Mutation breeding of Cavendish bananas for resistance to Fusarium oxysporum f. sp. cubense tropical race 4
| dc.contributor.advisor | Viljoen, Altus | en_ZA |
| dc.contributor.advisor | Rose, Lindy J. | en_ZA |
| dc.contributor.advisor | Mostert, Diane | en_ZA |
| dc.contributor.advisor | Jankowicz-Cieslak, Joanna | en_ZA |
| dc.contributor.author | Bothma, Sheryl | en_ZA |
| dc.contributor.other | Stellenbosch University. Faculty of AgriSciences. Dept. of Plant Pathology. | en_ZA |
| dc.date.accessioned | 2021-03-07T20:29:42Z | |
| dc.date.accessioned | 2021-04-22T10:14:11Z | |
| dc.date.available | 2023-03-18T03:00:10Z | |
| dc.date.issued | 2021-03 | |
| dc.description | Thesis (MScAgric)--Stellenbosch University, 2021. | en_ZA |
| dc.description.abstract | ENGLISH ABSTRACT: Bananas (Musa spp.) are among the world’s top ranking agricultural commodities and are cultivated in more than 120 tropical and subtropical countries. The crop provides a stable source of nutrition and household income to millions of people around the world. Among the hundreds of bananas cultivated, the Cavendish banana is the most popular, accounting for 47% of global production. Commercial Cavendish plantations are established from tissue cultured material and are cultivated in large monoculture systems. These cultivation practices leave the Cavendish banana susceptible to many biotic and abiotic stresses. Banana Fusarium wilt, caused by the soil-borne fungus Fusarium oxysporum f. sp. cubense (Foc), is present in most banana-growing regions in the world. Foc is classified into three races based on its pathogenicity to different banana varieties. Foc races 1 and 2 cause disease to Gros Michel, several dessert varieties, and some cooking bananas like Bluggoe. Foc race 4 is divided into subtropical (STR) and tropical (TR4) race 4 strains, which affect Cavendish bananas in both the subtropics and tropics, respectively. Foc TR4 is considered a global threat to banana production due to its devastating effect on Cavendish and other banana varieties susceptible to Foc races 1 and 2. The resilience of its chlamydospores, which can remain viable for decades, makes Foc a challenging pathogen to manage. Prevention of the banana Fusarium wilt through phytosanitary regulation and the use of clean planting material is important. However, once the Foc has established in a field, the only reliable management option is the replacement of susceptible with resistant banana varieties. Currently, no resistant banana variety meets the requirements of growers and consumers to replace the Cavendish banana on the global export market. Resistance to Foc TR4 in banana can be obtained by conventional or unconventional breeding. Bananas developed by conventional breeding are often not popular with consumers due to the unfavourable change in its taste. Unconventional breeding has produced a genetically modified Cavendish banana resistant to Foc TR4, which is not accepted by the general public. Mutation breeding is, however, not considered genetic modification, and has successfully produced crops with improved yield, performance and disease resistance. In this study, mutation breeding was used to develop Cavendish banana mutants resistant to Foc TR4. Meristem cutting produced in vitro were first treated with a range of ethyl methane sulfonate (EMS) concentrations and gamma irradiation loads to determine their chemical toxicity and radio-sensitivity, respectively. Survival rate, growth characteristics and Fusarium wilt resistance were assessed after mutation induction, and the optimised dosages for bulk mutagenesis established as 1.5% for EMS and 20 Gray for gamma-irradiation. Twelve weeks after inoculation, one gamma-irradiated mutant and five EMS-derived mutants were identified as putatively resistant to Foc TR4. These mutants will in future be tested for field resistance to Foc TR4, agronomic performances and post-harvest fruit quality. If resistant with good agronomic traits, such a plant can be used to replace susceptible Cavendish bananas in fields infested with Foc TR4. | en_ZA |
| dc.description.abstract | AFRIKAANSE OPSOMMING: Piesangs (Musa spp.) is een van die belangrikste landbou-kommoditeite en word in meer as ‘n 120 tropiese en subtropiese lande verbou. Die gewas verskaf ‘n stabiele voedingsbron en dra by tot huishoudelike inkomste vir miljoene mense rondom die wêreld. Onder die honderde piesangs wat tans verbou word, is die Cavendish-piesang die gewildste, en dra by to sowat 47% van piesangs wat wêrelwyd verbou word. Kommersiële Cavendish-aanplantings word met weefselkultuurplantjies gevestig en as groot monokultuurstelsels bestuur. Hierdie kombinasie van verbouingspraktyke maak die Cavendish-piesang vatbaar vir biotiese en abiotiese faktore. Fusarium-verwelk, veroorsaak deur die grondgedraagde swam, Fusarium oxysporum f. sp. cubense (Foc), is in die meeste piesang-produserende gebiede ter wêreld teenwoordig. Foc word in drie rasse geklassifiseer op grond van patogenisiteit vir verskillende piesangvariëteite. Foc-ras 1 en 2 veroorsaak verwelk op Gros Michel, verskeie nageregvariëteite, en sommige piesangs soos Bluggoe. Foc-ras 4 is in subtropiese (STR) en tropiese (TR4) ras 4-stamme verdeel, wat Cavendish-piesangs in beide die subtrope en die trope beïnvloed. Foc TR4 word beskou as 'n wêreldwye bedreiging vir piesangproduksie vanweë die vernietigende uitwerking op Cavendish en ander piesangvariëteite wat vir Foc- rasse 1 en 2 vatbaar is. Die aanpasbaarheid van sy klamydospore, wat dekades lank lewensvatbaar kan bly, maak Foc 'n uitdagende patogeen om te bestuur. Voorkoming van Fusarium-verwelk deur fitosanitêre regulering en die gebruik van skoon plantmateriaal, is uiters belangrik. Sodra Foc in 'n veld gevestig is, is die vervanging van vatbare variëteite met weerstandbiedende variëteite die enigste volhoubare bestuurs-opsie. Huidig voldoen geen weerstandbiedende piesangvariëteit aan die vereistes van beide produsente en verbruikers om die Cavendish-piesang op die wêreldwye uitvoermark te vervang nie. Weerstand teen Foc TR4 in piesang kan verkry word deur konvensionele of onkonvensionele teling. Piesangs wat deur konvensionele teling ontwikkel is, is dikwels nie gewild onder verbruikers nie weens die ongunstige verandering in die smaak van die piesangvrug. Onkonvensionele teling het 'n geneties-gemodifiseerde Cavendish-piesang wat bestand is teen Foc TR4, geproduseer, maar dit word ongelukkig nie deur die algemene publiek aanvaar nie. Plante ontwikkel deur mutasie-teling word egter nie as geneties- modifiseerde plante beskou nie, en het reeds suksesvolle gewasse opgelewer met verbeterde opbrengs, prestasie en siekteweerstand. In hierdie studie is mutasie-teling gebruik om Cavendish-piesangmutante te ontwikkel wat teen Foc TR4 bestand is. Meristeempunte wat in weefselkultuur geproduseer is, is eers met 'n reeks van etielmetaansulfonaat (EMS) konsentrasies behandel, asook verskeie gamma-bestralingladings om onderskeidelik hul chemiese toksisiteit en radio-sensitiwiteit te bepaal. Die oorlewingstempo, groei-eienskappe en Fusarium-verwelkweerstand is ná mutasie-induksie bepaal, en die optimale dosisse vir grootmaat mutagenese is vasgestel as 1.5% vir EMS en 20 Gray vir gamma-bestraling. Twaalf weke ná inokulasie, is een gamma-bestraalde mutant en vyf EMS-verkrygde mutante geïdentifiseer as vermoedelik bestand teen Foc TR4. Hierdie mutante sal getoets word vir veldweerstand teen Foc TR4, agronomiese prestasies en vruggehalte ná oes. Indien die mutante bestand is met goeie agronomiese eienskappe, kan so 'n plant gebruik word om vatbare Cavendish-piesangs in lande, besmet met Foc TR4, te vervang. | af_ZA |
| dc.description.version | Masters | en_ZA |
| dc.embargo.terms | 2023-02-28 | |
| dc.identifier.uri | http://hdl.handle.net/10019.1/110325 | |
| dc.language.iso | en_ZA | en_ZA |
| dc.publisher | Stellenbosch : Stellenbosch University | en_ZA |
| dc.rights.holder | Stellenbosch University | en_ZA |
| dc.subject.lcsh | Mutation breeding | en_ZA |
| dc.subject.lcsh | Bananas -- Breeding | en_ZA |
| dc.subject.lcsh | Fusarium wilt of banana | en_ZA |
| dc.subject.lcsh | Cavendish bananas -- Disease and pest resistance -- Genetic aspects | en_ZA |
| dc.subject.name | UCTD | en_ZA |
| dc.title | Mutation breeding of Cavendish bananas for resistance to Fusarium oxysporum f. sp. cubense tropical race 4 | en_ZA |
| dc.type | Thesis | en_ZA |