The treatment of Fusarium Oxysporum F. SP. cubense in soil and water

Thesis (MScAgric)--Stellenbosch University, 2019.

ENGLISH ABSTRACT: Banana is an economically important food crop globally. It is, however, also severely affected by biotic and abiotic constraints, including banana Fusarium wilt (Panama disease). The causal agent of banana Fusarium wilt is the fungus Fusarium oxysporum f. sp cubense (Foc), which can survive as chlamydospores in soil for several years, making it difficult to control. The only effective way to manage Foc is by planting resistant cultivars and by preventing the fungus from being introduced into new areas. Resistant cultivars are often not acceptable to local and international markets, which makes disease prevention and reducing the spread of Foc to new areas an important disease management strategy. Foc can easily spread with contaminated soil and water. Contaminated soil attaches to boots, vehicles, plantation tools and machinery, and transfers the fungus over short or long distances. Heavy rainfall and typhoons may also carry infested soil with run-off water from infested to non-infested areas. The run-off water further contaminates irrigation sources such as rivers, dams and ponds. To prevent Foc from spreading, it is important to implement strict quarantine measures that prevent the movement of the pathogen on field equipment, shoes, vehicles and in contaminated water. Measures to do this include the use of footbaths and disinfestation areas, as well as the treatment of water used for irrigation. Limited studies, however, have been done on the survival and treatment of water contaminated with Foc. In this study, the sanitation products Sporekill, Saniwash, Farmcleanse, HTH and HyperCide were tested for efficacy against Foc race 1, STR4 and TR4 at their recommended dose and a 0.1 x dilution in the presence and absence of soil in water. The sanitisers were all tested at an exposure time of 0 s, 30 s and 2 min. All sanitisers were effective at both concentrations, but not in the presence of soil. Sporekill and Saniwash were the most effective sanitisers at the recommended dose upon contact (0 s) in the absence of soil and in the presence of soil after 2 min. This indicated that soil needs to be removed from shoes, field equipment and vehicles before being treated with Sporekill and Saniwash. The survival of Foc in 20-L buckets filled with water was determined in the presence and absence of soil. The water was either stirred or left stagnant. Water samples were extracted from the top, middle and bottom of the buckets 1, 7, 14, 30, 60 and 120 days after inoculation. The survival of Foc decreased over time, and the spores sunk to the bottom of water that remained stagnant. The contaminated water was also treated with ozone, UV radiation, HTH and the peracetic acid products (HyperCide and Tsunami 100) to determine the survival of Foc colony forming units in the presence and absence of soil. Ozone, HTH and HyperCide were only effective in the absence of soil, while UV radiation was ineffective. Thus, it is important that soil be removed for the treatment of irrigation water since Foc was able to survive for 4 months in water without agitation.

AFRIKAANSE OPSOMMING: Piesang is wêreldwyd ‘n ekonomies-belangrike voedselgewas. Dit word egter ook ernstig deur biotiese en abiotiese beperkings geaffekteer, insluitende piesang Fusarium-verwelk (Panama-siekte). Die veroorsakende agent van piesang Fusarium-verwelk is die swam Fusarium oxysporum f. sp cubense (Foc), wat as klamydospore in die grond vir verskeie jare kan oorleef, wat sodoende die beheer daarvan baie bemoeilik. Die enigste effektiewe manier vir die bestuur van Foc is deur die plant van weerstandbiedende kultivars en deur te voorkom dat die swam in nuwe areas ingebring word. Weerstandbiedende kultivars is dikwels nie vir plaaslike en internasionale markte aanvaarbaar nie, wat siekte-voorkoming en vermindering van die verspreiding van Foc na nuwe areas ʼn belangrike siektebestuurstrategie maak. Foc kan maklik met gekontamineerde grond en water versprei. Gekontamineerde grond sit aan skoene, voertuie, gereedskap en masjinerie vas, en dra die swam oor kort of lang afstande oor. Hewige reënval en tifone kan ook besmette grond met afloopwater vanaf besmette na onbesmette areas oordra. Die afloopwater kontamineer verder besproeiingsbronne soos riviere, damme en poele. Ten einde die verspreiding van Foc te voorkom, is dit belangrik om streng kwarantynmaatreëls te implementeer wat die beweging van die patogeen op veldgereedskap, skoene, voertuie en in gekontamineerde water verhoed. Maatreëls om dit te doen, sluit die gebruik van voetbaddens en ontsmettingsareas, asook die behandeling van water wat vir besproeiing gebruik word, in. Beperkte studies is egter al op die oorlewing en behandeling van water wat met Foc gekontamineer is, gedoen. In hierdie studie is die saniteerprodukte Sporekill, Saniwash, Farmcleanse, HTH en HyperCide vir effektiwiteit teen Foc ras 1, STR4 en TR4 getoets, teen hul aanbevole dosis en ʼn 0.1 x verdunning, in die aanwesigheid en afwesigheid van grond in water. Die saniteerders is almal by ʼn blootstellingsperiode van 0 s, 30 s en 2 min getoets. Al die saniteerders was teen beide konsentrasies effektief gewees, maar nie in die aanwesigheid van grond nie. Sporekill en Saniwash was die effektiefste saniteerders teen die aanbevole dosis gewees, op kontak (0 s) in die afwesigheid van grond en in die aanwesigheid van grond ná 2 min. Dit dui daarop dat grond vanaf skoene, veldgereedskap en voertuie verwyder moet word voordat dit met Sporekill en Saniwash behandel word. Die oorlewing van Foc in 20-L houers gevul met water, is in die aanwesigheid en afwesigheid van grond bepaal. Die water is óf geroer of staande gelos. Watermonsters is vanuit die boonste, middelste en onderste gedeelte van die houers 1, 7, 14, 30, 60 en 120 dae ná inokulasie geneem. Die oorlewing van Foc het oor tyd afgeneem, en die spore het na die bodem van water gesak wat staande gebly het. Die gekontamineerde water is ook met osoon, UV-bestraling, HTH en perasynsuur behandel ten einde die oorlewing van Foc kolonie-vormende eenhede in die aanwesigheid en afwesigheid van grond te bepaal. Perasynsuur was die effektiefste behandelingsmetode en het Foc in die aanwesigheid en afwesigheid van grond uitgewis. Osoon en HTH was slegs in die afwesigheid van grond effektief, terwyl UV-bestraling oneffektief was. Perasynsuur moet dus vir die behandeling van besproeiingswater gebruik word aangesien Foc in staat is om vir 4 maande in water wat nie geroer word nie, te oorleef.

Masters