Morphological and karyotypic differences within and among populations of Radopholussimilis.

Chunling Xu,Lu Yu,Xin Huang,Dong-Wei Wang,Hui Xie,Yun Li,Wen-Jia Wu

doi:10.3897/zookeys.444.8186

Abstract

Twenty populations of Radopholus similis from three countries and different hosts (19 populations from ornamental plants and one population from ginger) were compared using morphological characters, morphometrics and karyotype between progeny from both single females and 30 females of each population. Morphological diversity existed in and among the populations, even within the progeny nematodes from single nematodes compared to that of 30 females. The labial disc shape, the number of head annuli, the terminated position of lateral lips, the number of genital papillae before cloacal apertures and female and male tail terminal shape showed variation. In addition, genital papillae arranged in a double row before cloacal apertures was first found in two ornamental populations. The karyotype of all the 20 populations was n = 5. Combining our results and previous studies, we support that Radopholus citrophilus is a synonym of Radopholus similis, and that it is not possible to distinguish physiological races or pathotypes of Radopholus similis according to morphological characters or karyotype.

Highlights

The burrowing nematode, Radopholus similis (Cobb, 1893) Thorne, 1949, is an important parasitic plant nematode has made great damages on many economic crops, and is on the list of quarantined pests in many countries (Anonymous 2004; Haegeman et al 2010)
Huettel and Yaegashi (1988) reported that there were some differences in the morphology of the female labial disc, the lateral lip position, the number of annuli terminated at the vulva and the number of genital papillae anterior to the cloacal aperture in the male between the two races when viewed by scanning electron microscope (SEM)
All 20 populations of R. similis exhibited all of reported morphological characters (Tables 2, 3)

Summary

Introduction

The burrowing nematode, Radopholus similis (Cobb, 1893) Thorne, 1949, is an important parasitic plant nematode has made great damages on many economic crops, and is on the list of quarantined pests in many countries (Anonymous 2004; Haegeman et al 2010). Huettel and Yaegashi (1988) reported that there were some differences in the morphology of the female labial disc, the lateral lip position, the number of annuli terminated at the vulva and the number of genital papillae anterior to the cloacal aperture in the male between the two races when viewed by scanning electron microscope (SEM). These morphological differences were thought to be used to differentiate between the different races; Huettel et al (1984) proposed to treat the citrus race as an independent species, Radopholus citrophilus Huettel, Dickson, David & Kaplan, 1984. These findings were later confirmed by other studies (Koshy et al 1991, Elbadri et al 1998, Elbadri et al 1999a, 1999b)

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Conclusion