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Pilar Soengas, Maria Elena Cartea, Pablo Velasco, Guillermo Padilla and Amando Ordás

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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Pedro Revilla, William F. Tracy, Pilar Soengas, Bernardo Ordás, Amando Ordás and Rosa Ana Malvar

The genes sugary1 (su1) and shrunken2 (sh2) are commonly used to produce sweet and super-sweet corn (Zea mays L.), respectively. In this work we compare corn borer [european corn borer (ECB) (Ostrinia nubilalis Hbn.) and pink stem borer (PSB) (Sesamia nonagrioides Lef.)] susceptibility in seven pairs of su1 and sh2 near-isogenic sweet corn inbreds (101t, C23, C40, C68, Ia453, Ia5125, and P39) and the relationship between corn borer resistance and vegetative phase transition. The seven pairs of near-isogenic inbreds were evaluated under corn borer infestation during 3 years in northwestern Spain. Differences among inbreds were significant for most of the traits, although resistance was partial. Ia5125su1 and C40su1 were the most resistant inbreds. Differences between a few pairs of near-isogenic su1 and sh2 strains were significant for some vegetative phase change and corn borer damage-related traits. Generally su1 strains flowered earlier, had a shorter juvenile phase, fewer PSB, and more ECB larvae than sh2 strains. However su1 and sh2 strains did not differ significantly for most traits related to phase transition and corn borer damage; notably ear damage was not significantly different between su1 and sh2 strains. These results suggest that theoretical and practical results of sweet corn (sugary1) breeding for corn borer resistance could be capitalized for super-sweet corn (shrunken2) breeding.

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Bernardo Ordás, Pedro Revilla, Pilar Soengas, Amando Ordás and Rosa A. Malvar

The better emergence and seedling vigor of sweet corn (Zea mays L.) hybrids homozygous for the gene sugary1 (su1) make them more suitable for cultivation under European Atlantic conditions (cold, wet spring) than those homozygous for other traits. Elite sweet corn inbreds homozygous for both su1 and sugary enhancer1 (se1) could improve the table quality of su1 hybrids. The su1se1 inbreds for improving su1su1 hybrid performance can be chosen in several ways. The aim of this paper was to identify donors among su1se1 inbreds that might improve the quality of su1 hybrids. Eight su1se1 inbreds were crossed with eight su1 inbreds that were parents of fifteen su1 hybrids. Hybrids and inbreds were cultivated next to one another in two locations in northwestern Spain in 1999 and 2000. Several possible estimators for identifying su1se1 inbred donors with favorable alleles lacking in the su1 hybrid were determined. These estimators included the relative number of favorable alleles present in the donor but absent in the hybrid (μǴ), predicted three-way cross (PTC), minimum upper bound (UBND), net improvement (NI), probability of the net gain of favorable alleles when there is complete dominance (PNGg), probability of the net gain of favorable alleles when there is partial dominance or epistasis (PNGceg), and general combining ability (GCA). μǴ and NI were chosen for improving hybrid table quality. These estimators indicate that table quality and other traits of su1 hybrids can be improved by using germplasm from the su1se1 inbred lines. The best donor of quality for most of the hybrids was the inbred line IL731a.

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Pablo Velasco, Pilar Soengas, Marta Vilar, Maria Elena Cartea and Mercedes del Rio

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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Pilar Soengas, Pablo Velasco, Guillermo Padilla, Amando Ordás and Maria Elena Cartea

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.