Effet de la Période de Pollinisation Manuelle sur la Fructification de l’igname (Dioscorea rotundata Poir; Dioscoreaceae) en Côte d’Ivoire

D. rotundata is the most popular species among consumers in Cote d'Ivoire. However, its production is stagnating due to the many constraints associated with its cultivation, particularly virus diseases. The use of improved varieties from sexual reproduction could effectively contribute to sustainable production. This work aimed to evaluate the crossing period in order to increase fruiting rates in this species. A total of 28 intra-specific crosses were carried out using 4 female and 7 male clones from the CNRA-Bouake yam collection. Two time slots H1 (from 7:30 to 11:00) and H2 (from 11:00 to 13:30), selected for crossings, were compared to determine the optimal pollination period. Out of 30061 pollinated flowers, 2249 fruits were obtained i.e 7.48% with a variation range from 1.16 to 51.06% as the average fruiting rate depending on the clone combinations. Fruiting rates were significantly higher in H1 (8.53%) compared to 6.22% in H2. The female clone, Cnraigr09/00001, has recorded the highest fruiting rate especially in H1 (18.10%). Similarly, the male clones CIVCDr072, TDr00/00380 and TDr95/18555 have got the highest rates in H1 with 9.3; 9.8 and 16.3% respectively compared to those in H2. The couple Cnraigr09/00001 x TDr99/18555 recorded fruiting rates of 35.41% and 8.78% statistically different at schedule H1 and H2, respectively. A strong variation in the fruiting rate in favor of the H1 schedule was obtained between the different clone combinations.L’igname D. rotundata est l’espece la plus appreciee des consommateurs en Cote d’Ivoire. Cependant, sa production stagne du fait des nombreuses contraintes liees a sa culture notamment les viroses. L’utilisation de varietes ameliorees issues de reproduction sexuelle, pourrait contribuer efficacement a une production durable. Ce travail visait a evaluer la periode des croisements afin d’accroitre les taux de fructifications chez cette espece. Au total, 28 croisements intra-specifiques ont ete realises en utilisant 4 clones femelles et 7 clones mâles issus de la collection d’ignames du CNRA-Bouake. Deux plages horaires H1 (de 7h30 a 11h) et H2 (de 11h a 13h30), retenues pour les croisements ont ete comparees en vue de determiner la periode optimale de pollinisation. Sur 30061 fleurs pollinisees, 2249 fruits ont ete obtenus soit 7,48% avec une variation allant de 1,16 a 51,06% de taux moyen de fructification selon les combinaisons de clones. Les taux de fructifications ont ete significativement plus eleves en H1 (8,53%) contre 6,22% en H2. Le clone femelle, Cnraigr09/00001 a eu le taux de fructification le plus eleve et specialement en H1 (18,10%). De meme les clones mâles CIVCDr072, TDr00/00380 et TDr95/18555 ont eu les meilleurs taux en H1 avec respectivement 9,3 ; 9,8 et 16,3% par rapport a H2. Le couple Cnraigr09/00001 x TDr99/18555 a donne des taux de fructifications 35,41% et 8,78% statistiquement differents aux horaires H1 et H2, respectivement. Une forte variation du taux de fructification en faveur de l’horaire H1 a ete obtenue entre les differentes combinaisons de clones.