Population genetic structure results from the interaction between historical events, current ecological conditions and life traits. The genetic structure and gene flow between populations are important to species dynamics, mainly for rare and endangered species that are more vulnerable to landscape changes and fragmentation. Here we evaluated the genetic diversity, population structure and gene exchange in Petunia bonjardinensis, P. reitzii and P. saxicola, three rare species endemic to subtropical highland grasslands in southern South America. We analysed the genetic diversity and structure considering historical events, such as founder effect and climate changes, and biological traits of each species. We also estimated the conservation status for these three species. We collected samples from all adult individuals and occurrence sites that could be found at the same flowering season and genotyped them for 13 nuclear microsatellite markers. Our results indicate that rarity is probably historical for these species, given that we found no genetic evidence for recent bottlenecks. Petunia bonjardinensis, with the largest occurrence area and population sizes, displayed the higher diversity indices. The other two showed lower genetic diversity and are geographically most restricted. Gene exchange among these species was low, although they share some ancestral genetic polymorphism. Historical migration, founder effects and Pleistocene climate cycles ae the main factors explaining genetic diversity, and this was also influenced by reproductive biology and recent habitat loss, whereas the landscape influences the structure. Based on IUCN criteria, the three species are endangered, and the main risk for their survival is probably anthropic activity in the occurrence area. We recommend an urgent programme for the preservation of these species in situ and ex situ.
The present study was performed for the morphological and cytogenetic description of F 1 hybrids obtained from a cross between Passiflora coccinea Aubl. and Passiflora hatschbachii Cervi. Hybridization was confirmed by genomic in situ hybridization (GISH). Corona banding was the most relevant floral descriptor for separating the hybrids into two groups, the cultivars P. 'Vivis' and P. 'Jhovi', and the parents and hybrids had diploid chromosome number 2n = 18. The F 1 progenies exhibited normal meiotic behavior with normal tetrad production, which guaranteed high pollen viability (>70%) and fertile hybrids. Therefore, P. 'Vivis' and P. 'Jhovi' have the potential to be used for ornamental plants market.
Interspeci c hybrids can be studied using methodologies in which the male gamete with high reproduction potential, viability, and fertility is prioritized. Passi ora species, with lush, showy, and exotic colors, have great potential for the ornamental plant market. In addition, arti cial Passi ora hybrids were developed without many di culties because of weak reproductive barriers. Thus, meiotic and post-meiotic behaviors were analyzed with 2% acetic carmine staining. Con rmation of interspeci c hybridization was performed using SSR markers and GISH technique was used to detect genomic differentiation. The pollen viability of the parental and hybrids genotypes was tested using Alexander solution, uorescein diacetate and in vitro germination tests were performed using culture medium. The meiotic behavior was regular and displayed haploid number n = 9 with nine bivalent (II) chromosomal, pairing in 90% of the cells in diakinesis. There was a signi cant difference (p < 0.05) in terminal and interstitial chiasma frequencies. Meiotic irregularities observed were as follows: early and/or delayed chromosomes, disorientation of spindle bers, transverse spindles, tripolar spindles, and asynchrony; and consequently irregular post-meiotic products were observed: monads, dyads, triads, and polyads. GISH was used in the interspeci c hybrids and pairing between homeologous chromosomes, and bivalent and tetravalent formation were observed. From this study, we could conclude that hybrid genotypes are fertile and pollen grains are viable and can be used in breeding programs. We also hypothesize that interspeci c hybrid genotypes of Passi ora can be obtained with regular meiosis, which could be viable and fertile.
Interspecific hybrids can be studied using methodologies in which the male gamete with high reproduction potential, viability, and fertility is prioritized. Passiflora species, with lush, showy, and exotic colors, have great potential for the ornamental plant market. In addition, artificial Passiflora hybrids were developed without many difficulties because of weak reproductive barriers. Thus, meiotic and post-meiotic behaviors were analyzed with 2% acetic carmine staining. Confirmation of interspecific hybridization was performed using SSR markers and GISH technique was used to detect genomic differentiation. The pollen viability of the parental and hybrids genotypes was tested using Alexander solution, fluorescein diacetate and in vitro germination tests were performed using culture medium. The meiotic behavior was regular and displayed haploid number n = 9 with nine bivalent (II) chromosomal, pairing in 90% of the cells in diakinesis. There was a significant difference (p < 0.05) in terminal and interstitial chiasma frequencies. Meiotic irregularities observed were as follows: early and/or delayed chromosomes, disorientation of spindle fibers, transverse spindles, tripolar spindles, and asynchrony; and consequently irregular post-meiotic products were observed: monads, dyads, triads, and polyads. GISH was used in the interspecific hybrids and pairing between homeologous chromosomes, and bivalent and tetravalent formation were observed. From this study, we could conclude that hybrid genotypes are fertile and pollen grains are viable and can be used in breeding programs. We also hypothesize that interspecific hybrid genotypes of Passiflora can be obtained with regular meiosis, which could be viable and fertile.
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