Colonization of Strawberry Plants by Macrophomina phaseolina After Root or Crown Inoculations

Macrophomina phaseolina is an important pathogen causing charcoal rot on strawberry. The infection process of M. phaseolina on other hosts has been well documented, but this process has not been investigated on strawberry. The objective of this study was to determine if and where M. phaseolina can colonize strawberry plant tissues within 1 month of inoculation in the absence of charcoal rot symptoms. A greenhouse study was conducted with 'Monterey' strawberry plants and three inoculum treatments (control, root-inoculated, and crown-inoculated) sampled at five time points (3, 7, 14, 21, and 28 days postinoculation [dpi]). M. phaseolina was quantified in root and crown tissue using a culture-dependent technique that uses sodium hypochlorite to eliminate nontarget organisms in dried, ground strawberry tissues. Across all four trials, the number of colonies detected in roots at 28 dpi was significantly higher than at 3 dpi by factors of 12, 148, 62, and 2,977, suggesting active colonization of roots. However, all plant parts remained asymptomatic for the duration of the experiment, confirming that infection and abundant colonization of strawberry plants can occur before symptoms are apparent. Crowns were also assessed for colonization, but the results were inconclusive. This study is a first step toward elucidating the infection process of charcoal rot disease on strawberry.Copyright (c) 2025 The Author(s). This is an open access article distributed under the CC BY 4.0 International license.