Differential Response of Banana Root Exudates and its Components on the Growth and Development of Banana Wilt Pathogen

Plant roots and rhizospheric microbes share an intricate relationship. Plants produce a complex mixture of root exudates that significantly affect the rhizospheric microbiome. Understanding the composition and functional significance of root exudates is essential for elucidating ecological mechanisms that can be leveraged to reduce disease severity. The significance of banana root exudates in Fusarium wilt disease caused by Fusarium oxysporum f. sp. cubense (Foc) remains poorly understood. This study investigates the differential effects of root exudates and their specific constituents derived from resistant and susceptible banana cultivars on the growth and development of Foc. Root exudates collected from four banana cultivars were evaluated for their effect on Foc mycelial growth, conidiospore germination and chemotropism. Exudates from susceptible cultivars (Rasthali, Red banana) significantly stimulated Foc conidiospore germination and chemotropism index as compared to those from resistant cultivars (Grand Naine, cv. Rose). Among the components, fumaric and salicylic acid showed dose-dependent increase in Foc conidia germination and chemotropism index. Conversely, oxalic and malic acid showed inhibition of Foc conidia germination at 0.5 µM, while phthalic acid showed inhibitory effects at 5 µM. Interestingly, oxalic, malic and phthalic acid treatment showed increased chemotropism index at 0.5 µM whereas, cinnamic acid showed a dose-dependent decrease. Mass spectrometric analysis revealed distinct profiles of organic acids among the four cultivars, while phenolic acids were detected in all four samples. This study enhances our understanding of the banana-Fusarium interaction and offer valuable insights into natural defense mechanisms and potential biocontrol strategies.