Rapid diagnosis of Fusarium root rot in soybean caused by Fusarium equiseti or Fusarium graminearum using loop-mediated isothermal amplification (LAMP) assays

Rapid diagnostic assays for Fusarium root rot in soybean, caused by Fusarium equiseti or Fusarium graminearum were developed using the target gene CYP51C. Both assays amplified the target gene in 60 min at 62 °C, after which they were assessed for specificity and sensitivity. Specificity was evaluated against other Fusarium spp., other fungal species, and oomycetes. A positive yellow-green color (by the naked eye) or intense green fluorescence (under ultraviolet light) was observed only in the presence of F. equiseti or F. graminearum after adding SYBR Green I, whereas other strains showed either no color change or weak fluorescence. The detection limit of the CYP51C-Fe-LAMP assay was 10 pg. μL−1 genomic DNA per reaction, and as few as four conidia per gram of soil could be detected; and the detection limit of the CYP51C-Fg-LAMP assay was 100 pg. μL−1 genomic DNA per reaction, and 40 conidia per gram of soil could be identified. The assays also detected F. equiseti or F. graminearum from inoculated soybean tissues and diseased plants in the field. These results suggest that CYP51C-Fe-LAMP assay and CYP51C-Fg-LAMP assay are effective in rapidly diagnosing soybean root rot caused by F. equiseti and F. graminearum.