First Report of the Cactus Cyst Nematode, Cactodera cacti, on Cactus in Northern China.

During a survey for cyst nematodes from August to September 2011, nearly 15% of cactus (Cereus jamacaru) plants exhibited yellowing and wilting symptoms in greenhouses from Shenyang Botanical Garden, Liaoning Province, China. Cysts (averaging 50 per 100 g of samples) were detected by the sieving-decanting method on the roots and in rhizospheric soil. Second stage juveniles and eggs were isolated directly from cysts. Cysts, juveniles, and eggs were identified by morphology. Cysts (n = 12) were rounded to lemon-shaped with a protruding neck and vulva. The cyst wall had a zig-zag pattern. The vulval cone was circumfenestrate without underbridge and bullae but generally with vulval denticles. The cysts were characterized by body length excluding neck (range = 399.5 to 622.0 μm, mean = 524.9), body width (300.4 to 469.9 μm, 383.4), length to width ratio (1.1 to 1.7, 1.4), neck length (41.0 to 130.9 μm, 61.5) and width (55.0 to 98.7 μm, 76), and circumfenestral diameter length (24.6 to 30.2 μm, 28.4). Measurements of second-stage juveniles (n = 20) included length of body (range = 467.3 to 542.5 μm, mean = 513.8), stylet (23.0 to 25.8 μm, 24.6) with knobs rounded to slightly projecting anteriorly and concave on anterior surface, tail (45.9 to 59.5 μm, 52.2), and hyaline tail terminal (16.3 to 23.2 μm, 19.1). Eggs (n = 20) had heavy punctations on the shell surface. All morphological data and characteristics were consistent with Cactodera cacti (3). Molecular evidence confirmed the identification. DNA from a single cyst was extracted by using the protocol described by Subbotin et al. (2), the rDNA-internal transcribed spacer (ITS) and D2-D3 fragments of the 28S rDNA were amplified with universal primers TW81 (5'-GTTTCCGTAGGTGAACCTGC-3') and AB28 (5'-ATATGCTTAAGTTCAGCGGGT-3'), D2A(5'-ACAAGTACCGTGAGGGAAAGTTG-3') and D3B(5'-TCGGAAGGAACCAGCTACTA-3'), respectively. The ITS PCR product was digested with eight restriction enzymes (AluI, AvaI, Bsh1236I, BsuRI, CfoI, MvaI, PstI, and RsaI) to obtain restriction fragment length polymorphism profiles (4). The ITS and D2D3 sequences were cloned and assayed using an ABI-PRISM 3730 Genetic Analyzer (Applied Sangon, Shanghai, China) and were subjected to a database search using BLAST (National Centre for Biotechnology Information). The 980-bp ITS sequence exhibited 99% similarity with that of a C. cacti isolate from Iran (GenBank Accession No. AF498393.1) and the 787-bp D2D3 sequence exhibited 99% similarity with a C. cacti isolate from Germany (GenBank Accession No. DQ328702.1). Cactus cyst nematode has been mainly reported on ornamental plants of the family Cactaceae grown in greenhouses. Infested plants become reddish brown to yellow in color, wilted, stunted, with reduced flower production and shortening flower period. With high population densities of C. cacti, death of plants may occur (1). To the best of our knowledge, this is the first report of C. cacti in northern China. References: (1) R. P. Esser. Division of Plant Industry, 197:3, 1992. (2) S. A. Subbotin et al. Nematology, 2:153, 2000. (3) S. A. Subbotin et al. Systematics of Cyst Nematodes (Nematoda: Heteroderinae). Volume 8 Part A. Brill, Leiden, the Netherlands, 2010. (4) M. Z. Tanha et al. Nematology, 5:99, 2003.