Analysis of growth and physicochemical changes in apple cv. Anna in a high-altitude tropical climate

The objective of this research was to carry out an analysis of growth and physicochemical changes in cv. Anna apple in the Colombian high-altitude tropics using on the accumulation of growing degree days (GDD). Fruit samplings were taken every 15 days after anthesis (DAA) until harvest at 100 DAA (892.37 GDD). The dry and fresh weight and the equatorial and polar diameters followed a simple sigmoidal pattern. This was confirmed with the behavior of the growth rates. The equatorial and polar diameters increased drastically between 455.39 and 589.32 GDD (45 and 60 DAA), while the weight did not, indicating that the void spaces increased in the pulp during this period. The respiratory rate had the highest value (61.93±6.79 mg CO2 kg-1 h-1) at 159.61 GDD (15 DAA) and then decreased continuously until harvest. The firmness increased from 159.61 to 455.39 GDD and, then continuously decreased, at harvest, it was 38.38±3.48 N. The total soluble solids increased and had an ending value of 8.58±0.37ºBrix. The total titratable acidity increased from 159.61 to 319.79 GDD (30 DAA), and then decreased until the end of the study with an acidity of 0.71±0.03%. The color index increased linearly as a function of development, but the values were <0 at harvest. These results are an important advance for knowledge on the behavior of apple cv. Anna under high-altitude tropical conditions.