HARNESSING THE MICROBIOME OF VERMI-COMPOST TO PROTECT SOLANUM LYCOPERSICUM AGAINST FUSARIUM WILT
Tomato (Solanum lycopersicum L.) is consumed globally as a fresh vegetable. It is highly nutritional and has antioxidant properties. However, soil-borne diseases such as bacterial wilt and Fusarium wilt can significantly reduce its yield and quality. The use of agrochemicals to combat these diseases can produce chemical residues, pesticide resistance, and environmental pollution. Alternative protection strategies are thus needed. One of the most promising solutions is to harness microbial communities that can inhibit disease and promote plant growth and immunity. Most suppressive soils lose their activity when sterilized, which is strong evidence of the important role played by soil microorganisms in pathogen suppression. An agricultural practice that can enhance this microbiological activity is the addition of compost, an organic soil amendment with suppressive properties against several soil-borne pathogens, including Fusarium spp. This study evaluated the impact of vermi-compost on the growth of tomato and its possible suppressive effects on phytopathogen Fusarium oxysporum f. sp. lycopersici (Fol). It also sought to gather information about the microbial community residing in the compost. To study plant growth, vigor parameters (stem length, fresh weight, dry weight, water content and fluorescence intensity) were analyzed in seedlings after they had been growing for 21 days in mixtures of sterile and non-sterile substrates. The ability of the compost to suppress the phytopathogen was studied in vitro with bacterial and fungal isolates through a plate inhibition assay, and in vivo by inoculating Fol on the 21-day-old seedlings. The presence of 30% compost in the growth mixture allowed for greater plant development, growth and use of nutrients. Likewise, the compost reduced the severity of disease in the seedings by 12%. Scanning electron microscopy was used to study the mycoparasitic activity of a Trichoderma sp. isolated from the compost against Fol. Bacterial isolates, on the other hand, were identified with three molecular markers: 16S ribosomal RNA, DNA gyrase subunit A (gyrA), and RNA polymerase beta subunit (rpoB). Both a Bacillus sp. and the Trichoderma sp. were capable of inhibiting the growth of the pathogen. These findings confirm the suppressiveness of the compost and the PGPR aptitudes of the residing microorganisms. The complete isolated genome of the bacterial species will be elucidated in the context of a project approved to be part of GetGenomes GGLatAm2024 initiative. Moreover, the cyclic lipopeptides generated by this species will be studied by HPLC-mass spectrometry.