Characterization and pathogenicity of Pratylenchus vandenbergae stat. nov. (Tylenchina: Pratylenchidae), a highly pathogenic root-lesion nematode parasitizing crops in Kenya and South Africa

Abstract

A highly fecund root-lesion nematode parasitizing a variety of crops was discovered and found to be widespread in Kenya and South Africa. These populations were molecularly identical to Pratylenchus teres teres and P. teres vandenbergae based on D2-D3 of 28S rDNA and Hsp90 sequences. However, based on morphological differences with the original description of P. teres and its different geographical distribution, Pratylenchus vandenbergae stat. nov., previously known as subspecies P. teres vandenbergae, is recognized as a separate species. This species is characterized by a slightly offset labial region with three annuli, en face morphology belonging to Group II, lateral field with four incisures with two outer bands areolated as observed under a light microscope and the inner band also partially areolated at the vulva region as observed in scanning electron microscopy view, a robust stylet (14–17 μm) with rounded knobs and subcylindrical tail with annulated tail tip. This important and common species remained largely under the radar, probably due to identifications based only on sequence similarity, including mislabelled Pratylenchus bolivianus sequences in GenBank. Pathogenicity of P. vandenbergae stat. nov. in finger millet roots was confirmed through acid fuchsin staining, and reproduction and pathogenicity tests in maize, soybean, sunflower and tomato plants demonstrated its capacity to affect crop growth. Life cycle comparison with P. penetrans in vitro showed a similar life cycle length but significantly higher fecundity. Finally, significant differences in pathogenicity and reproduction of P. vandenbergae stat. nov. were found both at genotype level (finger millet genotypes OKHALE-1 & KNE1034) and crop level (maize, soybean, sunflower and tomato plants).