[show abstract][hide abstract] ABSTRACT: Genetic characterization of Japanese plum cultivars (Prunus salicina) using SSR and ISSR molecular markers. Cien. Inv. Agr. 39(3): 533-543. The genetic characterization of 29 elite Japanese plum cultivars (Prunus salicina) and 4 Prunus cultivars was carried out by analyzing 122 Simple Sequence Repeat (SSR) alleles and 232 binary Inter Simple Sequence Repeat (ISSR) loci. A high level of genetic variability was found for these two molecular markers among the Japanese plum cultivars compared to other Prunus species. On average, the variability found by analyzing the SSR alleles were Na = 12.1, Ne = 5.2, Ho = 0.9, He = 0.8 and F= -0.127, whereas ISSR yielded values of h = 0.15 and I = 0.27. The genetic relationship among cultivars was estimated with Principal Coordinate Analysis (PCA) and a Bayesian clustering approach using the software program Structure. This program identified 2 subgroups (k=2). The first group included cultivars of 4 Prunus species: P. salicina, P. armeniaca, P. domestica and P. ceracifera, whose memberships ranged between 0.74 and 1.0. The second group included 19 Japanese plum cultivars and 1 plumcot cultivar, with memberships between 0.57 and 0.99. With some exceptions, similar relationships among cultivars were foundPCA. The level of genetic differentiation between two groups was low (G st =0.055 and ST =0.04), and a low level of linkage disequilibrium (LD) was observed for all allele combinations. These results suggest that the high level of genetic variability, the low level of LD and the scarce degree of differentiation detected by Structure between the two genetic groups can be explained by the self-incompatibility mechanism that favors the exchange between genetically distant Prunus cultivars and by the intra-and interspecific hybridization strategies frequently used in plum breeding programs.
Ciencia e investigación agraria 01/2012; 39:533-543. · 0.44 Impact Factor
[show abstract][hide abstract] ABSTRACT: Beyond their participation in fruit pigmentation and because of their high antioxidant activity, flavonoids are considered important constituents of fruits and vegetables. We have previously reported that in the ripe receptacles of Fragaria chiloensis only traces of flavonoids can be found, while cinnamic acid derivatives are highly accumulated. In order to characterize the molecular background of this uncommon phenotype we analyzed the transcriptional profile of different biosynthetic genes, with special regard to the gene encoding Cinnamate 4-Hydroxylase (C4H), the enzyme transforming cinnamic acid into the next intermediary of the phenylpropanoid pathway. Northern blot and quantitative RT-PCR showed low transcript abundance for the gene encoding C4H and also for a series of structural genes responsible for flavonoid biosynthesis. Together with this, high transcript levels were found for a repressive transcription factor, suggesting that the pathway would be inhibited at the transcriptional level, thus correlating to our previous findings on the chemical phenotype. Our results contribute to the comprehension of the pigmentation phenotype in strawberries, allowing the utilization of Fragaria chiloensis as a model system for the study of antioxidant pigment biosynthesis.
[show abstract][hide abstract] ABSTRACT: Fruit softening is associated with cell wall modifications produced by a set of hydrolytic enzymes and proteins. Expansins are proteins with no catalytic activity which have been associated with several processes during plant growth and development. A role for expansins has been proposed during fruit softening, and many fruit-specific expansins have been identified in a variety of species. A fruit-specific expansin gene from mountain papaya (Vasconcellea pubescens) was isolated and characterised: VpEXPA2, a 851 bp cDNA encoding a polypeptide of 258 amino acids, which contained all the characteristics of α-expansins. DNA gel blot analysis showed that VpEXPA2 is member of a small multigene family in the mountain papaya's genome. Real-time polymerase chain reaction (qPCR) analyses revealed transcript accumulation during the softening of control fruit, with maximum level after 5 d of storage at 20 °C. A reduction in transcript expression level was observed in fruit treated with an ethylene perception blocker (1-methylcyclopropene), while an earlier and higher transcript level was observed in ethylene-treated fruit, suggesting that VpEXPA2 expression is regulated by this plant hormone.
[show abstract][hide abstract] ABSTRACT: Abstract: Gomortega keule (Molina) Baillon is a rare Chilean species classified as endangered and currently under conservation. Currently, conservation of this species is carried out by private companies and government agencies, but is done so based more on pragmatic criteria than scientifically based strategies. In this context, information concerning the genetic variability of the species among the different populations over its entire distribution range is incomplete, making it difficult to coordinate management and conservation strategies. Here we report a study to evaluate the genetic variability and population structure of G. keule over its entire distribution in Chile. Twenty-five ISSR primers for 223 individuals from 11 geographical populations were tested to evaluate genetic variability. Results showed a high level of genetic diversity for the species. A high level of genetic differentiation among populations was found, while genetic structure of the geographic populations was also shown by using STRUCTURE 2.1 software. Despite the fact that this species has been highly affected by human intervention and habitat destruction, a high level of genetic diversity was present. A likely explanation for this is that it reflects the previous distribution of this long-lived species and the current lack of sexual regeneration. Genetic diversity data must be considered in the development of a management strategy for further developing the protected areas, for identifying isolated small populations for conservation, and using larger populations with higher genetic diversity as seed sources for ex situ propagation and replanting. Résumé : Le Gomortega keule (Molina) Baillon constitue une espèce rare menacée, présentement en observation. Actuellement, des entreprises privées et gouvernementales en assurent la conservation sur la base de critères pragmatiques plutôt que scientifiques. Ainsi, l’information sur la variabilité génétique de cette espèce dans les différentes populations et sur l’ensemble de son aire de distribution demeure incomplète, ce qui rend difficile la coordination des stratégies d’aménagement et de conservation. Les auteurs ont effectué une étude sur la variabilité génétique et les structures des populations G. keule, sur l’ensemble de son aire de distribution au Chili. Ils ont évalué 25 amorces ISSR sur 223 individus provenant de 11 populations géographiques, afin d’en déterminer la variabilité génétique. Les résultats montrent une grande variabilité génétique chez cette espèce. On observe également un haut degré de différenciation génétique au sein des populations ainsi que dans la structure génétique des populations géographiques, en utilisant le logiciel STRUCTURE 2.1. En dépit du fait que cette espèce ait été fortement affectée par l’activité humaine, notamment la destruction d’habitats, on observe toujours un fort degré de diversité génétique. Ce qui pourrait expliquer cette situation, c’est qu’elle reflète la distribution ancienne de cette espèce longivive ainsi que le manque de régénération sexuelle actuel. On doit considérer les données sur la diversité génétique lorsqu’on développe des stratégies d’aménagement pour implanter de nouveaux sites de protection, afin d’identifier les petites populations isolées pour leur conservation, et en utilisant les populations plus étendues avec une plus forte diversité génétique comme sources de semences pour la propagation ex situ et la transplantation.
Canadian Journal of Botany 01/2008; 86(11):1299-1310. · 1.40 Impact Factor
[show abstract][hide abstract] ABSTRACT: The Chilean strawberry (Fragaria chiloensis) is noted for its good fruit quality characters and is one of the wild parents of the commercial strawberry (Fragaria × ananassa). However, the fruit of the Chilean strawberry shows a higher level of softening than that of F. × ananassa, a factor that can affect its shelf-life and reduce its keeping quality. Fruit of both species were collected at different developmental and ripening times, and classified into four stages according to weight and color: stages 1 and 2 correspond to small, unripe and hard fruit, while stages 3 and 4 correspond to color-breaker and ripening fruit. Two full-length cDNAs were isolated from F. chiloensis, FcPG1 and FcPL1 encoding polygalacturonase (PG) and pectate lyase (PL) proteins, respectively. In F. chiloensis a considerable increase in PG transcripts was observed between stages 2 and 3, while a lower expression level was observed in F. × ananassa in the same developing stages. The expression pattern of PL in F. chiloensis revealed a gradual increment in the transcript level between stages 2 and 4, with a higher increment between stages 2 and 3 in F. × ananassa than in F. chiloensis. The increase in expression of both genes correlated well with the decrease in firmness observed in the fruit. The faster softening observed in F. chiloensis may result from the earlier and higher level expression of PG. In addition, Southern blot analyses showed that PG and PL genes belong to a multigene family in both species. This study highlights the participation of PG and PL during softening of F. chiloensis fruit, and gives an indication of target genes that can be used to help strawberry breeding programmes.
[show abstract][hide abstract] ABSTRACT: The first noticeable event during the ripening of mountain papaya (Vasconcellea pubescens) is the rapid degreening of the skin, followed by climacteric ethylene and flesh softening. When ethylene perception is blocked by 1-methylcyclopropene (1-MCP, 0.3 μl l−1 for 16 h at 20 °C), the increase in ethylene evolution is avoided, and softening and color development are partially delayed. This indicates that ethylene perception is an absolute requirement for ethylene production during ripening and that softening and color development are only partially dependent on ethylene. Our data also suggest that the changes in pH, titratable acidity, and soluble solids are not dependent on ethylene. Mountain papaya fruit displayed the typical climacteric rise in ethylene production, reaching maximum values of 1.8–3.2 μmol kg−1 h−1, and so confirmed the climacteric nature of the fruit. The activity of ACC oxidase paralleled changes in ethylene production. Nevertheless, when 1-MCP treated fruit recover ethylene sensitivity, a big increase in ACC oxidase activity is observed followed by a further increase, but at a reduced level, of ethylene; the reduced ACC content suggests that in these fruit the availability of ACC is limiting ethylene biosynthesis. Finally, our results indicate that treatment of mountain papaya with 1-MCP delays the onset of the climacteric phase, and therefore can be used commercially to extend effectively the short shelf life of this fruit.