| Summary: | The soil fungus <i>Macrophomina phaseolina</i>, the charcoal rot disease agent, poses a major threat to cotton fields. In Israel, highly infected areas are also inhabited by the maize pathogen <i>Magnaporthiopsis maydis</i>. This study reveals the relationships between the two pathogens and their impact on cotton sprouts. Infecting the soil 14 days before sowing (DBS) with each pathogen or with <i>M. phaseolina</i> before <i>M. maydis</i> caused a strong inhibition (up to 50–65%) of the sprouts’ development and survival, accompanied by each pathogen’s high DNA levels in the plants. However, combined or sequence infection with <i>M. maydis</i> first led to two distinct scenarios. This pathogen acted as a beneficial protective endophyte in one experiment, leading to significantly high emergence and growth indices of the plants and a ca. 10-fold reduction in <i>M. phaseolina</i> DNA in the sprouts’ roots. In contrast, <i>M. maydis</i> showed strong virulence potential (with 43–69% growth and survival suppression) in the other experiment, proving its true nature as an opportunist. Interestingly, soil inoculation with <i>M. phaseolina</i> first, 14 DBS (but not at sowing), shielded the plants from <i>M. maydis</i>’ devastating impact. The results suggest that the two pathogens restrict each other, and this equilibrium may lead to a moderate disease burst.
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