Browsing by Author "Knoetze, R."
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- ItemDifferentiation of South African potato cyst nematodes (PCN) by analysis of the rDNA internal transcribed spacer region(SA ePublications, 2006) Knoetze, R.; Malan, Antoinette P.; Mouton, C.Cysts from nematode-infested plots on eight potato farms in the Sandveld and Ceres regions of South Africa were analysed by means of rDNA-RFLP. The size of the PCR amplification products for all populations was typical for the genus Globodera. Restriction digestion of the amplified products with MspI and HinfI confirmed Globodera rostochiensisto be present in both the Sandveld and Ceres regions and Globodera pallidato be absent from South African potato cyst nematode populations. However, several populations from the Sandveld region showed no recognition of the HinfI restriction site and no digestion took place, indicating them to be a distinct Globodera species. Sequencing of the ITS1 region confirmed the presence of G. rostochiensis and an unknown Globodera species, and the absence of G. pallida in South Africa. Species-specific primers for the identification of G. rostochiensis and G. pallida were optimised.
- ItemHeterorhabditis noenieputensis n. sp. (Rhabditida: Heterorhabditidae), a new entomopathogenic nematode from South Africa(Cambridge University Press - CUP, 2012-12) Malan, Antoinette P.; Knoetze, R.; Tiedt, L.A new entomopathogenic nematode in the genus Heterorhabditis is described from South Africa, from two singular isolates found 1000km from each other, from beneath a fig tree and in a citrus orchard, respectively. Morphological and molecular studies indicate both isolates to be the same and a new undescribed Heterorhabditis species. Comparison of sequences of the internal transcribed spacer (ITS) rDNA and the D2D3 region of the 28S rDNA gene with available sequences of other described species within the genus, indicate the two isolates as a new species. Phylogenetic analysis of the sequence data concerned placed the new species, H. noenieputensis n. sp., closest to H. indica and H. gerrardi in the indica-group. The new species, H. noenieputensis n. sp., is distinguished from other species in the genus by a combination of several morphological traits of the males and the infective juveniles (IJs). The new species differs from all other species previously described, as regards the body length of the IJs, except for H. indica and H. taysearae, in which the IJ is smaller. The IJ also differs from that of H. indica in the length of the oesophagus, the body diameter, the length of the tail and the E%. In addition, males of H. noenieputensis n. sp. differ from their closest relative, H. indica, in the position of the excretory pore, SW% and D%; and from H. gerrardi in the length of the oesophagus and SW%. The seventh pair of genital papillae of H. noenieputensis n. sp. are normally developed, while for H. indica they are often branched or swollen at the base, while 8 and 9 are usually absent in both species.