ARS | Publication request: MANGANESE ACCUMULATION IN HYPOCOTYL LESIONS OF SOYBEANS INOCULATED WITH PHYTOPHTHORA SOJAE

Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: September 25, 1997
Publication Date: N/A

Technical Abstract: The relationship of manganese deficiency and disease severity has been documented with several crops. Roles of Mn2+ and Mn4+ have been emphasized in healthy and diseased tissue, respectively. To evaluate the role of Mn in Phytophthora root rot, soybean isolines with the rps and Rps 1-k genes were inoculated with P. sojae race 2 or 25. Hypocotyl tissue was analyzed for Mn content and oxidation state using micro-X-ray absorption near edge structure spectroscopy (XANES). The fraction of Mn4+ in inoculated tissue was only slightly elevated in both susceptible and resistant tissue. Total Mn was higher in inoculated than in control and wounded tissue regardless of the disease reaction; however, Mn accumulation was influenced by race of P. sojae and Rps gene interaction. Soybeans with the Rps 1-k gene (susceptible to race 25 and resistant to race 2) had significantly higher Mn (4-fold) than non-inoculated plants, whereas, soybeans with the rps gene (susceptible to both race 2 and 25) had significantly higher Mn (4-fold) than the controls when inoculated with race 2 but only a 2-fold increase when inoculated with race 25. This is the first study documenting differences in total Mn accumulation between non-inoculated and inoculated tissue.