Self-incompatibility in passion fruit: cellular responses in incompatible pollinations

Diversity and genetic structure of yellow passion fruit in Boyacá-Colombia using microsatellite DNA markers

The Yellow passion fruit belongs to the Passifloraceae family with great economic, nutritional and social importance in Colombia. It presents a great phenotypic and genotypic diversity, which has not yet been explored or used in genetic improvement programs. The objective of this study was to evaluate the genetic diversity of 84 cultivars of Passiflora edulis f. flavicarpa from nine farms in the municipality of Miraflores, Boyacá, using eight microsatellite markers (SSR). On the basis of this information, estimates of genetic diversity parameters, molecular variance analysis (AMOVA), genetic distances, and cluster of cultivars were obtained. Low levels of genetic differentiation between cultivars were observed in the Bayesian analysis using Structure software, as well as the absence of correlation between genetic and geographic distances. The observed heterozygosity (0.50) was greater than the expected heterozygosity (0.43), suggesting a significant number of heterozygous individuals. The number of alleles per locus varied from 2 to 4, with a mean 2.88. In general, SSR were classified as informative (0.36). The average value of the Shannon Index was 0.71, which shows moderate variability in this cultivar. AMOVA showed higher diversity within cultivars (98%). The gene flow (Nm=28.4) was moderate, this can be explained by the flow of pollen between the different cultivars, the reproduction system of the species, self-incompatibility and the introduction of genotypes from other sites by farmers. The genetic diversity identified in this study is sufficient to initiate breeding programs aimed at identifying cultivars with higher yields.

Full-sib progenies show greater genetic diversity than half-sib progenies in sour passion fruit: an approach by ssr markers

BACKGROUND

Genetic variability is the most important parameter in plant breeding based on selection. There is a need for morpho-agronomic and molecular characterization of Passiflora species, to exploit their genetic resources more efficiently. No study has yet been carried out to compare half-sib and full-sib families in relation to the magnitude of the genetic variability obtained in them, and then to elucidate the advantages or disadvantages of each one.

METHODS AND RESULTS

In the present study, SSR markers were used to evaluate the genetic structure and diversity of half-sib and full-sib progenies of sour passion fruit. Two full-sib progenies (PSA and PSB), and a half-sib progeny (PHS), together with their parents, were genotyped with a set of eight pairs of SSR markers. Discriminant Analysis of Principal Components (DAPC) and Structure software were used to study the genetic structure of the progenies. The results indicate that the half-sib progeny has lower genetic variability, although it has higher allele richness. By the AMOVA most of the genetic variability was found within the progenies. Three groups were clearly observed in the DAPC analysis, while two hypothetical groups (k = 2) were observed in the Bayesian approach. The PSB progeny showed a high genetic mixture between the PSA and PHS progenies.

CONCLUSION

Lower genetic variability is found in half-sib progenies. The results obtained here allow us to suppose that the selection within full-sib progenies will possibly provide better estimates of genetic variance in sour passion fruit breeding programs, since they provide greater genetic diversity.

A genome sequence resource for the genus Passiflora, the genome of the wild diploid species Passiflora organensis

The genus Passiflora comprises a large group of plants popularly known as passionfruit, much appreciated for their exotic flowers and edible fruits. The species (∼500) are morphologically variable (e.g., growth habit, size, and color of flowers) and are adapted to distinct tropical ecosystems. In this study, we generated the genome of the wild diploid species Passiflora organensis Gardner by adopting a hybrid assembly approach. Passiflora organensis has a small genome of 259 Mbp and a heterozygosity rate of 81%, consistent with its reproductive system. Most of the genome sequences could be integrated into its chromosomes with cytogenomic markers (satellite DNA) as references. The repeated sequences accounted for 58.55% of the total DNA analyzed, and the Tekay lineage was the prevalent retrotransposon. In total, 25,327 coding genes were predicted. Passiflora organensis retains 5,609 singletons and 15,671 gene families. We focused on the genes potentially involved in the locus determining self-incompatibility and the MADS-box gene family, allowing us to infer expansions and contractions within specific subfamilies. Finally, we recovered the organellar DNA. Structural rearrangements and two mitoviruses, besides relics of other mobile elements, were found in the chloroplast and mt-DNA molecules, respectively. This study presents the first draft genome assembly of a wild Passiflora species, providing a valuable sequence resource for genomic and evolutionary studies on the genus, and support for breeding cropped passionfruit species.