The National Collection of Nematodes — The Microscopic Giants
The National Collection of Nematodes (NCN) was established in 1955 by Prof Juan Heyns as a reference collection due to the agricultural importance of nematodes. Over 50 000 microscope slides are currently housed in the collection. These slides contain more than 200 000 specimens representing 314 genera and 1 395 species of preserved free-living, plant-parasitic and entomopathogenic nematodes from various parts of the world.
More than 7 000 type specimens are housed in this collection including 422 holotypes and 6 771 paratypes.
The NCN also house the Meloidogyne collection, that was established in 1981, and consists of 14 750 slide-mounted specimens containing the material of a Meloidogyne survey of South Africa and various other countries. In 1991, Dr Kent Kleynhans compiled a monograph on the root-knot nematodes (Meloidogyne) of South Africa. The monograph was based on the specimens of the Meloidogyne collection.
The NCN also house the Juan Heyns Collection that was donated by the late Prof Heyns of the Rand Afrikaans University (now University of Johannesburg) to the NCN in 1999. This comprehensive collection contains 7 300 slides, representing about 21 900 specimens of plant as well as free-living and aquatic nematodes.
These collections are important for various reasons. The NCN collection is the biggest reference collection in Africa (to our knowledge it is the only national collection of nematodes in Africa); the collection is one of the largest nematode collections globally with over 220 000 specimens deposited; oldest holotype deposited in 1957; the collection also houses a literature collection linked to every described species deposited in the collection; and finally the collection is fully digitised in the NCN and South African Plant-Parasitic Nematode Survey (SAPPNS) databases.
Plant-parasitic nematodes are known pests of various agricultural crops globally. According to the American Society of Phytopathology, plant-parasitic nematodes cause an estimated 14 % yield losses in the agricultural sector world-wide, equal to almost 125 billion dollars annually (Mesa-Valle et al,. 2020).
The correct identification of these nematode species is crucial to enable the correct and sustainable management plans. Staff of the NCN provides diagnostic services to the agriculture community that is backed by taxonomic expertise, an extensive literature collection and historic data. Annually the Nematology unit identifies more than 2 million nematode specimens and characterise the nematode communities of 254 different crops.
Subject to data transfer agreements, datasets from the NCN are available to interested parties. Datasets from the Nematode System have also been used in several scientific papers. The most recent highlight in the use of Nematology data was in Van den Hoogen et al. (2019) and Van den Hoogen et al., (2020) where 6 759 georeferenced samples were used, to which the Nematology Unit contributed, to generate a mechanistic understanding of the patterns of the global abundance of nematodes in the soil and the composition of their functional groups.
The resulting maps show that 4.4 ± 0.64 × 1020 nematodes (with a total biomass of approximately 0.3 gigatonnes) inhabit surface soils across the world, with higher abundances in sub-Arctic regions (38% of total) than in temperate (24%) or tropical (21%) regions.
Staff at the NCN have also been involved in nematode surveys across South Africa in protected areas and with the background of the collection and the expertise as taxonomists several species lists were compiled and published.
Written by Chantelle Girgan and Mariette Marais
Contact person: Chantelle Girgan — JansenC@arc.agric.za
