Additional information on an atypical population of Meloidogyne exigua Goldi, 1887 (Tylenchida: Meloidogynidae) parasitising rubber tree in Brazil

Abstract

Females, males and second-stage juveniles of an unusual population of Meloidogyne exigua race 3 that only parasitises the rubber tree were examined by light and scanning electron microscopy. Previous molecular characterisation, using SCAR markers, showed consistency with other M. exigua populations from coffee. However, RAPD analysis showed high polymorphism (43.1-57.8%) but with 100% bootstrap support among populations from coffee and rubber tree. In addition, this population showed the main M. exigua esterase band (Rm: 1.5) and an additional band (Rm: 1.6) not detected in the coffee population. The morphology of this atypical population was very close to M. exigua from coffee in major diagnostic characters such as perineal pattern and male head region. However, minor differences occurred in morphological and morphometric features, particularly in the female and male stylet morphology. Cytogenetic studies confirmed the occurrence of meiotic parthenogenesis with haploid chromosome number (n = 18).