生物质炭介导生防微生物抑制辣椒疫霉的作用

生物质炭可有效防控土传病害，筛选并鉴定出生物质炭介导下的生防微生物，可为研究生物质炭防病机理和强化生物质炭防病效果提供理论依据。本研究首先进行秸秆生物质炭防控辣椒疫病盆栽试验，利用定量PCR和平板计数明确生物质炭在防控辣椒疫病时可富集的已知生防微生物，再通过选择性培养基初筛和定殖复筛筛选出生物质炭可富集的潜在生防微生物菌株，最后研究各菌株在土壤中对辣椒疫霉的抑制作用。结果表明，秸秆生物质炭使根际辣椒疫霉数量显著降低95.1%、辣椒疫病发生率显著降低91.1%，并使具有生防功能的木霉菌、青霉菌、曲霉菌、芽孢杆菌、假单胞菌和鞘氨醇单胞菌数量显著增加2.22倍、4.09倍、3.89倍、2.45倍、1.45倍和1.30倍。通过平板初筛得到可能被生物质炭富集的22株潜在生防菌株。定殖复筛剔除部分假性生物质炭介导菌株，获得可明确被生物质炭富集的2株木霉菌、3株青霉菌、2株曲霉菌、3株芽孢杆菌、3株假单胞菌、3株链霉菌和2株鞘氨醇单胞菌。木霉菌（TR1和TR3）、青霉菌（PE1）、曲霉菌（AS1和AS2）、芽孢杆菌（BA1、BA2和BA3）、假单胞菌（PS1和PS3）、链霉菌（ST1、ST4和ST5）13个菌株可显著削减土壤辣椒疫霉数量。其中，所有木霉菌和曲霉菌菌株（TR1、TR3、AS1和AS2）及芽孢杆菌（BA1和BA2）、假单胞菌（PS1和PS3）和链霉菌（ST1）9个菌株与生物质炭具有显著的协同抑制辣椒疫霉效果。因此，防控辣椒疫病时，木霉菌、曲霉菌、芽孢杆菌、假单胞菌和链霉菌是生物质炭介导下的主要防病微生物。

Inhibitory effect of biochar-enriched biocontrol agents on Phytophthora capsici

Biochar is known to effectively control the Phytophthora blight of pepper. To further understand the mechanisms of biochar-mediated disease control, we screened the biochar-enriched beneficial microorganisms and evaluated their antagonistic activities against Phytophthora capsici. A pot experiment was conducted to determine the effects of straw biochar on the control of Phytophthora blight. Both qPCR and dilution-plate methods were used to identify the biochar-enriched biocontrol microorganisms in rhizosphere soils. Potential antagonistic strains, which were biochar-enriched, were screened using the selective isolation method and rhizosphere colonization assay, after which their antagonistic activity against P. capsici in soil was determined. The results showed that biochar amendment could significantly reduce the abundance of P. capsici and severity of the Phytophthora blight of pepper by 95.1% and 91.1%, respectively. In addition, biochar amendment significantly increased the abundances of Trichoderma, Penicillium, Aspergillus, Bacillus, Pseudomonas, and Sphingomonas by 2.22, 4.09, 3.89, 2.45, 1.45, and 1.30 times, respectively. Twenty-two potential biocontrol strains that can be enriched by biochar were screened from biochar-amended rhizosphere soils using the selective isolation method. Comparing the colonization between the biochar-amended and control rhizosphere soils, two strains of Trichoderma, three strains of Penicillium, two strains of Aspergillus, three strains of Bacillus, three strains of Pseudomonas, three strains of Streptomyces, and two strains of Sphingomonas were confirmed to be enriched by biochar. Trichoderma (TR1 and TR3), Penicillium (PE1), Aspergillus (AS1 and AS2), Bacillus (BA1, BA2, and BA3), Pseudomonas (PS1 and PS3), and Streptomyces (ST1, ST4, and ST5) strains could significantly reduce the abundance of P. capsici in the soil. Among these antagonistic stains, Trichoderma (TR1 and TR3), Aspergillus (AS1 and AS2), Bacillus (BA1 and BA2), Pseudomonas (PS1 and PS3), and Streptomyces (ST1) strains in synergism with biochar facilitated a significant increase in the inhibition of P. capsici. Thus, Trichoderma, Aspergillus, Bacillus, Pseudomonas, and Streptomyces enriched by biochar might play an import role in the suppression of Phytophthora blight of pepper under biochar amendment.