Reproduction of Meloidogyne enterolobii on Onion and Potential Yield Suppression

Meloidogyne enterolobii, is an emerging root-knot nematode species in the southern United States. To date, no studies have evaluated the host status of onions to M. enterolobii. This study aimed to assess the reproduction and pathogenicity of M. enterolobii on onion cultivars commonly grown in Georgia. Six Vidalia onion cultivars ('Rio del Sol', 'Sapelo', 'Sweet Magnolia,' 'Tania,' 'Vidora,' and 'NUN 1011'), three red onion cultivars ('Red Duke,' 'Red Halen,' and 'Red Maiden'), and a white onion cultivar ('Monjablanca') were evaluated. Each cultivar was inoculated with 8,000 eggs of M. enterolobii in a repeated greenhouse trial with six replications each. Twelve weeks post-inoculation, plants were harvested to determine reproduction and pathogenicity based on the reproduction factor (Rf = final nematode population/initial nematode inoculum) and reductions in bulb and shoot weights, respectively. All tested cultivars were susceptible to M. enterolobii, with Rf values greater than 1, though significant differences were observed. 'Vidora' and 'Tania' exhibited the highest galling index and Rf values, while 'Sweet Magnolia' and 'Sapelo' had the lowest. All red onion cultivars showed significant reductions in weight for both bulbs and shoots, whereas among the Vidalia cultivars, only 'NUN 1011' exhibited notable reductions in bulb and shoot weights. These findings suggest that onions are suitable hosts for M. enterolobii, and that the nematode's reproduction and pathogenicity vary with onion type and cultivar.