Location: Subtropical Plant Pathology ResearchTitle: A nylon membrane bag assay for determination of the effect of chemicals on soilborne plant pathogens in soil Author
Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/11/2011
Publication Date: 2/1/2010
Citation: Lin, Y., Zhenli, H., Rosskopf, E.N., Conn, K., Powell, C., Lazarovits, G. 2010. A nylon membrane bag assay for determination of the effect of chemicals on soilborne plant pathogens in soil. Plant Disease. 94:2:201-206 Interpretive Summary:
Technical Abstract: A new nylon membrane bag assay was developed that can rapidly and effectively determine the impact of chemicals added to soil on soilborne plant pathogens for which there are no selective media or for which a selective medium is expensive or difficult to prepare. This assay consists of placing pathogens inside a bag made of small pore (0.22-0.45 µm) nylon filtrate membrane which is placed in soil and later retrieved to determine survival of the pathogens on non-selective media. Chemicals, but not microorganisms, can enter the bag from the soil. Using this assay, Streptomyces scabies, Fusarium oxysporum f. sp. lycopersici (FOL), and Ralstonia solanacearum were successfully recovered from soil after 72 hours as demonstrated by growth on a semi-selective STR medium (S. scabies) or non-selective potato dextrose agar (PDA) medium (FOL and R. solanacearum) with minimal microbial contamination. Addition of acetic acid (200 mM water component of soil) to soil killed 100% of S. scabies. SPK (a mixture of organic chemicals) at a concentration of 1500 mg kg-1 soil killed 83.3% of FOL mycelium, 100% of FOL spores, and 97.2% of R. solanacearum cells. SPK at 1000 mg kg-1 soil killed 50% FOL mycelium, 68.2% FOL spores, and 12% of R. solanacearum. Benlate (500 to 1500 mg kg-1 soil) did not kill the mycelia (mycelium plugs) of FOL but reduced the growth rate of FOL mycelia. Benlate (500, 1000, and 1500 mg kg-1 soil) reduced FOL spore germination by 39.4%, 49.3%, and 50.4%, respectively. Streptomycin sulphate (1500, 800, 400, and 200 mg kg-1 soil) caused 75.3%, 21%, 11.9%, and, 0.9% mortality of R. solanacearum, respectively.