Evaluation and Modeling of Rate-Reducing Resistance of Soybean Seedlings toPhytophthora sojae

Abstract

Lesion length and rate of lesion expansion on taproots of aeroponically grown soybeans infected with Phyrophrhora sojae provided an accurate assessment of rate-reducing resistance. Four days after inoculation with race 3 of P. sojae (1,000 zoospores/plant), mean lesion lengths for the cultivars Corsoy, Sloan, Cumberland, Williams, Asgrow 3127, Agripro 26, and Asgrow 2575 were 8.7, 8.6, 7.0, 7.0, 7.7, 5,2, and 4.0 cm, respectively (LSD 0.05 =0.84). Linear spline regression models consisting of two intersecting straight lines with slopes B 1 and B 2 were used to describe lesion expansion over a 14-day period for each cultivar []