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Cyclolipopeptides fengycin and iturin A as postharvest fungicides on pome fruit
Thesis (MScAgric)--Stellenbosch University, 2022.
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| Language: | en_ZA |
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Stellenbosch : Stellenbosch University
2022
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| _version_ | 1867614081373962240 |
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| access_status_str | Open Access |
| author | Magwebu, Sinovuyo |
| author2 | Lennox, Cheryl L. |
| author_browse | Lennox, Cheryl L. Magwebu, Sinovuyo |
| author_facet | Lennox, Cheryl L. Magwebu, Sinovuyo |
| author_sort | Magwebu, Sinovuyo |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (MScAgric)--Stellenbosch University, 2022. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/125135 |
| institution | Stellenbosch University (South Africa) |
| language | en_ZA |
| last_indexed | 2026-06-10T12:46:21.556Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2022 |
| publishDateRange | 2022 |
| publishDateSort | 2022 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/125135 Cyclolipopeptides fengycin and iturin A as postharvest fungicides on pome fruit Magwebu, Sinovuyo Lennox, Cheryl L. Meitz-Hopkins, Julia C. Stellenbosch University. Faculty of AgriSciences. Dept. of Plant Pathology. Apples Pears Fruit -- Diseases and pests -- South Africa Postharvest diseases and injuries -- Biological control Edible coatings Biofungicides -- Mechanism of action UCTD Thesis (MScAgric)--Stellenbosch University, 2022. ENGLISH ABSTRACT: Postharvest diseases on apples and pears have become a major constraint in South Africa’s pome fruit industry because of large economic losses incurred. For this reason, the industry is currently seeking more reliable and sustainable strategies to control postharvest decay-causing pathogens. The major pathogens responsible for pome fruit decay include Penicillium expansum (blue mould) and Botrytis cinerea (grey mould). Postharvest diseases are primarily managed by various synthetic fungicides. The use of fungicides is effective, but they are accompanied by extreme risks when applied repeatedly over time, resulting in fungicide resistance within the pathogen population, environmental and potential human health risks. Therefore, alternative methods that reduce the number of fungicides used postharvest need to be studied. This study aimed to test the biological fungicide efficacy of cyclolipopeptides (CLPs), which can be extracted from Bacillus amyloliquefaciens cell-free supernatant against B. cinerea and P. expansum. Initially, the species identity of the pathogens was confirmed using polymerase chain reaction (PCR) and Restriction Fragment Length Polymorphism (RFLP) molecular techniques and furthermore, the B. cinerea population was tested for any shift towards dicarboximides resistance and a microtiter assay was optimised to determine the pathogens sensitivity to iturin A and fengycin biofungicides in vitro. In vivo, the acid precipitate from B. amyloliquefaciens (D747) cell free supernatant containing CLPs was combined with wax and edible coating and applied on the untreated fresh ‘Packham’s Triumph’ pears and ’Cripps Pink’ apples using a curative and protective method of application to evaluate the incidence and severity of the decay on the fruits. The B. cinerea and P. expansum isolates were confirmed using molecular identification. Amongst the B. cinerea isolates used, only one was found to be resistant to dicarboximides because the gene mutation occurred in the amino acid substitution at codon 365 (isoleucine to serine). The in vitro microtiter assay results revealed that iturin A biofungicide can suppress the spore germination of both pathogens (B. cinerea and P. expansum) while no inhibition was seen when using fengycin at low doses in the optimisation of microtiter assay. Iturin A tested at 0.01 mg.L⁻¹ and had a marginal effect of inhibiting pathogen growth in vitro, indicating that higher doses need to be tested to verify any significant direct fungitoxicity. In fruit trials, CLPs application as the edible coating was most effective in reducing blue mould incidence preventatively (11% control, equivalent to fludioxonil in the edible coating), while no significant effect was found for grey mould incidence on pears. Application of wax or edible coating alone did not reduce the incidence of P. expansum or B. cinerea on the infected fruit. Penicillium expansum showed a mean reduction of 40% in lesion diameter and B. cinerea a mean reduction of 30-35% when CLPs was applied in wax or zein edible coating at pH 8.0. Thermofogging application of CLPs at pH 8.0 did not effectively reduce grey mould and blue mould incidence. The results indicate that in combination with other alternative control measures CLPs could contribute to effective alternative pathogen management for the control of blue and grey mould on pome fruit in an optimized formulation. AFRIKAANSE OPSOMMING: Na-oessiektes op appels en pere het 'n belangrike beperking op die Suid-Afrikaanse kernvrugtebedryf geword as gevolg van groot ekonomiese verliese wat oor die jare heen ontstaan het. Om hierdie rede is die bedryf tans op soek na meer betroubare en volhoubare strategieë om die patogene wat na-oesbederfsiektes veroorsaak, te beheer. Die belangrikste patogene wat verantwoordelik is vir die bederf van kernvrugte, is Penicillium expansum (blouskimmel) en Botrytis cinerea (grysvrot). Na-oessiektes word tans deur sintetiese swamdoders bestuur. Die gebruik van swamdoders is effektief, maar gaan gepaard met uiterste risiko's wanneer dit herhaaldelik oor lang tydperke toegedien word, wat swamdoderweerstand binne die patogeenpopulasie, en omgewings- en potensiële menslike gesondheidsrisiko's tot gevolg het. Alternatiewe metodes wat die aantal swamdoders wat na-oes gebruik word, verminder, moet dus bestudeer word. Hierdie studie het die biobeheer potensiaal van die rowwe ekstrak van Bacillus amyloliquefaciens siklolipopeptiede (CLPs) iturien A en fengycin, is teen B. cinerea en P. expansum in vitro en in vivo getoets. Die eerste stap was om die B. cinerea en P. expansum isolate spesie-identiteit te bevestig gebaseer op polimerase kettingreaksie (PCR) en Restriction Fragment Length Polymorphism (RFLP) molekulêre tegnieke. Verde was die B. cinerea populasie evalueer vir enige verskuiwing na dikarboksimiede weerstand en ‘n mikrotiter- in vitro toets was optimaliseer om die patogene se sensitiwiteit vir iturien A en fengycin-bioswamdoders. Die suurneerslag van siklolipopeptiede van B. amyloliquefaciens (D747), gekombineer met ‘n eetbare bedekking, is op die onbehandelde vars 'Packham's Triumph' pere en 'Cripps Pink' appelvrugte toegedien, deur gebruik te maak van óf ʼn genesende óf ʼn beskermende toedieningsmetode om die voorkoms en erns van die na-oesbederf op die vrugte te evalueer. Die B. cinerea en P. expansum isolate se identiteit was bevestig met behulp van molekulêre identifikasie. Van die B. cinerea-isolate wat gebruik is, is gevind dat slegs een weerstandbiedend is teen dikarboksimiede omdat die geenmutasie plaasgevind het in die aminosuurvervanging by kodon 365 (isoleusien na serien). Die resultate van die in vitro mikrotitertoets het aan die lig gebring dat iturien A bioswamdoder die spoorontkieming van beide patogene (B. cinerea en P. expansum) kan onderdruk terwyl geen inhibisie gesien is wanneer fengysien teen lae dosisse gebruik word in die optimalisering van mikrotitertoets nie. Iturien A is getoets teen 0.01 mg.L⁻¹ en het 'n marginale effek gehad om patogeengroei in vitro te inhibeer, wat aandui dat hoër dosisse getoets moet word om enige beduidende direkte swamtoksisiteit te verifieer. In vrugteproewe was CLPs-toediening as die eetbare laag die doeltreffendste om blouskimmel voorkoms voorkomend te verminder (11 % beheer, gelykstaande aan fludioxonil in die eetbare laag), terwyl geen beduidende effek vir grysskimmel voorkoms op pere gevind is nie. Penicillium expansum het 'n gemiddelde verlaging van 40 % in letsel deursnee getoon en B. cinerea 'n gemiddelde verlaging van 30-35 % wanneer CLP's in was of zein eetbare laag by pH 8.0 toegedien is. Toediening van eetbare laag alleen het nie die voorkoms van P. expansum of B. cinerea op die besmette vrugte verminder nie. Termofogging-toediening van CLP's by pH 8.0 het nie die voorkoms van grysvrot en blouskimmel effektief verminder nie. Die resultate dui daarop dat in kombinasie met ander alternatiewe beheermaatreëls CLP's kan bydra tot effektiewe alternatiewe patogeenbestuur vir die beheer van blouskimmel en grysvrot op kernvrugte in 'n geoptimaliseerde formulering. Masters 2022-03-08T10:55:42Z 2022-04-29T12:55:30Z 2022-09-08T03:00:13Z 2022-04 Thesis http://hdl.handle.net/10019.1/125135 en_ZA Stellenbosch University x, 75 pages : illustrations application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Apples Pears Fruit -- Diseases and pests -- South Africa Postharvest diseases and injuries -- Biological control Edible coatings Biofungicides -- Mechanism of action UCTD Magwebu, Sinovuyo Cyclolipopeptides fengycin and iturin A as postharvest fungicides on pome fruit |
| title | Cyclolipopeptides fengycin and iturin A as postharvest fungicides on pome fruit |
| title_full | Cyclolipopeptides fengycin and iturin A as postharvest fungicides on pome fruit |
| title_fullStr | Cyclolipopeptides fengycin and iturin A as postharvest fungicides on pome fruit |
| title_full_unstemmed | Cyclolipopeptides fengycin and iturin A as postharvest fungicides on pome fruit |
| title_short | Cyclolipopeptides fengycin and iturin A as postharvest fungicides on pome fruit |
| title_sort | cyclolipopeptides fengycin and iturin a as postharvest fungicides on pome fruit |
| topic | Apples Pears Fruit -- Diseases and pests -- South Africa Postharvest diseases and injuries -- Biological control Edible coatings Biofungicides -- Mechanism of action UCTD |
| url | http://hdl.handle.net/10019.1/125135 |
| work_keys_str_mv | AT magwebusinovuyo cyclolipopeptidesfengycinanditurinaaspostharvestfungicidesonpomefruit |