Effect of Planting Density and K2O:N Ratio on the Yield, External Quality, and Traders' Perceived Shelf Life of Pineapple Fruits in Benin.

Quality, shelf life, and yield of a pineapple fruit are the important attributes for the producers and customers in the pineapple value chain of Benin, whereas poor quality, short shelf life, and low yield are the main constraints. We quantified the effects of planting density and K2O:N fertilizer ratio on the pineapple yield, external quality, and perceived shelf life in four on-farm experiments with cv. Sugarloaf in Benin; two experiments were installed in the long rainy season and two in the short rainy season. A split-plot design was used with the planting density as the main factor at three levels: 54,000, 66,600, and 74,000 plants.ha-1. The K2O:N ratio was a subfactor with three levels: K2O:N = 0.35 (farmers' practice), K2O:N = 1, and K2O:N = 2. The results showed that both factors had no effect on the crop development variables (such as the number of functional leaves and D-leaf length) at the moment of flowering induction. The planting density had no effect on the total weight per fruit, infructescence weight, total fruit length, infructescence length, crown length, or the fruit shelf life as perceived by traders. The yield increased from 54.9-69.1 up to 90.1 t.ha-1 with an increase in the planting density. The yield increase was not at the expense of the fruit weight. Increased K2O:N ratio led to a higher fruit weight whereas the fruit length was not affected. The shelf life of fruits produced at a K2O:N ratio of 1 and as perceived by traders was 6 days longer than that of fruits produced at a ratio of 0.35 (farmers' practice). Based on these results, we suggest the fresh pineapple farmers in Benin to use a combination of 66,600 plants.ha-1 with a K-fertilization scheme based on a K2O:N ratio of 1 to meet the expectation of both producers and customers in terms of fruit yield and fruit quality.

Trade-Offs of Flowering and Maturity Synchronisation for Pineapple Quality.

In the pineapple sector of Benin, poor fruit quality prevents pineapple producers to enter the European market. We investigated effects of common cultural practices, flowering and maturity synchronisation, (1) to quantify the trade-offs of flowering and maturity synchronisation for pineapple quality and the proportion of fruits exportable to European markets, and (2) to determine the effect of harvesting practice on quality attributes. Four on-farm experiments were conducted during three years using cultivars Sugarloaf and Smooth Cayenne. A split-split plot design was used in each experiment, with flowering induction practice as main factor (artificial or natural flowering induction), maturity induction practice as split factor (artificial or natural maturity induction) and harvesting practice as the split-split factor (farmers' harvest practice or individual fruit harvesting at optimum maturity). Artificial flowering induction gave fruits with lower infructescence weight, higher ratio crown: infructescence length, and a lower proportion of fruits exportable to European markets than natural flowering induction. The costs of the improvements by natural flowering induction were huge: the longer durations from planting to flowering induction and harvesting, the higher number of harvestings of the fruits increasing the labour cost and the lower proportion of plants producing fruits compared with crops from artificially flowering-induced plants. Artificial maturity induction decreased the total soluble solids concentration in the fruits compared with natural maturity induction thus decreasing the proportion of fruits exportable to European markets, at a benefit of only a slightly shorter time from flowering induction to harvesting. Harvesting individual fruits at optimum maturity gave fruits with higher total soluble solids in naturally maturity induced fruits compared with the farmers' harvest practice. Given the huge costs of natural flowering induction, options to use artificial flowering induction effectively for obtaining high fruit quality are discussed.

Selective pruning in pineapple plants as means to reduce heterogeneity in fruit quality.

Heterogeneity in fruit quality (size and taste) is a major problem in pineapple production chains. The possibilities were investigated of reducing the heterogeneity in pineapple in the field by pruning slips on selected plants, in order to promote the fruit growth on these plants. Slips are side shoots that develop just below the pineapple fruit during fruit development. Two on-farm experiments were carried out in commercial fields in Benin with a cultivar locally known as Sugarloaf, to determine (a) the effect of slip pruning on fruit quality; (b) whether the effect of slip pruning depends on the pruning time; and (c) whether slip pruning from the plants with the smallest infructescences results in more uniformity in fruit quality. A split-plot design was used with pruning time (2 or 3 months after inflorescence emergence) as main factor and fraction of pruned plants (no plants pruned (control); pruning on the one-third plants with the smallest infructescences; pruning on the two-thirds plants with the smallest infructescences; pruning on all plants) as sub-factor. Fruit quality characteristics measured at harvest were the fruit (infructescence + crown) weight and length, the infructescence weight and length, the crown weight and length, the ratio crown length: infructescence length, the total soluble solids, the juice pH and the flesh translucency. Results indicated that pruning of slips of any fraction of the plants at 2 or 3 months after inflorescence emergence did not lead to a consistent improvement in quality or uniformity. Consequently it is not recommended to farmers in Benin to prune the slips.

Heterogeneity in pineapple fruit quality results from plant heterogeneity at flower induction.

Heterogeneity in fruit quality constitutes a major constraint in agri-food chains. In this paper the sources of the heterogeneity in pineapple in the field were studied in four experiments in commercial pineapple fields. The aims were to determine (a) whether differences in pineapple fruit quality among individual fruits are associated with differences in vigor of the individual plants within the crop at the time of artificial flower induction; and (b) whether the side shoots produced by the plant during the generative phase account for the fruit quality heterogeneity. Two pineapple cultivars were considered: cv. Sugarloaf and cv. Smooth Cayenne. Plant vigor at the time of artificial flower induction was measured by three variates: the number of functional leaves, the D-leaf length and their cross product. Fruit quality attributes measured at harvest time included external attributes (weight and height of fruit, infructescence and crown) and internal quality attributes [total soluble solids (TSS), pH, translucent flesh]. Results showed that the heterogeneity in fruit weight was a consequence of the heterogeneity in vigor of the plants at the moment of flower induction; that effect was mainly on the infructescence weight and less or not on the crown weight. The associations between plant vigor variates at flower induction and the internal quality attributes of the fruit were poor and/or not consistent across experiments. The weight of the slips (side shoots) explained part of the heterogeneity in fruit weight, infructescence weight and fruit height in cv. Sugarloaf. Possibilities for reducing the variation in fruit quality by precise cultural practices are discussed.

Influence of weight and type of planting material on fruit quality and its heterogeneity in pineapple [Ananas comosus (L.) Merrill].

Cultural practices can affect the quality of pineapple fruits and its variation. The objectives of this study were to investigate (a) effects of weight class and type of planting material on fruit quality, heterogeneity in quality and proportion and yield of fruits meeting European export standards, and (b) the improvement in quality, proportion and yield of fruits meeting export standards when flowering was induced at optimum time. Experiments were conducted in Benin with cvs Sugarloaf (a Perola type) and Smooth Cayenne. In cv. Sugarloaf, experimental factors were weight class of planting material (light, mixed, heavy) and time of flowering induction (farmers', optimum) (Experiment 1). In cv. Smooth Cayenne an additional experimental factor was the type of planting material (hapas, ground suckers, a mixture of the two) (Experiment 2). Fruits from heavy planting material had higher infructescence and fruit weights, longer infructescences, shorter crowns, and smaller crown: infructescence length than fruits from light planting material. The type of planting material in Experiment 2 did not significantly affect fruit quality except crown length: fruits from hapas had shorter crowns than those from ground suckers. Crops from heavy planting material had a higher proportion and yield of fruits meeting export standards than those from other weight classes in Experiment 1 only; also the type of planting material in Experiment 2 did not affect these variates. Heterogeneity in fruit quality was usually not reduced by selecting only light or heavy planting material instead of mixing weights; incidentally the coefficient of variation was significantly reduced in fruits from heavy slips only. Heterogeneity was also not reduced by not mixing hapas and ground suckers. Flowering induction at optimum time increased the proportion and yield of fruits meeting export standards in fruits from light and mixed slip weights and in those from the mixture of heavy hapas plus ground suckers.

Artemisinin and sesquiterpene precursors in dead and green leaves of Artemisia annua L. crops.

This paper analyses the accumulation and concentrations of the antimalarial artemisinin in green and dead leaves of Artemisia annua crops in two field experiments. Concentration differences were analysed as being determined by (a) the total production of artemisinin plus its upstream precursors dihydroartemisinic acid, dihydroartemisinic aldehyde, artemisinic aldehyde and artemisinic alcohol and (b) the conversion of precursors towards artemisinin. Concentrations of the total of artemisinin plus its precursors were higher in green leaves than in dead leaves in the younger crop stages, but were comparable at the final harvests. In every crop stage, the conversion of precursors to artemisinin was more advanced in dead leaves than in green leaves. This resulted in the molar concentrations of artemisinin being higher in dead leaves than in green leaves at the final harvests. The molar quantity of dihydroartemisinic acid, the last enzymatically produced precursor, was higher than that of artemisinin in green leaves, but only 19 - 27% of that of artemisinin in dead leaves. Dead leaves were very important for the final artemisinin yield. They constituted on average 34% of the total leaf dry matter and 47% of the total artemisinin yield at the final harvests. The possibility to convert a larger part of dihydroartemisinic acid into artemisinin during post-harvest handling is discussed.