Aristolochia Embergeri, esp\ue8ce nouvelle de la for\ueat dense ivoirienne

Volume: 4Start Page: 101End Page: 10

Morphogenèse à partir du stade juvénile de Vitis vinifera L. issu de graine ou de culture in vitro

Des observations concordantes ont été faites sur des individus de Vitis vinifera L. issus de multiplications in vitro et sur d’autres provenant de semences. Elles laissent penser que les différences de morphogenèse de ces plantes par rapport aux individus d’origine sont le fait d’un fonctionnement du matériel héréditaire en phase juvénile. Celui-ci peut être perpétué du fait de contraintes écologiques (peut-être la culture in vitro, sûrement le climat) associées à des pratiques agronomiques (taille). Des éléments sont ainsi fournis pour améliorer la gestion agronomique de Vitis vinifera.Identical observations were made on Vitis vinifera L. individuals produced either by in vitro multiplication or from sccd. The morphogenetic differences between these plants and their plants of origin, are the result of a malfunction of their genetic material stabilized in a juvenile state. This state can be perpetuated by ecological constraints (in vitro culture possibly, climate certainly, and ccological constraints associated with agronomical techniques such as pruning. Information is thus given on better management of Vitis vinifera L

Grapevine Resistance to the Nematode Xiphinema index

Breeding for varieties carrying natural resistance (R) against plant-parasitic nematodes is a promising alternative to nematicide ban. In perennial crops, the long plant-nematode interaction increases the risk for R breaking and R durability is a real challenge. In grapevine, the nematode has a high economic impact by transmitting (GFLV) and, to delay GFLV transmission, rootstocks resistant to this vector are being selected, using in particular as an R source. To optimize this strategy, the durability has been studied under controlled conditions in F1 and BC1 muscadine-derived resistant accessions previously obtained from either hardwood-cutting or in vitro propagation. After inoculation with a mix, in equal proportions, of four lines representative of the diversity, multiplication on plants has been monitored 3 to 6 years. The nematode reproduction factor remained lower than 1 in resistant plants obtained from hardwood cuttings while it increased at values far beyond 1 in resistant plants of in vitro origin. Data for nematode numbers per gram of roots mostly paralleled those obtained for the reproduction factor. The effect of the propagation type on resistance over years was also evaluated for the ratio female/juvenile and the frequency of males. Altogether our results illustrate that the muscadine-derived resistance based on hardwood cuttings is durable. By contrast, in resistant and reference accessions obtained from in vitro, our data suggest that the increased nematode multiplication might be mainly due to the modification of root architecture consecutive to this propagation method