Development of a new field inoculation technique to assess partial resistance in soybean to Sclerotinia sclerotiorum

The use of appropriate techniques to assess disease resistance is crucial to understanding the genetic control of host resistance to pathogens to develop resistant plant varieties. The objective of this study was to develop and evaluate a novel field-based inoculation technique for sclerotinia stem rot in soybean [Glycine max (L.) Merr.], caused by Sclerotinia sclerotiorum (Lib.) de Bary. The barley kernel inoculation technique involves stem inoculation using an infected barley kernel inserted into a wound made in the soybean stem. The damage on soybean plants is measured by the length of the lesion on inoculated stem and expressed as inoculation severity index (ISI). Soybean varieties were evaluated for 2 yr at different sites using the barley kernel inoculation technique, and compared with other controlled environment and natural infection-based techniques. The ISIs obtained at Elora, ON, were significantly correlated (r = 0.21, P = 0.021) between the 2 test years (1998 and 1999), and in 1998 with natur...