title: Dynamics of verticillium species microsclerotia in field soils in response to fumigation, cropping patterns, and flooding.
abstract: Verticillium dahliae is a soilborne, economically significant fungal plant pathogen that persists in the soil for up to 14 years as melanized microsclerotia (ms). Similarly, V. longisporum is a very significant production constraint on members of the family Brassicaceae. Management of Verticillium wilt has relied on methods that reduce ms below crop-specific thresholds at which little or no disease develops. Methyl bromide, a broad-spectrum biocide, has been used as a preplant soil fumigant for over 50 years to reduce V. dahliae ms. However, reductions in the number of ms in the vertical and horizontal soil profiles and the rate at which soil recolonization occurs has not been studied. The dynamics of ms in soil before and after methyl bromide+chloropicrin fumigation were followed over 3 years in six 8-by-8-m sites in two fields. In separate fields, the dynamics of ms in the 60-cm-deep vertical soil profile pre- and postfumigation with methyl bromide+chloropicrin followed by various cropping patterns were studied over 4 years. Finally, ms densities were assessed in six 8-by-8-m sites in a separate field prior to and following a natural 6-week flood. Methyl bromide+chloripicrin significantly reduced but did not eliminate V. dahliae ms in either the vertical or horizontal soil profiles. In field studies, increases in ms were highly dependent upon the crop rotation pattern followed postfumigation. In the vertical soil profile, densities of ms were highest in the top 5 to 20 cm of soil but were consistently detected at 60-cm depths. Six weeks of natural flooding significantly reduced (on average, approximately 65% in the total viable counts of ms) but did not eliminate viable ms of V. longisporum.
authors.affiliation: First, seventh, and ninth authors: Department of Plant Pathology, and second author: The Genome Center and Department of Plant Sciences, University of California, Davis, 1636 E Alisal St., Salinas 93905; third author: Gulf Coast Research and Education Center, University of Florida, IFAS, Wimauma 33598; fourth author: University of California Cooperative Extension, 1432 Abbott Street, Salinas 93901; fifth author: United States Department of Agriculture-Agricultural Research Service (USDA-ARS), San Joaquin Valley Agricultural Sciences Center, 9611 S. Riverbend Ave, Parlier, CA 93648; sixth author: Department of Plant Pathology, China Agricultural University, Beijing 100193; and eighth author: USDA-ARS, 1636 E. Alisal St., Salinas, CA 93905.
authors.forename: Dylan P G
authors.initials: DP
authors.lastname: Short
authors.affiliation: First, seventh, and ninth authors: Department of Plant Pathology, and second author: The Genome Center and Department of Plant Sciences, University of California, Davis, 1636 E Alisal St., Salinas 93905; third author: Gulf Coast Research and Education Center, University of Florida, IFAS, Wimauma 33598; fourth author: University of California Cooperative Extension, 1432 Abbott Street, Salinas 93901; fifth author: United States Department of Agriculture-Agricultural Research Service (USDA-ARS), San Joaquin Valley Agricultural Sciences Center, 9611 S. Riverbend Ave, Parlier, CA 93648; sixth author: Department of Plant Pathology, China Agricultural University, Beijing 100193; and eighth author: USDA-ARS, 1636 E. Alisal St., Salinas, CA 93905.
authors.forename: German
authors.initials: G
authors.lastname: Sandoya
authors.affiliation: First, seventh, and ninth authors: Department of Plant Pathology, and second author: The Genome Center and Department of Plant Sciences, University of California, Davis, 1636 E Alisal St., Salinas 93905; third author: Gulf Coast Research and Education Center, University of Florida, IFAS, Wimauma 33598; fourth author: University of California Cooperative Extension, 1432 Abbott Street, Salinas 93901; fifth author: United States Department of Agriculture-Agricultural Research Service (USDA-ARS), San Joaquin Valley Agricultural Sciences Center, 9611 S. Riverbend Ave, Parlier, CA 93648; sixth author: Department of Plant Pathology, China Agricultural University, Beijing 100193; and eighth author: USDA-ARS, 1636 E. Alisal St., Salinas, CA 93905.
authors.forename: Gary E
authors.initials: GE
authors.lastname: Vallad
authors.affiliation: First, seventh, and ninth authors: Department of Plant Pathology, and second author: The Genome Center and Department of Plant Sciences, University of California, Davis, 1636 E Alisal St., Salinas 93905; third author: Gulf Coast Research and Education Center, University of Florida, IFAS, Wimauma 33598; fourth author: University of California Cooperative Extension, 1432 Abbott Street, Salinas 93901; fifth author: United States Department of Agriculture-Agricultural Research Service (USDA-ARS), San Joaquin Valley Agricultural Sciences Center, 9611 S. Riverbend Ave, Parlier, CA 93648; sixth author: Department of Plant Pathology, China Agricultural University, Beijing 100193; and eighth author: USDA-ARS, 1636 E. Alisal St., Salinas, CA 93905.
authors.forename: Steven T
authors.initials: ST
authors.lastname: Koike
authors.affiliation: First, seventh, and ninth authors: Department of Plant Pathology, and second author: The Genome Center and Department of Plant Sciences, University of California, Davis, 1636 E Alisal St., Salinas 93905; third author: Gulf Coast Research and Education Center, University of Florida, IFAS, Wimauma 33598; fourth author: University of California Cooperative Extension, 1432 Abbott Street, Salinas 93901; fifth author: United States Department of Agriculture-Agricultural Research Service (USDA-ARS), San Joaquin Valley Agricultural Sciences Center, 9611 S. Riverbend Ave, Parlier, CA 93648; sixth author: Department of Plant Pathology, China Agricultural University, Beijing 100193; and eighth author: USDA-ARS, 1636 E. Alisal St., Salinas, CA 93905.
authors.forename: Chang-Lin
authors.initials: CL
authors.lastname: Xiao
authors.affiliation: First, seventh, and ninth authors: Department of Plant Pathology, and second author: The Genome Center and Department of Plant Sciences, University of California, Davis, 1636 E Alisal St., Salinas 93905; third author: Gulf Coast Research and Education Center, University of Florida, IFAS, Wimauma 33598; fourth author: University of California Cooperative Extension, 1432 Abbott Street, Salinas 93901; fifth author: United States Department of Agriculture-Agricultural Research Service (USDA-ARS), San Joaquin Valley Agricultural Sciences Center, 9611 S. Riverbend Ave, Parlier, CA 93648; sixth author: Department of Plant Pathology, China Agricultural University, Beijing 100193; and eighth author: USDA-ARS, 1636 E. Alisal St., Salinas, CA 93905.
authors.forename: Bo-Ming
authors.initials: BM
authors.lastname: Wu
authors.affiliation: First, seventh, and ninth authors: Department of Plant Pathology, and second author: The Genome Center and Department of Plant Sciences, University of California, Davis, 1636 E Alisal St., Salinas 93905; third author: Gulf Coast Research and Education Center, University of Florida, IFAS, Wimauma 33598; fourth author: University of California Cooperative Extension, 1432 Abbott Street, Salinas 93901; fifth author: United States Department of Agriculture-Agricultural Research Service (USDA-ARS), San Joaquin Valley Agricultural Sciences Center, 9611 S. Riverbend Ave, Parlier, CA 93648; sixth author: Department of Plant Pathology, China Agricultural University, Beijing 100193; and eighth author: USDA-ARS, 1636 E. Alisal St., Salinas, CA 93905.
authors.forename: Suraj
authors.initials: S
authors.lastname: Gurung
authors.affiliation: First, seventh, and ninth authors: Department of Plant Pathology, and second author: The Genome Center and Department of Plant Sciences, University of California, Davis, 1636 E Alisal St., Salinas 93905; third author: Gulf Coast Research and Education Center, University of Florida, IFAS, Wimauma 33598; fourth author: University of California Cooperative Extension, 1432 Abbott Street, Salinas 93901; fifth author: United States Department of Agriculture-Agricultural Research Service (USDA-ARS), San Joaquin Valley Agricultural Sciences Center, 9611 S. Riverbend Ave, Parlier, CA 93648; sixth author: Department of Plant Pathology, China Agricultural University, Beijing 100193; and eighth author: USDA-ARS, 1636 E. Alisal St., Salinas, CA 93905.
authors.forename: Ryan J
authors.initials: RJ
authors.lastname: Hayes
authors.affiliation: First, seventh, and ninth authors: Department of Plant Pathology, and second author: The Genome Center and Department of Plant Sciences, University of California, Davis, 1636 E Alisal St., Salinas 93905; third author: Gulf Coast Research and Education Center, University of Florida, IFAS, Wimauma 33598; fourth author: University of California Cooperative Extension, 1432 Abbott Street, Salinas 93901; fifth author: United States Department of Agriculture-Agricultural Research Service (USDA-ARS), San Joaquin Valley Agricultural Sciences Center, 9611 S. Riverbend Ave, Parlier, CA 93648; sixth author: Department of Plant Pathology, China Agricultural University, Beijing 100193; and eighth author: USDA-ARS, 1636 E. Alisal St., Salinas, CA 93905.
authors.forename: Krishna V
authors.initials: KV
authors.lastname: Subbarao
mesh_terms: D019607:Brassicaceae / Q000382:microbiology*; D005651:Fumigation; D025301:Hyphae / Q000502:physiology; D010935:Plant Diseases / Q000382:microbiology; D012987:Soil; D012988:Soil Microbiology; D020172:Verticillium / Q000502:physiology*; D014867:Water / Q000502:physiology
chemical_list: D012987:Soil; D014867:Water