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RESEARCH FOR ACTION M. Pugliese 1 , A. Cucu 2 , G. Gilardi 2 , M. L. Gullino 2,3 , A. Garibaldi 2 1 AgriNewTech srl, Torino, Italy. E-mail: [email protected] 2 Agroinnova – Centre of Competence for the innovation in the agro-environmental field, University of Torino, Italy. 3 Department of Agricultural, Forest and Food Sciences (DISAFA), University of Torino, Italy. EFFECT OF COMPOSTS AND BCAS ON LETTUCE FUSARIUM WILT AND ON MICROBIAL COMMUNITIES EUCLID Conference Avignon, September 12 th , 2019 Lettuce Fusarium wilt, caused by Fusarium oxysporum f. sp. lactucae, represents a major problem in most lettuce production areas worldwide. The seed transmission of this pathogen and the capacity of inoculums to survive in the soil for years, makes soil disinfection only partially effective. The use of biological control agents (BCAs) and of suppressive composts starting from the nursery is considered a more effective and sustainable strategy. Composts, applied in nursery at 10% and in soil mixture before transplanting at 1 kg/m2, provided a consistent Fusarium wilt reduction from 51 to 69%. The application of BCAs at the nursery level also provided a disease reduction from 44% to 60% in the field trials (Table 2). The use of composts and BCAs appears as an effective and safe strategy to implement sustainable crop protection strategies. Two composts and different commercially available and experimental BCAs were applied (Table 1), in a naturally infested field experiment, against lettuce wilting, over two lettuce cultivar ‘Novelsky’ cropping seasons (Fig. 1). The effects on rhizosphere and soil indigenous total microbial communities, nitrifiers and different functional genes (fungal chitinase, bacterial 2,4-diacetylphloroglucinol and HCN synthase) were also investigated. Treatments Bacillus subtilis QST 713 (Serenade max) Trichoderma asperellum ICC 012 + T. gamsii ICC 080 (Remedier) Pseudomonas putida strains FC7B+ FC8B +FC9B Green compost + Trichoderma sp. TW2 (ANT’s compost M) Green compost (ANT’s compost) Trichoderma sp. TW2 Azoxystrobin (Ortiva) Table 1 - Treatments, dosage and timings applied in the trials. Treatments Disease severity % Disease reduction % Fresh weight g/12 plants Trial 1 Trial 2 Bacillus subtilis QST 713 (Serenade max) 24.5 ±1.6 ab* 60 ab 3135.6 ±128.9 a 2727.2 ±371.5 ab Trichoderma asperellum ICC 012 + T. gamsii ICC 080 (Remedier) 28.6 ±2.7 ab 54 ab 2731.0 ±79.0 a 2868.4 ±348.7 ab Pseudomonas putida strains FC7B+ FC8B +FC9B 31.65 ±2.6 ab 49 ab 3090.7 ±49.6 a 1528.0 ±67.2 bc Green compost + Trichoderma sp. TW2 (ANT’s compost M) 19.15 ±2.9 a 69 a 3256.3 ±267.6 a 3766.0 ±481.6 a Green compost (ANT’s compost) 30.5 ±2.5 ab 51 ab 3323.9 ±146.7 a 3747.6 ±130.1 a Trichoderma sp. TW2 34.3 ±2.7 b 44 b 2815.7 ±78.6 a 1917.6 ±134.7 bc Azoxystrobin (Ortiva) 22.3 ±4.0 ab 64 ab 3014.0 ±185.3 a 3360.4 ±273.0 a Untreated control 61.7 ±3.5 c 0 c 1745.7 ±93.0 b 770.8 ±243.1 c Table 2 – Effect of the treatments with BCAs and composts on Fusarium wilt of lettuce. Treatment Bacillus subtilis - Serenade max - SM 5.063 a 5.435 a Trichoderma spp. - Remedier - RM 4.221 c 4.120 d Pseudomonas putida - Pp 3.985 c 4.326 c ANT's compost M - CM 4.505 b 4.802 b ANT's compost V - CV 3.986 c 4.328 c Trichoderma sp. - TW2 3.647 d 3.903 d Untreated control - C 3.616 d 3.875 d P(F) Treat 0.000 Bacillus subtilis - Serenade max - SM 4.316 b 3.915 c Trichoderma spp. - Remedier - RM 4.221 b 4.128 c Pseudomonas putida - Pp 4.760 a 4.644 a ANT's compost M - CM 4.809 a 4.408 b ANT's compost V - CV 4.086 b 4.060 c Trichoderma sp. - TW2 3.695 c 3.795 c Untreated control - C 3.465 c 3.243 d P(F) Treat 0.000 Bacillus subtilis - Serenade max - SM 3.962 d 2.915 c Trichoderma spp. - Remedier - RM 4.297 c 3.180 bc Pseudomonas putida - Pp 3.991 cd 3.414 b ANT's compost M - CM 4.953 b 3.979 a ANT's compost V - CV 4.534 c 4.117 a Trichoderma sp. - TW2 5.667 a 3.926 a Untreated control - C 3.767 e 2.839 c P(F) Treat 0.000 Trichoderma (log copy gene g¯¹ dry soil) Bacillus (log copy gene g¯¹ dry soil) Pseudomonas (log copy gene g¯¹ dry soil) Rhizosphere soil Bulk soil Table 3 – Abundance of Bacillus sp., Trichoderma sp. and Pseudomonas sp. genes in the rhizosphere and bulk soil at the end of both trials. *Different letters indicate significant differences between treatments according to Tukey’s HSD (p<0.05) Figure 1 - Field trial on lettuce cv Novelsky. Furthermore, the treatments improved the abundance of Bacillus sp., Trichoderma sp. and Pseudomonas sp. in the rhizosphere and bulk soil (Table 3), while they did not influence negatively the non-target microbial communities.
