The role of auxin in susceptibility of soybean to Phytophthora sojae
A. STASKO (1), J. Lin (2), J. Blakeslee (2), A. Dorrance (1) (1) Department of Plant Pathology The Ohio State University-Ohio Agricultural Research and Development Center, U.S.A.; (2) Department of Horticulture and Crop Science The Ohio State University-Ohio Agricultural Research Development Center, U.S.A.

Phytophthora root and stem rot is a devastating disease of soybean that occurs in all areas of production. It is effectively managed using host resistance. One approach to identify resistance is to consider factors that make the host more susceptible to the pathogen and to select against these factors.  Previous work indicated that several auxin-related genes were up-regulated in the susceptible cultivar, Sloan, compared to the partially resistant cultivar Conrad. We hypothesized that differences in auxin transport and metabolism contribute to the difference in response to P. sojae. Tissue samples were collected at the inoculation site from ten seedlings of each cultivar at 12, 24, and 48 hours after inoculation (hai) and at the leading edge of the lesion margin at 72 hai. Auxin and auxin metabolites in these samples were quantified using liquid chromatography tandem mass spectrometry (LC-MS/MS). Sloan had higher levels of auxin than Conrad at 48 hai, indicating a potential correlation between higher levels of auxin and heightened susceptibility to P. sojae. Additionally, treatment with 10 µM N-1-naphthylphtalamic acid (NPA), an auxin transport inhibitor, decreased the number of plants that were successfully inoculated with P. sojae, while treatment with 10 µM 1-naphthaleneacetic acid (1-NAA), a synthetic auxin, increased the lesion length. These preliminary data support the conclusion that accumulations of auxin contribute to susceptibility of soybean to P. sojae. 

Abstract Number: P16-473
Session Type: Poster