METHODOLOGICAL FACTORS AFFECTING THE PREDICTION OF BITTER PIT THROUGH FRUIT INFILTRATION WITH MAGNESIUM SALTS IN THE APPLE CV. ‘BRAEBURN’

Experiments were carried out using vacuum infiltration of magnesium salts (VIMg) in apples cv. ‘Braeburn’ in order to: 1.- improve the predictive capacity of bitter pit (BP) and, 2.- study how fruit Mg infiltration triggers the development of “bitter pit-like” symptoms.
For objective 1, it was evaluated: the period of VIMg (vacuum for 1 or 4 minutes), the number of times the infiltrating solution was used (1, 4 or 8 times), and the molarity of MgCl₂ in the infiltrating solution (0.05 or 0.1 M of MgCl₂ for 2 min.). For estimating the predictive capacity, BP levels detected in VIMg fruit collected before harvest were compared with “real” BP present in fruit stored for 90 d at 2 C + 10 d at 18 C. To satisfy objective 2, VIMg was performed including Toluidine blue dye to establish entry sites of VIMg and its distribution within the fruit.
Besides, Ca, Mg and K concentrations were compared at 0, 8 and 16 d after infiltration between infiltrated (I) and non-infiltrated (NI) fruit at 2 depths (0-2 and 6-8 mm below the epidermis). Vacuum level used in all experiments was 500 mm Hg.
No significant differences in BP predictive capacity were found with the various combinations of infiltration period and number of times the infiltrating solution was used, no differences were also found in using different MgCl₂ concentrations.
Besides, it was observed that the infiltrating solution enters the fruit mainly through the lenticels and that VIMg increases fruit Mg levels (316 ppm in NI vs 330 ppm in I) in the first 2 mm below the epidermis.
These results will help optimize commercial use of VIMg for BP prediction.

IV International Symposium on Mineral Nutrition of Deciduous Fruit Crops

J.B. Retamales, L. León, K. Tomala

Physiological disorders, calcium nutrition, fruit quality, Malus domestica, postharvest life, fruit Mg, K, Ca distribution

https://doi.org/10.17660/ActaHortic.2001.564.10