猪粪沼液防治辣椒疫病机理研究--沼液中铵与腐殖酸的作用

为探明猪粪沼液对作物土传病害的防治效果与机制,设纯化肥处理为对照,采用盆栽试验比较了猪粪沼液(ADP1)、外源添加铵沼液(ADP2)、除铵沼液(ADP3)、除腐殖酸沼液(ADP4)施用对辣椒疫病的防治效果。结果表明,猪粪沼液(ADP1)可以显著降低辣椒疫病的发病率(防效40.8%),去除沼液中的铵或腐殖酸后,对辣椒疫病的防治效果显著下降,其发病率与病原菌对照(PC)无显著差异。定量PCR检测结果表明,ADP2处理土壤疫霉数量最少(2.51×103copies.g 1),ADP3、ADP4沼液处理的辣椒根际疫霉数量较多,分别为8.19×103copies.g 1、1.38×104copies.g 1;土壤中辣椒疫霉菌的数量低于9.54×103copies.g 1时,辣椒疫病发病率与土壤中病原菌数量有较好的对应关系。不同沼液处理对细菌、真菌和放线菌数量的影响不同。病原菌存在下,ADP1处理的细菌、真菌、放线菌数量均最多,ADP2处理的真菌数量最少。孢子萌发试验表明,随着铵和腐殖酸处理浓度的增加,对疫霉菌游动孢子萌发的抑制率均逐渐增大。浓度为500 mg.L 1、1 000 mg.L 1、1 500 mg.L 1NH4+对疫霉菌孢子萌发的抑制率分别为77.6%、81.8%、95.4%。用浓度为25 mg(C).L 1、50 mg(C).L 1、75 mg(C).L 1、150mg(C).L 1的猪粪沼液腐殖酸处理疫霉菌游动孢子6 h,游动孢子萌发率分别比无菌水对照下降了27.8%、54.5%、70.0%、87.5%。研究表明铵和腐殖酸可能是沼液的主要抑菌因子,沼液作为土传病害抑制剂具有一定的应用前景。

Control mechanism of phytophthora blight of chilli pepper by anaerobically digested pig slurry - The roles of ammonium and humic acid in biogas slurry

Anaerobic digestion is promising in treatments of large amounts of animal manure from animal husbandry. It has been apparent that new methods of utilizing anaerobically digested slurry were needed to achieve sustainable management of husbandry wastes. Anaerobically digested slurry has shown suppressive effects on different soil-borne pathogens and its application to soils has been proposed as a new way to control several plant diseases. The objective of this study was to evaluate the potential use of anaerobically digested pig slurry (ADP) to suppress Phytophthora capsici, the causative agent of phytophthora blight in chilli pepper. The study also aimed to clarify the roles of ammonium and humic acid in ADP inhibition of pathogen growth. A pot experiment was conducted to study the effect of untreated anaerobically digested pig slurry (ADP1), ammonium-intensified pig slurry (ADP2), ammonium-removed pig slurry (ADP3) and humic acid-removed pig slurry (ADP4) on controlling phytophthora blight in chilli pepper. The results showed that ADP1 effectively reduced the incidence of phytophthora blight with a relative control efficiency of 40.8%. Disease incidence of plants treated with ADP3 and ADP4 was not significantly different from that of pathogen control (PC). This suggested that removing ammonium or humic acid from ADP significantly reduced ADP control efficiency. Real-time PCR analysis showed that P. capsici number in rhizhospheric soils of ADP2 was the least (2.51×10³ copies·g^-1), with significantly larger numbers for ADP3 (8.19×10³ copies·g^-1) and ADP4 (1.38×10⁴ copies·g^-1) treatments. When P. capsici density in the soil dropped below 9.54×10³ copies·g ^-1, disease incidence became strongly correlated with P. capsici count. Different ADPs had different effects on the growth of soil microorganisms. The numbers of soil total bacteria, fungi and actinomycete were largest in ADP1 treatment. The least number of fungi was observed in ADP2 treatment. In-vitro experiments showed that NH4+ concentrations of 500 mg·L^-1, 1 000 mg·L^-1 and 1 500 mg·L^-1 reduced zoospore germination by 77.6%, 81.8% and 95.4%, respectively. Zoospore germination rates in treatments with 25 mg(C)·L^-1, 50 mg(C)·L^-1, 75 mg(C)·L^-1 and 150 mg(C)·L^-1 of humic acid extracted from ADP1 decreased by 27.8%, 54.5%, 70.0% and 87.5%, respectively. The study suggested that ammonium and humic acid were major ADP inhibitors of P. capsici growth. ADP was promising in terms of inhibiting and controlling soil-borne diseases.