Molecular identification of Heterodera spp., an overview of fifteen years of research

During the last 15 years, researchers have collected and characterised more than 40 species of nematodes from the genus Heterodera. The species were identified by sequcncing the ITS-rRNA genes and by PCR-RFLP profiles; these tools remain the best available for identifying cyst-forming nematodes. By restricting the lTS amplicons with one or a combination of seven restrietion enzymes (AIuI, Aval, Bsh 12361, BsuRI, C/ol, MvaI, and Rsal), researchers ean distinguish most of the agrieulturally important eyst nematode species from one another and from their sibling species. Species from the Avenae group ean be differentiated from one another using the enzymes Alul, C/o I, Hinfl, !tal, Pstl, RsaI, Taql and 7hl9I. However, in some cases, it is not possible to use sequences of ITS-rRNA genes and PCR-RFLPs in diagnostic work. In these eases, morphometrie eharaeteristies are better for differentiating these species. Intraspeeifie polymorphism in the lTS sequences can make identification even more diffieult; here, more eonclusive moleeular identification tools are needed to diagnose some species. In the future, end-point PCR and semi-quantitative PCR (SYBR Green I) with species-specific primers (already developed for Heterodera glycines and H. schachtii) will be the likely choices for fast and reliable deteetion and quantifieation of eyst nematodes in samples