New host record for Meloidogyne javanica: implications for jambu cultivation in the Amazon region

The occurrence of Meloidogyne spp. in vegetables is well known, but little is known about the infestation of this root-knot nematode in the toothache plant ( Acmella oleracea ), a non-conventional vegetable from the Amazon region of Brazil. To this end, samples were taken in in August 2019 in a cultivation area of the toothache plant (jambu, in Portuguese) in the municipality of Santa Isabel do Pará, Pará, Brazil. There, chlorotic plants with underdeveloped aerial parts and a strong proliferation of galls in the root system were observed. Soil and root samples were taken and the presence of Meloidogyne javanica in the toothache plant was confirmed. This result was based on the morphological characteristics of the adults with respect the perineal configuration of the females and the labial region of the males. Morphological analysis revealed that the perineal region of females has a low trapezoidal dorsal arch with two lines on the sides, while males have broader basal nodules with a non-raised labial disk, with the head region not separated from the body. Molecular confirmation was obtained by genetic sequencing and sequence-characterized amplified region (SCAR) markers. Thus, this is the first report of the toothache plant as a host of M. javanica in Brazil and worldwide. • Meloidogyne javanica infects A cmella oleracea in Brazil. • A. oleracea is a importance non-conventional vegetable from the Amazon. • This is the first report of A. oleracea as a host for M. javanica in Brazil in world.