Root-knot nematodes (Meloidogyne spp.) are common parasites attacking turfgrasses in the United States, but the species of these nematodes is typically unresolved unless targeted surveys are performed (3). Using morphometric analysis and an RFLP method (3), an investigation of a golf course green in Florida with a history of infestation by root-knot nematodes was conducted to identify the species present. This ‘Tifdwarf’ bermudagrass (Cynodon dactylon × C. transvaalensis) putting green at the University of Florida Research Unit in Citra, FL, exhibited irregular patches of declining turf. Turf roots in these symptomatic areas had galled root tips with adhering egg masses, characteristic of infection from Meloidogyne spp. Mean populations of 5,149 ± 708 Meloidogyne second stage juveniles per 100 cm3 of soil were extracted from the rhizosphere of these symptomatic plants. Morphological measurements from 20 of these juveniles were slightly less than those published previously for M. marylandi, but were still distinct enough to discriminate them from M. graminis, which commonly infects bermudagrass in Florida (3). Body length averaged 396.1 ± 4.9 (376.7 to 420.0) μm with a mean width of 16.3 ± 0.5 (13.3 to 18.3) μm, stylet lengths were 11.2 ± 0.7 (6.7 to 12.3) μm, tail lengths averaged 54.7 ± 1.9 (47.5 to 65.0) μm with the hyaline region of the tails 9.9 ± 0.7 (8.3 to 14.2) μm. Mature females extracted from symptomatic root tissue lacked a posterior cone-like protuberance of the vulva typical of M. graminis. DNA was extracted from 15 single juveniles using a NaOH digestion method (2). The mitochondrial DNA region was amplified with PCR using the primers C2F3/1108 5′-GGTCAATGTTCAGAAATTTGTGG-3′ and 5′-TACCTTTGACCAATCACGCT-3′ (3). This resulted in a DNA fragment 520 bp in length, which upon digestion with SspI restriction enzyme produced four bands 148, 103, 91, and 67 bp in length, similar to what has been reported for M. marylandi (3). The PCR products were purified with a QIAquick PCR purification kit (QIAGEN, Valencia, CA) and sequenced at the University of Florida, Cancer Research and Genetics Institute. Sequences were compared with those in GenBank by means of BLAST search. The comparison showed a sequence similarity of 98% with M. marylandi (GenBank Accession No. JN241918.1). Although M. marylandi has been reported on bermudagrass in many areas of the United States and other places throughout the world (1,3,4), to our knowledge, this is the first detection of this nematode in Florida. Further studies will be conducted to determine the prevalence, incidence, severity of damage caused by M. marylandi, and determine a possible mode of dispersal on turfgrasses.
References: (1) A. M. Golden. J. Nematol. 21:453, 1989. (2) J. Hübschen et al. Euro. J. Plant Pathol. 110:779, 2004. (3) M. A. McClure et al. Plant Dis. 96:635, 2012. (4) Y. Oka et al. Nematol. 5:727, 2003.