Long-term suppression of Pythium abappressorium induced by Brassica juncea seed meal amendment is biologically mediated

► Brassica juncea seed meal provides long-term Pythium root rot control in apple. ► Long-term disease suppression was not directly the result of isothiocyanate activity. ► Disease suppression was AITC-dependent but required activity of orchard soil biology. ► Distinct changes in fungal community composition were associated with disease control.