Effect of fruit thinning on the mineral composition of loquat (Eriobotrya japonica Lindl.) fruit and its connection with purple spot

Abstract

This work studies the effect of competition among developing fruits on the mineral concentration of the flesh and rind tissues of loquat fruit and its relation to the incidence of purple spot. When fruit reached 10 mm in diameter, the trees were hand-thinned to 1, 3 or 5 fruits per panicle, using non-thinned trees as control trees. In flesh tissue, K concentration significantly increased and Fe concentration significantly decreased at colour break in response to thinning. In rind tissue, N, K, Mg and Fe concentration diminished at colour break, depending on the thinning intensity, down to 23%, 21%, 27% and 41%, respectively, for one fruit per panicle treatment. Changes in the mineral composition of fruits caused by thinning significantly increased the gradient of concentration of N, K, Ca and Mg between the rind and the flesh tissue. This increase in the mineral gradient correlates positively and significantly with the percentage of purple-spotted fruit.