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First Report of the Cereal Cyst Nematode Heterodera latipons on Wheat in Morocco

From May to June 2011, during a survey of the wheat-growing areas in Meknes in the Saïs Region of Morocco, several cyst nematode populations were detected. Sampling was performed 1 month before wheat (Triticum durum) harvest, in fields showing patches of stunted plants. Plants were growing poorly, had chlorotic lower leaves, and a reduced numbers of ears. Root systems were short and had a bushy appearance because of increased secondary root production. No cysts were visible on the roots, but were found in the soil. Cysts were collected from soil on 200-μm sieves by the modified Cobb decanting and sieving method (1) and identified by morphology and internal transcribed spacer (ITS)-rDNA sequencing. All isolates were identified as Heterodera avenae except the isolate from Aïn Jemâa. From the latter, key morphological features from cysts and second-stage juveniles (J2) were determined. The cysts (n = 10) had the following characteristics: bifenestrate vulval cone, body length without neck 590 μm (551 to 632 μm), body width 393 μm (310 to 490 μm), neck length 75 μm (65 to 90 μm), fenestra length 64 μm (60 to 72 μm) and width 21 μm (18 to 25 μm), underbridge length 96 μm (85 to 115 μm), vulval slit length 8 μm (7 to 9 μm), vulva bridge width 27 μm (24 to 33 μm), and bullae absent. The J2s (n = 10) had the following characteristics: body length 445 μm (412 to 472 μm), body width 19 μm (19 to 21 μm), stylet length 24 μm (23 to 25 μm), four lateral lines, tail length 50 μm (46 to 54 μm), and hyaline terminal tail 28 μm (24 to 31 μm). Values of the morphological characters were within the range of H. latipons reported by Handoo (3). The bifenestrate cysts with a strong underbridge and no bullae and J2 with a tail length greater than 40 μm, a stylet longer than 15 μm, and four incisures in the lateral field were typical for H. latipons. To confirm the identification, molecular observations were made. DNA was extracted from three juveniles from three different cysts separately (4). The ITS-rDNA region was amplified using the primers 5′-CGT AAC AAG GTA GCT GTA G-3′ and 5′-TCC TCC GCT AAA TGA TAT G-3′ as described by Ferris et al. (2). This resulted in a 1,040-bp DNA fragment. The PCR-products were purified and sequenced (Macrogen, Inc., Seoul, Korea). All sequences obtained (GenBank Accession Nos. per cyst: JQ319035, JQ319036, and JQ319037) were compared with sequences available from the GenBank database (www.ncbi.nlm.nih.gov), including several species of Heterodera. This comparison revealed a sequence similarity of 97 to 99% with H. latipons and 89% or lower with any other species of Heterodera. Morphological and molecular identification demonstrated that the population of cyst nematodes from a wheat field in Aïn Jemâa, Morocco was H. latipons. In the patches with poor growing plants, 65 cysts per 100 cm³ soil were found. To our knowledge, this detection represents a new record of H. latipons. Since the nematode can cause considerable damage to wheat, one of the main cereals produced in Morocco, care should be taken to prevent the spread to other regions.

References: (1) K. R. Barker. Page 19 in: An Advanced Treatise on Meloidogyne. Vol II. Methodology. C. C. Carter and J. N. Sasser, eds. North Carolina State University Graphics, Raleigh, 1985. (2) V. R. Ferris et al. Fundam. Appl. Nematol. 16:177, 1993. (3) Z. A. Handoo. J. Nematol. 34:250, 2002. (4) M. Holterman et al. Mol. Biol. Evol. 23:1792, 2006.