xiphinema

Longidoridae is a family of plant-parasitic nematodes belonging to the order Dorylaimida, that cause damage to most agricultural crops especially fruit trees by direct damage and also transmitting some plant pathogenic viruses. Considering the lack of prior research studies on this topic in the fruit orchards of Rafsanjan region, identifying and monitoring their population is important.

In a study that was conducted to identify plant-parasitic nematodes of horticultural products in Rafsanjan city, some soil samples were collected from the rhizosphere of various fruit trees, in 2020. The nematodes were extracted from the soil samples using two methods, centrifugal flotation-sieving and tray technique, fixed and transferred to the anhydrous glycerin. After preparing permanent slides, the nematodes were studied using a light microscopy. The nematode species were identified based upon morphological and morphometric data using relevant valid references.

In this study, three species of Dorylaimida order belonging to the Longidoridae family including the two genera: Longidorus (L. africanus) and Xiphinema (X. vuittenezi and X. index) were obtained from the rhizosphere. Also, in order to confirm the traditional identification of X. vuittenezi, this species was molecularly studied using D2-D3 extension fragment of LSU rDNA. The obtained sequence of the species was 100% identical to the sequences of the other populations of X. vuittenezi in the GenBank.

This study shows that regional nematode population monitoring needs more attention.

Plant parasitic nematodes are distributed in all agricultural soils and attack nearly all crops, damage and cause disease. In studying biology, management and other aspects of plant parasitic nematodes, their precise identification should be carried out up to species level. Kahaq region, Maragheh, East Azarbaijan province, is a natural ecosystem and under cultivation of agricultural crops as well. Fruit trees such as walnut, almond, apple, quince and crops like wheat, barley, chickpea and fruitless trees as spruce and willow are grown in the region. Due to the paucity of previous studies the current study set out for the identification of nematode fauna in soils of this region.
In order to identify plant parasitic nematodes, 70 soil samples were collected from the rhizosphere of different vegetations in Kahaq region, Maragheh, East Azarbaijan province during 2014 and 2015. The samples were transferred to laboratory and nematodes extracted by centrifugal flotation technique were transferred to anhydrose glycerin according to the modified De Grisse (1969) method. Permanent slides were prepared from the extracted nematodes and some cross sections were also made from different parts of some nematode bodies if needed. The nematodes were studied under light microscope. The morphometric data were taken using a drawing tube attached to the microscope. Drawings were done using Corel DRAW X7 software. Pictures were taken using DP50 digital camera attached to the microscope.
The results of this study led to the identification of Amplimerlinius globigerus, Criconemoides informis, Mesocriconema antipolitanum, Ogma cobbi, Pratylenchus neglectus, P. thornei, Pratylenchoides erzurumensis, Xiphinema index, X. pyrenaicum, Xiphinema sp. and Zygotylenchus guevarai.
Morphological and morphometric characteristics of two plant parasitic nematodes out of 11 identified species were described in details. Ogma cobbi shows much similarity with O. nemorosus, but the latter differs from the former species because of fewer number of body annuli (45-54 vs 58-61), shape of scales in mid-body (triangular, with rounded tip vs rather acute), empty spermatheca vs full of sperm, occasional presence of smaller scales between rows, especially on posterior half of body (vs not). Xiphinema sp. becomes more similar to X. brevisicum, but is separated from it by lower a value (53-67 vs 72.5-98), cˊ value (1.5-2 vs 2.2-3.1), greater odontostyle length (77-86 vs 57-65 μm) and shorter tail length (27-31 vs 35-47 μm). It also differs from other species of the genus and, hence, considered as an undescribed species.