English

Abstract

Five healthy, vigorous cultivars of sweet potato [Ipomoea batatas (L.) Lam] were cultivated under root-knot nematode Meloidogyne incognita challenge to distinguish levels of resistance to infection. Roots and soil samples were collected 84 days’ post-infection and evaluated for specific host responses to nematode infection by visual screening analysis and quantitative assessments of symptoms of infection. Resistant control cultivar Nugget showed the highest degree of resistance manifested in lower necrosis and galling, high fresh root weights and low nematode and egg counts. Necrosis and galling scores were highest in susceptible cultivars Georgia Jet and DMO1 where extensive root cracking was observed in Georgia Jet, and storage root development was severely restricted in DMO1 which also produced the highest egg counts. TUO2 and Whatley Loretan were considered intermediately resistant based on egg counts and necrosis and galling. Our results suggest that genotypic differences between cultivars were apparent in multiple host responses to root-knot nematode infection. We have also provided initial evidence to support the identification of newly developed sweet potato cultivars with intermediate resistance to root-knot nematodes. Key words: Plant-parasitic nematodes, host plant resistance, Ipomoea batatas, Meloidogyne incognita