Improving the food quality of yams (Dioscorea spp) is an ongoing challenge to yam breeders and researchers. Forty accessions of D alata were evaluated for the suitability of their tubers for the preparation of two dominant food forms (boiled and pounded) as part of an effort to identify potential parents for use in genetic improvement. Trained panellists were presented with randomised, replicated and coded samples of boiled yam tuber pieces and asked to rate them for mealiness, colour, wetness, softness and taste. The sensory attributes considered for pounded yam (dough from boiled and pounded tubers) were consistency, colour, sheen, smoothness, stickiness, elasticity and hardness. Ratings were based on hedonic scales. Cluster analysis revealed groupings of accessions into eight and nine similarity clusters for boiled yam and pounded yam respectively. The mean scores for general preference were regressed on individual attribute scores. Mealiness, colour and taste were important in the general preference for boiled yam. Consistency, colour and stickiness determined the general preference for pounded yam. Of the accessions, 67% were identified as being suitable for preparation as a boiled vegetable, while 55% were assessed to be good for pounded yam, based on the respective quality attributes evaluated.

Amplified fragment length polymorphism (AFLP) markers were employed to assess intraspecific variability in water yam (Dioscorea alata L.). Fifty-three accessions of diverse geographic origins in West and Central Africa (Benin, Côte d'Ivoire, Ghana, Nigeria and Chad) and Puerto Rico were analysed using three AFLP primer combinations. Of the 342 amplification products generated, a mean of 53.4% were polymorphic. Genetic similarity coefficients ranged from 0.29 to 0.95. The accessions could be clustered into three major genetic groups with one outlier. Each group was a mixture of accessions of different geographical origin indicating that geography has not played a major role in the differentiation of the species. A few accessions clustered very tightly suggesting that there may be duplicate accessions in the collection. The wide genetic variation observed constitutes a good basis for genetic improvement of yam.

No abstract

No abstract

No abstract

No abstract

No abstract

SummaryLitter was collected from 18‐year‐old Tectona grandis (teak) and 13‐year‐old Terminalia superba (afara) planted at various square spacings at Gambari Forest Reserve, Southwestern Nigeria. Litter was collected throughout the year in both species with the rate of fall being particularly high in the dry season in the case of teak and in the wet season in the case of afara. The peak of litter fall in teak may be related to the degree of desiccation or water stress and that of afara to diurnal temperature range and rainfall. The mean annual litter production (kg/ha) in Tectona grandis amounted to 5067, 4688, 4998 and 5196 in square spacings (m2) of 1·37, 1·98, 2·9 and 3·96, respectively. The mean annual litter production (kg/ha) in Terminalia superba amounted to 4157, 3873, 3108 and 4032, in square spacings (m2) of 1·8, 2·8, 4·2 and 6·1, respectively. There were no significant differences in the amount of litter produced and nutrient contents between the various spacings in both species.RésuméOn a collecté la litière sous des Tectona grandis (Teak) de 18 ans et des Terminalia superba (Afara) de 13 ans, plantés à des écartements variables dans la Réserve de Gambari Forest, au sud‐ouest du Nigéria. On a récolté la litière tout au long de l'année pour les deux espèces, les chutes étant particulièrement importantes pendant la saison sèche pour le ‘teak’ et en saison des pluies pour l“afara‘. Le pic de la chute des feuilles du ’teak‘ peut être lié au degré de dessiccation ou au manque d'eau, et celui de l”afara’à la temperature diurne et aux chutes de pluie. La production annuelle moyenne de litière (en kg/ha) de Tectona grandis atteint 5067, 4688, 4998, et 5196 pour des espacements (en m2) de 1,37, 1,98, 2,9, et 3,96 respectivement. Pour Terminalia superba, ces chiffres (en kg/ha) sont de 4157, 3873, 3108 et 4032 pour des espacements (en m2) de 1,8, 2,8, 4,2 et 6,1 respectivement. Il n'y a pas de différence significative dans les quantités de litière produites et le contenu en éléments nutritifs selon la variation d'espacement, pour les deux espèces.