Coffee Root-knot Nematode - Morphology and Anatomy

Morphology and Anatomy

Meloidogyne exigua females are small with medium stylet (12-14 µm) and strong basal knobs. This genus has sexual dimorphism; females are swollen and males keep vermiform as adults. The female has a pear shape when swollen. It is not possible differentiate one species from other on coffee in the field due to coffee being a host of several species of Meloidogyne. M. exigua can be found in Brazil, Guatemala, Colombia and Costa Rica. M. coffeicola has a long neck and brownish body color. Its stylet is 15-17.6 µm long with no prominent knobs. Females also swell, less than M. exigua, however. This species is found in Brazil, exclusively. Another way to distinguish Meloidogyne species is by the perineal patterns. The perineal pattern involves anus, vagina and surrounding area. Each species has a unique pattern that can distinguish them, but only a trained nematologist is able to verify those small differences. Meloidogyne exigua‘s perineal pattern has a hexagonal shape, with a dorsal arch above the anus and lateral lines not very pronounced on the perineal pattern, while M. coffeicola pattern have a more simple conformation with striations between vulva and anus forming a target. Due to difficulties to identify Meloidogyne species just by perineal pattern, other reliable techniques were developed, such as Isoenzyme characterizations. Oliveira reported difficulties to use perineal pattern and Isoenzymes helped to confirm species without mistakes. M. exigua is distinguished by its esterase phenotypes E1 and E2, while M. coffeicola by Est C2.