APS Homepage

Poster: Biology & Disease Mgmt: Genetics of Resistance


Effectiveness of a seed plate assay evaluating charcoal rot resistance in soybean
M. DA SILVA (1), P. Chen (1), J. Rupe (1) (1) University of Arkansas, U.S.A.

Charcoal rot (Macrophomina phaseolina) of soybean (Glycine max (L.) is a disease of economic significance in the United States. While there is moderate host resistance in soybean cultivars, identifying and quantifying that resistance are difficult. Current assay methods, such as cut-stem inoculation and colony-forming unit index (CFUI), can be time consuming, and data may vary between tests. The objective of this research was to compare results of a seed plate assay to published results of the cut-stem and CFUI assays. Ten surface disinfested seeds of eight differential soybean genotypes, including LS94-3207, LS98-0358 and Pharaoh, susceptible and DT97-4290, DT98-7553, DT99-16864, DT99-17554 and DT99-17483 as resistant, were placed on water agar plates that had been inoculated with an isolate of M. phaseolina five days before. Plates were incubated at room temperature in the dark for 7 days and the number of seeds that germinated were determined. Noninoculated plates served as controls. In general, germination results from the plate assay were in agreement with the cut-stem and CFUI assays. Germination of resistance lines range from 58% to 84% and susceptible lines from 46% to 54%. Addition data will be presented later.