Chromosome characterization and variability in some Iridaceae from Northeastern Brazil

The chromosomes of 15 species of Iridaceae of the genera Alophia, Cipura, Eleutherine, Neomarica and Trimezia (subfamily Iridoideae) were examined after conventional Giemsa staining. The karyotypes of Alophia drummondii (2n = 14+1B, 28, 42 and 56), Cipura paludosa (2n = 14), C. xanthomelas (2n = 28) and Eleutherine bulbosa (2n = 12) were asymmetric; Neomarica candida, N. caerulea, N. humilis, N. glauca, N. gracilis, N. northiana and Neomarica sp. (2n = 18); N. cf. paradoxa (2n = 28), Trimezia fosteriana (2n = 52), T. martinicensis (2n = 54) and T. connata (2n = 82) were all generally symmetric. New diploid numbers of 2n = 56 for Alophia drummondii, 2n = 18 for N. candida, N. humilis, N. glauca, and N. gracilis, 2n = 28 for N. cf. paradoxa, and 2n = 82 for T. connata are reported. The karyotypic evolution of the studied species is discussed

Karyological features and cytotaxonomy of the tribe Vernonieae (Asteraceae)

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Chromosome numbers are reported for 29 populations of 19 Vernonieae taxa collected mainly in the northeastern region of Brazil. Among them, data for five genera (Blanchetia, Rolandra, Pithecoseris, Stilpnopappus and Vanillosmopsis) are here reported for the first time, and the first chromosome counts are presented for 12 species. Chromosome numbers are quite diverse among and sometimes within genera, especially in the controversial and large subtribe Vernoniinae. The numbers varied from 2n = 18 to 2n = similar to 72. The main karyoevolutionary mechanism seems to be dysploidy, while polyploidy is probably associated with ancient hybridization processes generating most paleotetraploid genera. All studied species presented semi-reticulated interphase nuclei and proximal-early condensing behavior in prophase to prometaphase. In one species (Vernonia condensata with 2n = 40) fluorochrome staining with CMA/DAPI revealed five chromosome pairs bearing subterminal CMA(+)/DAPI(-) heterochromatin, probably NOR-associated, revealing the existence of low amounts of satellite DNA. The role of these features in the evolution of the tribe is discussed, revealing some interesting aspects for understanding of the Vernonieae karyoevolution, especially regarding neotropical members.28541732189199Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

A Plant-Defensin from Sugarcane (Saccharum spp.)

Comparing available Poaceae defensins with sugarcane ESTs, a putative defensin gene was identified in sugarcane and cloned from genomic sugarcane DNA. The deduced encoded peptide shows the structure and amino acid composition typical of other plant defensins. Using RT-PCR, defensin expression in sugarcane and differences between "normal" and infected sugarcane were evidenced

Chromosomal diversity in Philodendron (Araceae): taxonomic significance and a critical review

The genus Philodendron is a highly diverse Neotropical group of the monocot family Araceae. Despite chromosome counts being relatively abundant for the family, information on the karyotype evolution within the genus is still scarce and very confusing. Therefore, we report diploid numbers and additional cytological features for 43 species of Philodendron, discussing the importance of our results and reviewing previous data. Species were collected in four different Brazilian biomes (Caatinga, Cerrado, Amazon basin and Atlantic Forest) and chromosome counts were based on Giemsa standard staining procedures. First chromosome counts are given for 35 species, while for another eight species counts are reported for new provenances. The majority of the species (27) presented the diploid number of 2n = 32, while the number 2n = 34, the second most frequent, was observed in eight taxa. Uncommon chromosome numbers were observed for seven species: P. callosum and P. uliginosum with 2n = 28, P. hastatum and P. melinonii with 2n = 30, P. corcovadense and P. saxicola with 2n = 36 and P. brevispathum with 2n = 40. On the other hand, two species showed variation in chromosome numbers among analysed cells: P. insigne with 2n = 30-32 and P. pulchrum with 2n = 26-28. Regarding chromosome morphologies, a prevalence of submetacentric and metacentric pairs could be observed in most species, with some taxa having a tendency to asymmetry and a higher number of acrocentric pairs. A list of all available chromosomal data is presented, considering the actual taxonomic circumscription and synonyms. Considering the present analysis and the literature data, we suggest n = 16 instead of n = 18 as the primary basic number of the genus, from which secondary base numbers n = 17, 18 and (less frequently) 15, 14 and 13 have probably been derived. Dysploidy seems to be the prevalent karyoevolutionary trend within the genus. © 2013 Springer-Verlag Wien