Efficacy of Organic Amendments and Soil Solarization against Wilt Severity and their Effects on Pathogenic Fungi and Tomato Production

Abstract

Soil solarization coupled or not with three soil amendments (cattle manure, bio-compost, and Biocat-15) was evaluated for its efficacy against vascular wilt severity on tomato plants grown under greenhouse conditions in a naturally infested soil. In solarized plots, wilt severity, estimated through the vascular discoloration extent and noted on randomly selected tomato plants, was significantly reduced following all the tested organic amendments. Complete wilt suppression was achieved using cattle manure. Vascular wilt severity noted on symptomatic tomato plants was 28% higher in non-solarized plots than in solarized ones and this for all organic amendments combined. Plots amended with Biocat-15 showed 29% less disease severity as compared to the two other treatments. Fungal isolations performed on Potato Dextrose Agar medium from roots, collars and stems of symptomatic and randomly selected plants, revealed the involvement of Fusarium oxysporum, F. solani, Rhizoctonia solani, Colletotrichum coccodes and R. bataticola in the observed wilts. Their isolation frequencies varied depending on wilt severity, solarization treatments (solarized or non-solarized) and tested soil amendments. Tomato production varied significantly depending on solarization treatments and tested organic amendments. Plants amended with cattle manure yielded significantly comparable production in the solarized and non-solarized plots while this production parameter was reduced by 19 and 27% following Biocompost and Biocat-15 treatments, respectively, on tomato plants grown in non-solarized plots. As for solarization effects, for all organic amendments combined, tomato production was significantly reduced by about 15% in the non-solarized greenhouse compared to the solarized one. Results from the current study showed that, under natural Tunisian conditions, single application of solarization combined with organic amendment not only reduced wilt severity, but also significantly enhanced tomato production. Thus, the repetitive combination of solarization and organic amendments could be a credible alternative for managing various soilborne fungal diseases and improving tomato yield in heavily infested fields.