Soil-Borne Nematodes: Impact in Agriculture and Livestock and Sustainable Strategies of Prevention and Control with Special Reference to the Use of Nematode Natural Enemies

Soil-borne parasitic nematodes cause severe deterioration in the health of crops and supply animals, leading to enormous economic losses in the agriculture and livestock industry worldwide. The traditional strategy to control these parasites has been based on chemically synthesised compounds with parasiticidal activity, e.g., pesticides and anthelmintic drugs, which have shown a negative impact on the environment. These compounds affect the soil’s beneficial microbiota and can also remain as toxic residues in agricultural crops, e.g., fruits and legumes, and in the case of animal products for human consumption, toxic residues can remain in milk, meat, and sub-products derived from the livestock industry. Other alternatives of control with much less negative environmental impact have been studied, and new strategies of control based on the use of natural nematode enemies have been proposed from a sustainable perspective. In this review, a general view of the problem caused by parasitic nematodes affecting the agriculture and livestock industry, traditional methods of control, and new strategies of control based on eco-friendly alternatives are briefly described, with a special focus on a group of natural nematode antagonists that have been recently explored with promising results against plagues of importance for agricultural and livestock production systems.

First record of Aphelenchoides stammeri (Nematoda: Aphelenchoididae) from Turkey

In previous surveys for the investigation of Bursaphelenchus xylophilus in Turkey, several Bursaphelenchus species, except B. xylophilus, were detected. To determine the insect vectors of these previously reported Bursaphelenchus species, trap trees of each pine species (Pinus brutia and P. nigra) were cut and kept in the field from April to September in 2011. Aphelenchoides stammeri was isolated from wood chip samples of P. nigra from Isparta (Sütçüler). A. stammeri was first identified by using morphological features and allometric criteria of females and males. In addition, molecular analysis using sequences of 18S and 28S ribosomal (rRNA) genes of A. stammeri was performed. This is the first report of A. stammeri from Turkey.

Morphological and molecular characterisation of Aphelenchoides primadentus n. sp. (Nematoda: Aphelenchoididae) from northern Iran

Aphelenchoides primadentusn. sp. is described and illustrated based on its morphological, morphometric and molecular characters. It was recovered from natural forests of northern Iran in association with mosses. The new species is characterised by its body length of 502-613μm in females and 461-564μm in males, presence of three lines in the lateral fields, a low lip region slightly offset by a shallow depression, 11.1-13.8μm long stylet in females, its conus being longer than the shaft (m = 53.0-68.5) and bearing well-developed, rounded basal knobs, the excretory pore located atcaone body diam. posterior to the metacorpus, a conical tail with a multipapillate terminus or with a single, warty, wide mucron-like structure at the tip, and males with 19-22μm long arcuate spicules that lack a well-developed condylus and rostrum. The new species was morphologically compared with species of the genus having three lines in the lateral field and a multipapillate tail tip or tail with warty mucron, namelyA. iranicusandA. heidelbergi. Compared toA. ensete,A. huntensisandA. gorganensis, three species with a multipapillate tail tip or warty mucron at the tail tip, the new species has a basic difference in the number of lines in the lateral field and, compared to two species,A. composticolaandA. petersi, which have three lines in the lateral field and a similar overall morphology, the new species has basic differences in tail tip morphology. The results of phylogenetic analyses using partial sequences of ribosomal small subunit RNA (SSU) and mitochondrial cytochrome c oxidase 1 (COImtDNA) genes revealed there is currently no sequenced species of the genus phylogenetically close to the new species being sequenced for these two genomic and non-genomic regions. The new species forms a clade withA. ritzemabosiin SSU, and three other species,A. besseyi,A. ritzemabosiandA. fujianensis, in theCOItree.

Description of Aphelenchoides giblindavisi n. sp. (Nematoda: Aphelenchoididae), and Proposal for a New Combination

One new and one known species of the genus Aphelenchoides from Iran are studied. Aphelenchoides giblindavisi n. sp. is mainly characterized by having five lines in the lateral fields at mid-body, and a single mucro with several tiny nodular protuberances, giving a warty appearance to it, as revealed by detailed scanning electron microscopic (SEM) studies. The new species is further characterized by having a body length of 546 to 795 μm in females and 523 to 679 μm in males, rounded lip region separated from the rest body by a shallow depression, 10 to 11 μm long stylet with small basal swellings, its conus shorter than the shaft ( m  = 36-43), 52 to 69 µm long postvulval uterine sac (PUS), males with 16 to 18 μm long arcuate spicules, and three pairs of caudal papillae. The new species was morphologically compared with two species of the genus having five lines in the lateral fields namely A. paramonovi and A. shamimi and species having a warty-surfaced mucro at tail end and similar morphometric data ranges. The morphological features and morphometrics of the second studied species, A. helicus , agreed well with the data given for the type population. However, detailed study of fresh females revealed it has three drop-shaped stylet knobs and long PUS, making it typologically similar to the genus Robustodorus , meriting its taxonomic revision, i.e., transferring to it. In molecular phylogenetic analyses using partial small and large subunit ribosomal RNA gene (SSU and LSU rDNA) sequences, the new species formed a clade with A. heidelbergi in both SSU and LSU D2-D3 trees. The species A. helicus , however, clustered inside a well-supported clade of the genus Robustodorus in both trees, corroborating its newly proposed taxonomic placement as Robustodorus helicus n. comb.