Trichodorus

Abstract: Longidoridae and Trichodoridae represent the only families of nematodes within the Class Enoplea proven to be plant-parasitic. The Longidoridae are classified within the subclass Dorylaimia (order Dorylaimida, superfamily Dorylaimoidea), while the Trichodoridae belong to the subclass Enoplia (order Triplonchida, superfamily Diphtherophoroidea). Longidoridae: The family Longidoridae includes some 480 species of the subfamily Longidorinae with six genera: Longidorus (144 spp.), Longidoroides (13 spp.) and Paralongidorus (72 spp.) in the tribe Longidorini, and Australodorus (1 sp.), Paraxiphidorus (3 spp.) and Xiphidorus (8 spp.) in the tribe Xiphidorini and the subfamily Xiphineminae with one genus Xiphinema (some 240 spp.). At present, there is no consensus about the status of the genus Longidoroides Khan, Chawla and Saha, 1978 (see Decraemer and Coomans, 2007). Longidorus, Paralongidorus and Xiphinema are virus vectors. A wealth of information on Longidorus, Paralongidorus and Xiphinema can the found in papers on polytomous keys and subsequent supplements: Xiphinema (Loof and Luc, 1990; Loof and Luc, 1993; Loof et al., 1996), Longidorus (Chen et al., 1997; Loof and Chen, 1999) and Paralongidorus (Escuer and Arias, 1997) as well as in Coomans et al. (2001), a monography on the genus Xiphinema dealing with character analysis, phylogeny and biogeography. The main diagnostic features of Longidoridae at the genus level are the structure of the odontostyle and odontophore, the structure and position of the guide ring, the shape of the amphidial fovea, shape and size of amphid opening and the position and size of the pharyngeal gland nuclei. Additional features at species level next to morphometric data are the shape and size of the amphidial fovea and opening, the development and structure of the female reproductive system (didelphic, monodelphic, pseudomonodelphic) with uterine differentiation and inclusions in Xiphinema and genera of the Xiphidorini, the tail shape in all developmental stages and presence or absence of males. Phylogenetic analyses of the Longidoridae based on sequence data and morphological data were carried out by He et al. (2003). Olivera and Neilson (2004) have a comprehensive review article showing the systematics, virus vectoring species and morphological differences among the Longidorid genera, and Decraemer and Coomans (2007) discussed relationships within the family Longidoridae. Trichodoridae: The Trichodoridae include 100 species and five genera: Trichodorus Cobb, 1913, Paratrichodorus Siddiqi, 1974, Monotrichodorus Andrassy, 1976, Allotrichodorus Rodriguez-M, Sher and Siddiqi, 1978 and Ecuadorus Siddiqi, 2002. The two largest genera Trichodorus (54 spp.) and Paratrichodorus (34 spp.) are didelphic in females and occur worldwide. The three remaining genera, Monotrichodorus (4 spp., one subspecies), Allotrichodorus (6 spp.) and Ecuadorus (2 spp.), have fewer species, and females are monodelphicprodelphic; so far, these three genera have only been recorded from Central America and the northern part of South America. The main diagnostic characters to differentiate the genera of the Trichodoridae are: in females, (i) the reproductive system (didelphic or monodelphic); (ii) length of vagina, (iii) development of vaginal sclerotized pieces and (iv) presence of advulvar lateral body pores; and in males, (i) presence or absence of caudal alae, (ii) degree of development of copulatory muscles and related habitus and (iii) development of capsule of spicule suspensor muscles (Decraemer and Geraert, 2006). Additional features at species level, apart from morphometric data, are: in females, (i) the vaginal sclerotized pieces (size, shape, orientation, distance), (ii) presence/absence and location of sperm cells; in males and females, structure of sperm cell and nucleus, and in males, (i) the spicules (shape, ornamentation), (ii) number and arrangement of ventromedian cervical papillae and (iii) ventromedian precloacal supplements. Decraemer (1995) gives a comprehensive review of morphological and systematic information on this group.

Abstract: In an attempt to evaluate the occurrence and economic importance of plant-parasitic nematodes in organic farming in Germany, a survey was conducted with the main emphasis on vegetable and cereal production systems. For vegetables, the survey included quantification and identification of plant-parasitic nematodes in soil samples and a questionnaire for growers querying production factors and damage levels. For cereals, the survey focused on quantification and identification of plant-parasitic nematodes in soil and plant samples. Overall, Pratylenchus and Tylenchorhynchus were the most prominent nematode genera under both production systems with an incidence of over 90% of the samples. Meloidogyne was detected in 51% of the samples in both systems. Other nematode genera showed differences between the two production systems. In production systems with a high frequency of vegetables, Paratylenchus was detected in 56% of the samples and Heterodera in 15%, whereas in rotations with a high cropping frequency of cereals, incidences of plant-parasitic nematodes were 56% for Heterodera, 47% for Trichodorus and 45% for Paratylenchus. Yield losses could exceed 50% on carrots, onions and cereals and were most pronounced on sandy soils. In many cases, nematode problems started 5 to 10 years after conversion to organic farming. The survey indicated that plant-parasitic nematodes are widely spread in organic farming in Germany and can cause severe damage which may result in complete loss of the crop.

Abstract: Plant parasitic nematodes of the family Trichodoridae cause substantial yield losses in many agricultural crops. Rapid and accurate identification of trichodorids to the species level is critical for selection of appropriate measures for control. This study analysed 99 sequences of the D2–D3 expansion segments of the 28S rRNA gene and 131 sequences of the 18S rRNA gene from the stubby nematodes belonging to the genera Nanidorus, Paratrichodorus and Trichodorus. Species delimiting was based on the integration of morphological identification, which is not provided in the present article, and molecular-based phylogenetic inference and sequence analysis. Twenty-two valid species and several species complexes were identified among nematodes included in the analysis. PCR-RFLPs of the partial 18S rDNA and the D2–D3 expansion segments of the 28S rDNA were tested and proposed for identification of these nematodes. Gel PCR-RFLP profiles and tables with restriction fragment lengths for several diagnostic enzymes are provided for identification. Some problems of taxonomy and phylogeny of nematodes of the family Trichodoridae are also discussed.

Abstract: Trichodorus primitivus (de Man 1880) is redescribed and ten new species of Trichodorus are described, including the species first reported to cause stubby-root disease in Florida, U.S.A. The species descriptions and illustrations present details of the morphology of both males and females and indicate the presence of two distinct species groups in the genus. The morphology of the onchiostyle is discussed and illustrated and evidence is presented to indicate that the onchiostyle in Trichodorus is not a hollow axial spear but is dorsal to the lumen of the esophagus. A key to the species is presented as an aid to identification.