The Journal of Horticultural Science & Biotechnology
Vol. 87 No: 4
Relationships between storage disorders and fruit calcium contents, lipoxygenase activity, and rates of ethylene evolution and respiration in ¿Royal Delicious¿ apple (Malus × domestica Borkh.)
R.R. SHARMA, R.K. PAL, D. SINGH, J. SINGH, M.R. DHIMAN and M.R. RANA
Experiments were conducted to determine the relationships between the occurrence of storage disorders in ‘Royal Delicious’ apple (Malus ×domestica Borkh.) and fruit Ca2+ ion contents, rates of ethylene evolution and respiration, and lipoxygenase (LOX) activity.
Apples were stored at 0º ± 1ºC and 90 – 95% relative humidity and sampled each month, up to 6 months, for storage disorders, fruit Ca2+ ion contents, rates of ethylene evolution and respiration, and LOX activity.
Storage disorders such as bitter pit, cork spot, and brown core appeared after 3 months and increased in frequency at subsequent samplings.
Regardless of the presence or absence of storage disorders, fruit showed a decline in Ca2+ ion concentration during storage.
Ca2+ ion concentrations (means of 3, 4, 5, and 6 month samples) were significantly higher in disorder-free fruit [0.419 mg g-1 dry weight (DW)] than in fruit showing bitter pit (0.329 mg g-1 DW) or cork spot (0.340 mg g-1 DW), but were not significantly higher than in fruit with brown core (0.393 mg g-1 DW). Conversely, LOX activity was significantly lower in disorder-free fruit [0.168 μmoles linolenic acid oxidised min-1 g-1 fresh weight (FW)] compared to symptomatic fruit.
LOX activity increased with the duration of storage in all fruit samples.
The rates of ethylene evolution (58.5 μl C2H4 kg-1 FW fruit h-1) and respiration (16.0 ml CO2 kg-1 FW fruit h-1) were significantly lower in disorder-free fruit than in symptomatic fruit.
The rates of ethylene evolution and respiration increased between 3 – 5 months in storage.
After 5 months in storage, they remained stable or declined in all fruit.
The correlations (R2) between Ca2+ ion content vs. the presence of physiological disorders such as bitter pit (–0.77), cork spot (–0.75), and brown core (–0.64), and between Ca2+ ion contents vs. LOX activity were strongly negative (–0.94). In contrast, the correlation between LOX activity vs. physiological disorders was strongly positive.
Our study concluded that an inverse relationship existed between fruit Ca2+ ion content and the occurrence of bitter pit, cork spot, and/or brown core, and between fruit Ca2+ ion content and LOX activity.
Moreover, the relationship between LOX activity and the presence of storage disorders was strongly positive.
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