Effect of different organic amendments on lettuce Fusarium wilt and on soilborne microorganisms

G. Gilardi, M.A. Cucu, M. Pugliese, M.L. Gullino, A. Garibaldi
This research has been aimed at establishing the potential of organic amendments to reduce yield losses due to Fusarium wilt on lettuce and their effects on soil microorganisms. A first set of trials was carried out under controlled conditions, with artificial inoculation of Fusarium oxysporum f. sp. lactucae (FOL), and the impact of organic amendments (compost from biodegradable municipal solid waste, cattle and chicken manure, Brassica carinata, used as defatted seed meal and flour) was considered on wilt severity and pathogen density, on the total fungi and on fluorescent Pseudomonas spp. after two subsequent lettuce crop cycles. The results showed that the Brassica amendments and compost reduced Fusarium wilt by between 52 and 79% and from 49 to 67%, respectively, while the cattle and chicken manure only provided partial control, compared with the untreated control. In general, an increase in the population density of Pseudomonas species as well as a significant reduction in the total fungal population and pathogen density were observed in the growing medium after two consecutive lettuce crops. In a second set of trials, experiments were carried out in a naturally infested soil, and some encouraging results, related to Fusarium wilt management through compost, were obtained in the case of its possible early application in nurseries. In the presence of medium-to-high disease incidence, compost applied in a nursery at 10% and in a soil mixture before transplanting (1 kg m-2) resulted in a consistent wilt reduction of 60-75%, and demonstrated a positive effect on the fresh weight. The effect of compost on the rhizosphere and soil indigenous total microbial communities, nitrifiers and different functional genes (fungal chitinase chiA, bacterial 2,4-diacetylphloroglucinol phlD and HCN synthase hcnAB) was also investigated. The results showed a great suppression effect of the tested compost on the FOL density, especially at the rhizosphere level. Moreover, the use of compost did not have a negative effect on the abundance of the total and functionally relevant indigenous soil microorganisms.
Gilardi, G., Cucu, M.A., Pugliese, M., Gullino, M.L. and Garibaldi, A. (2020). Effect of different organic amendments on lettuce Fusarium wilt and on soilborne microorganisms. Acta Hortic. 1270, 117-126
DOI: 10.17660/ActaHortic.2020.1270.12
compost, Brassica carinata pellets, rhizosphere, Fusarium oxysporum f. sp. lactucae

Acta Horticulturae