A survey is given about the number and chromosomal position of rDNA loci in 45 Brassicaceae species. For 34 species, 5S and 45S rDNA loci have been localized by two-colour fluorescence in situ hybridization for the first time. These data show the variability of rDNA within karyotypes of the Brassicaceae, provide anchor points for (comparative) genetic maps, and might be important for studies on concerted evolution of internal transcribed sequence types of rDNA in cruciferous plants.

Background and Aims Brassicaceae, with nearly 340 genera and more than 3350 species, anchors the low range of angiosperm genome sizes. The relatively narrow range of DNA content (0.16 pg < 1C < 1.95 pg) was maintained in spite of extensive chromosomal change. The aim of this study was to erect a cytological and molecular phylogenetic framework for a selected subset of the Brassicacae, and use this as a template to examine genome size evolution in Brassicaceae. Methods DNA contents were determined by flow cytometry and chromosomes were counted for 34 species of the family Brassicaceae and for ten Arabidopsis thaliana ecotypes. The amplified and sequenced ITS region for 23 taxa (plus six other taxa with known ITS sequences) were aligned and used to infer evolutionary relationship by parsimony analysis. Key Results DNA content in the species studied ranged over 8-fold (1C = 0.16-1.31 pg), and 4.4-fold (1C = 0.16-0.71 pg) excluding allotetraploid Brassica species. The 1C DNA contents of ten Arabidopsis thaliana ecotypes showed little variation, ranging from 0.16 pg to 0.17 pg. Conclusions The tree roots at an ancestral genome size of approximately 1x = 0.2 pg. Arabidopsis thaliana (1C = 0.16 pg; approximately 157 Mbp) has the smallest genome size in Brassicaceae studied here and apparently represents an evolutionary decrease in genome size. Two other branches that represent probable evolutionary decreases in genome size terminate in Lepidium virginicum and Brassica rapa. Branches in the phylogenetic tree that represent probable evolutionary increases in genome size terminate in Arabidopsis halleri, A. lyrata, Arabis hirsuta, Capsella rubella, Caulanthus heterophyllus, Crucihimalaya, Lepidium sativum, Sisymbrium and Thlaspi arvense. Branches within one clade containing Brassica were identified that represent two ancient ploidy events (2x to 4x and 4x to 6x) that were predicted from published comparative mapping studies.

Ascia monuste Godart, known as the kale caterpillar, has a specialized diet on Brassicaceae and represents one of the main herbivores of this family in the Neotropical region. The objective of the present study was to determine the performance and oviposition preference of A. monuste for common kale Brassica oleracea (Brassicaceae, var. acephala) of different ages. The parameters used to assess performance were time to pupation and emergence, emergence rate, digestive indices, relative consumption and growth rates, number of eggs per female, hatching rate, and weight of the imagoes. Chemical and physical properties of young and old kale leaves were determined. In general, caterpillars feeding on new leaves showed better performance than those feeding on old leaves. However, no significant difference in the number of eggs per female was observed, indicating a strategy of compensation, as old leaves contain a lower amount of nitrogen and are harder than young leaves. A. monuste females prefer to lay eggs on young leaves. | Ascia monuste Godart, conhecida como a lagarta-da-couve, é especialista em Brassicaceae e representa um dos principais herbívoros dessa família na região neotropical. O objetivo do presente estudo foi determinar a performance e a preferência de oviposição de A. monuste por folhas de couve Brassica oleracea (Brassicaceae, var. acephala) de diferentes idades. Os parâmetros utilizados para medir a performance foram tempo para pupação e para emergência, porcentagem de emergência, índices digestórios, taxas de consumo e crescimento relativos, número de ovos por fêmea, porcentagem de eclosão e peso dos imagos. Análises químicas e físicas de folhas jovens e velhas de couve foram feitas. Em geral, imaturos que se alimentam de folhas jovens exibem melhor performance que aqueles que se alimentaram de folhas velhas. Entretanto, não houve diferença no número de ovos por fêmea, indicando mecanismos de compensação, uma vez que folhas velhas possuem menor quantidade de nitrogênio e maior dureza. Fêmeas de A. monuste preferem ovipositar em folhas jovens.

Glucosinolates are biologically active secondary metabolites that display both intra- and interspecific variation in the order Brassicales. Glucosinolate profiles have not been interpreted within a phylogenic framework and little is known regarding the processes that influence the evolution of glucosinolate diversity at a macroevolutionary scale. We have analyzed leaf glucosinolate profiles from members of the Brassicaceae that have diverged from Arabidopsis thaliana within the last 15 million years and interpreted our findings relative to the phylogeny of this group. We identified several interspecific polymorphisms in glucosinolate composition. A majority of these polymorphisms are lineage-specific secondary losses of glucosinolate characters, but a gain-of-character polymorphism was also detected. The genetic basis of most observed polymorphisms appears to be regulatory. In the case of A. lyrata, geographic distribution is also shown to contribute to glucosinolate metabolic diversity. Further, we observed evidence of gene-flow between sympatric species, parallel evolution, and the existence of genetic constraints on the evolution of glucosinolates within the Brassicaceae.

Pollen morphology of 4 species belonging to 4 genera of thefamily Brassicaceae from Pakistan has been examined by the lightmicroscope. Pollen grains are 3-colpate, isopolar, prolate, prolatespheriodal, speriodal, subprolate, tectum reticulate. However, there isvariation in thickness of exine.

The new combination Boechera holboellii (Hornem.) Lööve & Lööve var. pendulocarpa (A. Nelson) N. Snow is made to accommodate this taxon at the rank of variety in that genus for the Southern Rocky Mountain Flora project.

Of the 340 genera in the Brassicaceae, apomictic reproduction is found only in the North American genus BOECHERA: We investigated phylogenetic relationships, ability to hybridize, mating system, and ploidy levels of 92 lines sampled from 85 populations and representing 19 Boechera species. Phylogenetic analyses based on chloroplast DNA sequences identified three lineages in the genus. Reciprocal crosses of each line were made to a common sexual diploid B. stricta tester. The resulting F₁ progeny were analyzed for the inheritance of polymorphic microsatellite loci, genome size, and seed production. Intraspecific B. stricta crosses confirmed that this species is mostly diploid and sexual. Interspecific crosses revealed many other species were diploid and sexual and could be successfully hybridized with the tester. We also found obligate and facultative apomictic diploid and triploid lines. De novo F₁ polyploids (either triploids or tetraploids) were derived from the union of nonreduced (from an apomictic parent) and reduced (from the tester) gametes. However, seed production of these F₁ plants was generally low, suggesting a failure in the transmission of apomixis. The creation of a wide array of segregating genetic populations will facilitate future research on the evolution and inheritance of quantitative variation in BOECHERA:

Nickeliferous soils are invaded predominantly by members of the Brassicaceae, Cyperaceae, Cunoniaceae, Caryophyllaceae, Fabaceae, Flacourtiaceae, Euphorbiaceous, Lamiaceae, Poaceae and Violaceae, and many of these plants are metal tolerant. About 300 Ni hyperaccumulating plants been identified. These members exhibit unusual appetite for toxic metals and elemental defense. Hyperaccumulators provide protection against fungal and insect attack. Investigations suggested that Ni-hyperaccumulation has a protective function against fungal and bacterial pathogens in Streptanthus polygaloides and Thlaspi montanum. Significance of nickelophilous plants and their significance in phytotechnologies are discussed in this paper. | Solos ricos em Ni, niquelíeros, são invadidos predominantemente por membros de Brassicaceae, Cyperaceae, Cunoniaceae, Caryophyllaceae, Fabaceae, Flacourtiaceae, Euphorbiaceous, Lamiaceae, Poaceae e Violaceae, e muitas dessas plantas são tolerantes e metais. Aproximadamente 300 plantas que superacumulam Ni (hiperacumuladoras) já foram identificadas. Estas plantas apresentam capacidade não usual de acumular metais tóxicos e defesa contra eles. O acúmulo excessivo de metais fornece proteção contra o ataque de insetos e fungos. Investigações sugerem que a hiperacumulação de Ni tem como função a proteção contra fungos e bactérias patogênicos em Streptanthus polygaloides e Thlaspi montanum. A importância de plantas niquelíferas e a sua significância em fitotecnologias são discutidas nesta revisão.

Self-compatibility and adaptations to self-fertilization are often found in plant populations at the periphery of species' ranges or on islands. Self-compatibility may predominate in these environments because it provides reproductive assurance when pollinators or availability of mates limits seed production. This possibility was studied in Leavenworthia alabamica, a flowering plant endemic to the southeastern United States. Populations at the center of the species' range retain sporophytic self-incompatibility, but peripheral populations are smaller, self-compatible, and have adaptations for self-fertilization. A reciprocal-transplant experiment was designed to test whether there is pollen limitation of seed set and to examine its strength in central and peripheral populations. Self-compatible genotypes produced more fruit and 17-22% more seed than self-incompatible genotypes in all environments, suggesting that the transition to self-compatibility may be favored by natural selection in all populations inhabited by L. alabamica. Sequence analyses demonstrated that two peripheral populations have 90-100% reductions in genetic variation, consistent with the effects of small population size or historical bottlenecks. Although pollen limitation of seed set occurs in all environments, self-compatibility may evolve at the periphery in L. alabamica because the benefits of reproductive assurance are influenced by population size or bottlenecks following extinction and colonization.

Latitudinal variation in climate is predicted to select for latitudinal differentiation in sensitivity to the environmental cues that signal plants to flower at the appropriate time for a given climate. In Arabidopsis thaliana, flowering is promoted by exposure to cold temperatures (vernalization), and several vernalization pathway loci are known. To test whether natural variation in vernalization sensitivity could account for a previously observed latitudinal cline in flowering time in A. thaliana, we exposed 21 European accessions to 0, 10, 20, or 30 d of vernalization and observed leaf number at flowering under short days in a growth chamber. We observed a significant latitudinal cline in vernalization sensitivity: southern accessions were more sensitive to vernalization than northern accessions. In addition, accessions that were late flowering in the absence of vernalization were more sensitive to vernalization cues. Allelic variation at the flowering time regulatory gene FLC was not associated with mean vernalization sensitivity, but one allele class exhibited greater variance in vernalization sensitivity.