Abstract
Resistance to internal browning of pineapple fruits depends on several factors such as the cultural techniques through mineral fertilization. The objective of this work is to study the effects of the potassium fertilization for pineapple on internal browning of fruit in post-harvest conservation. The experiments have been carried out on the site of the University Nangui Abrogoua (Abidjan, Côte d’Ivoire) of July 2015 to the end of October 2016. Potassium has been applied according to four modalities of treatments (T0; T1; T2 and T3) made in 2nd, 4, 6 and 7th months (respectively) after plantation. The incidence of internal browning (IB), the phenolic content, sugars and ascorbic acid have been determined after post-harvest conservation of fruit. The activity of phenolic biosynthesis enzymes (PAL and TAL) and oxidation enzymes (PPO and POD) were evaluated. The results showed that BI intensity in pineapple fruit decreases with the potassium amount applied in field. This IB drop was correlated with the content of reducing sugars, total phenols, activity of PAL and the PPO. No symptom of IB was observed on pineapple fruits under treatment T2 (34 g of K2O/plant). Potassium has a depressive effect on phenolic biosynthesis. In effect, it inhibits the IB in the both varieties of pineapple studied that are Smooth Cayenne and MD2.
Highlights
The pineapple is one of the main export crops of Côte d'Ivoire
The internal browning of the pulp is shows more intense in the pineapple Smooth Cayenne that among the variety MD2
The application of a high amount of potassium in pineapple cultivation leads to a decrease in phenol biosynthetic enzymes which are phenylalanine ammonia-lyase (PAL) and tyrosine ammonia-lyase (TAL), a reduction of total phenol content in the pineapple fruits
Summary
The pineapple is one of the main export crops of Côte d'Ivoire. In the recent past, pineapple export generated more than 45 billion CFA per year to the Ivorian State and contributed 0.6% to the GDP [1]. There has been a drastic decline of the Ivorian production (213 620 tones in 1999 to 20 900 tones in 2014), followed by the loss of its status as a premier supplier of fresh pineapple on the European market The causes of this crisis are multiple, among which there was the aging of planting material, the depletion of soils due to the monoculture, the acidity of the fruit, the high rate of chemical residues, the internal browning etc. Potassium is absorbed by the plants under its ionic form K+ to regulate the osmotic pressure as well as the opening and closing of the stomata [5, 6]. This mineral is used as a cofactor in the enzymatic reactions and biochemical [5]. According to Antonio, et al [7], the application of a high amount of potassium in the pineapple inhibits the internal browning of the fruit at maturity
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