Meloidogyne luci n. sp. (Nematoda: Meloidogynidae), a root-knot nematode parasitising different crops in Brazil, Chile and Iran

A new root-knot nematode parasitising vegetables, flowers and fruits in Brazil, Iran and Chile, is described as Meloidogyne luci n. sp. The female has an oval to squarish perineal pattern with a low to moderately high dorsal arc and without shoulders, similar to M. ethiopica. The female stylet is robust and 15-16 μm long; the distance from the dorsal pharyngeal gland orifice to the stylet base (DGO) is 3-4 μm. Males have a high, rounded head cap continuous with the body contour. The labial disc is fused with the medial lips to form an elongated lip structure. The head region is not marked by incomplete annulations. Male stylet robust, 20.8-23.0 μm long with rounded knobs; the DGO is 2.5-4.5 μm. The stylet of second-stage juveniles (J2) is 12.0-13.5 μm long and the DGO to the stylet base is 2.3-3.3 μm. The J2 tail is conoid with finely rounded terminus and is 40.0-48.5 μm long. Biochemically, the esterase phenotype L3 (: 1.05, 1.10, 1.25) is unique and is the most useful character to differentiate M. luci n. sp. from all other Meloidogyne species. Reproduction is by mitotic parthenogenesis (2n = 42-46 chromosomes). In a differential host test, the population from Lavandula spica, Caxias do Sul, RS State, Brazil, reproduced on tomato cv. Rutgers, tobacco cv. NC95 and pepper cv. California Wonder. No reproduction occurred on watermelon cv. Charleston Gray, cotton cv. Deltapine 61 or peanut cv. Florunner. In Neighbour-Joining analyses of ITS and D2-D3 rRNA sequences, populations of M. luci n. sp. from Brazil, Chile and Iran clustered together and were clearly separated from other Meloidogyne spp., thus confirming that all three populations are very similar and conspecific.

First Report of the Root-Knot Nematode Meloidogyne arenaria Infecting Noni in China

Noni (Morinda citrifolia) is an important medicinal plant and its fruit and root are of high value. In recent years, noni has been cultivated widely on Hainan Island, China. A survey of eight commercial noni fields in four counties found that most fields had plants with symptoms consistent with damage caused by root-knot nematodes. Above-ground symptoms included reduced vigor, plant stunting, and chlorosis. Affected roots were galled, swollen, cracked, and rotten. Fruit loss associated with diseased plants was quantified as 85%. In each field, three samples were taken consisting of 15 cm wide × 20 cm deep soil (containing roots). The nematode population was extracted and quantified according to Barker (1). Nematodes were found in all soil and root samples with population densities ranging from 450 to 835 eggs and second-stage juveniles (J2s) per 200 g subsample of soil, and 685 to 985 eggs and J2s per 10 g sub-sample of fresh roots. Three single egg masses were respectively hand-picked from one sample of diseased noni roots and inoculated onto tomato plants grown with sterilized soil at 20 to 28°C in the greenhouse. After 8 weeks, nematodes were extracted from the roots of tomato plants and identified by morphology, enzyme analysis, and molecular characterization. Morphology of the female perineal patterns showed a low dorsal arch with large lateral lines separating the striae of the dorsal and ventral sectors, leading to the tail terminus; and wavy, coarse striae with forking at lateral lines and short irregular striae near the lateral lines. Enzyme analysis of the esterase phenotype was also typical of the A1 phenotype in M. arenaria. Based on the perineal pattern and esterase phenotype, the Meloidogyne species was identified as M. arenaria (Est A1) (3). Total genomic DNA was extracted from ca. 10 μl of packed second-stage juveniles (J2s) using the method of Cenis (2). The primers C2F3 (5′-GGTCAATGTTCAGAAATTTGTGG-3′) and 1108 (5′-TACCTTTGACCAATCACGCT-3′) (4) was used to amplify the intergenic region between COII and LrRNA genes of the mtDNA and an amplification product (1,700 bp) was obtained, similar to M. hispanica, M. incognita, and M. javanica. Root-knot nematodes (Meloidogyne spp.) have been reported to be cause disease on noni in Hawaii. However, to our knowledge, this is the first report of M. arenaria (Est A1) infecting noni in China. References: (1) K. R. Barker. Pp. 19 in: An Advanced Treatise on Meloidogyne. Vol. II, Methodology. K. R. Barker et al. eds. North Carolina State University Graphics, Raleigh, 1985. (2) J. L. Cenis. Phytopathology 83:76,1993. (3) P. E. Esbenshade and A. C. Triantaphyllou. J. Nematol. 17:6,1990. (4) T. O. Power and T. S. Harris J. Nematol. 25:1,1993.

First Report of the Root-Knot Nematode Meloidogyne arenaria on Cheeseweed Mallow (Malva parviflora) in the United States

During a 2010 field trial for examining alternatives to methyl bromide soil fumigation for the production of field-grown cut flowers, weeds were collected for identification and evaluated for their potential as hosts for plant pathogenic nematodes. In one cut flower field located in Martin County, FL, six cheeseweed mallow (Malva parviflora L.) plants were collected that had root-galling typical of infection by a root-knot nematode (Meloidogyne spp.). Field collected plants were used for species identification of the weed and maintained in the greenhouse for seed production. Several gravid female nematodes were extracted from field collected mallow roots and individually identified as Meloidogyne arenaria based on their esterase phenotype (PhastSystem, GE Healthcare) (1). A single egg mass was then extracted from the field collected mallow roots and inoculated onto a tomato plant (Solanum lycopersicum, ‘Rutgers’) grown in steamed builders sand in the greenhouse. The single egg mass culture was increased for 8 weeks, until galling was sufficient to produce adequate nematode inoculum to complete Koch's postulates on the original mallow host. Ten mallow plants were inoculated with single egg masses originally isolated from mallow and increased on tomato. Ten additional plants were maintained in the greenhouse as uninoculated controls. Inoculated and control mallow plants were grown in the greenhouse for 8 weeks, after which the roots were evaluated for galling, and root-knot nematode J2 were extracted from roots and soil and counted. All inoculated plants produced galled roots and control plants did not. Gravid females were extracted from mallow roots and identified as M. arenaria based on esterase phenotype as previously described. Ten gravid females for each DNA extraction were collected from mallow roots and DNA was isolated with the PowerSoil DNA Isolation Kit (MO BIO Laboratories, Inc., Carlsbad, CA). Identification of M. arenaria was confirmed by using species-specific primers F5′-TCGAGGGCATCTAATAAAGG-3′ and R5′-GGGCTGAATAATCAAAGGAA-3′ (2) and F5′-TCGGCGATAGAGGTAAATGAC-3′ and R5′-TCGGCGATAGACACTACAACT-3′ (4), which produced single amplicon bands of the expected size of 420 and 950 bp, respectively. This weed species has been reported as a host for M. javanica in Algeria and as an experimental host in Egypt (3), but this report, to our knowledge, constitutes the first documentation of Malva parviflora as a natural host of M. arenaria. The importance of weeds as hosts for plant parasitic nematodes cannot be over emphasized. As growers, particularly in Florida and California, continue to lose tools for broad-spectrum pest control, the ability of nematodes to reproduce on uncontrolled weeds will become increasingly important. References: (1) J. A. Brito et al. Nematology 10:757, 2008. (2) K. Dong et al. Nematropica 31:273, 2001. (3) M. Quader et al. Australas. Plant Pathol. 30:357, 2001. (4) C. Zijlstra et al. Nematology 2:847, 2000.

Meloidogyne izalcoensis n. sp. (Nematoda: Meloidogynidae), a root-knot nematode parasitising coffee in El Salvador

A new root-knot nematode parasitising coffee in the region of the Izalco volcano, Sansonate, El Salvador, is described as Meloidogyne izalcoensis n. sp. The suggested common name is El Salvador coffee root-knot nematode. The perineal pattern is characterised by the moderately high to high, squareish to rounded, dorsal arch, striae coarse, smooth to wavy, sometimes zigzaggy, usually without a distinct whorl, and similar to that of M. incognita and M. paranaensis. The female head region set off from body, sometimes annulated, and the labial disc has two prominent elevations or bumps on the ventral side that are slightly raised above the medial lips. The female stylet is robust, 15.0-16.0 μm long and with the DGO at 4.5-6.0 μm posterior to the knobs. Males have a high, round, head cap continuous with the body contour and the labial disc is fused with the medial lips to form an elongated structure. The head region is never marked by incomplete annulations. The stylet is robust, 23.0-26.0 μm long, and has rounded, backwardly sloping, knobs with the DGO located at 4.0-7.0 μm posteriorly. The stylet of second-stage juveniles is 12.0-13.0 μm long and the DGO is located 3.0-4.0 μm posterior to the stylet base; the tail is 45-48 μm long, conoid, with a rounded terminus. Biochemically, the esterase phenotype I4 (= Sa4) (Rm: 0.86, 0.96, 1.24, 1.30) is unique and is the most useful character to differentiate M. izalcoensis n. sp. from all other species.

Characterisation of Meloidogyne spp. (Tylenchida: Meloidogynidae) from coffee plantations in Central America and Brazil

Isozymes (Esterases, MDH, SOD, GOT) and perineal patterns were studied in 29 isolates of Meloidogyne spp. collected on coffee (Coffea arabica) plantations in four Central American countries and on one isolate collected in Brazil. Five species were clearly diagnosed and six new multi-enzyme phenotypes were also revealed corresponding to within-species diversity or possible new species. Meloidogyne exigua was found in Costa Rica, Nicaragua and Honduras, M. arenaria in El Salvador and M. incognita ('M1a' esterase phenotype) in Brazil. Meloidogyne arabicida was found in Costa Rica and has a new esterase phenotype, 'M1F1b'. Nematodes with the 'F1' esterase phenotype were found in Guatemala and their specific status is discussed. Two isolates from El Salvador displayed unknown esterase phenotypes ('M1F1a' and 'Sa4'). One isolate from northern Guatemala was clearly identified as Meloidogyne hapla and another from the same area was related to M. enterolobii or M. mayaguensis. Neither of these latter isolates was able to develop in coffee roots under our growing conditions. The diversity of root-knot nematodes parasitising coffee roots in this region is discussed.