Micropropagation of Cyrtopodium paludicolum (Orchidaceae) from root tip explants

An efficient protocol for in vitro plant propagation of Cyrtopodium paludicolum has been developed using root tips dissected from well-developed seedlings. Root tips were cultured on Knudson medium supplemented with α-naphthaleneacetic acid (NAA), and/or thidiazuron (TDZ). TDZ did not induce protocorm-like bodies (PLBs) in the NAA absence, indicating phytoregulators synergistic effect. Medium supplemented with 1.34 μM NAA and 2.27 μM TDZ resulted in better response on PBLs, and subsequent shoot differentiation (55.25 shoots per explant), and in better rooting number and root length responses, favoring acclimatization with 90% of survived plants. However, the medium supplemented with only NAA (1.34 μM) resulted in 33.50 shoots per explant. Histological sections confirmed that only one PLB was induced per responsive root tip, and it showed numerous dispersed and extended meristemoids, or division centers that originated new PBLs. Additionally, this protocol could be an excellent model to study molecular aspects of root to shoot conversion

In vitro propagation of Cyrtopodium saintlegerianum rchb. f. (orchidaceae), a native orchid of the Brazilian savannah

In order to enable production of large quantities of plantlets for reintroduction programs, as well as economic exploration, Cyrtopodium saintlegerianum seeds were sown on Knudson culture medium. After seed germination, the protocorms were inoculated on Knudson culture medium supplemented with 6-benzyladenine (BA) and α-naphthaleneacetic acid (NAA). The obtained shoots were individually inoculated in Knudson supplemented with gibberellic acid (GA3 ) in order to promote elongation. Seedlings were evaluated and then transplanted into trays containing commercial substrate Plantmax®-HT, or crushed Acuri leaf sheath. Auxin/ cytokinin ratio influenced in vitro propagation of C. saintlegerianum, resulting in increased shoot number when 2.0 mg L-1 BA was added to the culture medium in the absence or presence of 0.5 mg L-1 NAA. This species proved to be promising for massal in vitro multiplication. Despite having incremented in vitro shoots elongation, the use of GA3 is unnecessary since it contributed negatively in the acclimatization of plants

Colletotrichum gloeosporioides, pathogen of orchids in the northeast of Argentina

4 ilus. 10 ref.El objetivo de este trabajo fue identificar el agente causal de manchas foliares detectadas en plantas Orchidaceae del noreste (NE) de Argentina. Desde el 2001, se recolectaron muestras con s?ntomas de enfermedad en invernaderos de las ciudades de Corrientes, Resistencia (Chaco) y Formosa, y muestras procedentes de Esteros de Iber? (Corrientes). Los cultivos sobre agar-papa-glucosa produjeron abundantes colonias de micelio a?reo gris y conidios unicelulares, oblongos, hialinos, con extremos redondeados de 16,0 a 24,0 ?m x 4,0 a 6,0 ?m. Las setas fueron rectas y oscuras. Sobre la base de caracter?sticas morfol?gicas, el hongo se identific? como Colletotrichum gloeosporioides Penz. Sacc. Se manifest? el teleomorfo Glomerella cingulata. Se determin? la patogenicidad de un aislamiento sobre hojas de Cattleya intermedia x C. walkeriana, Dendrobium nobile Lind. y Miltonia flavescens Lind. en inoculaciones con heridas, y se observaron s?ntomas una semana despu?s de la inoculaci?n. Se reaisl? a C. gloeosporioides como pat?geno. Este es el primer informe de C. gloeosporioides afectando diversas especies de orqu?deas en el NE de Argentina. The aim of this study was to identify the causal agent of leaf spots detected in Orchidaceae plants from the Argentinian northeast (NE). Since 2001, samples with symptoms were collected in greenhouses from the cities of Corrientes, Resistencia (Chaco) and Formosa, and from Esteros del Iber? (Corrientes). Cultures on potato-glucose-agar yielded abundant, gray aerial mycelium and unicellular, hyaline, oblong conidia, with rounded ends. Conidial size ranged from 16.0 to 24.0 ?m x 4.0 to 6.0 ?m. Setae were straight and dark. Based on morphological characteristics, the fungus was identified as Colletotrichum gloeosporioides Penz. Sacc. The teleomorph Glomerella cingulata was developed. Pathogenicity of the fungus was determined on leaves of Cattleya intermedia x C. walkeriana, Dendrobium nobile Lind. and Miltonia flavescens Lind. Seven days after inoculation, symptoms appeared that were similar to those originally observed on the orchid leaves. C. gloeosporioides was isolated again from infected leaves, confirming it as the pathogen. The fungus was reported as a pathogen on 19 genera and species of orchids. This is the first report of C. gloeosporioides as a pathogen of several orchid species in the Argentinian NE

Regeneration of plants from anthers of Stevia rebaudiana Bertoni (Compositae) cultivated in vitro

Plants were regenerated from anthers of Stevia rebaudiana Bertoni cultured in vitro under defined conditions. Anthers (containing uninucleate microspores were induced to form callus when aseptically cultured on Murashige and Skoog liquid medium supplemented with 0.1 mg.L(-1) and 1 mg.L(-1) BAP. Regeneration of shoots was readily achieved by transferring pieces of callus to fresh solid medium with the same composition. Shoots were induced to form roots upon transfer to medium with 0.1 mg.L(-1) NAA. Plantlets were successfully potted. Citologycal studies of root tips from regenerated plants revealed a normal diploid number of chromosomes (2n=22)

Cryopreservation of seeds and in vitro-cultured protocorms of Oncidium bifolium Sims. (Orchidaceae) by encapsulation-dehydration

Encapsulation-dehydration was employed for cryopreserving seeds and in vitro-cultured protocorms of Oncidium bifolium. Freshly harvested seeds, 120 days after pollination, were encapsulated in beads containing 1/2 MS medium with 3% sucrose and 3% calcium alginate and subsequently pretreated in agitated (80 rpm) liquid medium supplemented with 0.15 M sucrose (24 h) followed by 0.25 M sucrose (48 h), 0.5 M sucrose (24 h) and 0.75 M sucrose (24 h). The beads with seeds were dehydrated with silica gel for 5 h to 19.2% moisture content and immersed in liquid nitrogen for I h, thawed at 30 degrees C for 2 min, post-treated using the same series of liquid media [0.5 M sucrose (24 h), 0.25 M sucrose (48 h), 0.15 M sucrose (24 h)], and recultured on 1/2 MS medium with 0.1 M sucrose and 0.7% agar. As much as 4.8% of the cryopreserved seeds produced complete plants. In-vitro cultured protocorms were successfully cryopreserved following the same procedure, allowing 11.3% of them to produce plants