In Vitro Assessment of Fusarium Wilt Disease Expression in Banana Population: A Fast-Track Approach for Resistance Screening

Abstract

This study aimed at standardizing an efficient in vitro bioassay for the early selection of Foc TR4-resistant banana populations. An in vitro bioassay was optimized using a conidial concentration of 10? conidia mL^-1 for 100 F? progenies from a cross between a susceptible wild Musa acuminata (WB3) and a tolerant local cultivar, Pisang Jari Buaya (PJB). The disease symptoms were calculated using the Disease Severity Index (DSI), and progenies were statistically categorized into resistance categories according to previously developed criteria. The optimized in vitro bioassay was highly reproducible and effectively induced the full range of disease symptoms. Screening the F? population showed a continuous distribution of DSI values, with a mean of 3.58 and a range of 1.7 to 6.0. This indicates quantitative inheritance. Notably, the population showed transgressive segregation, with individual offspring exhibit traits beyond the range of either parent. Using established statistical criteria, the offspring were classified into resistance categories: 7.6% as Highly Resistant, 15.2% as Resistant, and 60.9% as Moderately Resistant. This grouping confirms the successful introduction and segregation of resistance alleles. Furthermore, a broad-sense heritability estimate of 52% highlighted a significant genetic component behind the observed phenotypic variation. However, this study demonstrates that the in vitro bioassay as a fast, reliable, and cost-effective tool for high-throughput phenotyping of banana breeding populations. The resistant progenies identified provide promising candidates for further field testing and genetic mapping, providing a clear path to accelerate the development of Foc TR4 resistant varieties.