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B. Nigra (b + nigra)

Distribution by Scientific Domains
Life Sciences100%

Selected Abstracts

Trade-offs in oviposition choice?

ENTOMOLOGIA EXPERIMENTALIS ET APPLICATA, Issue 2 2007
Food-dependent performance, defence against predators of a herbivorous sawfly
Abstract The sawfly Athalia rosae L. (Hymenoptera: Tenthredinidae) is a feeding specialist on plant species of the Brassicaceae, which are characterised by secondary metabolites, called glucosinolates. The larvae can take up the respective glucosinolates of their hosts and concentrate them in their haemolymph to protect themselves against predators. Oviposition preferences of naïve females were tested for three species, Sinapis alba L., Brassica nigra (L.) Koch, and Barbarea stricta Andrz., and were related to larval performance patterns. Larvae were reared on either one of these plants and it was investigated how host-plant quality influences both the developmental times and growth of larvae (bottom-up) and the defence efficiency against predators (top-down). Innately, almost all adult females avoided B. stricta for oviposition and clearly preferred B. nigra over S. alba. On average, larvae developed best on B. nigra. Female larvae reached similar final body masses on all host-plant species, but males reared on S. alba were slightly lighter. The developmental time of larvae reared on B. stricta was significantly longer than on the other two plants. However, larvae reared on B. stricta were best protected against the predatory wasp Polistes dominulus Christ (Hymenoptera: Vespidae). The wasps rejected these larvae most often, while they attacked larvae reared on S. alba most frequently. Thus, larvae feeding on B. stricta theoretically run a higher risk of predation due to a prolonged developmental time, but in practice they are better protected against predators. Overall, oviposition preferences of A. rosae seem to be more influenced by bottom-up effects on larval performance than by top-down effects. [source]

Transferability and genome specificity of a new set of microsatellite primers among Brassica species of the U triangle

MOLECULAR ECOLOGY RESOURCES, Issue 1 2002
Andrew J. Lowe
Abstract We present a new set of 12 highly polymorphic simple sequence repeat primer sequences for use with Brassica species. These new primers, and four from A.K.S. SzewcMcFadden and colleagues, were tested in four Brassica species (B. rapa, B. napus, B. oleracea and B. nigra). Most primers successfully amplified products within all species and were polymorphic. Due to the risk of gene flow from GM oilseed rape to its wild relatives, hybrid formation in the Brassicaceae is of great interest. We identify six primer pairs as specific to the A, B or C genomes that could be used to identify such hybrids. [source]

Utility of AFLP markers for the assessment of genetic diversity within Brassica nigra germplasm

PLANT BREEDING, Issue 1 2004
M. S. Negi
Abstract Genetic diversity of 18 Brassica nigra accessions was estimated using amplified fragment length polymorphism (AFLP) marker technology. Two B. rapa and two B. juncea accessions were selected as outliers in the study. Eight AFLP primer combinations generated a total of 426 bands, of which 79% were polymorphic. The UPGMA method was employed to construct a dendrogram based on the Jaccard's similarity coefficient. The accessions of B. rapa separated from those of B. nigra at a genetic similarity coefficient of 0.27 while those of B. juncea did so at 0.5. The genetic similarity coefficients within the B. nigra accessions ranged from 0.58 to 0.86. Based on these coefficients it was concluded that the B. nigra accessions show high levels of genetic variation. These results have significant implications in the crop improvement programmes for the agronomically important crop B. juncea, an amphidiploid of B. nigra and B. rapa. Two incorrectly labelled B. nigra accessions were also identified. These accessions were found to cluster with those of B. juncea accessions. This result demonstrates the great value of AFLP markers in the management of genebanks. [source]

Potential for using host resistance to reduce production of pseudothecia and ascospores of Leptosphaeria maculans, the blackleg pathogen of Brassica napus

PLANT PATHOLOGY, Issue 4 2004
S. J. Marcroft
Pseudothecial density of the blackleg fungus Leptosphaeria maculans and discharge of ascospores was measured from stubble of a range of Brassica species, including Brassica napus (canola) cultivars, with a range of blackleg resistance. Since ascospores are the primary inoculum, these parameters reflect inoculum potential for blackleg. Stubble from a representative line of each of B. carinata, B. nigra, Sinapis alba and B. napus cv. Surpass 400 (incorporates blackleg resistance from B. rapa ssp. sylvestris) had lower pseudothecial density and discharged fewer ascospores than stubble of other B. napus cultivars (Karoo, Oscar, Emblem, Dunkeld and Columbus). These latter B. napus cultivars and a representative B. juncea line had higher pseudothecial densities and discharged higher numbers of ascospores. If this trait of low blackleg inoculum from stubble could be introgressed into commercial canola cultivars, blackleg disease severity could be substantially reduced, resulting in higher and more stable canola yields. However, the trait of reduced ascospore discharge may not be stable, as demonstrated by the B. rapa ssp. sylvestris -derived resistance already being overcome by the blackleg fungus in Australia. [source]

Genome redundancy and plasticity within ancient and recent Brassica crop species

BIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 4 2004
LEWIS N. LUKENS
The crop species within the genus Brassica have highly replicated genomes. Three base ,diploid' species, Brassica oleracea, B. nigra and B. rapa, are likely ancient polyploids, and three derived allopolyploid species, B. carinata, B. juncea and B. napus, are created from the interspecific hybridization of these base genomes. The base Brassica genome is thought to have hexaploid ancestry, and both recent and ancient polyploidization events have been proposed to generate a large number of genome rearrangements and novel genetic variation for important traits. Here, we revisit and refine these hypotheses. We have examined the B. oleracea linkage map using the Arabidopsis thaliana genome sequence as a template and suggest that there is strong evidence for genome replication and rearrangement within the base Brassicas, but less evidence for genome triplication. We show that novel phenotypic variation within the base Brassicas can be achieved by replication of a single gene, BrFLC, that acts additively to influence flowering time. Within the derived allopolyploids, intergenomic heterozygosity is associated with higher seed yields. Some studies have reported that de novo genomic variation occurs within derived polyploid genomes, whereas other studies have not detected these changes. We discuss reasons for these different findings. Large translocations and tetrasomic inheritance can explain some but not all genomic changes within the polyploids. Transpositions and other small-scale sequence changes probably also have contributed to genomic novelty. Our results have shown that the Brassica genomes are remarkably plastic, and that polyploidy generates novel genetic variation through gene duplication, intergenomic heterozygosity and perhaps epigenetic change. © 2004 The Linnean Society of London, Biological Journal of the Linnean Society, 2004, 82, 665,674. [source]