Vol. 82 No: 4

Title:
Comparison of sampling strategies for determining fruit mineral concentrations in 'Hass' avocado (Persea americana Mill.)

Authors:
L.M. BOYD, A. HANCOCK, A.B. WOOLF, N. DE SILVA, T.G. THORP and I.B. FERGUSON

pp: 611-621

Abstract:
Spatial and temporal variation in mineral and dry matter (DM: % dry weight) concentrations were examined in ‘Hass’ avocado (Persea americana Mill.) fruit to identify sampling strategies for examining fruit mineral, DM and fruit quality relationships. Calcium (Ca), magnesium (Mg), potassium (K), and DM concentrations were compared from different parts of the same fruit, from fruit harvested from different shoot types and locations within the same tree, and at different stages during the growing season, from fruit set to commercial harvest. The main source of variation within fruit was longitudinal, with K and DM concentrations being higher at the distal end of the fruit. Sampling methods based on equatorial plugs of tissue provided the best estimates of whole fruit values for DM and mineral nutrients. While there was much variability in the internal distribution of minerals within the fruit, the distribution was the same for fruit from both the northern and southern aspects of the tree. During the first 4 months after fruit set, fruit from determinate floral shoots (i.e., with a flower in the terminal position) had higher Ca and Mg concentrations than fruit from indeterminate shoots (i.e., with a shoot in the terminal position). After this time, fruit Mg and Ca concentrations were higher on indeterminate shoots, possibly because of changes in sink-strength and increased transpirational flow associated with new leaf growth on indeterminate shoots. The data showed that shoot type was a source of fruit-to-fruit variability in an avocado crop, and that care should be taken in sampling fruit tissues for nutrient analyses.

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