The root lesion nematode Pratylenchus penetrans is known to damage major crops of economic importance. For the development of environmentally friendly control practices, a good understanding of the biological and genetic diversity of this species is required. This study aimed to characterize the diversity among seven isolates of P. penetrans collected from different geographical regions based on morphometric and genetic characteristics, their level of reproduction and their pathogenicity on selected hosts. To establish pure cultures of P. penetrans different methods were compared and optimized. Best method in terms of establishment and maintenance of P. penetrans isolates was monoxenic culturing on carrot discs. The identities of P. penetrans isolates were confirmed by morphological and molecular analysis. To characterize the host status of cover crops, reproduction fitness and pathogenicity of the seven P. penetrans isolates, a standard test system was developed. The host status of the tested cover crops ranged from non-hosts (ribwort plantain) through maintenance hosts (daikon radish, rocket and black oat cultivars Panche and Silke) to excellent hosts (lentil and common vetch). The reproductive fitness of the seven P. penetrans isolates was tested in vitro on carrot discs and in vivo on lentil and common vetch. Pathogenicity of those P. penetrans isolates was studied on alfalfa, carrot, fodder radish and French marigold. Differences in reproductive fitness and pathogenicity were observed among P. penetrans isolates. In general, reproductive fitness correlated positively with plant damage, i.e. the higher the reproduction, the higher the damage. Morphometrics of P. penetrans isolates were within the range of the original descriptions, but showed differences in some features to populations reported from other countries, such as body length, a, b and c ratio, maximum body width, tail length and length of the post-vulval uterine sac. According to RAPD analysis, the seven P. penetrans isolates showed a high level of intraspecific genetic variability. Furthermore, genetic similarities between some P. penetrans isolates were reflected in similarities in reproductive fitness, pathogenicity and morphometrics. For example, isolates MN and UK were genetically and morphological similar and showed similar reproductive fitness and pathogenicity. In contrast, isolates BL and MN showing the largest genetic and morphological differences also showed the largest differences in reproductive fitness and pathogenicity.
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