Comparison of screening methods for resistance to Fusarium root rot in common beans (Phaseolus vulgaris L.)

Root rot, caused by Fusarium solani f. sp. phaseoli, is one of the main root diseases impacting production of common beans throughout the world. Because resistance of common beans to root rot is a quantitative trait that is strongly influenced by environmental factors, reproducible methods to screen bean plants for resistance to root rot are critical to the selection process. In this study, we adapted the inoculum layer method (ILM) developed for screening soybeans for resistance to Phytophthora rot and compared it with the traditional liquid inoculum method (LIM) for screening common beans for resistance to Fusarium root rot. In addition, two methods of evaluating resistance using the ILM were compared. The most significant Pearson correlation coefficient between trials involving 80 recombinant inbred lines was achieved with the ILM and counting discoloured vascular bundles in the lower stem (r(p) = 0.7113***) compared to rating the discoloration on root and hypocotyl (r(p) = 0.5555***). The traditional (LIM) screening method and rating the discolouration on roots resulted in a non-significant correlation between trials (r(p) = 0.1084).