Abstract
Olive (Olea europaea L.) shows alternate bearing, with unreliable cropping patterns and inconsistent fruit size and quality every year. In many countries, thinning with naphthaleneacetic acid (NAA) is used to minimise alternate bearing behavior in olives. However, in Italy, growers are reluctant to employ this practice and no detailed knowledge is available for specific cultivars. We evaluated the effects of spraying NAA on various dates on the productive and vegetative characteristics of the main Italian table olive cultivar'Nocellara del Belice'. Trunk cross-sectional area, fruit set, fruit drop, fruit size, pit size, yield per tree, crop density and flesh to pit ratio were analysed. The NAA treatment applied on the earliest of the dates selected increased fruit weight and flesh to pit ratio, by reducing crop density and enhancing the leaf to fruit ratio, without reducing yield. Two distinct negative relationships were found between fruit weight and crop density during "on" and "off" years, but a unique relationship between pit weight vs. crop density in both years, suggested that the pit is the strongest sink. Fruit size and quality of'Nocellara del Belice' can be enhanced by NAA application, thereby increasing economic returns in the "on" year.
Highlights
In many fruit species, part of the crop is removed in the early stages of fruit development to improve the quality of the remaining crop, mainly in terms of fruit size
We evaluated the effects of spraying naphthaleneacetic acid (NAA) on various dates on the productive and vegetative characteristics of the main Italian table olive cultivar ‘Nocellara del Belice’
In table olive (Olea europaea L.), heavy crop loads result in small fruit of lesser value, late maturity, poor quality leading to depressed prices (Martin et al, 1980)
Summary
Part of the crop is removed in the early stages of fruit development to improve the quality of the remaining crop, mainly in terms of fruit size. Chemical thinning with products that reduce crop load by reducing bloom (Baratta et al, 1992; Lavee and Spiegel-Roy, 1967) or enhancing fruitlet abscission are applied to improve fruit size, and to moderate alternate bearing (Hartmann, 1952; Krueger et al, 2002). The main Italian table olive cultivar - ‘Nocellara del Belice’ - is characterised by an average fruit weight of 7.4 g (Marra et al, 2013) and a production of 5 ton ha–1 in the “on” year. We report successive refinements of previous research conducted in Sicily focusing on ‘Nocellara del Belice’ to determine the optimal timing of NAA application to improve fruit size and quality and possibly to control alternate bearing
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