Plant-Parasitic Nematodes of Legume Fields and Their Distribution in Kermanshah Province, Iran

Legumes may be considered as the second most important source of high-quality protein after cereals. According to available reports, more than 35 species of nematodes belonging to 20 different genera of plant parasitic or fungal nematodes including Aphelenchoides, Basiria, Boleodorus, Criconemoides, Helicotylenchus, Hemicriconemoides, Heterodera, Hoplolaimus, Malenchus, Meloidogyne, Merlinius, Paratylenchus, Pratylenchoides, Pratylenchus, Rotylenchulus, Trophorus, Tylenchorhynchus, Tylenchus, Xiphinema and Zygotylenchus are reported from the legume fields worldwide. Kermanshah province with a cultivated area of 135060 hectares is the second legume producer in Iran. Plant parasitic nematodes associated with legumes have been identified in some provinces of Iran including Markazi (Khomein county), Lorestan and North Khorasan. Despite the fact that the province has been cultivated in such large area and the amount of legume production has been high in the country, so far no comprehensive study has been done on the identification of plant parasitic nematodes in Kermanshah province. In a few surveys, only three species of plant parasitic nematodes namely Pratylenchus thornei, Pratylenchoides ritteri and Paratylenchus elachistus have been recovered from chickpea fields in this province. Therefore, the aim of this research was to identify and determine the dominant species of important plant parasitic nematodes in the legume fields and determine their distribution in Kermanshah province. In order to identify and determine distribution of the most common plant parasitic nematodes, 173 root and soil samples were collected from legume fields (chickpea, lentil and faba bean) in several localities of Kermanshah province, during years 2016-2017. After extraction, fixation and transferring to anhydrous glycerol, the nematodes were mounted on microscopic slides and studied by using a light microscope, equipped with digital camera. Finally, they were identified using available identification keys. Based on morphometric and morphological characteristics, in this study, 19 species of the infraorder Tylenchomorpha viz. Aphelenchoides graminis, A. obtusus, Aphelenchus avenae, Ditylenchus adasi, D. equalis, D. medicaginis, D. myceliophagus, D. parvus, Filenchus vulgaris, Helicotylenchus scoticus, Merlinius brevidens, Nagelus obscurus, Neopsilenchus magnidens, Pratylenchus thornei, Pratylenchoides ritteri, Scutylenchus rugosus, S. tartuensis, Trophorus ussuriensis and Tylenchorhynchus parvus were identified. The species F. vulgaris, D. medicaginis, P. ritteri, H. scoticus, M. brevidens and T. parvus were the most common species in the legume fields of Kermanshah province with 33.8, 29.4, 27.9, 26.5, 13.2 and 13.2 percent frequency rates, respectively. Among 12 cities under legumes cultivation in the province, Kermanshah with 16 species, Ravansar and Gilan gharb each with nine species, Eslam Abad and Kerend Gharb each with seven species, had highest number of the nematode species. In chickpea fields, F. vulgaris, P. ritteri, H. scoticus and D. medicaginis were the most prevalent species, in lentil fields D. medicaginis, H. scoticus, T. parvus, F. vulgaris and S. tartuensis had higher frequency rates, and in faba bean fields D. medicaginis, M. brevidens and A. avenae were highly distributed species. The species Aphelenchoides obtusus, which has not been previously described in Iran, is described in full, and the males of A. obtusus is reported for the first time from Iran. Also A. graminis, D. medicaginis and P. ritteri which are more common or have morphological or morphometric diversity were described briefly. Seven species namely Aphelenchoides graminis, A. obtusus, Ditylenchus equalis, Nagelus obscurus, Scutylenchus tartuensis, Trophurus usuriensis and Tylenchorhynchus parvus are reported for the first time from legume fields in Iran. These seven species with together six other species namely D. adasi, D. parvus, Helicotylenchus scoticus, Merlinius brevidens, S. rugosus and Neopsilenchus magnidens are reported for the first time from Kermanshah province. In the present paper, description of four species with together their morphometric data and illustrations (line drawings or photomicrographs) are provided. Also discussions were made on the diagnosis and relationships of these four species either with other populations or closely related species. Among the 19 identified species, it seems that Pratylenchoides ritteri (with potential damaging effects on legumes), and Ditylenchus medicaginis and Helicotylenchus scoticus (with high frequency and distribution in the studied regions) should be considered as important species for conducting further supplemental surveys in Kermanshah province. A very damaging species of nematodes to legumes, Pratylenchus thornei, was found only in 4.4 % of the studied fields, and the other important group of nematodes, root-knot nematodes (Meloidogyne spp.) were not recovered from the legume fields of Kermanshah province.