|Vega-Sanchez, M - OHIO STATE UNIVERSITY|
|Dorrance, A - OHIO STATE UNIVERSITY|
Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: March 12, 2003
Publication Date: August 14, 2003
Citation: Vega-Sanchez, M.E., Redinbaugh, M.G., Dorrance, A.E. 2003. Basal levels of expression of defense-related genes in soybean cultivars varying in partial resistance to phytophthora sojae. Phytopathology. 93:S87. Technical Abstract: Phytophthora sojae is an oomycete pathogen that causes economically important root and stem rot diseases of soybean. Quantitative or partial resistance in this pathosystem is characterized by containment of the pathogen to the lower stem and tap root, but the genetic and/or biochemical mechanisms underlying the expression of partial resistance to P. sojae in soybean are poorly understood. To explore the hypothesis that higher basal expression levels of defense-related genes correlate with quantitative disease resistance, Northern blot analysis of root and cotyledon total RNA from 14 soybean cultivars varying in partial resistance levels to P. sojae was carried out. Ranking of cultivars into low, moderate and high partial resistant groups was done based on a standard lesion growth test. The coding sequences of eight defense-related genes including pathogenesis-related (PR) proteins and enzymes of the phenylpropanoid pathway were used to design primers for RT-PCR. The cDNAs representing a portion of the coding regions were cloned into a plasmid vector and used as probes. Preliminary results show that no clear-cut associations exist between constitutive defense-related gene expression levels and quantitative resistance to P. sojae in soybean. However, differential basal levels of expression of defense genes were observed between roots and cotyledons: most transcripts were at higher levels in roots than in cotyledons, with some mRNAs (PR1 and basic peroxidase) being undetectable in cotyledons. Two exceptions were matrix metalloproteinase (GmMMP2) and beta-1, 3-endoglucanase which were expressed at higher levels in cotyledons than roots.