Author Identifier

Mahmood Ul Hasan: https://orcid.org/0000-0002-4044-1391

Date of Award

2025

Document Type

Thesis - ECU Access Only

Publisher

Edith Cowan University

Degree Name

Doctor of Philosophy

School

School of Science

First Supervisor

Zora Singh

Second Supervisor

Andrew Woodward

Third Supervisor

Eben Afrifa-Yamoah

Abstract

Persimmon is an important fruit crop grown in a wide range of climatic regions worldwide, where it is consumed fresh, processed and frozen, and has a pleasant taste and a high nutritional profile. Australia is one of many countries that produce persimmon fruit. The persimmon industry is challenged by constraints including a short marketing period, delayed colour development (particularly in early maturing cultivars), and high susceptibility to chilling injury (CI) during cold storage, which limit profits to growers. This research project aimed to evaluate the effects of pre- and postharvest interventions on regulation of colour development, modulation of harvest maturity, and overall maintenance of fruit quality of persimmons during cold storage. To address early colour development, the efficacy of methyl jasmonate (MeJA) and s- (+)-cis, trans-abscisic acid (S-ABA) on promotion of early colour was evaluated by spraying different concentrations on ‘Yoho’ and ‘Jiro’ persimmon trees before their anticipated harvest. Preharvest spray application of MeJA on ‘Yoho’ and ‘Jiro’ persimmons one month before anticipated harvest notably improved fruit colour by increasing colour coordinates: a*, b*, chroma and colour index after one, and two weeks of post-application respectively. MeJA spray application increased chlorophyll degradation, reduced soluble tannins, and enhanced peel and pulp carotenoids. It further up-regulated phenolic metabolism by enhancing total phenolics, the activity of shikimate dehydrogenase (SKDH) and phenylalanine ammonia-lyase (PAL), and antioxidant enzymes such as catalase (CAT), superoxide dismutase (SOD) and peroxidase (POD). The effects of single spray application of S-ABA on ‘Yoho’ persimmons two weeks before anticipated harvest were investigated, with 50 mg L-1 S-ABA significantly improving fruit colour within one week, and 25 mg L-1 found effective after two weeks of spray application. S-ABA spray enhanced soluble solids content (SSC) and up-regulated total phenolics, flavonoids and antioxidant capacity in ‘Yoho’ persimmons. The effects of postharvest application of melatonin (MLT), oxalic acid (OA) and cinnamon bark oil (CBO), either as an individual treatment or in combination with modified atmosphere packaging (MAP) were investigated for their ability to alleviate chilling injury (CI) in ‘Fuyu’ persimmons during cold storage at 0 ± 1 °C for up to 63 days. The combined application of MLT (100 µmol L-1 , two-minute dipping) followed by packaging in MAP bags significantly attenuated peel and flesh CI in ‘Fuyu’ persimmons by reducing ethylene production rate (EPR), restricting reactive oxygen species (ROS) accumulation, and maintaining the ascorbate-glutathione cycle in persimmon fruit. Postharvest application of CBO fumigation (4 µmol for 12 hours) followed by MAP resulted in a significant reduction in CI, EPR and lipid peroxidation, and maintained a higher ascorbate glutathione antioxidant system. In both experiments, combined applications of MLT + MAP and CBO + MAP resulted in highly persevered endogenous levels of total flavonoids and total antioxidants, and higher ascorbic acid and glutathione content, with increased activities of ascorbate peroxidase (APX), monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR) and glutathione reductase (GR) enzymes. Individual and combined treatments resulted in a significant reduction in malondialdehyde (MDA) and hydrogen peroxide (H2O2) content, activity of the lipoxygenase (LOX) enzyme, as well as lower membrane permeability by lowering electrolyte leakage (EL), compared to the untreated control. The effects of postharvest dip application of OA (5 mmol L-1 for two minute), individually or in combination with MAP on chilling injury, EPR and degradation of cell wall polysaccharides, was investigated. The combined application of OA + MAP, followed by alone MAP or OA resulted in lower CI incidence and EPR, and retained textural quality with higher pectin fractions: total pectin (TP), chelate soluble pectin (CSP), sodium carbonate soluble pectin (NSP), and cellulose, compared to untreated control fruit. The combined and individual applications lowered the activities of pectin methyl esterase (PME), pectate lyase (PL), polygalacturonase (PG) and cellulase (CEL) in ‘Fuyu’ persimmons during 60 days of cold storage followed by one day at shelf conditions. Exogenous preharvest spray applications of gibberellic acid (GA3, 50 µg L-1 ), perlan (100, 200, 300 µL L-1 ) containing GA4+7 and a cytokinin (6-benzyladenine) mixture 15 days before anticipated harvest, were investigated for delaying on-tree ripening of ‘Fuyu’ persimmons. Single spray application of perlan significantly delayed on-tree ripening of ‘Fuyu’ persimmons up to 65 days, and late harvested (65 days) fruit following packaging in MAP bags, exhibited lower CI and EPR after 25 days of cold storage (0 ± 1 °C), and two days at ambient room conditions. Perlan application significantly delayed change in fruit colour, lowered the accumulation of carotenoids in pulp and SSC, preserved higher textural quality (hardness, cohesiveness and gumminess), and conserved higher pectin fractions including TP, NSP and CSP, while water soluble pectin (WSP) was observed to be lower in treated fruit, with progress in the harvest period. In conclusion, preharvest spray application of MeJA (6 mmol L-1 , one month before anticipated harvest) and to a lesser extent S-ABA (25 mg L-1 and 50 mg L-1 , two weeks before anticipated harvest) could be potentially employed for improving colour development in early season maturing ‘Yoho’ and ‘Jiro’ persimmon fruit. Postharvest application of MLT, CBO, and OA combined with MAP significantly alleviated CI in ‘Fuyu’ persimmons, reduced EPR and oxidative stress, enhanced the ascorbate glutathione cycle, and delayed degradation of cell wall polysaccharides. Preharvest spray application of perlan could be an effective approach for delaying on-tree ripening of ‘Fuyu’ persimmons up to 65 days, following cold storage of late harvested fruit for 25 days, and two days at shelf conditions. However, the implications of pre- and postharvest interventions can be variable in their efficacy depending upon different agroclimatic conditions, time of application and dose of treatment, harvest maturity stage, storage time and condition and cultivars.

Access Note

Access to this thesis is embargoed until 4th November 2030

DOI

10.25958/t3sp-6n63

Download

Available for download on Monday, November 04, 2030

Share

 
COinS