Composts, compost extracts and bacterial suppressive action on Pythium aphanidermatum in tomato

Abstract

The effects of three composts (C1, C2 and C3) produced from Solid Olive Mill wastes (SOMW), Posidonia oceanica (Po) and Chicken Manure (CM), at different proportions, were tested on Pythium aphanidermatum. To evaluate the fungal pathogen inhibition, In vitro and In vivo tests were carried out. In vitro tests aimed to study the inhibitive effect of pure compost extracts and the isolated antagonist bacteria. In vivo tests drench and dip root inoculations were done on tomato seedlings. Pure extracts inhibited the fungal pathogen growth. Isolated bacteria also showed an antagonistic action on the mycelial growth of P. aphanidermatum and the 16sRNA identification showed that Bacillus subtilis and B. thuringiensis had the highest inhibition. In vivo tests showed that drench inoculated tomato seedlings sown in substrates with composts resisted to P. aphanidermatum. Root dip inoculated seedlings had a more sustained growth in substrates mixed with composts. Results showed that tested composts acted by both their chemical composition and microorganisms and could be used at appropriate proportions as biological fertilizers.