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  • Author or Editor: Maria Elena Cartea x
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Four clustering methods were compared for classification of a collection of 148 kale landraces (Brassica oleracea L. acephala group) from northwestern Spain based on morphologic characters: the unweighted pair group method using arithmetic averages (UPGMA) and the Ward method, hierarchical cluster algorithms, and the modified location model (MLM) applied to both the UPGMA and the Ward method (UPGMA-MLM and Ward-MLM, respectively). Comparisons were based on five criteria and on subjective considerations about the structure of each method and the characteristics of the material evaluated. Although the UPGMA-MLM was superior according to the objective criteria, its slight advantage with respect to the Ward-MLM strategy did not overcome the fact that the initial UPGMA cluster generated a classification with little value. The Ward-MLM strategy generated five homogeneous groups with defined morphologic characteristics. Moreover, the Ward-MLM strategy allowed the identification of redundant landraces, which would permit the number of accessions in further critical trials to be reduced.

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Brassica napus includes economically important crops such as oilseed rape, rutabaga, and leaf rape. Other vegetable forms of Brassica napus, namely nabicol and couve-nabiça, are grown in northwestern Spain and north of Portugal, respectively, and their leaves are used for human consumption and fodder. The relationship of nabicol with other Brassica napus leafy crops was studied before, but its origin remained unclear. The aims of this work were to study the genetic relationships among nabicol landraces and other B. napus crops based on microsatellites and to relate the genotypic differences with the use of the crop. The relationship among 35 Brassica napus populations representing different crops was studied based on 16 microsatellite markers. An analysis of molecular variance was performed partitioning the total variance into three components. The source of variation resulting from groups was defined considering the main use of the crop and accounted for a smaller percentage of variation than other sources of variation, proving that this division is not real. Populations clustered into seven different clusters using a similarity coefficient of 0.82. No clear association was evident between clusters and the main use of populations, suggesting genetic differences among populations could reflect differences in their origin/breeding or domestication. Spanish nabicol could have originated from a sample of couve-nabiças, and couve-nabiças could be used to improve nabicol landraces, because they have a narrow genetic basis that limits their potential for breeding.

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A Brassica napus L. crop called nabicol traditionally has been grown by farmers in northwestern Spain for many years and is an important horticultural product during the winter season. The relationship of nabicol to other B. napus crops has been studied based on simple sequence repeat (SSR) data. However, molecular and morphologic classifications often disagree. The objectives of this research were to study the morphologic and agronomic relationships of nabicol landraces to other B. napus crops and to compare those relationships with the ones already known, based on SSR data. Thirty-five B. napus populations from different geographic origins and uses were evaluated. Data were recorded on 17 morphologic and agronomic traits. Principal component analysis and cluster analysis were performed to classify the populations. Eight principal components (94% of the total variability) were standardized to produce the Mahalanobis' generalized distances, and a cluster analysis was conducted using the unweighted pair group method with arithmetic averages. There are no major differences between B. napus var. pabularia (DC.) Rchb. (nabicol, couve-nabiça, forage rape) and B. napus var. oleifera DC. (oilseed rape), and they probably share a common origin. Rape kale (B. napus var. pabularia) and rutabaga [B. napus var. napobrassica (L.) Rchb.] cultivars are separated from the rest and probably they have an independent origin or domestication. Molecular and morphologic classifications are complementary, and both are necessary to classify germplasm correctly and to clarify genetic relationships among B. napus crops.

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The glucosinolate profile of leaves and seeds of 33 Brassica napus L. crops, including leafy crops, forage, rutabaga, and oilseed crops, was compared by high-performance liquid chromatography to investigate the relation between the consumable product of each crop and the glucosinolate profile. Glucosinolate concentration was higher in seeds than in leaves, varying from 3.8-fold in oilseed crops to 7.1-fold in root vegetable crops. Aliphatic glucosinolates predominated in both organs. In seeds, aliphatic glucosinolates represented between 91% to 94% in the different groups, whereas in leaves there was more variation. For root vegetable crops, aliphatic glucosinolates represented 80% of the total glucosinolate concentration. For leafy and forage types, aliphatic glucosinolates represented approximately 90% and for oilseed crops represented 92%. Indole glucosinolates were more abundant in leaves (5% to 17%) than in seeds (5% to 8%). The total glucosinolate content in leaves ranged from 14 to 24 μmol·g−1 dry weight (DW) in oilseed and forage types, respectively, whereas in the seeds, it ranged from 55 to 115 μmol·g−1 DW in oilseed and forage types, respectively. Significant differences were noted among the four groups in glucosinolate concentration and glucosinolate composition. In the seeds, progoitrin was found as the main glucosinolate in all groups. In the leaves, two different glucosinolate profiles were found depending on the crop: forage and root vegetable crops showed high levels of progoitrin, whereas glucobrassicanapin was the main glucosinolate for oilseed and leafy crops. We suggest that different selection criteria applied on B. napus crops according to their use could have led to an indirect selection for glucosinolate profile in leaves.

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