A Simple and Efficient Inoculation Method for Fusarium Dry Rot Evaluations in Potatoes

Fusarium dry rot (FDR), caused by Fusarium species is an important potato disease world-wide and causes post-harvest rotting and seed-piece decay after planting. In this study, we compared two inoculation methods - cork borer wounding (CBW) and plastic screw wounding (PSW) – for consistent and reproducible disease development in potatoes. A plastic screw was used as a tool to make nearly identical wounds and simultaneously deliver similar quantities of inoculum into tubers, while at the same time sealing the wound in a single step. The PSW method resulted in tuber dry rot severities comparable to that obtained using the traditional CBW method. Tuber rot severities obtained using the two methods were highly correlated in the same sets of tubers, among the three inoculations conducted at different time periods ( r values ranging from 0.56–0.95; p < 0.001) for both years of the study. The PSW inoculation method condensed the wounding, inoculum delivery and wound sealing into a single step, thus saving considerable time when compared to the CBW inoculation method. The single use of individual plastic screws can also prevent cross-contamination from non-target microorganisms, which may reside inside the surface-sterilized tubers. The PSW method can be efficiently used to screen potato breeding lines for resistance to Fusarium dry rot.