (VIFR) e distribuicao na planta (VIPL), bem como para verrugose nos frutos e ramos (VEFR e VERA, respectivamente) e antracnose nos frutos (ANFR). Houve alta variabilidade para resistencia as doencas, embora poucos acessos tenham sido classificados como resistentes a VIFO, VIFR e VIPL, sendo que apenas um acesso de P. setacea (BGM237) foi considerado resistente aos tres tipos de avaliacoes para virose. A maioria dos acessos de maracujazeiro- amarelo e roxo possui algum grau de suscetibilidade a um ou outro sintoma da virose. Quanto a VERA, acessos de P. alata e P. cincinnata foram mais resistentes, embora P. alata demonstre maior resistencia a VEFR. Alguns acessos de P. edulis comportam-se como moderadamente resistente a VERA e VEFR. A maioria dos acessos de P. alata, P. cincinnata e P. setacea nao apresentou sintomas de antracnose nos frutos. A escala de severidade adotada mostrou-se eficiente para a separacao dos acessos de maracujazeiro em diferentes classes de resistencia a doencas.

Development and characterization of microsatellite markers for the wild South American Passiflora cincinnata (Passifloraceae)

PREMISE OF THE STUDY We developed the first set of microsatellite markers for the passion fruit, Passiflora cincinnata, to provide tools for further study of its genetic diversity and to support current conservation and genetic studies. METHODS AND RESULTS We used a microsatellite-enriched library approach to isolate and characterize 25 new molecular markers. Seven primer pairs successfully amplified polymorphic microsatellite regions, with an average of five alleles per locus. The mean values of expected and observed levels of heterozygosity were 0.516 and 0.525, respectively. CONCLUSIONS The microsatellite markers identified in this study may be valuable tools for population genetic studies, and this set of markers also may be useful in the design of a genetic conservation strategy, mating system, and hybridization studies.

Plant selection in F2 segregating populations of papaya from commercial hybrids.

The objective of this paper was to estimate the genetic parameters and additive genetic values in segregating populations of papaya using the mixed model methodology. Two F2 populations from Tainung and Calimosa hybrids were evaluated. The experimental design was an augmented block with four replicates, and Golden and Calimosa cultivars were the common treatment. Estimates of individual heritability were high for fruit length (FL) and weight (FW), moderate for fruit diameter (FD), and low for total soluble solids (TSS) and fruit firmness (FF). Considering FF and TSS as main traits for selection, genotypes of Calimosa-F2 population showed better performance to FF, but worse concerning TSS. It was selected 18.3% and 24.6% of plants from Tainung-F2 and Calimosa-F2 populations, respectively. Negative correlation between TSS and FF was not able to reduce the genetic gains. The segregating populations from Calimosa hybrid are more promising for the selection of papaya lines.

Diversidade genética em seleção recorrente de maracujazeiro-amarelo detectada por marcadores microssatélites

The objective of this work was to estimate the genetic variability in two recurrent selection cycles of the yellow passion flower (Passiflora edulis), and to evaluate the impact of selection on the progenies selected via changes in allele frequency, detected by microsatellite markers. Twenty-three microsatellites were used for genotyping 66 full-siblings. Allele frequency, expected (He) and observed (Ho) heterozygosity, polymorphic information content (PIC) and inbreeding coefficient (f) were estimated. Thirty-two alleles were found in these populations, of which only two were lost during selection. The average number of alleles per locus was 2.46 in the first cycle, and 2.30 in the second. The differences in allele frequencies in the two cycles were not significant. The mean He in the first cycle was 0.20 per locus, slightly higher than Ho (0.15). In the second selection cycle, the mean value of Ho was lower than of He, with an average of 0.12. The mean values of f increased in the second selection cycle, from 0.26 to 0.32. Most of the loci showed negative values of f, which suggests high levels of heterozygosity. The mean value of PIC decreased from 0.18 to 0.16 in the second cycle. There were small losses of variability and changes in allele frequencies; however, these variations can be considered normal when selection is practiced.

Selection of morpho-agronomic descriptors for characterization of papaya cultivars

This study was conducted to define a list of sufficient minimum descriptors to distinguish between papaya genotypes quickly and precisely. To this end, 30 quantitative and 21 multi-category descriptors related to plant characteristics, such as leaves, flowers, fruit and seeds were evaluated in 27 genotypes of papaya, including crops, local varieties and improved lines. The quantitative descriptors were subjected to principal components analyses using the Singh and direct selection methods, whereas a correlation analysis was conducted for the qualitative descriptors. Eighteen and fifteen quantitative descriptors were discarded by the Singh and direct selection methods, respectively. However, considering the simultaneous analyses of these methodologies, 60% of the descriptors were selected to maximize the total variation of the genotypes. Six of the multi-category descriptors were monomorphic, and two were highly correlated with other characteristics and were discarded. The minimum descriptors that were selected had high discrimination potentials when they were analyzed together. Thus, for the purposes of the protection of varieties and the classification of the genotypes of papaya, there were found to be 18 quantitative and 13 multi-category minimum descriptors that contributed significantly to the total variation and possessed low correlation with each other. The elimination of descriptors did not entail a loss of information. Those descriptors that contributed most significantly to the first three principal components were the stem diameters, fruit lengths and widths, inflorescence peduncle lengths, thickness of fruit skin, leaf widths, dry and fresh seed weights and ratio between fruit lengths and widths and between total soluble solids and total titratable acidities.

Potential of SNP markers for the characterization of Brazilian cassava germplasm

Key messageHigh-throughput markers, such as SNPs, along with different methodologies were used to evaluate the applicability of the Bayesian approach and the multivariate analysis in structuring the genetic diversity in cassavas.AbstractThe objective of the present work was to evaluate the diversity and genetic structure of the largest cassava germplasm bank in Brazil. Complementary methodological approaches such as discriminant analysis of principal components (DAPC), Bayesian analysis and molecular analysis of variance (AMOVA) were used to understand the structure and diversity of 1,280 accessions genotyped using 402 single nucleotide polymorphism markers. The genetic diversity (0.327) and the average observed heterozygosity (0.322) were high considering the bi-allelic markers. In terms of population, the presence of a complex genetic structure was observed indicating the formation of 30 clusters by DAPC and 34 clusters by Bayesian analysis. Both methodologies presented difficulties and controversies in terms of the allocation of some accessions to specific clusters. However, the clusters suggested by the DAPC analysis seemed to be more consistent for presenting higher probability of allocation of the accessions within the clusters. Prior information related to breeding patterns and geographic origins of the accessions were not sufficient for providing clear differentiation between the clusters according to the AMOVA analysis. In contrast, the FST was maximized when considering the clusters suggested by the Bayesian and DAPC analyses. The high frequency of germplasm exchange between producers and the subsequent alteration of the name of the same material may be one of the causes of the low association between genetic diversity and geographic origin. The results of this study may benefit cassava germplasm conservation programs, and contribute to the maximization of genetic gains in breeding programs.

Identification of passion fruit genotypes resistant to Fusarium oxysporum f. sp. passiflorae

This study aimed to characterize the resistance of 31 passion fruit (Passiflora sp.) genotypes to Fusarium oxysporum f. sp. passiflorae (FOP). About 20 seedlings of each genotype were inoculated by immersing the roots in a suspension of 106 macroconidia mL-1 for five minutes and then transplanting them into pots containing a mixture of soil and sterile substrate. They were evaluated daily for 120 days for the occurrence of wilt symptoms and death. These data were used to calculate the area under the disease progress curve, for survival analysis and grouping. The mortality rate ranged from 0 to 100% and the AUDPC ranged from 0 for genotypes without symptoms of the disease to 6,650.63 for the hybrid HFOP-01. Genotypes were classified into four subgroups: resistant, moderately resistant, susceptible and highly susceptible. The resistance was genotype dependent, but no significant variation was found between the purple and the yellow P. edulis.