Rachel Fatima Gagliardi

In vitro plant regeneration from seed explants of wild groundnut species (Genus Arachis, Section Extranervosae)

In vitro regeneration of wild groundnut species from Section Extranervosae (Arachis villosulicarpa, A. macedoi, A. retusa, A. burchellii, A. pietrarellii, A. prostrata, A. aff. prostrata and a new species) was examined for the purpose of germplasm renewal and conservation. Seeds of different ages, stored at the seed bank of CENARGEN/EMBRAPA were either inoculated on culture medium or used as a source of embryo axis and cotyledon explants. Whole seeds failed to germinate on MS either without growth regulators (MS0) or supplemented with 10 μM TDZ. Embryo axes cultured on MS0 produced only single plants. In the presence of 8.8 μM BAP these explants showed multi-shoot formation. Cotyledons cultured on MS supplemented with 110 μM BAP developed adventitious shoots through direct organogenesis. Plant regeneration was obtained from A. villosulicarpa, A. macedoi, A. retusa, A. burchellii and A. pietrarellii both from embryo axes and cotyledons. Explants from A. prostrata and A. aff. prostrata did not produce regenerants. Rooting of shoots was induced in the presence of 5.4 μM NAA. Primary plants derived from these explants were further multiplied by culturing nodal segments on MS medium plus 2.7 μM NAA.

Germplasm Preservation of Wild Arachis Species through Culture of Shoot Apices and Axillary Buds from In Vitro Plants

A study was conducted to evaluate in vitro techniques for germplasm preservation of wild species of Arachis. Nodal segments excised from in vitro-grown plants of A. retusa, A. macedoi and A. burchellii were used to examine the effects of explant position and age of the donor plant. Explants were excised from plants maintained in culture for 30, 60, 90 or 180 d, numbered I – V from top to bottom and cultured on MS medium supplemented with 2.7 µM NAA or different BAP concentrations (0, 4.4, 13.2 and 22 µM). The age of the donor plant has not influenced the responses of the four genotypes studied. In contrast, shoot regeneration ability was significantly affected by the original explant position, decreasing from top to bottom. In media supplemented with different BAP concentrations, multishoot formation was induced from apical segments at low frequencies (10 – 20%) and segments of all positions originated calluses at the explant basis after 30 d of culture. The culture of nodal segments in the presence of 2.7 µM NAA as the sole growth regulator is recommended for the multiplication of in vitro collections of wild groundnut species in order to avoid callusing and adventitious shoot formation.

Volatile constituents from in vitro and ex vitro plants of Petiveria alliacea L.

In this work, the volatile compounds extracted by simultaneous distillation and extraction as well as the volatile constituents by solid phase micro-extraction (SPME) from different structures (in vitro and ex vitro roots, leaves, and inflorescence) of Petiveria alliacea were analyzed by GC/FID and GC/MS. Forty-one different compounds were identified. Differences were observed between plant structures and origin (either in or ex vitro). However, sulfur compounds were common to all samples, like bis(phenyl-methyl)-disulfyde, isothiazole (1,2-thiazole), 2-thiopropane, dimethyl sulphyde, ethylene disulfyde, and 2,3-dimethyl-thiirane. In vitro plant roots exhibited higher chemical diversity among the analyzed plant structures. Substances found in all analyzed structures of P. alliacea by SPME were benzaldehyde, calamenene and the hydrocarbons dodecane, tridecane, and tetradecane.

Plant regeneration in Arachis stenosperma Krapov. and W. C. Gregory from roots and calluses derived from leaflets of in vitro plants

Seed explants of A. stenosperma were cultured on MS medium supplemented with 6-benzylaminopurine with the aim of rescuing nonviable accessions stored in seed bank conditions. The regeneration potential of leaf explants from in vitro plants derived from embryonic axes was studied by using whole leaflets and leaflet segments. Explants were cultured on Murashige and Skoog (MS) medium supplemented with different concentrations of 6-benzylaminopurine and naphthalene acetic acid. Indirect organogenesis was observed in response to 6-benzylaminopurine, either alone or in association with naphthalene acetic acid, in both explant types. Media supplemented with naphthalene acetic acid as the sole growth regulator induced rhizogenesis in whole leaflets and leaflet segments, with subsequent shoot production directly from the roots.

Genetic and epigenetic analyses of in vitro-grown plants of Arachis villosulicarpa Hoehne (Leguminosae) obtained from seed explants through different regeneration pathways

Summary In vitro conservation techniques are considered suitable strategies for ex situ conservation of wild species of Arachis. However, there is a potential risk of genetic and epigenetic alterations induced by tissue culture conditions. The goal of this work was to determine the influence of explant type and regeneration pathway on sequence modifications and changes in the DNA methylation status of in vitro-grown plants of A. villosulicarpa using Amplified Fragment Length Polymorphism (AFLP) and Methylation-Sensitive Amplified Polymorphism (MSAP) analyses. Regeneration from embryo axes occurred through multiplication of pre-existing meristems. Cotyledons and embryonic leaflets displayed direct and indirect organogenesis, respectively. No polymorphic AFLP amplification fragments were detected among the regenerants. Conversely, MSAP analysis showed a decrease in the levels of DNA methylation in cotyledon- and embryonic leaflet-derived plants.

In vitro regeneration and conservation of wild species of Arachis

Summary Wild species of Arachis are restricted to South America and generally occur in regions under intensive environmental disturbance. Both in situ and ex situ conservation strategies are required in order to maintain the availability of these genotypes. This work developed in vitro regeneration systems from seed explants of 17 wild species of Arachis from six Sections (Heteranthae, Caulorrhizae, Triseminatae, Erectoides, Procumbentes and Arachis). After seed disinfection, embryonic axes, leaflets and cotyledons were excised aseptically and cultured on Murashige and Skoog (MS) medium supplemented with 8.8 µM, 22 µM or 110 µM 6-benzylaminopurine (BAP). Cultures were maintained in a growth chamber at 28° ± 2°C with a 16 h photoperiod. Regeneration patterns from seed explants were similar among species from all Sections. Embryonic axes produced plants through meristematic amplification or multiple shoot formation, while cotyledons and embryonic leaflets produced shoots at significantly lower frequencies through direct and indirect organogenesis, respectively. Shoots obtained from all explants were transferred to MS medium without growth regulators to induce root formation.