Decomposition solutions from brassica and cereal residues suppress tomato bacterial wilt disease by regulating rhizosphere microbial communities.

Cover crops can suppress the following crop diseases and alter soil microbial communities, but the mechanisms of such disease suppressive effects remain uncertain. Here, we studied the effects of brassica and cereal cover crops, along with decomposition solutions from these crop residues, on tomato growth and bacterial wilt. Moreover, tomato rhizosphere microorganisms were analyzed by qPCR and high-throughput sequencing. Rhizosphere transplant experiment was conducted to validate the disease suppressive potential of rhizosphere microorganisms mediated by decomposition solutions from these crop residues. Our findings revealed that brassica and cereal cover crops especially wheat, pakchoi and rape significantly enhanced tomato growth and inhibited bacterial wilt disease. Decomposition solutions from brassica and cereal residues had inhibitory effects on Ralstonia solanacearum and this disease. Moreover, such decomposition solutions can differently alter the abundances, compositions and diversities of tomato rhizosphere bacterial and fungal communities. Notably, decomposition solutions from wheat, pakchoi and rape residues increased the inverse Simpson diversity and the abundances of Bacillus spp. community. In addition, decomposition solutions from wheat and pakchoi residues significantly increased bacterial beta diversity, and decomposition solutions from rape residue significantly increased fungal beta diversity. Rhizosphere transplant experiment confirmed that the rhizosphere microbial changes induced by decomposition solutions contributed to the suppressiveness of tomato bacterial wilt disease. These suppressive effects were stronger in decomposition solutions from wheat, pakchoi and rape residues than those from oilseed rape, wild rocket and Indian mustard residues. Overall, our results demonstrated that decomposition solutions from brassica and cereal residues enhance disease suppression by shaping a beneficial rhizosphere microbiota, providing a promising strategy for sustainable management of bacterial wilt in tomato cultivation.