Effect of bearing position on fruit quality of mandarin types

Abstract

Differences in juice quality are associated with positional differences in canopy microclimate and exposure of individual fruit to light and temperature. Differences of internal fruit quality between fruit from different sectors of the tree were investigated. The trials were carried out with ‘Mihowase’ Satsuma and ‘Nules’ Clementine trees on Troyer citrange rootstock in Stellenbosch (34°S; 19°E) and ‘Fairchild’ and ‘Temple’ tangor trees on rough lemon rootstock in Citrusdal (32°30'S; 19°E), South Africa. Fruit were harvested from four sectors in each tree, viz. north, south, east and west. Within each sector, fruit were harvested from three sub-sectors, i.e. the top, and the inside and outside bottom sub-sectors. Fruit from each sector were scored for colour, size, juice content, total soluble solids (TSS), titratable acidity (TA) and TSS: TA ratio. (i) Colour: ‘Fairchild’ fruit from all sub-sectors were fully coloured (orange) at harvest. There were no fruit colour differences between the sub-sectors in each sector for each of the other cultivars. The north sector had significantly greener fruit than the south sector for Satsumas, Clementines and ‘Temple’, (ii) Fruit size: For Satsumas, Clementines and ‘Temple’ the top fruit were the largest and inside bottom fruit the smallest, but the opposite occurred for in ‘Fairchild’. (iii) Juice content: The % juice content in all four cultivars was the lowest in top fruit and the highest in inside bottom fruit, (iv) Total soluble solids (TSS): The TSS in all four cultivars was the highest in top fruit and the lowest in inside bottom fruit. The TSS in fruit from the north sector was significantly higher than fruit from the south sector for ‘Fairchild’ and ‘Temple’, with no differences for Satsumas and Clementines, (v) Titratable acidity (TA): For Satsumas and Clementines the inside bottom fruit had the highest TA levels and outside bottom fruit the lowest levels, with no trends for ‘Fairchild’ and ‘Temple’, (vi) TSS:TA ratio: Outside bottom fruit (Satsumas) and top fruit (Clementines, ‘Fairchild’ and ‘Temple’) had the highest TSS:TA ratios and inside bottom fruit the lowest. The north sector in all the cultivars had higher TSS:TA ratios than the south sector. Top and outside bottom fruit had the best quality. This study provides information that can be used to set a standard for sampling fruit for quality determinations, as a guide for spot-picking and harvesting, and in developing pruning strategies.