| Secondary metabolite lipopeptides produced by Bacillus spp.are excellent surfactants and antibiotics while kaolinite and nano titanium dioxide(TiO2)with good surface adsorption activity are commonly used as practicable adsorbents.How to prepare composites using lipopeptides and mineral adsorbents for controlling plant diseases is little-known.In this study,lipopeptides were produced by using strain Bacillus amyloliquefaciens XZ-173 in solid-state fermentation of agricultural wastes,and two lipopeptide-mineral composites were gained by combination of lipopeptides with peeled kaolinite or nano-TiO2 as well as plant micronutrients.Greenhouse experiments were conducted to study the effects of the composites on controlling bacterial wilt of tomato(BWT)and promoting tomato plant growth.The results were expected to supply scientific evidence on application of lipopeptide-mineral composites in controling of plant diseases.In this study,lipopeptides were produced by strain XZ-173 in solid-state fermentation,peeled kaolinite was prepared by urea intercalation and ultrasonic heating,and nano-Ti02 were prepared according to the sol-gel method.Anlysises showed that lipopeptides had very strong antagonistic ability against tomato pathogen Ralstonia solanacearum and the antagonistic ability increased as the concentration of lipopeptides increased.The peeled kaolinite had less stacking particles,thinner sheet layer,smaller size and larger specific surface area than the primary kaolinite.For the nano-TiO2,the sizes of agglomerated nano-TiO2 particles with an average crystallite size about 22 nm ranged from 10 nm to 40 nm,and the specific surface area was 60.72 m2/g.Lipopeptide-peeled-kaolinite composite was prepared by mixing lipopeptides and peeled kaolinite.FT-IR indicated that the composite was comprised of inorganic and organic chemical functional groups.Inhibition ability test showed that the minimal inhibitory concentration of the composite powders was 9 mg/mL.Greenhouse pot experiment showed that spraying the lipopeptide-peeled-kaolinite composite had the best effect against BWT with a control efficiecy 87.76%for 40 d,and the more significant promotion of tomato plant growth as compared with other treatments,for example,root irrigation and shoot injection.Further,lipopeptides,microelements solution,peeled kaolinite or nano-TiO2 were mixed to prepare a lipopeptide-peeled-kaolinite-microelement composite and a lipopeptide-nano-TiO2-microelement composite.FT-IR indicated that the two composites were comprised by their characteristic inorganic and organic chemical functional groups.The inhibition ability tests showed that the minimal inhibitory concentrations of lipopeptide-peeled-kaolinite-microelement composite powders and lipopeptide-nano-TiO2-microele-ment composite powders were 9.6 mg/mL and 1.2 mg/mL,respectively.Greenhouse pot experiments showed that spraying the two composites both had best biocontrol effects against BWT and can inhibit the growth of Ralstonia solanacearum in rhizosphere soil as compared with other treatments.Additionally,the results from plants growth promotion experiment showed that both of the two composites by spraying can effectively improve the shoot height,the stem diameter,the chlorophy Ⅱ content,the shoot and root biomass of plants and promote the growth of tomato plants. |
