Search

Meloidogyne enterolobiiis an aggressive root-knot nematode (RKN) species that has emerged as a significant pathogen of sweetpotato in the Southeastern United States.M. enterolobiiis spread primarily through the movement of infected ‘seed’ sweetpotatoes used for propagation. The RKN resistance in commercially grown sweetpotato cultivars has proven ineffective against this nematode. Detecting RKN in sweetpotato by eye is unreliable, and further distinguishingM. enterolobiifrom other RKN species that infect sweetpotato is labor intensive; relying on molecular tests conducted on individual nematodes dissected out of host roots by trained technicians. Here, we have developed a high-throughput survey method to collect skin samples and extract total DNA from batches of sweetpotato storage roots. Combining this method with species-specific PCR assays allowed for quick and sensitive detection ofM. enterolobiiand other RKN species infecting sweetpotatoes. We tested this method using batches of infected storage roots at varying levels ofM. enterolobiiinfection. We also inoculated skin samples with varying numbers of individualM. enterolobiieggs to determine the method’s detection threshold and used this method to conduct surveys for RKN on fresh market sweetpotatoes. Our results show that this method can consistently and reliably detectM. enterolobiiin sweetpotato batches at levels as low as 2 eggs per 10 mL skin sample. This method will be a useful tool to help screen for the presence ofM. enterolobiiin ‘seed’ sweetpotatoes before they are replanted, thereby helping to slow the spread of this nematode toM. enterolobii-free sweetpotato growing operations.

Often research efforts that address both the practical concerns of managing Meloidogyne spp. and understanding their basic biology involve greenhouse reproduction assays. However, there is little consensus in regards to what parameters should be used to conduct greenhouse assays. The goal of this research was to evaluate how pot size, Meloidogyne spp. inoculation life stage, inoculation density, and time of assay impacted final reproduction factor (RF = initial nematode density/final nematode density) values. In experiments with M. incognita, the factor of the pot size mattered, with higher RF values in pots containing 500 g soil vs. pots with 100 g soil; larger pots containing 3,000 g soil did not have RF values different from the aforementioned sizes. Inoculating with M. incognita J2 resulted in RF values on average of >2 fold higher then when inoculating with eggs at comparable densities. Inoculation density of M. incognita did not have an impact on final M. incognita RF values. In experiments that considered time of assay, three species were evaluated: M. incognita, M. chitwoodi, and M. hapla. There was no difference in M. incognita RF values when assays were conducted for 5 wk, 6 wk, 7 wk, and 8 wk. However, a longer assay time resulted in higher RF values for M. hapla and M. chitwoodi, with at least a 7 week assay required. In conclusion, a moderate pot size (500 g of soil) inoculated with M. incognita J2 resulted in maximum RF values. The length of the assay required will depend on the Meloidogyne spp. in question, with longer duration assays required for M. hapla and M. chitwoodi than for M. incognita.

Often research efforts that address both the practical concerns of managing