Phylogenetic position of Mononchus species (Nematoda: Mononchida) associated with tomato using 28S rDNA from South Africa

Predatory nematodes are the main nematodes that live in the soil assisting with the biological control of the plant parasitic nematodes associated with various crops. Mononchus species is a predatory nematode and therefore can feed on the other nematodes that exist in the soil. This species is important due to its critical role in the biocontrol strategy and therefore must be identified correctly. The soil samples were collected from a tomato field in Limpopo Province in South Africa. This molecular study was conducted in 2022 at Limpopo University to identify the nematode species from South Africa's soils using 28S rDNA marker. The recovered nematode was extracted using the tray method, and then its DNA was extracted using the chelex method. The nematode was identified as Mononchus sp. Afterwards, 28S rDNA was amplified using specific primers to identify the nematode at the molecular level. The Nblast analysis based on the large subunit ribosomal DNA showed South African Mononchus sp. had 99 % similarity (KY750781) with a Mexican population. Phylogenetic analysis using maximum likelihood placed this species with those molecularly identified as Mononchus in the same clade with highly supported (100) bootstrap values. In conclusion, this is the first 28S rDNA of a Mononchus from South Africa. Additionally, though this species was identified using 28S rDNA however, the use of other rDNA markers such as ITS rDNA and 18S rDNA for a better understanding of Mononchus phylogeny is recommended.
