Root-knot Nematode Species Research Articles

Host suitability and response of different vegetable genotypes to Meloidogyne incognita race 2 and Meloidogyne javanica in South Africa

The host suitability of 20 locally available genotypes of Capsicum, 10 of Daucus carota, 7 of Beta vulgaris- and 3 of Spinacea oleracea were assessed in separate greenhouse studies for resistance to Meloidogyne incognita race 2 and M. javanica, respectively. Substantial variation existed amongst the vegetable genotypes in the greenhouse screenings with regard to their host status to the respective root-knot nematode species. None of the genotypes of D. carota, B. vulgaris and S. oleracea showed resistance to the nematode species tested. However, resistance to M. incognita race 2 was identified in Capsicum genotype “Tobasco”, which was subsequently verified in a follow-up microplot trial using a range of initial population densities together with a susceptible Capsicum genotype “Paprika”. Reproduction factors of the nematodes were used as the main criterion to evaluate resistance. In the microplot trial, genotype “Tobasco” showed resistance at the lower inoculum levels but not at the higher nematode population levels. The need exists for more frequent and extensive screenings of the various vegetable genotypes in order to provide small-scale farmers with better options for improved and sustainable yields.

Transgenic Nicotiana tabacum cultivar Samsun plants carrying the wild sugar beet Hs1pro1 gene have resistance to root-knot nematodes

Nematodes are the principal animal parasites of plants, causing annual crop losses of more than US$100 billion worldwide. Conventional control measures against nematode infection include toxic nematicide application to soil, crop rotation practices, and classical breeding approaches. However, due to the limitations of each technique, biotechnology presents itself as an effective alternative in nematode control. To date, several resistance genes against nematodes have been cloned. One such gene, Hs1^{pro1}, cloned from wild sugar beet, Beta procumbens, shows resistance to the cyst nematode Heterodera schachtii. Recent studies showed that Hs1^{pro1} has a broad target pathogen range. In this study, we transformed Nicotiana tabacum cultivar Samsun plants with the Hs1^{pro1} gene and assayed transgenic plants for nematode resistance. Our analysis suggests that compared to wild-type plants, Hs1^{pro1}-carrying transgenic plants are more resistant to 2 different root-knot nematode species, Meloidogyne incognita and Meloidogyne javanica. The results in this study support previous findings of the broad host range of Hs1^{pro1} and are promising in terms of the genetic engineering of economically important susceptible crop plants such as potato and tomato against nematode and secondary damage from other soil-pathogen damage.

Meloidogyne lopezi n. sp. (Nematoda: Meloidogynidae), a new root-knot nematode associated with coffee (Coffea arabica L.) in Costa Rica, its diagnosis and phylogenetic relationship with other coffee-parasitising Meloidogyne species

Coffee (Coffea arabica L. cv. Catuai) seedlings with abundant small root galls caused by an unknown root-knot nematode were found in southern Costa Rica. Morphology, esterase and malate dehydrogenase isozyme phenotypes and DNA markers differentiated this nematode from known Meloidogyne spp. A new species, M. lopezi n. sp., with common name Costa Rican root-knot nematode, is suggested. Meloidogyne lopezi n. sp. is distinguished from other coffee-associated Meloidogyne spp. by size of female lips and stylet, male body length and stylet and second-stage juvenile body and tail morphology. The region of the mitochondrial genome between COII and 16S rRNA showed a unique amplicon size of 1370 bp, and digestions with restriction enzymes HinfI, AluI, DraI and DraIII revealed characteristic PCR-RFLP patterns that differed from the tropical root-knot nematode species M. arabicida, M. incognita, M. izalcoensis, M. javanica and M. paranaensis. Characterisation of the protein-coding map-1 gene and phylogenetic analyses suggested that M. lopezi n. sp. might reproduce by mitotic parthenogenesis. Phylogenies estimated using Bayesian analyses based on the region between the COII and 16S rRNA mitochondrial genes, as well as the 18S and 28S ribosomal nuclear genes, indicated that M. lopezi n. sp. is closely related to other tropical Meloidogyne spp. that infect coffee, especially M. arabicida, M. izalcoensis and M. paranaensis from Central and South America. Isozyme analyses and PCR-RFLP of the COII-16S rRNA mitochondrial gene region enable a clear diagnostic differentiation between these species.

The plant genetic background affects the efficiency of the pepper major nematode resistance genes Me1 and Me3

The plant genetic background influences the efficiency of major resistance genes to root-knot nematodes in pepper and has to be considered in breeding strategies. Root-knot nematodes (RKNs), Meloidogyne spp., are extremely polyphagous plant parasites worldwide. Since the use of most chemical nematicides is being prohibited, genetic resistance is an efficient alternative way to protect crops against these pests. However, nematode populations proved able to breakdown plant resistance, and genetic resources in terms of resistance genes (R-genes) are limited. Sustainable management of these valuable resources is thus a key point of R-gene durability. In pepper, Me1 and Me3 are two dominant major R-genes, currently used in breeding programs to control M. arenaria, M. incognita and M. javanica, the three main RKN species. These two genes differ in the hypersensitive response induced by nematode infection. In this study, they were introgressed in either a susceptible or a partially resistant genetic background, in either homozygous or heterozygous allelic status. Challenging these genotypes with an avirulent M. incognita isolate demonstrated that (1) the efficiency of the R-genes in reducing the reproductive potential of RKNs is strongly affected by the plant genetic background, (2) the allelic status of the R-genes has no effect on nematode reproduction. These results highlight the primary importance of the choice of both the R-gene and the genetic background into which it is introgressed during the selection of new elite cultivars by plant breeders.

Occurrence of Meloidogyne fallax in North America, and Molecular Characterization of M. fallax and M. minor from U.S. Golf Course Greens.

Several species of root-knot nematodes (Meloidogyne spp.) are known to have significant presence on turfgrass in golf course greens, particularly in the western United States. Nematodes isolated from a golf course in King County, WA were identified as Meloidogyne minor based on analysis of the large ribosomal subunit (LSU 28S D2-D3 expansion segment), the internal transcribed spacers 1 and 2 (ITS rDNA), the intergenic spacer region 2 (IGS2), and the nuclear protein-coding gene Hsp90. Sequence-characterized amplified region (SCAR) primers that were originally designed to be specific for M. fallax were found to cross-react with M. minor. A population from California was determined to be M. fallax based on juvenile tail morphology and analysis of the ribosomal markers and Hsp90, comprising the first report of this species in North America. Using trees based on Hsp90 genomic alignments, the phylogenetic relationships of these populations and known root-knot nematode species were congruent with previous trees based on ribosomal genes. Resolution of M. fallax and M. chitwoodi using Hsp90 was equivalent to species separation obtained with 28S or 18S rDNA alignments. The strengths and weaknesses of ribosomal and Hsp90 markers, and the use of SCAR polymerase chain reaction as diagnostic tools are discussed.

Bitlis ili patates üretim alanlarında Kök-ur nematodu (Meloidogyne chitwoodi Golden, O'Bannon, Santo et Finley, 1980)'nun saptanması

The root knot nematode (Meloidogyne chitwoodi Golden, O’Bannon, Santo et Finley, 1980) is an important pest of potatoes throughout the world. It is in international quarantine list of many countries. This species was first reported in Nigde and Nevsehir in 2009 Turkey. The objective of the study was to identify the species of root-knot nematodes collected from potato fields in the province of Bitlis where potatoes are grown extensively in 2010. 16 potato tubers were found infected with the root knot nematode. Egg masses and females of root knot nematodes were obtained using binocular stereo microscope from the infected tubers. For the morphological identification of individuals, female vulva and second term juveniles were prepared. At the same time DNA was extracted from egg masses of nematodes and SCAR primers (JMV1, JMV2 and JMVhapla) were used in PCR. Specific SCAR fragment were obtained from the extracted DNA. The multiplex PCR reaction produced the 540 bp fragment for M. chitwoodi. Both the morphological and molecular methods showed that the samples were M. chitwoodi. This study was the first to show the existence of the species in Eastern Anatolian region. The species attacks potato tubers and make them unmarketable due to deformation, lowers the quality of potato chips and french fries for the processing industry.

Diversity and Evolution of Root-Knot Nematodes, Genus Meloidogyne: New Insights from the Genomic Era

Root-knot nematodes (RKNs) (Meloidogyne spp.) are obligate endoparasites of major worldwide economic importance. They exhibit a wide continuum of variation in their reproductive strategies, ranging from amphimixis to obligatory mitotic parthenogenesis. Molecular phylogenetic studies have highlighted divergence between mitotic and meiotic parthenogenetic RKN species and probable interspecific hybridization as critical steps in their speciation and diversification process. The recent completion of the genomes of two RKNs, Meloidogyne hapla and Meloidogyne incognita, that exhibit striking differences in their mode of reproduction (with and without sex, respectively), their geographic distribution, and their host range has opened the way for deciphering the evolutionary significance of (a)sexual reproduction in these parasites. Accumulating evidence suggests that whole-genome duplication (in M. incognita) and horizontal gene transfers (HGTs) represent major forces that have shaped the genome of current RKN species and may account for the extreme adaptive capacities and parasitic success of these nematodes.

시판 토마토품종의 고구마 뿌리혹선충과 땅콩 뿌리혹선충에 대한 저항성

국내에서 시판되고 있는 토마토 36품종을 이용하여 국내 시설재배지에서 가장 많이 분포하고 있는 두 종의 뿌리혹선충, Meloidogyne arenaria와 M. incognita에 대한 저항성을 검정하였다. 방울토마토 중에서는 '텐텐', '캐딜락', '큐티', '스위트', '뽀또', '리코핀-9' 등 6품종, 완숙토마토 중에서 '러브리240', '도테랑다이아', '큐피랑', '도테랑마스터', '슈퍼도태랑', '도태랑시즌', '마이로꾸', '호용' 등 8품종, 대목은 '스페셜', '파이팅', '마그네트' 등 3품종이 두 종류의 뿌리혹선충에 모두 강한 저항성이었다. Root-knot nematodes (Meloidogyne spp.) are among the main pathogens of greenhouse crops worldwide. Plant resistance is currently the method of choice for controlling these pests. To select resistant tomato against two common species of root-knot nematodes, M. incognita and M. arenaria, 36 commercial tomato (Lycopersicon esculentum Mill.) cultivars were screened. Seventeen tomato cultivars were resistant to both root-knot nematodes: six in cherry tomato, 'Tenten', 'Cadillac', 'Cutti', 'Sweet', 'Ppotto', 'Lycopin-9', eight in globe tomato, 'Lovely 240', 'Dotaerang Dia', 'Cupirang', 'Dotaerang Master', 'Super Dotaerang', 'Dotaerang Season', 'Miroku', 'Hoyong', and three in root stock, 'Special', 'Fighting', and 'Magnet'.

Soil Nematode Assemblages in Natural European Peatlands of the Horná Orava Protected Landscape Area, Slovakia

An investigation of the soil nematode communities in four natural European peatlands of the Protected Landscape Area Horna Orava, Slovakia, was conducted to determine the diversity of the associated soil nematode community structures. A total of 112 nematode species belonging to 66 nematode genera were detected. Nineteen species, including a root-knot nematode species Meloidogyne kralli, were recorded in Slovakia for the first time, increasing the number of soil nematodes recorded from 704 to 723. This high diversity was associated with the occurrence of taxa preferring the wet soil conditions such as Ditylenchus intermedius, Epidorylaimus agilis, Metateratocephalus crassidens, Helicotylenchus hydrophilus, Mesorhabditis irregularis, Semitobrilus pellucidus. The number of species and genera did not correlate with the nematode abundance, as the highest number of species and genera where not found in sites with the highest number of nematodes. Feeding type composition was similar at all of the investigated peatlands and bacteriovores were the dominant trophic group (50 %) with a preponderance of Rhabditis nematodes. The ecological indices (MI, PPI, ∑MI, MI2-5 and PPI/MI ratio) indicated that the native ecosystems studied were relatively mature and stable, with a B/F ratio indicating a prevalence of bacterial decomposition pathways corresponding to high values of the NCR index

Infestation assessment of root-knot nematodes (Meloidogyne spp.) associated with cucumber in the Pothowar region of Pakistan

Studies to estimate root-knot nematode infestations on cucumber were conducted during mid- to late-season at 378 randomly selected sites in 126 villages of the four districts across the Pothowar zone of the country. The overall mean infestation of root-knot nematodes in the region was found to be 15.66%. The studies revealed variations in the incidence and severity of root-knot nematodes in the four districts. The incidence of root-knot nematodes was the highest in Rawalpindi district (21.86%), followed by 13.89% in Attock. Of the four districts, the minimum incidence of 10.97% was recorded in Jhelum district. The maximum mean severity (3.79), measured in terms of the galling index, was found in Rawalpindi district, while the minimum (1.86) was observed in Jhelum district. The mean severities of root-knot nematodes in the districts of Attock and Chakwal were 2.66 and 2.19 respectively. Variations in incidence and severity were also observed among subdivisions of the districts. Of all the associated species of root-knot nematodes, Meloidogyne incognita constituted 78.53%, Meloidogyne javanica 19.03%, Meloidogyne arenaria 1.82% and Meloidogyne hapla 0.62%. M. incognita and M. javanica were recorded in all of the districts, with M. incognita predominating. M. incognita as a pure population was recorded in 29.63% of the villages, while the other three species were found as mixtures. The most common mixed population was M. incognita and M. javanica, observed in 70.37% of villages in the region. M. arenaria and M. hapla were not found together in any of the population mixtures. The results indicate that cucumber is severely attacked by root-knot nematodes, warranting adoption of strict control measures for its management.

Survey of Root-Knot Nematodes Infecting Vegetables in Northern Nigeria

Systematic surveys of root-knot nematodes were conducted in three states (Jos, Kaduna and Katsina) of Northern Nigeria. Infected root samples of vegetables were collected in polythene bags and brought to the laboratory. Root galls were dissected for mature females and perineal patterns were prepared from each sample. Species of root-knot nematodes were identified on the basis of perineal patterns. Two species Meloidogyne incognita and M. javanica were found to be associated with vegetables crops. M. incognita was present on all the vegetables, while M. javanica was present on few vegetables. Frequency of M. incognita was greater than M. javanica. Overall, incidence of disease was found 49.3% and intensity (gall index/egg mass index) was ranged from 2–4/0–4 with variation on different vegetables.

Wystąpienie guzaka północnego Meloidogyne hapla Chitwood, 1949 (Nematoda: Meloidogynidae) w sadzeniakach na terytorium Polski

During official controls of seed potatoes performed by the State Plant Health and Seed Inspection Service in 2011–2012, the presence of the northern root-knot nematode (Meloidogyne hapla Chitwood, 1949) was revealed in 21 tuber samples originating from the area of Lubelskie Voivodeship in Poland. In 2011 the level of infestation was 2.61% (11 from among 422 tested samples were infested) and in 2012 – 2.81% (the nematodes were found in 10 samples from among 356 tested). The results of the morphological and morphometric analyses of females and J2 juveniles isolated from all 21 positive samples were confirmed by results of conducted molecular tests (PCR-ITS – Polymerase Chain Reaction-Internal Transcribed Spacer, PCR-SCAR – Polymerase Chain Reaction-Sequence Characterized Amplified Regions and PCR-RFLP – Polymerase Chain Reaction-Restriction Fragment Length Polymorphism) which simultaneously excluded presence of quarantine root-knot nematode species Meloidogyne chitwoodi (Golden et al. 1980) and M. fallax (Karssen 1996). Podczas urzędowych kontroli sadzeniaków ziemniaka prowadzonych przez Państwową Inspekcję Ochrony Roślin i Nasiennictwa w latach 2011–2012 stwierdzono obecność guzaka północnego (Meloidogyne hapla Chitwood, 1949) w 21 próbach bulw pochodzących z terenu województwa lubelskiego. W roku 2011 stopień porażenia wynosił 2,61% (porażonych było 11 spośród 422 badanych prób), natomiast w 2012 r. – 2,81% (nicienie stwierdzono w 10 próbach spośród 356 badanych). Wyniki analiz morfologicznych i morfometrycznych samic i osobników młodocianych J2 nicieni wyizolowanych ze wszystkich 21 prób pozytywnych zostały potwierdzone przez wyniki przeprowadzonych testów molekularnych (PCR-ITS – Polymerase Chain Reaction-Internal Transcribed Spacer, PCR-SCAR – Polymerase Chain Reaction-Sequence Characterized Amplified Regions and PCR-RFLP – Polymerase Chain Reaction-Restriction Fragment Length Polymorphism), które jednocześnie wykluczyły przynależność nicieni do kwarantannowych gatunków Meloidogyne chitwoodi (Golden i wsp. 1980) i M. fallax (Karssen 1996).

시판 고추품종에 대한 뿌리혹선충 저항성 검정

국내에서 시판되고 있는 고추 92품종을 이용하여 국내 시설재배지에서 가장 많이 분포하고 있는 두 종의 뿌리혹선충, Meloidogyne arenaria와 M. incognita에 대한 저항성을 검정하였다. M. arenaria에는 시판 고추 품종 모두가 저항성이었으며(난낭수 0-3/plant), M. incognita에는 모두 감수성이었다(난낭수 76-678/plant). M. incognita에는 모두가 감수성이었으나 품종별로 약간의 차이는 있었는데 거목(동부한농)과 신태풍(명산종묘) 2품종은 난낭이 포기당 100개 이하로 발생되어 불꽃처럼(누넴종묘) 등 29품종의 포기당 난낭수 300개 이상에 비해 상대적으로 적었다. 뿌리혹선충 피해가 심한 시설재배지 중에서, M. arenaria가 감염된 농가에서는 윤작작물로 고추를 심는 것을 적극 추천하고 반면, M. incognita가 감염된 포장에 고추는 윤작작물로 적절하지 않다. Ninety two pepper (Capsicum annuum L.) cultivars were screened for resistance to two common species of root-knot nematodes, Meloidogyne incognita and M. arenaria. All 92 pepper cultivars were resistant to M. arenaria (0-3 eggmass/plant) but were susceptible to M. incognita (76-678 eggmass/plant). Susceptibility to M. incognita were slightly differed; 'Geomok' and 'Shintaepung' had relatively less eggmass (<100 eggmass/plant) when compared to those 29 very susceptible culivars such as 'Bulggotcheoreum' (>300 eggmass/plant). Therefore, pepper is highly recommended as a high-valued rotation crop to only those greenhouses infested with M. arenaria, but should restrict for M. incognita.

Biometrical, biological, biochemical and molecular characteristics of Meloidogyne incognita isolates and related species

Meloidogyne incognita is one of the most polyphagous species of root-knot nematodes occurring in Brazil and worldwide. Eight M. incognita isolates were studied, representing two enzymatic phenotypes (esterase and malate desydrogenase: I1/N1, I2/N1) and four cryptic Meloidogyne sp.1 (S2/N1) isolates, representing one cytological type (3n = 40–46). Three M. hispanica isolates (Hi3/N1, 2n = 32–36) and two of an atypical Meloidogyne sp.2 (S2a/N3, 3n = 40–44) were included in this study for comparison. All isolates were tested with three M. incognita-specific molecular markers. The primer pairs B06F/R, miF/R and incK14F/R amplified three species-specific fragments of 1,200 bp, 955 bp and 399 bp, respectively for M. incognita and Meloidogyne sp.1 isolates. No amplification occurred in the M. hispanica and Meloidogyne sp.2 isolates, except with primers miF/R (1,650 bp). The genetic variability of the Meloidogyne spp. isolates was evaluated, using RAPD and ISSR markers. The phylogenetic analyses revealed two strongly supported monophyletic clades: clade I, consisting of M. hispanica and the atypical Meloidogyne sp.2 isolates, and clade II, clustering together all M. incognita and the Meloidogyne sp.1 isolates. Considering the biometrical, cytological and molecular approaches, it was possible to conclude that the isolates with three enzymatic phenotypes (I1/N1, I2/N1 and S2/N1) presented the characteristics described for M. incognita. Some correlations were detected between the isozymatic phenotypes and the tree topology (S2a/N3, Hi3/N1, I1/N1, S2/N1), but no strict correlation could be observed for the phenotype I2/N1 and one isolate of S2/N1. Morphologically, the Msp.2 isolates differ from M. incognita and M. hispanica by the female stylet features presenting straight cone tip and round pear shaped knobs, posteriorly sloping. The results of this study suggested that the Msp.2 isolates with phenotypes S2aN3 belong to a new or an unidentified species closely related to M. hispanica.

The map-1 Gene Family in Root-Knot Nematodes, Meloidogyne spp.: A Set of Taxonomically Restricted Genes Specific to Clonal Species

Taxonomically restricted genes (TRGs), i.e., genes that are restricted to a limited subset of phylogenetically related organisms, may be important in adaptation. In parasitic organisms, TRG-encoded proteins are possible determinants of the specificity of host-parasite interactions. In the root-knot nematode (RKN) Meloidogyne incognita, the map-1 gene family encodes expansin-like proteins that are secreted into plant tissues during parasitism, thought to act as effectors to promote successful root infection. MAP-1 proteins exhibit a modular architecture, with variable number and arrangement of 58 and 13-aa domains in their central part. Here, we address the evolutionary origins of this gene family using a combination of bioinformatics and molecular biology approaches. Map-1 genes were solely identified in one single member of the phylum Nematoda, i.e., the genus Meloidogyne, and not detected in any other nematode, thus indicating that the map-1 gene family is indeed a TRG family. A phylogenetic analysis of the distribution of map-1 genes in RKNs further showed that these genes are specifically present in species that reproduce by mitotic parthenogenesis, with the exception of M. floridensis, and could not be detected in RKNs reproducing by either meiotic parthenogenesis or amphimixis. These results highlight the divergence between mitotic and meiotic RKN species as a critical transition in the evolutionary history of these parasites. Analysis of the sequence conservation and organization of repeated domains in map-1 genes suggests that gene duplication(s) together with domain loss/duplication have contributed to the evolution of the map-1 family, and that some strong selection mechanism may be acting upon these genes to maintain their functional role(s) in the specificity of the plant-RKN interactions.

Plant-parasitic nematodes and yellowing of leaves associated with black pepper plants in Vietnam

Thirty-five nematode species belonging to 19 genera were extracted from 432 soil and root samples collected in 19 districts in six provinces in the North Central Coast, Central Highlands and Phu Quoc Island. Based on our study, the predominant nematode species associated with black pepper plants in Vietnam is Meloidogyne incognita: almost every soil and root sample examined during our study was infected with this root-knot nematode species. No difference in frequency of occurrence of M. incognita among the three agro-ecological regions surveyed was observed. However, the root population density of M. incognita in black pepper plants was on average about five times higher in the North Central Coast and Central Highlands than in Phu Quoc Island. Large differences in root population density of M. incognita on black pepper plants were observed in different districts within the same agro-ecological region. Black pepper roots infected with M. incognita showed the same type of galls as described in the literature. The percentage of root galling averaged about 40% in all the three agro-ecological regions. The percentage of black pepper plants with yellow leaves was on average about 20–25% in the North Central Coast and Central Highlands, which was somewhat higher compared to Phu Quoc Island (16.9%). Large differences in percentage of black pepper plants with yellow leaves were observed in different districts within the same agro-ecological region. The same type of yellow leaves as described in the literature for black pepper plants infected with Meloidogyne species was observed in our study. In general, a positive relationship between the soil and root population densities of M. incognita on black pepper plants and percentage of plants with yellow leaves was observed. However, in one district (Quang Tri) a relatively low nematode population density was associated with a high percentage of plants with yellow leaves. Five nematode species were recorded for the first time on black pepper plants in Vietnam. Our study reconfirms previous reports that Radopholus similis does not occur in Vietnam.

Identification of root-knot nematode species occurring on tomatoes in Kenya: use of isozyme phenotypes and PCR-RFLP

Root-knot nematodes (RKN) are serious pests of tomato production in Kenya. Accurate identification of the plant parasitic nematodes is important for their effective management. A study conducted to assess their prevalence and identify RKN occurring on tomatoes in Central Kenya showed infestation of the crop in all the three districts. Of the total sampled plants (N = 900), the RKN infestation level ranged from 28 to 62%. RKN disease severity ranged from 2.5 to 5.3 in all the locations. Meloidogyne incognita,M. javanica and M. arenaria were the only species found infesting tomatoes in these areas. Female nematodes sampled from the symptomatic root system that had root galls characteristic of RKN were analysed by isozyme phenotypes of esterase (EST) and malate dehydrogenase (MDH). EST phenotype was polymorphic and enabled identification of the three different species, while MDH was monomorphic. Polymerase chain reaction-restriction fragment length polymorphism with region between mitochondrial cytochrome oxidase subunit II and large subunit ribosomal RNA (mtDNA COII-LSUrRNA) using HinfI showed that all isolates of M. incognita could be digested into three restriction fragments of about 1300, 400 and 100 bp, except for one species that showed an additional restriction site, giving four fragments of 900, 420, 380 and 100 bp. The 1800 bp PCR product of M. javanica was not digested by HinfI. Meloidogyne arenaria (EST phenotype A1) PCR product was digested into two restriction fragments of about 1700 and 100 bp, while M. arenaria (EST phenotype A2) had two restriction fragments at 1100 and 100 bp.

Indications of variation in host suitability to root-knot nematode populations in commercial tomato varieties

The host suitability of 21 local, commercial tomato varieties were evaluated in concurrent greenhouse trials for resistance to Meloidogyne incognita race 2 and Meloidogyne javanica, respectively. M. incognita race-2-resistance identified in variety ‘Rhapsody’ during the latter study was subsequently verified in a follow-up microplot trial using differential initial population (Pi) densities and as well as in a field trial with four soil amendments. Substantial variation existed among the tomato varieties in the greenhouse screening with regard to resistance to the respective root-knot nematode species. Comparison of the different indicators of resistance used for the two species showed that labelling of specific varieties as resistant should not only be based on one criterium, since it could be insufficient. Strong non-linear relationships were shown in the microplot trial between Pi and Pf in the roots of both tomato varieties but nematode reproduction was poor on the resistant ‘Rhapsody’. Significantly lower Pf in roots and J2 in soil was obtained for ‘Rhapsody’ compared to the susceptible Moneymaker. In the soil-amendment field trial, ‘Rhapsody’ also maintained significantly lower M. incognita numbers compared to ‘Moneymaker’ in all treatments. These results confirm the superior resistance of ‘Rhapsody’ to local M. incognita race-2 populations used in this study. More frequent and extensive screenings of commercial tomato material are recommended in order to provide resource-poor producers with better options for improved and sustainable yields.

Genetic characterization of Meloidogyne incognita isolates from Turkey using sequence-related amplified polymorphism (SRAP)

Southern root knot nematode Meloidogyne incognita is the most widespread-species, causing serious yield losses in protected vegetables fields in the West Mediterranean region of Turkey. The knowledge of genetic variation within M. incognita is required for disease management and improvement of resistant varieties by breeding programs. In the present study, the isolates were classified into different groups based on sequence-related amplified polymorphism (SRAP) fingerprints. To our knowledge, this is the first study carried out on the characterization of M. incognita isolates using SRAP. The schematic diagram by tested primers to differentiate of M. incognita isolates was formed in discrimination of nematodes as an effective molecular tool since it is cost effective and easiness. Data presents a genetic variation on root-knot nematode species. These selected SRAP markers can be used to follow genetic structure and differentiation on M. incognita isolates in a certain region.

A field study on the host status of different crops for Meloidogyne minor and its damage potential on potatoes

For several years, a new species of root-knot nematode, Meloidogyne minor, has been reported from parts of The Netherlands, Belgium, UK and Ireland. So far, this species causes most problems on golf courses but has also been reported from a potato field in Zeijerveld (The Netherlands) where it caused strong growth reduction on potato plants, but no damage to potato tubers. As The Netherlands is a potato-producing country, field experiments were set up to evaluate the potential risks this species poses. We tested the host status of some common crops for M. minor under field conditions and, more importantly, also tested its potential to harm potato production in terms of quantity as well as quality. In a 2-year field experiment (2007-2009), the host status of potato (cv. Bartina), rye, annual ryegrass, sugar beet, and maize was tested in the first growing season. Afterwards, these plots were used to evaluate the damage potential of M. minor on two commonly cultivated potato cultivars (cvs Astérix and Markies). In general, only potato seemed to be a good host for this nematode species with a Pf∕Pi-ratio about 1.5. Reproduction was observed mostly on roots but also on tubers, which increases the spread of M. minor by seed potatoes. However, there was no reduction in potato production, neither in yield nor in tuber quality. No significant reproduction could be observed on the other plants (Pf∕Pi values close to zero). From these results one might conclude that this nematode will not become a major threat to European agriculture. However, care has to be taken as within additional glasshouse experiments potato tubers were susceptible for damage caused by M. minor. Thus, further studies on the general biology and ecology of M. minor are needed to make a better risk assessment on this new nematode pest.