A High-Throughput Sampling Method for Detection ofMeloidogyne enterolobiiand Other Root-Knot Nematodes in Sweetpotato Storage Roots

Abstract

AbstractMeloidogyne 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.