Use of sewage sludge compost and Trichoderma asperellum isolates to suppress Fusarium wilt of tomato

Abstract

It has been reported that plant growth media amended with composted bark suppress Fusarium wilts whereas media amended with composted municipal sludge aggravate this disease. However, in this study, a compost prepared from vegetable and animal market wastes, sewage sludge and yard wastes showed a high ability to suppress Fusarium wilt of tomato caused by Fusarium oxysporum f. sp. lycopersici race 1. The ability of this compost to suppress Fusarium wilt of tomato was compared with that of a peat mix (peat:vermiculite, 1:1 v/v) and a naturally suppressive soil from Chateaurenard, France. The compost and the soil from Chateaurenard were highly suppressive, whereas the peat mix was highly conducive. Amendment with this compost significantly ( P<0.05) increased the suppressiveness of the peat mix. Biotic and abiotic properties were compared among these substrates. The peat mix was acidic, and had a low EC, whereas the compost was basic and a high EC. The compost–peat mix had a similar pH to the compost, however EC was approximately half that of the compost. The bacterial populations and microbial activity were highest in the compost and the compost–peat mix. Compost (10%; v/v), Trichoderma asperellum isolates isolated from natural compost–peat mix, and the nonpathogenic biocontrol agent F. oxysporum Fo47 isolated from Chateaurenard soil were inoculated into sterilized compost–peat mix and Chateaurenard soil to assess their ability to restore suppressiveness in the sterilized substrates. Both the natural compost and the T. asperellum isolates significantly ( P<0.05) increased the suppressive ability of sterilized compost–peat mix and Chateaurenard soil. Fo47 was relatively the most effective biocontrol agent. The incidence of Fusarium wilt was lowest in tomato plants grown in either sterilized compost–peat mix or Chateaurenard soil inoculated with this strain. Our results show that the use of some composted sewage sludge in the plant growth medium is effective for suppression of Fusarium wilt at the early stage of plant growth. In addition, the T. asperellum isolates isolated from the suppressive compost–peat mix appear to have the potential to be a new alternative of biocontrol of Fusarium wilt.