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Studies on the application and efficacy of orange oil as a postharvest disease management strategy on fruit
Thesis (PhD)--Stellenbosch University, 2025.
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Stellenbosch : Stellenbosch University
2025
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| _version_ | 1867614054530416640 |
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| access_status_str | Open Access |
| author | Njombolwana-Swartz, Ncumisa |
| author2 | Lennox, Cheryl |
| author_browse | Lennox, Cheryl Njombolwana-Swartz, Ncumisa |
| author_facet | Lennox, Cheryl Njombolwana-Swartz, Ncumisa |
| author_sort | Njombolwana-Swartz, Ncumisa |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (PhD)--Stellenbosch University, 2025. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/132543 |
| institution | Stellenbosch University (South Africa) |
| language | English |
| last_indexed | 2026-06-10T12:45:56.159Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2025 |
| publishDateRange | 2025 |
| publishDateSort | 2025 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/132543 Studies on the application and efficacy of orange oil as a postharvest disease management strategy on fruit Njombolwana-Swartz, Ncumisa Lennox, Cheryl Meitz-Hopkins, Julia Monteiro, Sara Stellenbosch University. Faculty of AgriSciences. Dept. of Plant Pathology. Orange oil Citrus -- Postharvest diseases and injuries -- Biological control Fruit -- Postharvest losses -- Prevention Fruit -- Quality Essences and essential oils -- Processing Botrytis cinerea Penicillium digitatum Stone fruit -- Postharvest diseases and injuries -- Biological control Strawberries -- Postharvest diseases and injuries -- Biological control UCTD Thesis (PhD)--Stellenbosch University, 2025. Njombolwana, N. 2025. Studies on the application and efficacy of orange oil as a postharvest disease management strategy on fruit. Unpublished doctoral dissertation. Stellenbosch: Stellenbosch University [online]. Available: https://scholar.sun.ac.za/items/c8f75b83-59ad-4f4a-8b89-db3aea4b6b83 ENGLISH ABSTRACT: Plant essential oils form a part of generally regarded as safe (GRAS). They are made up of complex volatile compounds which have been proven effective against plant pathogens including postharvest pathogens such as Botrytis cinerea and Penicillium digitatum. Orange oil extracted from sweet oranges has shown potential in the management of other pathogens but there is limited information on its contribution to the management of B. cinerea and P. digitatum on fruit. The study aimed to establish orange oil as an alternative application for postharvest disease management of green mould of citrus, and grey mould of stone fruit and strawberries. The effect of dip application of pure orange oil, orange oil-based formulations and pure thyme oil against P. digitatum on citrus fruit and or B. cinerea on plums and strawberries was determined. On plums, orange oil treatments showed superior curative control compared to protective treatments, with African Delight cultivar showing less susceptibility to B. cinerea compared to the cultivar Laetitia. On strawberries, treatments demonstrated beneficial effects by extending shelf-life to 14 days compared to the standard 7-10 days in practice. Penicillium digitatum on citrus was poorly controlled in comparison to imazalil. Encapsulation techniques assist in alleviating the degradation of essential oils emanating from their volatile nature when exposed to the environment. Thus, nanoparticles of orange and thyme oils at concentrations of 3.33, 4.44, 6.66, 8.88 and 17.78 mg mL-1were generated using the nanoprecipitation technique with AtlasTM G-5002L as a copolymer and characterized for shape, size and bioactivity against B. cinerea (both in vitro and in vivo) and P. digitatum (in vitro). Methods of application on fruit included spraying, incorporation in edible coating (for plums) or through active packaging. In both cases, encapsulated essential oils were more effective compared to the respective non-encapsulated oils. Thyme oil nanoparticles showed potential in controlling both pathogens in vitro. Orange oil nanoparticles also showed potential in controlling B. cinerea on strawberries, when incorporated with edible coating, and to a certain extent when applied as part of the active packaging strategy. Moreover, the effect of orange oil and thyme oil nanoparticles at selected concentrations on the defence signalling of pathogenesis related genes and regulatory signalling DELLA proteins following wounding and inoculation of plums with B. cinerea was investigated. Orange oil consistently resulted in the down regulation of PR genes. The upregulation of DELLA proteins was evident in the hormonal signalling upon wounding and the early response upon the application of both orange and thyme oil. Resembling the previous studies, thyme oil caused upregulation of chitinase type III, and further caused upregulation of ribonuclease-like, thaumatin-like and DELLA proteins in this study. This study has presented the encapsulated orange oil as an alternative for the management of B. cinerea on plums and enhancing shelf life of strawberries and has further contributed to the pool of studies currently available on thyme oil in postharvest disease control. AFRIKAANSE OPSOMMING: Essensiële olies van plante word as veilige produkte vir verbruik beskou (GRAS). Hulle bestaan uit komplekse vlugtige verbindings wat effektief teen plantpatogene werk, insluitend na-oes patogene soos Botrytis cinerea en Penicillium digitatum. Lemoenolie wat uit soet lemoene onttrek word, beheer patogene, maar daar is beperkte inligting oor die bydrae daarvan tot die beheer van B. cinerea en P. digitatum in vrugte. Hierdie studie het gemik om lemoenolie te vestig as 'n alternatiewe toepassing vir na-oes siektebestuur van groenskimmel op sitrus, en grysskimmel op steenvrugte en aarbeie. Die effek van diptoediening van suiwer lemoenolie, lemoenolie-gebaseerde formulerings en suiwer tiemieolie teen P. digitatum op sitrusvrugte en B. cinerea op pruime en aarbeie is bepaal. Op pruime het lemoenoliebehandelings superieure kuratiewe beheer getoon in vergelyking met voorkomende behandelings, met die kultivar African Delight wat minder vatbaarheid vir B. cinerea as die kultivar Laetitia getoon het. Op aarbeie het behandelings voordelige effekte ten op sigte van verlengde raklewe van 14 dae getoon in vergelyking met die standaard 7-10 dae gesien in die praktyk. Penicillium digitatum op sitrus was swak beheer, in vergeleke met imazalil wat meer doeltreffend was. Inkapsuleringstegnieke het gehelp om die afbraak van essensiële olies, wat voortspruit uit hul vlugtige aard, te verminder wanneer dit aan die omgewing blootgestel word. Dus, nanopartikels van lemoen- en tiemieolie is gegenereer deur die nanopresipitasietegniek deur die kopolimeer AtlasTM G-5002L. Die gegenereerde nanopartikels by 3.33, 4.44, 6.66, 8.88 en 17.78 mg mL⁻¹ vir lemoen- en tiemieolie is gekarakteriseer en die bioaktiwiteit teen B. cinerea (beide in vitro en in vivo) en P. digitatum (in vitro) is bepaal. Metodes van toediening op vrugte het bespuiting, kombinering met ‘n eetbare bedekking (vir pruime) of deur aktiewe verpakking ingesluit. In hierdie studie was albei geïnkapsuleerde essensiële olies meer effektief as die onderskeie nie-ingekapsuleerde olies. Tiemieolie-nanopartikels het potensiaal getoon om beide patogene in vitro te beheer. Lemoenolie- nanopartikels het ook potensiaal getoon om B. cinerea op aarbeie te beheer, wanneer dit as deel van ‘n eetbare bedekking toegedien is, en tot 'n sekere mate wanneer dit toegedien is as deel van die aktiewe verpakkingstrategie. Verder is die effek van lemoenolie- en tiemieolie-nanopartikels, teen geselekteerde konsentrasies, op die verdedigingssein van patogeneseverwante gene (PR) en regulatoriese DELLA- proteïene na verwonding en inokulering van pruime, met B. cinerea ondersoek. Lemoenolie het konsekwent gelei tot die afregulering van PR-gene. Die opregulering van DELLA-proteïene was duidelik in die hormonale sein tydens verwonding en die vroeë reaksie op die toediening van beide lemoen- en tiemieolie. Soos in die vorige studies, het tiemieolie opregulering van Chitinase tipe III, Ribonuklease-agtige, Thaumatin-agtige en DELLA proteïene in hierdie studie meegebring. Hierdie studie het geïnkapsuleerde lemoenolie bewys as 'n alternatief vir die bestuur van B. cinerea op pruime en die verbetering van raklewe van aarbeie en het verder bygedra tot die kennispoel wat tans beskikbaar is oor tiemieolie in na-oes siektebeheer. Doctoral 2025-06-11T05:55:43Z 2025-06-11T05:55:43Z 2025-03 Thesis https://scholar.sun.ac.za/handle/10019.1/132543 en Stellenbosch University xi, 174 pages : illustrations application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Orange oil Citrus -- Postharvest diseases and injuries -- Biological control Fruit -- Postharvest losses -- Prevention Fruit -- Quality Essences and essential oils -- Processing Botrytis cinerea Penicillium digitatum Stone fruit -- Postharvest diseases and injuries -- Biological control Strawberries -- Postharvest diseases and injuries -- Biological control UCTD Njombolwana-Swartz, Ncumisa Studies on the application and efficacy of orange oil as a postharvest disease management strategy on fruit |
| title | Studies on the application and efficacy of orange oil as a postharvest disease management strategy on fruit |
| title_full | Studies on the application and efficacy of orange oil as a postharvest disease management strategy on fruit |
| title_fullStr | Studies on the application and efficacy of orange oil as a postharvest disease management strategy on fruit |
| title_full_unstemmed | Studies on the application and efficacy of orange oil as a postharvest disease management strategy on fruit |
| title_short | Studies on the application and efficacy of orange oil as a postharvest disease management strategy on fruit |
| title_sort | studies on the application and efficacy of orange oil as a postharvest disease management strategy on fruit |
| topic | Orange oil Citrus -- Postharvest diseases and injuries -- Biological control Fruit -- Postharvest losses -- Prevention Fruit -- Quality Essences and essential oils -- Processing Botrytis cinerea Penicillium digitatum Stone fruit -- Postharvest diseases and injuries -- Biological control Strawberries -- Postharvest diseases and injuries -- Biological control UCTD |
| url | https://scholar.sun.ac.za/handle/10019.1/132543 |
| work_keys_str_mv | AT njombolwanaswartzncumisa studiesontheapplicationandefficacyoforangeoilasapostharvestdiseasemanagementstrategyonfruit |