Morphological variability in second-stage juveniles and males of Meloidogyne chitwoodi

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The morphology of Meloidogyne chitwoodi is relatively poorly characterised. In a recent study, morphological variation in adult females of M. chitwoodi was analysed. However, comparable data are lacking for adult males and second-stage juveniles (J2). Therefore, our studies of four M. chitwoodi isolates from the western USA, representing all currently known races and pathotypes, were designed to characterise intraspecific morphological variability in J2 and males and to compare it to variability found in adult females. Multivariate analysis of variance indicated statistically significant variation among isolates for both J2 and males. Moreover, for adult males, canonical discriminant analysis grouped races with their respective pathotypes. In addition, we analysed two morphological features that were previously uncharacterised for M. chitwoodi, i.e., stylet knob width and distance from secretory-excretory pore to anterior end. Both of these characters may be useful in distinguishing M. chitwoodi from closely related species. SEM clearly showed the presence of areolations along the bodies of J2, thereby separating M. chitwoodi from M. fallax and M. minor. In summary, this study indicates that M. chitwoodi J2 and adult males show substantially more intraspecific morphological variability than previously known. Consequences for diagnostics are discussed.

Nematology

International Journal of Fundamental and Applied Nematological Research

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Figures

  • Canonical discriminant analysis performed with 11 and 12 morphometric variables (Tables 1-3) for J2 (A) and males (B), respectively, from four Meloidogyne chitwoodi isolates representing distinct races and pathotypes. Enlarged symbols indicate means. This figure is published in colour in the online edition of this journal, which can be accessed via http://booksandjournals.brillonline.com/content/15685411.

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  • Photomicrographs of J2 tails from four isolates of Meloidogyne chitwoodi. A-D: WAMC1; E-H: WAMCRoza; I-L: WAMC27; M-P: CAMC2. (Scale bars = 20 μm.)

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  • Scanning electron micrographs of males and J2 from isolate WAMC1 of Meloidogyne chitwoodi. A-C, H, I: Males; D-G: J2.

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  • Scanning electron micrographs of males and J2 from isolate WAMCRoza of Meloidogyne chitwoodi. A-C, I: Males; D-H: J2.

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  • Scanning electron micrographs of males and J2 from isolate WAMC27 of Meloidogyne chitwoodi. A-C, H, I: Males; D-G: J2.

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  • Scanning electron micrographs of males and J2 from isolate CAMC2 of Meloidogyne chitwoodi. A-C, I: Males; D-H: J2.

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  • Photomicrographs of anterior end and stylet of males from four isolates of Meloidogyne chitwoodi. A-D: WAMC1; E-H: WAMCRoza; I-L: WAMC27; M-P: CAMC2. (Scale bars for anterior ends = 20 μm and for stylets = 10 μm.)

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