First Report of Root-knot Nematode, Meloidogyne graminicola on Brassica juncea in China

In southern China, the staple food rice (Oryza sativa) field is commonly rotated with brown mustard Brassica juncea. Root-knot nematodes (RKNs) are a major threat to rice production. From 2019 to 2021, B. juncea in 56 fields from 26 counties in Guangxi Province were observed with symptoms of leaf yellowing, stunting, and several hook-shaped galls on the roots. Females and egg masses of Meloidogyne sp. were found within the galls. The females, males, and second-stage juveniles (J2s) were collected, and identified with morphological and molecular characteristics and female perineal patterns. Brassica juncea was transplanted in pots and a pathogenicity test was conducted to confirm the species as Meloidogyne graminicola. In China, this is the first record of a natural infection of mustard with M. graminicola, and this finding has great importance for Chinese mustard production, since this nematode may damage mustard plants and become an additional problem for this crop.