Distribution and characterization of Pratylenchus bolivianus (Nematoda, Pratylenchidae) on rooibos (Aspalathus linearis) tea from South Africa

Pratylenchus bolivianus (Nematoda, Pratylenchidae) an important parasitic lesion nematode of ornamental and crop plants was found in association with rooibos (Aspalathus linearis) tea in the Cederberg region of South Africa. The population distribution and frequency of occurrence of P. bolivianus on the rooibos orchards were determined, and nematode characterization was done using a combination of traditional morphological characteristics, scanning electron microscopy (SEM), morphometrics and molecular marker by amplifying the D2-D3 expansion segment of the 28S ribosomal RNA gene. P. bolivianus occurred at 84.6% frequency in the sampled fields, with a mean population density that ranged between 10 and 770 lesion nematodes per 250 ml. The morphological features are similar to previous reports, with a slight variation in stylet length and ratio of 'a' due to intraspecific geographical variations. The en face view of the SEM shows pattern of the oral disc and first labial annule that is characteristic of P. bolivianus a pattern that falls under Group 2 classification. The phylogenetic relationships as inferred from Maximum Likelihood and Maximum Parsimony revealed a close relationship between the South African isolate of P. bolivianus and those published from other geographical locations. The study confirmed a morphological and genetic similarity between the amphimictic population of P. bolivianus from South Africa and those reported from Costa Rica.