Introduction. A recent laboratory study demonstrated a negative correlation between the ethylene production of fruit during ripening and the length of their commercial life. The aim of our work was to determine whether there is a putative relationship between ethylene production of fruit during ripening and the length of the growth period before ripening. A positive answer would make this an important parameter for early selection in breeding programs. Materials and Methods. Four banana varieties representing a broad range of growth period lengths were studied. Ethylene biosynthesis was examined through ethylene productionand content in free 1-aminocyclopropane-1-carboxylic acid (ACC)—the immediate precursor of the hormone—during fruit development and ripening. Fruit ripening was totally achieved on the plant. Results. Ethylene production started to be detected at the breaker stage. It peaked at the “fully dark-yellow–extremities included” stage for all varieties. Two varieties, i.e., Sowmuk and IDN 110, presented the highest production levels [(26 and 19) µL ethylene·h–1·kg–1 of fresh weight at peak, respectively). Galéo and Grande Naine had lower ethylene yields. The two most productive varieties also presented a drastic increase in free ACC at ripening onset. Conclusion. There is no relationship between ethylene production of bananas ripened on the plant and the length of the fruit growth period prior to ripening onset.

introduction. Le bananier plantain contribue à la sécurité alimentaire et aux revenus des populations de l’Afrique sub-saharienne. La qualité sanitaire du matériel végétal utilisé en bananeraies est un gage de leur pérennisation. Pour lever cette contrainte, les techniques de multiplication rapide du matériel végétal utilisent des méthodes de multiplication horticole in vivo ou de micropropagation in vitro. La micropropagation par bourgeonnement in vitro, qui permet une production massive de plants de bonne qualité sanitaire, ne fait appel habituellement qu’au bourgeon apical (bap) ou terminal du rejet, alors que celui-ci possède également des bourgeons axillaires (bax) dont nous avons évalué les potentialités. Matériel et méthodes. Nos expérimentations ont porté sur le cultivar Big Ebanga (groupe génomique AAB, sous-groupe des plantains, type faux-corne). Nous avons comparé, au cours de l’acclimatation en ombrière et en champ, les paramètres de croissance et de développement de vitroplants issus des deux types d’explants bax et bap. Des plants issus de rejets ont été utilisés comme témoins. Résultats. Les paramètres mesurés sur les plants issus de bax n’ont pas présenté de différences significatives à la fin de l’acclimatation par rapport aux plants issus des bap, hormis le rapport foliaire. De même, les paramètres de croissance végétative en champ et ceux liés au rendement n’ont pas été significativement différents entre les deux types de plants bax et bap. Les pourcentages de réversion du type « faux corne » vers le type « french » ont été de 0,6 % pour les plants bap et 1,2 % pour plants bax. Discussion et conclusion. Les plants issus de bap et bax se sont comportés de la même manière pendant l’acclimatation en ombrière et en champ. L’utilisation de bax permet d’augmenter les potentialités de production in vitro d’un matériel végétal de qualité. Le taux de réversion des plants bax a été faible. Les bax peuvent donc être utilisés comme explants pour la micropropagation du bananier. Des expérimentations effectuées sur d’autres cultivars appartenant à d’autres groupes génomiques permettront de confirmer ou infirmer ces résultats.

Introduction. The determination of an adequate container volume that combines rational use of substrate with maximization of vegetative growth is very important to optimize citrus nursery tree production. This experiment aims to evaluate the influence of container volumes on vegetative growth of citrus nursery trees. Materials and Methods. Pera sweet orange nursery trees [Citrus sinensis (L.) Osbeck] budded on Rangpur lime (Citrus limonia Osbeck) were produced in six container volumes [(3.0, 3.8, 4.5, 4.6, 5.0 and 5.8) L], with the respective container dimensions of [(20 × 32, 20 × 35, 22 × 32, 22.5 × 35, 25 × 32 and 25 × 35) cm]. Another 5.0-L container studied had the dimensions of 20 cm x 40 cm. Commercial substrate was composed of Pinus bark and a controlled-release fertilizer was used. Parameter evaluation started after moving the rootstocks from seedling trays, 3.5 months after sowing, to plastic containers and continued until nursery trees reached one year old. The studied parameters were shoot height, diameter and leaf area of rootstocks and nursery trees, bud take percentage and scion and root dry matter of nursery trees. Results and discussion. The development of Rangpur lime plants was not affected by any treatment until budding. The largest container volumes induced faster and more vigorous vegetative development of Pera sweet orange nursery trees budded on Rangpur lime. A 5.0-L container volume could be indicated as a technical and economical option for the production of containerized citrus nursery trees.

Introduction. Dacryodes edulis and Canarium schweinfurthii are two tropical multi-purpose trees in Cameroon which produce fruits (African pear and Black olive, respectively) for human consumption, which are marketed more and more on the national and international markets. This study aimed at characterising these two fruits starting from their physical and chemical properties. Materials and methods. Fruits were collected during the harvest peak in three agro-ecological zones of Cameroon. The physical properties measured were the weight, the length, the fruit circumference and the pulp thickness, while the chemical analyses included the moisture and protein, lipid and ash contents. Results. The fruits from the humid forest were largest (96 g), whereas the smallest came from the grassland (54 g). The highest pulp per fruit content (69% for the African pear and 57% for Black olive) was observed in fruits harvested in the humid forest zone. The strongest correlation (r = 0.25) between the fruit weight and that of pulp was observed for Black olive produced in the humid forest zone. The crude protein rate was highest (8%) in fruits from the humid forest, whereas that of the lipids (42%) prevailed in the semi-forest zone. Conclusion. The humid forest zone offers the best agro-ecological conditions for commercial production of the fruits of D. edulis and C schweinfurthii. These two fruits contain proteins and lipids in significant quantities and can, consequently, be used as alternative sources for these nutritive elements.

Introduction. The isolation of humic acid (Ha) from decomposed organic substances such as compost is time-consuming, as it takes not less than 24 h. We investigated whether the isolation time of Ha produced from composted pineapple leaves could be reduced. Materials and methods. Ha from 10 g of pineapple compost was extracted with 100 mL of 0.10 M NaOH. Different extraction times [(4, 8, 12, 16, 20 and 24) h] were tested. At the end of each time, the samples were centrifuged. The dark-colored supernatant liquor containing Ha was decanted and filtered; the pH of the solution was adjusted to 1.0. After acidification, the fractionation times tested were (3, 6, 9, 12, 15, 18, 21 and 24) h. At the end of each fractionation time, the supernatant liquor (fulvic acid) was siphoned off from the acidified extract. The remainder of the suspension was transferred to a polyethylene bottle. Ha was purified by suspending it in 50 mL distilled water, then centrifuged, and the supernatant was decanted. After repeating this procedure five times, the supernatant and the fulvic acid were analyzed for Ca, K, Mg, Mn, Na, Cu, Fe and Zn. The washed Ha was oven dried at 30 °C to a constant weight and the Ha samples were analyzed for ash and mineral matter. Results and discussion. The ash content was not more than 1%, the generally acceptable maximum value. The mineral contents decreased in Ha samples with washing. The yield of Ha significantly increased with increasing extraction time, except for the (20 and 24) h extraction times, which did not show statistically different Ha yield, meaning that the exchange sites of Ha of the pineapple compost might have been saturated with Na ions from 20 h. There was no significant difference among the fractionation times, indicating that Ha of the pineapple compost requires about 3 h to equilibrate or stand immediately after acidification for the H ions to replace the Na and the other cations. There was no significant interaction between the factors extraction and fractionation. Conclusion. The isolation of humic acids from composted pineapple leaves can be achieved with an extraction time of 20 h and a fractionation time of 3 h.

Introduction. L’espèce Ricinodendron heudelotii, plante aux amandes oléagineuses en voie de domestication au Cameroun, est attaquée par un cortège d’insectes phytophages. Parmi ceux-ci, Diclidophlebia xuani Messi et al. (Hemiptera, Psyllidae) constitue son principal ravageur. Un inventaire de la faune d’arthropodes associée à cette plante a été effectué afin d’identifier les ennemis naturels de ce psylle. Matériel et méthodes. Des échantillons ont été collectés de 2001 à 2002 dans les environs de Yaoundé. Les organes végétatifs attaqués de R. heudelotii ont été récoltés chaque semaine et observés sous stéréomicroscope pour récupérer les arthropodes. Résultats et dicussion. Outre D. xuani, de nombreux autres phytophages ont été identifiés, les plus importants étant des lépidoptères. Des prédateurs et parasitoïdes du psylle et des autres arthropodes phytophages ont également été identifiés. Parmi les prédateurs du psylle, les plus importants sont les Anthocoridae, Coccinellidae, Miridae et Syrphidae ; les araignées jouent également un rôle indéniable dans la régulation des populations de D. xuani ; celles-ci n’ont toutefois pas pu être identifiées. Très peu de parasitoïdes ont été trouvés, essentiellement des Encyrtidae. Conclusion. Malgré la diversité de la faune auxiliaire recensée sur R. heudelotii au Cameroun, son impact sur les populations du psylle est apparu limité.

Introduction. The distribution of shoots and fruits in the tree is an important consideration to improve peach cropping. Therefore, the effects of intensity of pruning were investigated for two years in trees with the same fruit load and, the following year, in trees with different fruit loads. Materials and methods. In an early-maturing peach orchard (cv. Alexandra), three pruning intensities were applied for three years: light, medium and severe. The first two years, the same fruit load was applied for the different pruning treatments; in the last year, three fruit loads per tree were tested: low, intermediate and high. Results and discussion. Increasing severity of pruning stimulated average fruit weight and fruit diameter, limiting (2nd year) or not (3rd year) fruit yield. Severe pruning also tended to enhance young shoot growth on the shoot bearing fruit and on the scaffold branch. Fruit diameter improvement with severe pruning might be therefore explained by the increase in vegetative growth likely to enhance available assimilates for fruit growth. However, severe pruning could favor an alternation in flower setting, as observed in the 2nd year. Increasing fruit load stimulated fruit yield, but, with the highest fruit load, no significant fruit yield enhancement was detected compared with the intermediate fruit load. On the contrary, average fruit weight and fruit soluble solids always decreased with increasing fruit load. Conclusion. Intensity of pruning and fruit load must be well adapted to ensure an appropriate peach production; excessive pruning and fruit load of an early-maturing peach cultivar should be avoided in order not to limit fruit yield and quality, respectively.

Introduction. Ficus carica L., well adapted to the Mediterranean climate, is ubiquitous in Tunisia. In spite of the large possibilities of its adaptation to the Tunisian climate, its cultivation remains traditional. In Tunisia, this species is represented by a large number of varieties which are facing genetic erosion. To save these genetic resources, we studied some of the Tunisian varieties using molecular markers. The aim of this analysis was to study the genetic diversity of some cultivars and to characterize them. Materials and methods. Six microsatellites were used to characterize 16 cultivars (Ficus carica L.) belonging to two fig tree collections in the south of Tunisia. Results. The molecular markers used appeared highly polymorphic in common fig trees since 4–12 alleles per locus and a mean of heterozygoty of 0.656 were scored. The resolving power (Rp ) of the six microsatellites tested ranged from 2.12 to 3.87 for the 16 cultivars studied, showing a significant genetic diversity (Ht = 0.762). Genetic differentiation between geographical groups was low (Gst = 0.032). The factorial correspondence analysis showed no well-defined relation between the 16 cultivars and their geographical origin. The genotype patterns allowed us to discriminate all of the cultivars. Conclusion. The characterization of the accessions belonging to different varieties was possible, showing the power and efficiency of the molecular tools used.