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A Bioassay Investigation of Calcium Nutrition and Tomato Shoulder Check Cracking Defect
Journal article   Peer reviewed

A Bioassay Investigation of Calcium Nutrition and Tomato Shoulder Check Cracking Defect

Jinsheng Huang and S. S. Snapp
Communications in soil science and plant analysis, Vol.35(19-20), pp.2771-2787
2004
DOI: https://doi.org/10.1081/CSS-200036440

Abstract

Tomato fruit quality Lycopersicon escultentum Fruit-wall rigidity Water uptake
Fruit physiological disorders such as shoulder check crack defects in tomato fruits are frequently inconsistent in appearance. This poses a challenge to researchers and growers. The severity and incidence of crack defects depends largely on weather conditions and may vary from almost nondetectable to causing severe yields losses. A bioassay was developed to consistently induce fruit cracking and to evaluate the effect of calcium (Ca) treatments. Detached vine ripe and mature green fruits were either waxed or not waxed with paraffin on the stem end (calyx scar) and immersed into water and 90 mM CaCl2 solutions for 4–l6 days at 25°C incubation conditions. Mature green fruit was a more sensitive indicator than red ripe fruit, showing rapid water uptake within 2 h of treatment and having a consistent cracking response. Large cracks occurred on unwaxed fruits immersed in water. Unwaxed fruit took up water rapidly, as shown by gain in fresh weight. Fruits with wax on the stem end either did not show incidence of cracking or cracks were small and slow to appear. Fruits immersed in 90 mM CaCl2 solution took up reduced amounts of water and had limited cracking compared to water-treated fruits. In a field experiment, weekly 50 mM CaCl2 sprays consistently reduced fruit-cracking incidence to a moderate degree. The role of calcium in prevention of shoulder check cracking may be related to the osmotic potential of the Ca solution, which will tend to limit water uptake by the fruit, or to the enhancement of epidermal calcium nutrition. The symptoms of fruit cracks induced by the bioassay were similar to the shoulder check crack symptoms that occurred in the field. Field and bioassay results were generally consistent. A measure of protection against shoulder check cracks may be provided by spraying Ca on fruit.

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