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The beet cyst nematode (BCN) (Heterodera schachtii), and beet curly top virus-severe (BCTV-Svr) (Curtovirus betae) are two important pathogens of sugar beet fields worldwide. Therefore, the reaction of 14 genotypes was separately assessed, using Jolgeh and Sanetta cultivars as susceptible and resistant controls, respectively, in completely randomized design experiments for BCN and BCTV-Svr. Reactions were based on the cyst and egg counts and symptoms severity index. Experiments were performed in the greenhouse of Tarbiat Modares University, Tehran, Iran, and were repeated twice independently. Based on the results of initial experiments, the S1-960090, S1-940324, S1-960294, and S1-960284 genotypes resistant to the BCN were selected for further investigation. Furthermore, the reaction of the four selected genotypes to BCN, BCTV-Svr, and the combination (mixture) of the two pathogens was evaluated by analyzing their growth, physiological, and biochemical characteristics, and virus accumulation. Resistant genotypes showed higher levels of defense-related enzymes such as catalase, guaiacol peroxidase, and polyphenol oxidase, whereas susceptible genotypes exhibited significant reductions in photosynthesis, greenness, and chlorophyll a, b, and carotenoid content compared to non-inoculated and resistant plants. This is the first study conducted to search for dual-resistance sources against two devastating pathogens that frequently occur in the sugar beet-growing regions of Iran. Based on the results of this experiment, genotypes S1-960090 and S1-940324 were identified as resistant to both pathogens and are recommended for breeding purposes.
 

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Two species of Pratylenchoides recovered from the grasslands in Sabalan region and one species recovered from natural habitats of Tehran are illustrated based on morphological, morphometric and molecular characters. The first species, P. crenicauda is characterized mainly by its lip region with three-four annuli, lateral field with four incisures areolated throughout the length and having rod shaped sperm cells. It is further distinguished by the positions of the pharyngeal glands nuclei. P. magnicauda was found in Tehran and its morphological characters and phylogenetic relations with other species are discussed. The Iranian populations of P. variabilis are characterized by three lip annuli, stylet 20-22 µm long, four and six incisures in lateral field, rounded sperm and one of the pharyngeal glands nuclei located posterior to pharyngo-intestinal valve. The phylogenetic tree inferred from the partial sequences of D2-D3 segment of 28S rDNA revealed the three sequenced species are separate from each other and form a clade with high (1.00) Bayesian posterior probability (BPP) in Bayesian inference (BI) and 86% bootstrap support value (BS) in maximum likelihood (ML) analyses with other two sequenced species of the genus for this genomic region.

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Ditylenchus azarbaijanensis n. sp. is described and illustrated based upon morphological and morphometric characters. The new species is mainly characterized by having six lines in the lateral field, rudimentary postuterine sac (PUS) ca. 0.2 vulval body width long, anteriorly inclined vagina and conical female tail with a pointed terminus, 48-70 µm long (c = 15-21, cʹ = 2.4-3.7). It is further characterized by having fine stylet 7.5-10.0 µm long with small knobs, small pyriform pharyngeal bulb offset from the intestine, and males with 26.5-31.0 µm long spicules. By having a rudimentary PUS, the new species is morphologically compared with three closely related species, namely Ditylenchus apus, D. deiridus and D. khani. Moreover, morphological differences of the new species with eight similar species of the genus, namely D. arachis, D. convallarie, D. dauniae, D. medicaginis, D. silvaticus, D. tenuidens, D. valveus, and D. virtudesae are presented. The status of the rudimentary or absent PUS of D. deiridus and the new species is also discussed.

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Three species belonging to three genera of the family Tylenchidae, namely, Cephalenchus leptus, Eutylenchus excretorius, and Lelenchus leptosoma were discovered as first reports for Iran's nematode fauna. They were characterized by morphological, morphometric and molecular phylogenetic studies. The two latter genera are new for Iran. Iranian population of Cephalenchus leptus is characterized by lateral field with six lines in females, stylet length of 16-20 µm and tail length of 153-290 µm with pointed tip. The recovered population of Eutylenchus excretorius is characterized by 848-1,038 µm long females’ body, stylet length of 20.0-21.5 µm, having advulval flaps and absence of male. The Iranian population of Lelenchus leptosoma is defined by its narrow slender body, flattened lip region, sinuous amphidial opening and absence of lateral field. The phylogenetic relationships of the three recovered species were studied using the partial sequences of 28S rDNA D2/D3 segment and revealed the genera Cephalenchus and Eutylenchus forming a monophyletic clade, while, Lelenchus was placed inside the clade of currently sequenced species of Malenchus in Bayesian tree.