Elisa Susilene Lisboa dos Santos

Genetic Breeding and Diversity of the Genus Passiflora: Progress and Perspectives in Molecular and Genetic Studies

Despite the ecological and economic importance of passion fruit (Passiflora spp.), molecular markers have only recently been utilized in genetic studies of this genus. In addition, both basic genetic researches related to population studies and pre-breeding programs of passion fruit remain scarce for most Passiflora species. Considering the number of Passiflora species and the increasing use of these species as a resource for ornamental, medicinal, and food purposes, the aims of this review are the following: (i) to present the current condition of the passion fruit crop; (ii) to quantify the applications and effects of using molecular markers in studies of Passiflora; (iii) to present the contributions of genetic engineering for passion fruit culture; and (iv) to discuss the progress and perspectives of this research. Thus, the present review aims to summarize and discuss the relationship between historical and current progress on the culture, breeding, and molecular genetics of passion fruit.

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.

New Microsatellite Markers for Wild and Commercial Species of Passiflora (Passifloraceae) and Cross-Amplification

Premise of the study: We developed the first microsatellites for Passiflora setacea and characterized new sets of markers for P. edulis and P. cincinnata, enabling further genetic diversity studies to support the conservation and breeding of passion fruit species. Methods and Results: We developed 69 microsatellite markers and, in conjunction with assessments of cross-amplification using primers available from the literature, present 43 new polymorphic microsatellite loci for three species of Passiflora. The mean number of alleles per locus was 3.1, and the mean values of the expected and observed levels of heterozygosity were 0.406 and 0.322, respectively. Conclusions: These microsatellite markers will be valuable tools for investigating the genetic diversity and population structure of wild and commercial species of passion fruit (Passiflora spp.) and may be useful for developing conservation and improvement strategies by contributing to the understanding of the mating system and hybridization within the genus.

Molecular Genetic Variability of Commercial and Wild Accessions of Passion Fruit (Passiflora spp.) Targeting ex Situ Conservation and Breeding

Passiflora species are distributed throughout Latin America, and Brazil and Colombia serve as the centers of diversity for this genus. We performed cross-species amplification to evaluate 109 microsatellite loci in 14 Passiflora species and estimated the diversity and genetic structure of Passiflora cincinnata, Passiflora setaceae and Passiflora edulis. A total of 127 accessions, including 85 accessions of P. edulis, a commercial species, and 42 accessions of 13 wild species, were examined. The cross-species amplification was effective for obtaining microsatellite loci (average cross-amplification of 70%). The average number of alleles per locus (five) was relatively low, and the average diversity ranged from 0.52 in P. cincinnata to 0.32 in P. setacea. The Bayesian analyses indicated that the P. cincinnata and P. setacea accessions were distributed into two groups, and the P. edulis accessions were distributed into five groups. Private alleles were identified, and suggestions for core collections are presented. Further collections are necessary, and the information generated may be useful for breeding and conservation.

Identificação de resistência genética do cacaueiro à podridão-parda

The objective of this work was to compare methods for characterizing the resistance of cacao (Theobroma cacao) to black pod (Phytophthora palmivora). The methods of disease scores, intensity of infection index and disease index were evaluated. Leaf discs of 103 genotypes were infected with 0.2 mL of a suspension with 3x105 zoospores of P. palmivora per milliliter, and symptoms were evaluated by the three methods. Three evaluations (replicates) composed by 20 discs each were carried out for every genotype. The disease index method was the most efficient to characterize the cacao resistance to P. palmivora.

New polymorphic microsatellite loci for Theobroma cacao: isolation and characterization of microsatellites from enriched genomic libraries

Seventeen polymorphic microsatellite markers were isolated from enriched genomic libraries for Theobroma cacao, providing additional tools for studying the genetic diversity and map saturation of this species. These markers were characterized in 32 accessions of the T. cacao germplasm collection from the Centro de Pesquisas do Cacau. The number of alleles at each locus varied from 2 to 8, with an average of 4.41 alleles per locus. The polymorphism information content varied from 0.060 to 0.695, with an average of 0.333. The markers characterized in this study will be employed in map saturation studies and diversity assessments of cacao genotypes.

Genetic Structure and Molecular Diversity of Cacao Plants Established as Local Varieties for More than Two Centuries: The Genetic History of Cacao Plantations in Bahia, Brazil.

Bahia is the most important cacao-producing state in Brazil, which is currently the sixth-largest country worldwide to produce cacao seeds. In the eighteenth century, the Comum, Pará and Maranhão varieties of cacao were introduced into southern Bahia, and their descendants, which are called ‘Bahian cacao’ or local Bahian varieties, have been cultivated for over 200 years. Comum plants have been used to start plantations in African countries and extended as far as countries in South Asia and Oceania. In Brazil, two sets of clones selected from Bahian varieties and their mutants, the Agronomic Institute of East (SIAL) and Bahian Cacao Institute (SIC) series, represent the diversity of Bahian cacao in germplasm banks. Because the genetic diversity of Bahian varieties, which is essential for breeding programs, remains unknown, the objective of this work was to assess the genetic structure and diversity of local Bahian varieties collected from farms and germplasm banks. To this end, 30 simple sequence repeat (SSR) markers were used to genotype 279 cacao plants from germplasm and local farms. The results facilitated the identification of 219 cacao plants of Bahian origin, and 51 of these were SIAL or SIC clones. Bahian cacao showed low genetic diversity. It could be verified that SIC and SIAL clones do not represent the true diversity of Bahian cacao, with the greatest amount of diversity found in cacao trees on the farms. Thus, a core collection to aid in prioritizing the plants to be sampled for Bahian cacao diversity is suggested. These results provide information that can be used to conserve Bahian cacao plants and applied in breeding programs to obtain more productive Bahian cacao with superior quality and tolerance to major diseases in tropical cacao plantations worldwide.

Resistance gradient of black pod disease in cocoa and selection by leaf disk assay

To characterize the gradient of resistance to black pod disease experimentally, the leaf disk assay was applied to 217 cocoa genotypes. The parameters time interval, number of leaves evaluated per genotype and distribution of experimental treatments were evaluated. Significant differences between genotypes were found, resulting in the grouping in five homogenous groups (p < 0.01). In the assessments with the leaf disk test, five and seven days after inoculation, the F value was highest after seven days, clearly separating the resistant from susceptible genotypes. There was no difference between the clones behavior and the use of more than one box to group the genotypes (p = 0.56) and the use of different leaves of the same genotype (p = 0.08). The resistance gradient observed indicates variability enough for mapping and cocoa breeding in the population.

The Genetic Diversity, Conservation, and Use of Passion Fruit ( Passiflora spp.)

The characterization of genetic variability is important for conservation and biodiversity as well as the strategies and research techniques that contribute to such characterizations of flora, including the use of morpho-agronomic descriptors and molecular markers. In this chapter, we present and discuss the issues related to the genetic diversity of passion fruit (Passiflora spp.) to provide the reader with an updated view on the advances and challenges associated with the characterization, conservation and genetic diversity of the genus Passiflora. Passiflora, whose species are commonly known as passion fruits, stands out in the family Passifloraceae both for its number of species (approximately 520) and its ecological and economic importance. Passion fruits grow in various countries, and they are diversely represented in the Americas; in particular, Colombia and Brazil grow approximately 170 and 150 species of Passiflora, respectively. Despite increasing interest in this genus, genetic characterization, and breeding programs remain modest, especially considering the number of species not yet studied. Because almost all passion fruit diversity estimates derive from accessions maintained in germplasm banks using ex situ conservation to reduce the loss of species genetic variability, the scientific community must increase the number of these accessions. In addition, an urgent need exists for estimations of the diversity of natural populations and expanded analyses of passion fruit accessions present in germplasm banks, to provide more realistic estimates regarding the diversity of Passiflora and its representation in germplasm banks, both for conservation and biodiversity.

Passion Fruit (Passiflora spp.) Breeding

The genus Passiflora, commonly known as passion fruit, is prominent in the family Passifloraceae due to its numerous species (approximately 520) and economic importance. The biodiversity of this genus is widely represented in the Americas, where Colombia and Brazil harbor approximately 170 and 150 species of Passiflora, respectively. The economic interest in passion fruit species emerged due to the beauty of their flowers, their active medicinal properties, their essential oils that can be extracted for the cosmetics industry and their production of fruit for consumption or for obtaining derivatives. Brazil is considered the largest producer of passion fruit, although its national productivity is low (an average of 14 mt/ha/year) compared with the potential for passion fruit cultivation (50 mt/ha/year). This low productivity is partly caused by a lack of cultivars adapted to different production regions and their susceptibility to major diseases. Although the number of passion fruit breeding programs has increased, the results obtained thus far have been modest compared with existing demands. Such programs therefore represent a burgeoning field of research and financial investment. Among the obstacles faced by breeders, the low representation of Passiflora in germplasm banks (considering its species richness and wide geographical distribution) and the scarcity of biological and agronomic information for most accessions are the most salient. Despite the difficulties encountered in Passiflora research over the past two decades, there has been a notable increase in the use of molecular tools for the characterization of this genus and in the number of cultivars registered and effectively available for the large-scale production of passion fruit. Thus, in this chapter, we present an overview of innovations and modern technologies, including advances in breeding programs and molecular tools, related to the availability of genetic resources for Passiflora. These technologies can be used as strategies to improve every stage of breeding programs, from pre- to post-breeding. Finally, we discuss future perspectives for studies leading to the genetic breeding of passion fruit (Passiflora spp.).