Abstract
Background and aimFusarium wilt (FW) is the major constraint on cape gooseberry (Physalis peruviana L.) production. Fungicides have been ineffective in disease control and alternative tools are not available. Bacillus velezensis (formerly Bacillus amyloliquefaciens) strain Bs006 has an antagonistic potential against Fusarium oxysporum f. sp. physali (Foph). However, results of in vivo tests have been variable. We examined the effect of biotic sources of variability on the biocontrol activity of Bs006.MethodsPot experiments in greenhouse were carried out to determine the influence of soil sterilization and concentration of both pathogen and antagonist in soil on biocontrol activity and the effect of pathogen on plant growth promotion by Bs006.ResultsEfficacy of Bs006 against FW was significantly lower under sterile than non-sterile soil condition. Diluted liquid culture of Bs006 at 1 × 106 and 1 × 107 cfu.mL−1 reduced FW by up to 97% under low Foph inoculum pressure (102 to 104 cfu.g−1 of soil) but at 1 × 108 cfu.mL−1 biological treatment significantly reduced FW only when the concentration of Foph was 1 × 104 cfu.g−1 by 71%. The evaluation of biomass of Bs006 (1 × 108 cfu.mL−1) and supernatant free of bacteria added at 10% allowed to observe that the supernatant was an additional source of biocontrol variability, since high volumes of supernatant favored the development of the disease. Plant growth promoting activity by Bs006 was reduced by the presence of Foph in the soil. Bs006 grew endophytically in cape gooseberry and had high population levels in the rhizosphere inoculated with Foph.ConclusionsThe efficacy of Bs006 to reduce FW was affected by soil sterilization, the concentration of both antagonist and pathogen, and high volumes of supernatant. This work has practical implications for the design of control strategies based on B. velezensis Bs006.
Highlights
Colombia was the main cape gooseberry (Physalis peruviana) producer and exporter for the 2000–2010 decade (Bonilla et al 2009)
Yield of cape gooseberry in Colombia has decreased from 18 t.ha−1 in 2008 to 10 t.ha−1 in 2014 (Ministerio de Agricultura 2016) mostly due to Fusarium wilt disease (FW), caused by Fusarium oxysporum (Estupiñan and Ossa 2007; Rodríguez 2013) recently designated f. sp. physali (Foph) (Simbaqueba et al 2018)
Commercial cape gooseberry seeds (Colombia ecotype) were washed with tap water to remove fungicide coating from the surface and surface disinfected in 3% NaOCl for 20 min and subsequently washed three times in sterile distilled water (SDW)
Summary
Colombia was the main cape gooseberry (Physalis peruviana) producer and exporter for the 2000–2010 decade (Bonilla et al 2009). Cape gooseberry is the second most important fruit crop in Colombia mainly due to exports to European countries, and currently its cultivation has expanded to other countries including Kenya, Zimbabwe, Australia, New Zealand, India and Ecuador (Fischer et al 2014). Yield of cape gooseberry in Colombia has decreased from 18 t.ha−1 in 2008 to 10 t.ha−1 in 2014 (Ministerio de Agricultura 2016) mostly due to Fusarium wilt disease (FW), caused by Fusarium oxysporum (Estupiñan and Ossa 2007; Rodríguez 2013) recently designated f. Fusarium wilt (FW) is the major constraint on cape gooseberry (Physalis peruviana L.) production.
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