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La micropropagation d’Annona glabra L. à partir de segments nodaux
- Soami Fernanda Caio Deccetti, Renato Paiva, Patricia Duarte de Oliveira Paiva, Magdi Ahmed Ibrahim Aloufa
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Introduction. La propagation in vitro d’A. glabra L. non encore étudiée pourrait permettre de remédier à certaines difficultés de multiplication de cette espèce fruitière ligneuse. Des techniques de micropropagation ayant été déjà expérimentées avec succès avec d’autres espèces d’Annona (A. squamosa, A. cherimola, A. muricata), nous avons cherché à développer un système complet de micropropagation d’A. glabra L. en utilisant des explants de jeunes plantules. Matériel et méthodes. Pour la phase de prolifération de bourgeons axillaires (durée 30 jours), des boutures de segments nodaux prélevées sur la tige de jeunes plantes matrices ont été mises en culture dans un milieu de base MS supplémenté en différentes concentrations de BAP, utilisée seule ou en combinaison avec différentes concentrations d’ANA, et avec ou sans 1,0 mg de GA3·L–1. À l’issue de cette phase, le nombre moyen de tigelles obtenues par explant et leur taille moyenne ont été mesurés pour chacun des traitements. Pour l’enracinement des tigelles obtenues à l’issue de cette prolifération, diverses concentrations d’AIB et différents pH du milieu ont été testés (durée 15 jours). À la fin de cette phase, le nombre moyen de racines obtenues par tigelle et leur taille moyenne ont été évalués. L’acclimatation des microplants a ensuite été suivie en conditions contrôlées pendant 21 jours. Résultats et discussion. Tous les traitements, même ceux dépourvus de régulateurs de croissance, ont permis d’obtenir en moyenne 1,5 tigelles par segment nodal. Toutefois, les tigelles les plus développées ont été obtenues en utilisant 0,5 mg·L–1 de BAP utilisé seul. L’addition de 1,0 mg de GA3·L–1 au milieu de multiplication n’a pas été favorable au développement des tigelles. Durant l’expérimentation in vitro, une nécrose de l’extrémité des tigelles et une abscission foliaire ont pu être observées ; cela pourrait être lié à un déficit en calcium et à l’accumulation d’éthylène à l’intérieur du récipient de culture. Le pourcentage le plus élevé de boutures enracinées et le plus grand nombre de racines produites par explant ont été obtenus sans addition d’AIB au milieu de culture, en utilisant 4,0 mg·L–1 de charbon actif et un pH de 5,0. Les microplants avec racines ont été acclimatés avec succès.
Stomatic behaviour and leaf water potential in young plants of Annona squamosa submitted to saline stress
- Mansur Custódio Nogueira Rejane Jurema, Aloufa Magdi Ahmed Ibrahim, Bandeira de Albuquerque Manoel
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Introduction. In saline soils, the water absorption process of the plants is negatively affected, due to the permeability of the roots, leading to hydric stress. Plants under saline stress close their stomas earlier than plants not in these conditions; this causes an increase in stomatal resistance due to the decrease in water potential. The aim of the present research was to detect alterations in the stomatic behaviour and leaf water potential in young plants of Annona squamosa submitted to saline stress. Materials and methods. Sixty-day-old seedlings of A. squamosa were acclimated for 15 days in a greenhouse, before being submitted to different saline treatments. Five treatments (T0 = 0 mM; T1 = 25 mM; T2 = 50 mM; T3 = 75 mM and T4 = 100 mM of NaCl in a nutritive solution) were applied with six replications. The evaluations of the stomatic response occurred on the 20th, 30th, 40th, 60th, 80th and 90th days after the beginning of the saline treatments. The transpiration measures, diffusive resistance and leaf temperature were registered in the first mature leaf. The photosynthetically active radiation, relative humidity and air temperature within the greenhouse were simultaneously assessed 60 and 90 days after the beginning of treatments; then the leaf water potential (Rleaf) was also measured. Results. During the time of the experiment the leaf temperature and its difference from the air temperature was not affected by NaCl levels, but only 90 days after the beginning of the treatments the values observed in the control plants were lower than those observed in the 25 mM treatment. The diffusive resistance after 40 days was increased in all NaCl treatments. The transpiration, independent of treatment, was reduced by 44.1% (at 60 days) and 13.4% (at 90 days) with the 100-mM treatment compared with the control treatment. The increment in NaCl induced a decrease in Rleaf in all treatments, but an equal reduction was observed for each treatment after 60 and 90 days. Conclusion. The NaCl levels affected the transpiration and leaf water potential; however, the leaf water potential showed an equal reduction in all treatments on the 60th and 90th days.
Efficiency of ampicillin and benomyl at controlling contamination of Annonaceae leaf segments cultured in vitro
- José Raniere Ferreira de Santana, Renato Paiva, Magdi Ahmed Ibrahim Aloufa, Eurico Eduardo Pinto de Lemos
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Introduction. For the micropropagation of woody species, contamination of in vitro cultured explants is a constant problem, which can compromise the development of the technique. The aim of our study was to evaluate the effects of an antibiotic and a fungicide on surface and endophytic microorganisms associated with Annona cauliflora, A. bahiensis and A. glabra (Annonaceae) tissue culture. Materials and methods. Our work made it possible to compare a standard disinfection of in vitro cultured explants and the use of either a commercial fungicide, Benlate 500 (50% of benomyl) at (0.0, 1.0, 2.0 and 4.0) ${\rm g} \cdot {\rm L}^{-1}$, or an antibiotic, ampicillin at (0.0, 1.0, 2.0 and 4.0) ${\rm mg} \cdot {\rm L}^{-1}$. Results. The study revealed considerable variations in the infection rates within species and according to the concentrations of benomyl and ampicillin used. Benomyl was effective at cleaning leaf segments, and, at a concentration of 1.0 ${\rm g} \cdot {\rm L}^{-1}$, this fungicide was sufficient to eliminate all fungi. Ampicillin treatments at (0.0 to 4.0) ${\rm mg} \cdot {\rm L}^{-1}$ were ineffective at controlling bacterial contamination. Conclusion. Referring to the difficulty in obtaining an aseptic in vitro culture starting from a woody species, the average number of healthy explants obtained after the disinfection of foliar explants of Annona sp. using the antimicrobial substances tested was significant. Further studies to evaluate the effects of the concentration of chemicals on in vitro plant regeneration for Annona species are needed to clarify the relationship between the concentration and phytotoxic effect of chemicals.
In vitro clonal mass propagation of Ximenia americana L.
- Magdi Ahmed Ibrahim Aloufa, Sandra M.L. Bezerra, Gyselle P.T. Jordâo
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Introduction.Ximenia americana is a species developed in Africa and South America. This fruit tree is threatened by a dangerous process of genetic erosion. In vitro techniques could be used for its rapid clonal propagation. Since there is still no report on vitroculture of the species, we tested its micropropagation using axillary buds from mature plants of X. americana. Materials and methods. Single node explants of X. americana shoots were cultured on a proliferation medium made up with a MS medium containing different concentrations (2.5-15 μM) of two cytokinins [benzyladenine (BA) or kinetin] used individually or in combination with 0.5 μM of an auxin [2,4-dichlorophenoxyacetic acid (2,4-D) or naphtaleneacetic acid (NAA)]. Data were recorded after 5 weeks of culture. From proliferated shoot clumps, shoot explants (approximately 3 cm in length) were excised and transferred to rooting media made up with MS medium with or without 0.5 M of indolebutyric acid (IBA) (pH = 5.8). Results. The most rapid and earliest proliferation was observed in media with the lowest concentrations of cytokinins. Absence of growth regulators in media and media with 2,4-D or NAA considerably delayed bud proliferation. The number of shoots per explant increased with the increase of cytokinins. The maximum number of shoots was achieved in 10 μM BA. When shoots were transferred to rooting media, media supplemented with 0.5 μM IBA improved the rooting frequency, root quality and number of roots per cutting. After rooting, the vitroplants were transplanted into small polybags with 1:1 non-sterile soil and sand, then in the field after 4 weeks. Eighty percent of the plants taken from regulator-supplemented media were acclimated versus 15% of those taken from auxin-free media. Conclusion. The rapid clonal propagation of X. americana is possible through in vitro culture of nodal explants. The best cytokinin for shoot multiplication was BA.