Somatic embryogenesis and ploidy stability in cassava (Manihot esculenta Crantz) cultivars regenerated by in vitro culture of young leaves.

The regeneration and cytogenetic analysis of 7 cassava (Manihot esculenta Crantz) cultivars obtained by organogenesis and somatic embryogenesis were investigated. In the first phase, callus formation was induced in young leaves using MS medium supplemented with 1.0, 5.0, 10.0, 15.0 and 20.0 mg/l of 2,4-D or without a growth regulator (control). In the second phase (development), the calli obtained in the above treatments were transferred to MS medium supplemented with factorial combinations of GA3 and BAP at 0, 0.5, 1.0, 1.5 and 2.0 mg/l. Results of the first phase showed that 2,4-D induced the formation of both friable and compact calli. The compact calli displayed root and shoot formation, whilst somatic embryos were obtained only from friable calli in the medium with 1.0 mg/l GA3. Plants obtained from somatic embryos were regenerated in MS medium supplemented with 0.04 mg/l NAA and 0.05 mg/l GA3. Cytogenetic analysis in 167 regenerated plants from somatic embryogenesis and 176 from organogenesis showed 2n= 36 as a normal diploid chromosome number

Estabelecimento do cultivo in vitro da pustumeira (Gromphrena elegans Mart. var. elegans -Amaranthaceae).

O presente trabalho teve como objetivo o estabelecimento do cultivo in vitro da pustumeira, utilizando-se segmentos nodais ou sementes provenientes de plantas selecionadas em coletas realizadas na região de Irecê, no Estado da Bahia

Karyotypic stability in asparagus (Asparagus officinalis L.) cultivars revealed by rDNA in situ Hybridization.

Four asparagus cultivars were cytologically studied by conventional staining and in situ hybridization, in order to evaluate both the variability among cultivars and the distribution pattern of 18S-25S rRNA genes. lhe mitotic and meiotic analysis with conventional chromosome staining did not show heteromorphisms or differences between cultivars. In situ hybridization with 18S and 25S rONA probes showed 6 chromosomes with 18S-25S rONA sites in the 4 studied genotypes. lhe New Jersey, Waltam Washington and G4X 14 cultivars presented 4 chromosomes with larger subterminal sites and 2 with interstitial sites of smaller size. In the Oeco cultivar, heteromorphism was verified in the size of the rONA sites, which were larger and subterminal in 3 chromosomes, and small and interstitial in 3 other chromosomes. lhe results suggest that asparagus cultivars may present only small differences in the number and distribution of rONA loci

Chromosome study in Schistocerca (Orthoptera-Acrididae-Cyrtacanthacridinae): karyotypes and distribution patterns of constitutive heterochromatin and nucleolus organizer regions (NORs).

Chromosome analyses were performed in two grasshopper species of the genus Schistocerca, S. pallens and S. flavofasciata. Both species shared the same diploid number (2n = 23, X in males; 2n = 24, XX in females); and a con- served karyotype composed exclusively of acrocentric chromosomes but differed in their distribution patterns of constitutive heterochromatin and nucleolus organizer regions (NORs). Constitutive heterochromatin was located in the pericentromeric region of alI chromosomes in both species. S. flavofasciata presented an additional C-band on the distal region of the long arm of a small autosome pair (S9). Nucleolus organizer regions (NORs), revealed by silver nitrate staining (Ag-NORs), were observed on a medium autosome pair (M5) in both species. S. pallens presented an additional NOR-bearing autosome (M6). The same sites were labeled after FISH with an rDNA probe in S. pallens cells

Estabelecimento de acessos de Passiflora cincinnata Mast. por organogênese direta in vivo de segmentos radiculares.

O maracujá-do-mato (Passiflora cincinnata Mast.) é uma das espécies nativas de potencial econômico do gênero Passiflora, sendo u ma importante alternativa em programas de melhoramento genético, principalmente para obtenção de variedades tolerantes e/ou resistentes a algumas doenças da principal espécie plantada comercialmente

New records of Pteridophytes in the semi-arid region of Brazil.

The goal of this paper is to enumerate the pteridophytes that occur in the semi-árid region of the State of Pernambuco, Brazil

Interaction between sucrose and pH during in vitro culture of Nephrolepis biserrata (Sw.) Schott (Pteridophyta).

Interaction between sucrose and pH during in vitro culture of Nephrolepis biserrata (Sw.) Schott (Pteridophyta)). The present work reports the effect of different pH and sucrose concentrations on in vitro propagation of Nephrolepis biserrata. Fronds aseptically obtained from stolon segment culture were cultivated in MS semi-solid medium supplemented with 0, 15, 30, 45 and 60 g.L -1 sucrose and pH adjusted to 3, 5, 7 and 9, in a factorial design. Frond number and length, pinnae number, raquis length and diam eter, fresh and dry matter weight were measured. Inhibition of shoot and leaf regeneration was observed in all the pH treatments in the abs ence of sucrose. On the other hand, when sucrose was added to the medium, the shoot number increased, reaching the maximum average values of 51.25 and 38.25 shoot per explant at pH 5 and 7, respectively. Sucrose concentrations from 15 to 45g.L -1 increased leaf length and diameter and the pH 9 did not affect the dry matter weight, and was still not adequate for development of new fronds. Young sporophytes were successfully acclimated