Host status of sweetpotato cultivars and germplasm to Rotylenchulus reniformis

Rotylenchulus reniformis (the reniform nematode) is an emerging pest of sweetpotato. The aim of this study is to (i) determine the host status of sweetpotato cultivars to R. reniformis, (ii) identify potential sources of resistance among sweetpotato germplasm, and (iii) evaluate R. reniformis parasitism on root biomass partitioning. Greenhouse trials evaluated R. reniformis reproduction and sweetpotato root weight with 10 commercial cultivars and 28 plant introductions (PIs). All commercial cultivars supported similar nematode reproduction to the susceptible control 'Beauregard', indicating widespread susceptibility. Four PIs ('Saing-Mi', 'Regal', 'Morada Sombica', and 'Tainung 63') had lower nematode reproduction compared to 'Beauregard'. Rotylenchulus reniformis infection increased fibrous root biomass by 28.4%, yet reduced storage root weight by an average of 30.4%, demonstrating yield penalties associated with R. reniformis parasitism. This is the first report identifying 'Covington' and 'Orleans' as highly susceptible to R. reniformis and confirms that R. reniformis significantly inhibits storage root production. These findings emphasize the negative impact of R. reniformis in sweetpotato production and highlight the lack of available host resistance.