Nursery treatments with resistant inducers, soil amendments and biocontrol agents for the management of the Fusarium wilt of lettuce under glasshouse and field conditions

Abstract

Lettuce Fusarium wilt, caused by Fusarium oxysporum f. sp. lactucae, represents a major problem in most lettuce production areas worldwide. In the present study, a number of resistance inducers, organic amendments and biocontrol agents were applied in a preventative way, in experimental and commercial situations, to soils artificially or naturally infested with race 1 of the pathogen, and to moderately susceptible lettuce cultivars. Potassium phosphite, acibenzolar-S-methyl, green composts, and Bacillus subtilis Q st713, Trichoderma asperellum + Trichoderma gamsii, and Pseudomonas strains achieved the most consistent disease control under the experimental conditions. Moreover, potassium phosphite, green compost, B. subtilis Qst713 and T. asperellum + T. gamsii, also showed a positive effect on plant development. In general, the results of the different treatments in naturally infested soil were similar to those observed in glasshouse trials under artificial inoculation. Potassium phosphite provided a consistent disease reduction (48%-62% in artificially infested soil and 60%-75% in naturally infested soil). The effects of adding 10% compost to a peat growing medium in the nursery, followed by a soil mixing application when lettuce was transplanted, significantly reduced the severity of Fusarium wilt (50%-59% efficacy) and increased fresh biomass production. Compost enrichment with Trichoderma TW2 generally further increased its efficacy. When tested under field conditions, the commercially available Trichoderma spp. and B. subtilis, together with experimental strains of Pseudomonas and Trichoderma spp., applied at the nursery level, provided a disease reduction of 30%-78%. Early application of the different control measures under nursery conditions and at lettuce transplant is noteworthy because it was carried out at a more localized level, with reduced amounts of products. Their use in practice should be integrated with other control strategies. K E Y W O R D SFusarium oxysporum f. sp. lactucae, organic farming, preventative treatments, vegetables | 99 GILARDI et AL.

A Compost Treatment Acts as a Suppressive Agent in Phytophthora capsici – Cucurbita pepo Pathosystem by Modifying the Rhizosphere Microbiota

“…In addition, Trichoderma was effective against PHC, as already reported by many authors (Ahmed et al, 2000;Ezziyyani et al, 2007;Lorito et al, 2010;Bae et al, 2011). Furthermore, in a previous study carried out in field conditions (Gilardi et al, 2019), the application of Trichoderma TW2 alone against Fusarium wilt in lettuce was less effective compared to the use of CM compost, in combination with Trichoderma TW2. Bonanomi et al (2018) reviewed several works on biocontrol agents (BCAs) compost enrichment and pointed out that this could be the most promising way to achieve a long-term suppressiveness against soil-borne pathogens.…”

“…In addition, Trichoderma was effective against PHC, as already reported by many authors ( Ahmed et al, 2000 ; Ezziyyani et al, 2007 ; Lorito et al, 2010 ; Bae et al, 2011 ). Furthermore, in a previous study carried out in field conditions ( Gilardi et al, 2019 ), the application of Trichoderma TW2 alone against Fusarium wilt in lettuce was less effective compared to the use of CM compost, in combination with Trichoderma TW2.…”

Bioactive compounds in lettuce: Highlighting the benefits to human health and impacts of preharvest and postharvest practices

“…The incidence of plant pathogens also represents a significant problem in most lettuce production areas and systems in which integrated production systems, based on accurate identification of plant pathogens and appropriate risk assessments, are required. Biocontrol agents have been applied in soils infested for disease control, but their use in practice should be integrated with other control strategies (Gilardi et al., 2019). These safety issues have to be strictly considered when designing strategies to enhance the bioactive content in lettuce using preharvest and postharvest approaches.…”

The effects of biological control agents, potassium phosphite and calcium oxide on race 1 of Fusarium oxysporum f. sp. lactucae of lettuce in closed soilless cultivation systems

“…In the present study, B. subtilis was only able to slightly reduce the severity of wilt symptoms caused by the pathogen (22%-48% efficacy). Other studies have demonstrated the ability of B. subtilis to reduce the Fusarium wilt of lettuce, particularly when it is first applied in the nursery (Gilardi et al 2016(Gilardi et al , 2019, or as a seed dressing (Lopez-Reyes et al 2014).…”