INTRODUCTION DE LA RESISTANCE AU FLETRISSEMENT BACTERIEN CHEZ LA POMME DE TERRE (SOLANUM TUBEROSUM L.) PAR HYBRIDATION SOMATIQUE AVEC DEUX ESPECES APPARENTEES, S. PHUREJA ET S. STENOTOMUM

ORSAY-PARIS 11-BU Sciences (914712101) / SudocSudocFranceF

Ralstonia solanacearum induces soluble amine-oxidase activity in Solanum torvum stem calli

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Overcoming germination barriers in four native Malvaceae shrub species of Reunion island to improve restoration in arid habitats

International audienceIslands are well-known to house an incredible biodiversity, higher level of threatened species and extinctions than mainlands. Because of human activities and climate change, these endangered regions required advanced conservation and restoration strategies. In this study, we investigated seed germination ecology of four native Malvaceae species (Dombeya acutangula, Dombeya populnea, Ruizia cordata and Thespesia populneoides) of degraded dry lowlands of Reunion Island. We measured seed imbibition, investigated the dormancy class of seeds, determined light requirements for germination and identified treatments to improve germination of these species. For this purpose, germination tests were performed over 32 days and two photoperiods (12 h/12 h or 0 h/24 h), by using seeds treated with H2O2, gibberellic acid and smoke water. Mechanical and chemical scarifications as well as heat treatment were also carried out. Germination percentages were analyzed by fitting generalized linear models (GLMs) with a logit link function.For the four species, a significant mass increase is detected for scarified seeds after a week imbibition (>60% mass increase). Germination percentages of seeds treated with H2O2, GA3 and smoke water were not significantly different from control seed. On the contrary, scarified seeds exhibited significantly higher germination percentages than control seeds. In addition, germination speed was also significantly higher for scarified seeds. These results are congruent with a physical dormancy phenomenon of seeds of the four Malvaceae shrubs. In addition, no particular light requirement was observed for germination. Artificial methods to break dormancy and stimulate germination described in this study could improve establishment success in arid habitats

Biological variation of Vanilla planifolia leaf metabolome

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Seed germination of five species from the subalpine shrubland of a mountainous oceanic island with high conservation value (Reunion Island)

International audienceLittle is known about the seed ecology of native plants from subalpine and alpine vegetation zones on oceanic islands, although their biodiversity is unique and vulnerable (e.g. facing fires and biological invasions). This study of seed germination focuses on five species, which are representative of the subalpine shrubland of Reunion Island. The main objectives are to identify the presence of dormancy and light requirements, and to evaluate whether GA 3 or a smoke-infused water could substitute for the light requirement for seed germination. Over one month, germination tests were performed under different conditions at three temperatures (15, 20 and 25 • C), in light (12-hours light/12-hours dark) and in dark. Seeds were also treated using a single spraying of gibberellic acid (GA 3 at 1000 ppm) and a smoke-infused water (named Smoke Water in the study). No dormancy was detected for Stoebe passerinoides. For Erica reunionensis, Agarista buxifolia, Hubertia tomentosa and Hypericum lanceolatum subsp. angustifolium, a potential non-deep physiological dormancy (with a conditional dormancy state) was detected. Moreover, for Agarista buxifolia and Erica reunionensis (Ericaceae), light is required for seed germination. Gibberellic acid (GA 3 at 1000 ppm) substitutes for light, except at 25 • C for E. reunionensis. Smoke Water does not improve seed germination, except at 15 • C in dark for E. reunionensis. A better understanding of seed germination for species from subalpine and alpine vegetation zones will mean better threat management and restoration actions

L'écologie de la germination au service de la restauration écologique et de la lutte contre les espèces exotiques envahissantes : Étude de cas de cinq espèces dans l'étage subalpin à La Réunion

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Overcoming dormancy and light requirements in seeds of Heteropogon contortus, a target species for savanna restoration

As observed at a world scale, in Reunion Island Heteropogon contortus savannas face major pressure and need to be preserved and restored. However, the use of this species in restoration projects is hampered by the limited knowledge about the seed germination ecology and more specifically about dormancy and light requirements. Dormancy state and light requirements for germination of H. contortus seeds were assessed over a 3-year after-ripening period (i.e. storage). Dormancy loss was observed after one year of storage. Between one and two years of after-ripening, H. contortus seeds exhibit significantly higher mean germination percentages in daily light than in darkness, demonstrating their positive photoblasty (i.e. requires light for germination). Smoke solutions significantly enhanced germination in both daily light and darkness during the first two years of dry storage. This study also demonstrated that smoke-infused water with beekeeping smoker fuel could be an efficient method to enhance germination of H. contortus seeds. Overall, this method could be adopted for large scale restoration projects due to its efficiency, its low cost and its reproducibility

Rôle écologique des diterpènes accumulés dans les graines de caféiers

Les caféiers produisent des graines albuminées qui accumulent de grandes quantités de métabolites secondaires, notamment des diterpènes (ca. 1-2% MS). Le cafestol et le kahweol sont les principaux diterpènes spécifiques des caféiers et ils sont stockés sous forme estérifiée à l'acide palmitique. Si leurs propriétés pharmacologiques ont été largement étudiées, leur rôle écologique est encore inconnu. Plusieurs études montrent l'implication de nombreux diterpènes dans la défense des plantes contre les bioagresseurs. Ainsi, nous avons testé l'activité des formes libres et estérifiées du cafestol sur la croissance d'un panel de bioagresseurs, comprenant six souches de champignons phytopathogènes et deux espèces de mouches des fruits. Le cafestol ralentit la croissance des champignons Colletotrichum gloeosporioides, Fusarium oxysporum, Fusarium proliferatum, Fusarium solani et Talaromyces stollii, dès 0,1mM. Il n'a pas d'effet sur Aspergillus niger. La consommation de cafestol par les larves de la mouche des fruits Bactrocera dorsalis entraîne un ralentissement de la pupation et une diminution du taux de pupation, de la masse des pupes et des mouches. La plupart de ces effets sont observés dès 1mM. Ce diterpène n'impacte pas le développement de la mouche Ceratitis capitata. Pour l'ensemble des organismes testés, aucun effet n'a été mesuré pour le palmitate de cafestol. Ces résultats suggèrent l'implication des diterpènes dans la défense de la graine in planta ou au sol. Pour déterminer si les diterpènes joueraient également un rôle dans la protection de la jeune plantule, nous avons étudié leur devenir au cours de son développement après la germination. La teneur et la composition en diterpènes des tissus de la graine (albumen et embryon) et de la plantule (racine, hypocotyle et cotylédon) ont été analysés par HPLC-DAD. Les quantités de cafestol et de kahweol diminuent dans l'albumen au cours de sa digestion et augmentent en parallèle dans tous les tissus de la plantule au cours de sa croissance. Ces résultats soutiennent l'hypothèse d'un transfert des diterpènes depuis l'albumen vers la plantule pour sa protection contre les bioagresseurs

Morphological and histological impacts of the laurina mutation on fructification and seed characteristics in Coffea arabica L

International audienceKey message The comparison between the cultivar Bourbon and its mutant, the Bourbon pointu, of Coffea arabica led to five novel findings on fruit development and three main impacts of the mutation. Abstract Coffea arabica 'Laurina' (Bourbon pointu) is a natural mutant of Coffea arabica 'Bourbon'. Relative to the 'Bourbon' cultivar, it is characterized by internode dwarfism, a Christmas tree shape, and lower caffeine content. The effects of the laurina mutation on fructification over time, the fruit structure and seed characteristics were studied here. Fruits of 'Bourbon' and 'Bourbon pointu' were monitored. The trees were grown in the same plot and flowered on the same day. Harvesting was done every 2 weeks from the 6th to the 26th week after flowering. Histological observations were carried out using multiphoton and conventional microscopes. The measurements concerned the fruit, parchment and seed. Five novel findings on fructification development were obtained: (1) a sigmoid model and nonlinear regression efficiently described the phenomenon; (2) a precise relationship was defined between the qualitative stages of fructification and quantitative observations, thus revealing key weeks in this process; (3) the parchment had a mesocarpic origin; (4) a meristematic zone was present close to the parchment; and (5) an endocarp with three cell layers was visible in young fruits. Three effects of the laurina mutation were highlighted: (1) fruit growth ended 1 week earlier in 'Bourbon', but without difference in fruit length. In contrast, fruits were wider on average in 'Bourbon'; (2) the parchment of narrow seeds in 'Bourbon pointu' was thicker than in other 'Bourbon pointu' and 'Bourbon' seeds; and (3) the narrow seed frequency in 'Bourbon pointu' depended on environmental conditions