First Detection of Root-knot Nematode Meloidogyne enterolobii (Nematoda: Meloidogynidae) Parasitizing Zucchini ( Cucurbita pepo L.) in Hidalgo, Mexico

In April 2025, soil and root samples were collected from a comercial zucchini (Cucurbita pepo L.) cv. Lupita grown under plastic mulch in Tecozautla, Hidalgo, Mexico (20.519236 N, 99.683387 W). At the end of harvest period, plants exhibited stunting, chlorosis, and severe root galling (Fig. 1). Galls were abundant and irregularly distributed throughout the root system. Approximately 90% of 20 inspected plants exhibited showed root-knot nematode symptoms. Ten symptomatic root samples were taken. Typical globose, pearly white females and egg masses of Meloidogyne spp. were extracted (Fig. 2). Species identification was based on female perineal pattern morphology and morphometric analysis of second-stage juveniles (J2) (Fig. 3). Female perineal patterns exhibited diagnostic characteristics consistent with Meloidogyne enterolobii. Morphometric measurements of J2 (n = 10) included body length of 496.0 µm (422.2–537.3 µm), stylet length of 10.7 µm (10.3–11.4 µm), tail length of 50.7 µm (39.8–64.7 µm), and hyaline tail terminus length of 16.4 µm (12.6–18.7 µm), which agreed with previous descriptions of M. enterolobii (Yang and Eisenback 1983; Brito et al., 2008). Representative permanent slides is deposited in the nematological collection (CNRF-N) of the General Directorate of Plant Health from Mexico on registration number CNRF-NA00874021834. For species confirmation, total DNA was extracted from three egg masses using the DNeasy Blood & Tissue Kit (QIAGEN). Amplification of the 750 bp fragment of mitochondrial region COII/16S confirms the identification of M. enterolobii (Brito et al. 2004). A 850 bp fragment of the mitochondrial cytochrome c oxidase subunit I (coxI) gene was amplified by PCR using the primer pair COIF5/COIR9 (Powers et al., 2018) and subsequently sequenced. BLAST analysis confirmed the identity with Meloidogyne enterolobii, with 99.9% sequence identity (E-value= 0.0). The sequences generated in this study were deposited in GenBank under accession numbers PZ245181 and PZ245182. Pathogenicity tests were performed under greenhouse conditions (25±2°C and 55% RH), by inoculating ten 1-month-old zucchini plants with 3,000 J2 per plant (Osuna-Rodríguez et al., 2025); ten non-inoculated plants served as control. Sixty days after inoculation, all inoculated plants developed severe galling, whereas control plants remained asymptomatic. The nematode was re-isolated from infected roots, fulfilling Koch’s postulates (Fig. 4). To our knowledge, this is the first report of Meloidogyne enterolobii infecting zucchini in Hidalgo, Mexico and the first documented occurrence of this species in the state. Its presence may pose a phytosanitary threat to zucchini and other susceptible crops in the region.