The use of computed tomography scans to evaluate broken stones in a susceptible Japanese plum (Prunus salicina Lindl.) cultivar

Stone breakage affects peaches and plums and leads to significant postharvest financial losses for the stone fruit industry in South Africa as affected fruit have to be marketed as Class 2, thus obtaining lower prices on international markets.
Since no information exists on the development of broken stones in Japanese plums, and it is generally only observed after harvest, the aim of this study was to determine when and why the defect develops during fruit development in a susceptible cultivar.
Data on the fruit growth pattern and how this affects the incidence of broken stones could help to forecast severity of the defect in some seasons, to aid with the marketing of the fruit, and/or support the South African plum breeding program to select for cultivars not susceptible to this defect.
Computed tomography was used in the 2013/2014 and 2014/2015 seasons to determine the growth characteristics and endocarp density of ‘Laetitia’ plums during fruit development, from 28 days after full bloom (dafb) until the completion of stone hardening.
Lignification started at the stylar end of the fruit and progressed towards the stem end between 28 to 63 dafb and this was accompanied by an increase in endocarp density.
Broken stones were first observed as soon as the stones started to harden (approx. 35 dafb) and occurred mostly near the stylar end of the fruit.
It is suggested that stone breakage occurs when the semi-rigid stone is subjected to rapid radial fruit growth in the direction where the stone is least dense.
It seems that the stones are not able to resist the strong pulling forces of the growing mesocarp when they are not completely hardened and this leads to the stones being pulled apart.
The effect of spring temperature on the severity of broken stone incidence will also be discussed.

VIII International Postharvest Symposium: Enhancing Supply Chain and Consumer Benefits – Ethical and Technological Issues

I. Kritzinger, E. Lötze, M.M. Jooste

density, endocarp, rapid fruit growth, stone hardening

https://doi.org/10.17660/ActaHortic.2018.1194.105