RESUMEN
Flow cytometry was conducted to evaluate genome size diversity among African diploid species of the Coffea genus. The study included 15 species and six new taxa from Congolese and Cameroonian forest regions which have yet to be botanically characterized. Between-population differences were also recorded in some cases. These evaluations using an internal standard were highly correlated with previous results obtained with an external standard, but differences of up to 18 % existed for some species, involving stoichiometric errors. Consequently, genome size variation between species and within species are discussed as true genome size differences or stoichiometric errors. Environmental and phenotypic correlations with genome size are also discussed.
Asunto(s)
Café/genética , Genoma de Planta , África Central , Núcleo Celular/química , Café/clasificación , ADN de Plantas/análisis , Diploidia , Geografía , Análisis de Regresión , Reproducibilidad de los Resultados , Clima TropicalRESUMEN
Eucalyptus grandis has a mixed-mating reproductive system. Malagasy Eucalyptus seed orchards were established 15 years ago with two aims both based on panmixia: open-pollinated seed production and genetic improvement. The panmixia hypothesis has never been confirmed in the seed orchard. From a seedling seed-orchard stand comprising 349 trees and using data obtained with six selected microsatellite markers, paternity analysis was performed for 724 offspring collected on 30 adult trees. Paternity assignment, based on exclusion procedures and likelihood-ratio method, was achieved with high accuracy; the exclusion probability value was 0.997. The outcrossing rate was very high (96.7%). More than 50% of potential male trees (199 out of 349) in the seed orchard contributed to pollination for 440 offspring of 30 progenies (8.6% of the basic population). The pollination rate from outside the seed orchard was high (39.2%), but might be due to the small size of this seed orchard. This study showed that "panmixia-like pollination" can be assumed.
Asunto(s)
Eucalyptus/genética , Genes de Plantas , Cruzamientos Genéticos , Ambiente , Eucalyptus/fisiología , Variación Genética , Madagascar , Repeticiones de Microsatélite , Polen/genética , Reproducción/genética , Semillas/genéticaRESUMEN
Male fertility of interspecific hybrids was analysed in one F1 and two backcrossed progenies originating from a cross between Coffea canephora and Coffea heterocalyx. Male fertility was tested using pollen stainability with acetic carmine. The results showed a marked decline in fertility at the F1 level, and fertility was almost fully restored after two backcrosses. The computed broad-sense heritability represented 47% of the variance. Quantitative trait loci (QTLs) locations and effects on pollen viability were estimated using an amplified fragment length polymorphism (AFLP) genetic linkage map constructed in the segregating BC1 population. Three significant QTLs (LOD>3 and p < 0.001 by ANOVA) were detected for pollen viability, two of which were responsible for the bimodal distribution of pollen viability in the segregating population. One QTL was involved in fertility variations among fertile BC1 plants. Fertility inheritance is discussed in relation with previously demonstrated chromosomal sterility in Coffea hybrids and the effect of detected QTLs. The potential use of genetic markers to overcome sterility in interspecific hybrids is also discussed.
Asunto(s)
Coffea/genética , Polen/fisiología , Sitios de Carácter Cuantitativo/genética , Selección Genética , Supervivencia Celular , Mapeo Cromosómico , Cruzamientos Genéticos , Ligamiento Genético , Marcadores Genéticos , Genotipo , Homocigoto , Polimorfismo de Longitud del Fragmento de Restricción , Carácter Cuantitativo HeredableRESUMEN
The trnL-trnF intergenic spacer of cpDNA has been sequenced from 38 tree samples representing 23 Coffea taxa and the related genus Psilanthus. These sequences were used for phylogenetic reconstruction using parsimony analyses. The results suggest a radial mode of speciation and a recent origin in Africa for the genus Coffea. Phylogenetic relationships inferred from the cpDNA analysis suggest several major clades, which present a strong geographical correspondence (i.e., west Africa, central Africa, east Africa, and Madagascar). The overall results agree well with the phylogeny previously inferred from nuclear genome data. However, several inconsistencies are observed among taxa endemic to west Africa, suggesting the occurrence of introgressive hybridization. Evidence is also obtained for the genetic origin of the allotetraploid species C. arabica.
Asunto(s)
Café/genética , ADN de Cloroplastos/genética , Variación Genética , Filogenia , Secuencia de Bases , ADN de Cloroplastos/análisis , ADN Ribosómico/genética , Evolución Molecular , Datos de Secuencia Molecular , Hojas de la Planta/genética , ARN de Transferencia de Leucina/genética , ARN de Transferencia de Fenilalanina/genética , Alineación de Secuencia , Análisis de Secuencia de ADNRESUMEN
Flow cytometry gave high resolution of genome size in two coffee taxa (Coffea liberica dewevrei and C. pseudozanguebariae). Propidium iodide (PI) and Petunia hybrida were used as dye and internal standard, respectively. Proportionally between the DNA content and the digitized fluorescence signal was checked. Five main results were evident. First, optimal experimental conditions were established for peak location estimation (mean or mode), staining time (at least 2 minutes), high voltage (557 V) for the photomultiplier tube (PMT), and PI concentration (333 micrograms/ml). Second, a parameterization of the effects of high voltage and PI concentration were deduced from curve fitting. Third, two biases in DNA content estimation were recorded for high voltage and PI concentration, and were minimized. Fourth, the genome sizes of C. liberica dewevrei and C. pseudozanguebariae were estimated with accuracy 2C = 1.421 +/- 0.005 pg and 2C = 1.129 +/- 0.005 pg, respectively. Fifth, between-genotype variance was emphasized within each taxon.