Identification and Characterization of a Virulent Meloidogyne incognita Population Breaking Tomato Mi-1-Mediated Resistance in Indiana

Abstract

High-tunnel production is increasing rapidly in the US due to its effectiveness in extending production seasons. Tomato is considered one of the most profitable crops grown in high tunnels. The elevated soil temperature and constant soil moisture in high tunnels lead to the buildup of root-knot nematodes (RKNs). Growing RKN-resistant tomato cultivars or grafting onto RKN-resistant tomato rootstocks is considered effective in managing RKNs. However, all of the RKN-resistant tomato cultivars or rootstocks carry the same resistance gene, Mi-1. This lack of diversity in resistance has led to the emergence of virulent RKN populations breaking tomato Mi-1 resistance. Here, we identified and characterized a virulent population of Meloidogyne incognita from a high tunnel in Indiana. The M. incognita population was confirmed as being able to infect and reproduce on two resistant tomato cultivars, Better Boy and Early Girl, carrying the Mi-1 gene, under a controlled environment at 24 °C. To our knowledge, this is the first report of a virulent M. incognita population breaking Mi-1 resistance in Indiana. Virulent M. incognita populations overcoming Mi-1 resistance were previously reported in California and Georgia in the US. This work emphasizes the importance of regularly monitoring RKN population virulence to sustainably manage the pest.