Early fruit thinning improves yield and quality of three low chill apples (M. domestica Borkh) cultivars in Central highlands of Ethiopia

Three low chill apple cultivars grafted on MM-106 semi dwarf rootstock were evaluated for fruit yield and quality attributes. The trial was carried out in a five years old orchard in central highlands of Ethiopia at Debrebirhan. Trees were treated as crop loads with 0 (unthinned) to 2, 3 and 4 fruits per spur to evaluate the influence of crop load on tree growth, fruit yield and quality. For the three cultivars tested, tree growth was reduced with an increasing crop load while total fruit yield per tree (kg) increased with high crop load. Average fruit weight and diameter differed significantly in all the tested cultivars, for which the highest value was recorded with the low crop load (2 fruits per spur). The mean values for fruit growth and yield indicate that fruits with marketable quality i.e. greater than 60 mm in diameter were recorded at low crop load (2 fruits per spur); for Anna, (76%), Dorsette golden, (50%) and Princesa, (64%). Similar analysis for fruit quality showed that at higher crop loads (more than three fruits per spur in cm2 TCSA); total soluble sugar concentration, titratable acidity, starch content, ripening index (RI) and red color were decreased significantly for all the tested cultivars. For lower crop load treatment, (2fruits per spur) in cm of trunk cross-sectional area (cm2 TCSA); fruit weight, soluble sugar contents (SSC) and red color values were significantly higher (P0.05) in all cultivars. Relationships between crop loads with fruit growth and yield variables revealed that fruit weight increases with low crop load (2 fruits per spur); for cultivar Anna (R2 = 0.79), Dorsette golden (R2 = 0.72) and Princesa (R2 = 0.85) were recorded. Our study also confirmed the relationships between different crop loads with quality parameters showed that trees under the heavier crop load (un thinned trees) expressed the lower percentage of soluble sugars, titratable acidity, starch contents, firmness and red color, whereas trees with lower crop loads (2 fruits per spur) showed a significant increments in these characteristics.

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DOI:

https://doi.org/10.21475/ajcs.2016.10.09.p7636

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