Phenotyping Assays for Pathogenicity Determination of Fusarium oxysporum f. sp. cubense Tropical Race 4

Fusarium oxysporum f. sp. cubense (Foc) is a lethal pathogen affecting banana plants. To manage this pathogen, resistance exploration, along with exclusion and eradication, is crucial. A simple and reproducible method of assessing pathogenicity is essential for identifying resistant candidate genotypes. In this study, we evaluated the pathogenicity of Foc tropical race 4 (TR4) on tissue-cultured banana plants (cv. NIGAB-1 and Grand Naine) using three inoculation methods: the pouring method (PM), the chlamydospore method (CM), and the kernel method (KM). The latency period for both varieties inoculated by the chlamydospore method was two weeks after inoculation (wai), whereas plants inoculated using the pouring and kernel methods showed symptoms after three weeks. Disease severity findings revealed significant differences at the end of the assessment period among the different inoculation methods. The pouring method proved to be more effective than the other two methods, yielding consistent, repeatable results with dose-dependent final disease severity. This method can be employed to evaluate the pathogenicity of Foc (TR4) and assess various disease control methods to identify effective solutions.