2018

Plant Disease

Rocznik: 2018 | Tom: 102 | Numer: 1

artykuł naukowy

angielski

EN Meloidogyne incognita is a serious pest of several economically important plants in tropical and subtropical regions. One such plant, tomato (Solanum lycopersicum L.), is one of the most widely grown vegetables on irrigated land in Cape Verde. In June 2015, tomato plants (cv. Savana) with symptoms of stunting, leaf wilting, and poor fruiting, were recorded in a field in Achada Colaço, Santiago Island (15°06′35.3″N, 23°31′31.9″W). Roots of these plants were galled, indicating the occurrence of root-knot nematodes. Detected nematodes were isolated and dissected from roots using standard procedures. Morphological and genetic studies revealed the presence of M. incognita. Female (n = 47) perineal patterns showed a high and squared dorsal arch composed of smooth to wavy striae; distinct lateral lines were absent. Stylet had cone curved dorsally, knobs broadly elongated and set off from the shaft. Males’ heads possessed a high and wide head cap with centrally concave labial disc. The measurements of males (n = 5) included: body length = 1,838 (1,605 to 2,016) µm, a = 51.9 (42.9 to 60.2), c = 139.1 (108.0 to 155.1), stylet = 23.1 (23.0 to 23.5) µm, dorsal esophageal orifice = 2.9 (2.4 to 3.6) µm, c′ = 0.6 (0.5 to 0.8), spicules = 32.8 (31.0 to 36.0) µm. Measurements of J2s (n = 26) included: body length = 349.2 (315.5 to 379.2) µm, a = 26.8 (22.2 to 30.9), c = 8.1 (6.6 to 9.6), stylet = 9.8 (9.5 to 10.5) µm, DGO = 2.6 (2.1 to 3.5) µm, tail = 43.5 (38 to 48.9) µm, hyaline tail terminus = 8.6 (6.7 to 11.8) µm. The morphology and morphometry of this species conformed with descriptions and measurements provided by Whitehead (1968). From each morphologically investigated female, corresponding J2s were used for molecular analyses. M. incognita was definitively identified by performing a PCR with species-specific primers Mi2F4/Mi2R1 (Kiewnick et al. 2013). The PCR produced an expected amplification product of 300 bp. In order to confirm the investigated nematode species belongs to the clade involving predominantly the thermophilic Meloidogyne spp. (clade 1, Tandingan De Ley et al. 2002), partial 18S and 28S sequences were also amplified using primer combinations as proposed by Holterman et al. (2006). The obtained PCR fragments were sequenced and deposited in GenBank (18S: KU578066; 28S; KU578062–65). The 18S and 28S showed 99 and 96% identity, respectively, to the available GenBank M. incognita sequences. The pathogenicity test was conducted in glasshouse conditions. Ten 5-week-old tomato plants were maintained in 1.5 dm3 pots and subsequently each plant was inoculated with 100 J2 specimens. Three uninoculated plants served as a negative control. After 10 weeks, above ground parts of all inoculated plants showed symptoms similar to those observed in the field. Furthermore, 70% of root system tissue were galled, and mean nematode reproduction factor (final population/initial population) was 5.3. The nematodes were reisolated from plant tissue and identified. No symptoms were observed on control plants. This is the first report of M. incognita parasitizing tomato in Cape Verde. This study should draw the attention of the phytosanitary services in this country.

253

10.1094/pdis-07-17-1020-pdn

https://apsjournals.apsnet.org/doi/10.1094/PDIS-07-17-1020-PDN

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