Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: 6/1/2011
Publication Date: 6/1/2011
Citation: Maruthachalam, K., Klosterman, S.J., Subbarao, K.V. 2011. Colonization of spinach (Spinacia oleracea L.) by GFP-tagged verticillium dahliae. Phytopathology. 101: S115. Interpretive Summary:
Technical Abstract: The soilborne fungus, Verticillium dahliae, causes wilt in a wide range of hosts, including spinach (Spinacia oleracea L.). The interaction between a green fluorescent protein (GFP)-tagged V. dahliae strain and spinach was studied by confocal laser scanning microscopy. The roots of spinach seedlings were inoculated with a conidial suspension of a GFP-tagged strain and pathogen colonization events were followed through seed production. At 24 to 96 hours post-inoculation (PI), conidia germinated and formed hyphal colonies on root tips and in the root elongation zones. Two weeks PI, hyphae of V. dahliae grew both intracellularly and intercellularly in the cortical tissues and penetrated into the xylem. At six to eight weeks PI, the fungus colonized the entire taproot xylem with abundant mycelia and conidia. Further colonization of the taproot and crown of inoculated plants led to vascular discoloration when foliar symptoms became apparent. At 10 weeks PI, xylem tissues of the upper stem were colonized that also extended to the inflorescence and the various spinach seed parts, including fruit wall, epicotyl meristem and integument. However, the fungus did not colonize the perisperm (the diploid maternal tissue) in the seed. This information is useful in administering effective seed treatments without compromising seed viability and ultimately the introduction of this very destructive pathogen via seed.