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Sixteen Meloidogyne isolates from tomato fields in California grown with resistant cultivars were multiplied on resistant tomato in a greenhouse. Of these resistance-breaking isolates, one was identified as M. javanica, and all others as M. incognita. The reproduction of the M. javanica isolate and four M. incognita isolates on six resistant tomato cultivars and on susceptible and resistant cultivars of pepper, sweetpotato, green bean, cotton, and cowpea was evaluated and compared to an avirulent M. incognita population in greenhouse pot trials. On resistant tomato cultivars, there were minor but significant differences between the resistance-breaking Meloidogyne isolates and between the different tomato cultivars. Of the other resistant crop cultivars, pepper was resistant to all isolates and green bean to all M. incognita isolates, while cotton and cowpea allowed reproduction of one of the resistance-breaking M. incognita isolates. The resistant sweetpotato cv. Bonita behaved like resistant tomato, allowing reproduction of all five resistance-breaking isolates but not of the avirulent M. incognita. Our results showed that variability exists among resistance-breaking Meloidogyne isolates, and that isolates overcoming resistance in tomato may also be virulent on resistant sweetpotato.

In 2021/2022, galls formed by a nematode, Anguina woodi, were found on the stems, leaves and leaf sheaths of dune grass, Ehrharta villosa var. villosa on Milnerton Beach, Blouberg Beach and Langebaan, Western Cape Province, South Africa. These galls were spongy in texture, deep purple to blackish in colour and non-pedunculate. They were found in clusters, but also as single entities. Larger, harder galls varying from beige to dark brown in colour, apparently caused by insects, were also found on the stems of dune grass at Blouberg Beach and Langebaan Nature Reserve. Some nematode galls were found immediately next to or on top of the insect galls. Those found on top of insect galls seemed to be harder and drier than those found on stems not infected by insect galls. The co-infection of insects and anguinid nematodes has not been reported from the current study areas and was thus included in the present study. Both molecular and morphological studies were conducted on the nematodes and wasps leading to the identification of a host specific, gall-forming nematode from all three localities. The wasps were identified morphologically and molecularly to the family Eurytomidae (Hymenoptera). No insect galls were found on dune grass from Milnerton Beach. The paper includes speculations on a probable association between nematodes and insects. [ABSTRACT FROM AUTHOR]

Root-knot nematodes (RKNs) of the genus Meloidogyne are one of themost damaging genera to cultivated woody plants with a worldwide distribution. The knowledge of the soil and rhizosphere microbiota of almonds infested with Meloidogyne could help to establish new sustainable and efficient management strategies. However, the soil microbiota interaction in deciduous woody plants infected with RKNs is scarcely studied. This research was carried out in six commercial almond groves located in southern Spain and infested with different levels of Meloidogyne spp. within each grove. Several parameters were measured: nematode assemblages, levels and biocontrol agents in Meloidogyne's eggs, levels of specific biocontrol agents in rhizoplane and soil, levels of bacteria and fungi in rhizoplane and soil, fungal and bacterial communities by high-throughput sequencing of internal transcribed spacer (ITS), and 16S rRNA gene in soil and rhizosphere of the susceptible almond hybrid rootstock GF-677 infested with Meloidogyne spp. The studied almond groves showed soil degradation by nematode assemblies and fungi:bacterial ratio. Fungal parasites of Meloidogyne eggs were found in 56.25% of the samples. However, the percentage of parasitized eggs by fungi ranged from1% to 8%. Three fungal species were isolated fromMeloidogyne eggs, specifically Pochonia chlamydosporia, Purpureocillium lilacinum, and Trichoderma asperellum. The diversity and composition of themicrobial communities were more affected by the sample type (soil vs rhizosphere) and by the geographical location of the samples than by the Meloidogyne density, which could be explained by the vigorous hybrid rootstock GF-677 and a possible dilution effect. However, the saprotrophic function in the functional guilds of the fungal ASV was increased in the highly infected roots vs the low infected roots. These results indicate that the presence of biocontrol agents in almond fields and the development of new management strategies could increase their populations to control partially RKN infection levels. [ABSTRACT FROM AUTHOR]

The Mi-1.2 gene confers resistance to a wide range of Meloidogyne species, being the most important resistance factor employed in tomato breeding so far. However, many aspects related to the interaction of Mi-1.2-carrying tomato cultivars and virulent/avirulent Meloidogyne populations have not yet been clarified. Herein, comparative histopathological analyses were carried after inoculation of the homozygous (Mi-1.2/Mi-1.2) tomato rootstock 'Guardião' and the susceptible cultivar 'Santa Clara' (mi-1.2/mi-1.2) with virulent and avirulent populations of M. javanica. In the susceptible control, it was possible to visualize second stage juveniles (J2) of avirulent population and feeding sites from 2 to 30 days after infection (DAI) with females reaching maturity at 24-34 DAI. In the resistant rootstock, the Mi-1.2 gene-mediated resistance was related mainly to early defense responses (pre-infection and hypersensitive reaction), which led to an immunity-like phenotype that completely prevented the reproduction of the avirulent Meloidogyne population. On the other hand, J2s of the virulent M. javanica population were able to penetrate roots much more than the avirulent population, migrated and developed normally, showing intense and similar pattern of penetration from 4 to 34 DAI in the root tissues of both resistant and susceptible tomato genotypes. The total numbers of J2, J3, J4, and females counted in 'Santa Clara' for the virulent population of M. javanica were higher than in 'Guardião'. [ABSTRACT FROM AUTHOR]

The study aimed to evaluate the nematicidal effect of powder extracts of different coloured radish seeds against Meloidogyne incognita on tomato (Gülizar F1, susceptibile to root-knot nematode) under controlled conditions. Extractions were obtained from radish seeds of different colours (white, black, red, yellow) by using ethanol and acetone solvents. The experiment was carried out using 2, 4 and 6 g powder/plant application of the extracts in the pot. The experiment was set up in a random plot design with 5 replication for each radish seed extract and concentration. Radish seed powder was applied one week after nematode inoculation (1000 M. incognita eggs). After 50 days, the number of galls and egg masses on the roots were counted. It was determined that radish colour, extraction solvents and concentrations of extracts differed significantly for their nematicidal effects. The mean number of galls and egg masses was found to be 56 units in the negative control. Compared to the negative control, all treatments and concentrations decreased the number of galls and egg masses. The number of galls and egg masses was lower in acetone extract than in ethanole extract. The nematicidal effect was higher in yellow and red radish seeds powder application. The highest nematicidal effect was determined at 6 g powder/plant application. While the mean number of galls was 1.4 unit in the yellow seed powder application at a concentration of 6 g/plant of the extract prepared with acetone solvent, it was found to be 3.0 units in the red seed powder application at 6 g/plant of the acetone extract. The number of egg masses was 1.0 unit in the yellow seed powder application, while it was 2.8 units in the red seed powder application at 6 g/plant of the acetone extract. The acetone extract of radish seed powder can be used as an alternative to chemicals in the root-knot nematodes control. [ABSTRACT FROM AUTHOR]

New-generation molecular approaches and methods are currently being developed to accurately identify species and establish species boundaries. Various approaches to species delimitation are utilized to evaluate the species richness of poorly studied and highly diverse taxa. DNA barcoding has proven to be a powerful tool for species identification and delimitation. While DNA barcoding studies have been conducted in the family Heteroderidae, there has been a lack of research on species delimitation. Therefore, in 2024, a study was undertaken at the University of Limpopo to compare species delimitation analyses within the Meloidogyne genus based on the cytochrome c oxidase I (COI) region. In this study, ASAP species delimitation approaches were employed. A total of 73 sequences from South Africa were utilised (GenBank), representing four species (Meloidogyne sp, M. incognita, M. javanica, and M. enterolobii). The phylogenetic analyses grouped all the species into two major clades, with M. enterolobii being distinctly separate. In conclusion, the ASAP results showed no significant differences among the species. Therefore, the COI marker is not a suitable marker for Meloidogyne species. [ABSTRACT FROM AUTHOR]

The decline in the yield of tomato (Solanum lycopersicum L.) is largely attributed to the prevalence of nematodes belonging to the Meloidogyne species, commonly known as root-knot nematodes. The Meloidogyne species of nematodes are regarded as the most significant contributing factor to the reduction in tomato yield. Therefore, the present investigation was conducted in 2023 at the University of Limpopo to reveal that Meloidogyne javanica (Treub) Chitwood was the identified cause of the nematode. The ITS rDNA was sequenced and amplified from female nematodes, following which the blast result showed that the South African population exhibited a high similarity (99% identity) to those populations studied in the United States (AF387094 and U96305) and China (AY438555). A comparison to the USA population (AF387094), revealed four nucleotide differences. Utilizing the maximum likelihood method for phylogenetic analysis, it was demonstrated that our population and the other populations of M. javanica form a robust clade (91% bootstrap values). [ABSTRACT FROM AUTHOR]

The presence of bioactive substance in plant extracts with nematicidal activity on Meloidogyne spp can reduce crop damage in nematode control and to minimized the use of chemical nematicide which may be toxic to man and the environment. An in vitro experiment was conducted to investigate the bioactive effects of aqueous and methanolic seed extract of neem on root-knot nematodes. The nematodes were isolated by modified funnel Baerman method and identified by comparative morphology, descriptions and lattice keys. Ten mils of homogenized nematodes suspension (50 juveniles) replicated 5 times and kept at room temperature were exposed to varied concentrations (50, 100, 150, 200, and 300 mg/ml) of the seed extracts of test plants for different time periods; 6, 12, and 24 hours. Distilled water served as a control. Data on dead nematodes was recorded for each period of exposure. The data was analysed using Analysis of Variance (ANOVA). Phytochemical screening of crude seed extracts was carried out using standard methods. The results showed that aqueous seed extract of A. indica caused 100 % nematode juvenile mortality at the highest’s concentration (300mg/ml) within 24 hours of exposure while the methanolic seed extract of A. indica caused 100% mortality within 8 hours of exposure. The results revealed that the higher the concentration of both aqueous and methanolic (50 mg/ml-300 mg/ml) seed extract of A. indica, the higher the mortality of rootknot juveniles. Mortality due to the extracts were significantly higher than those of the control at P < 0.05. The plant bioactive chemical screening of the test seed extract revealed the presence of anthraquinones, alkaloids, carbohydrates, cardiac glycosides, flavonoids, saponins, steroids and terpenes. Both methanolic and aqueous seed extract of Azadirachta indica had nematicidal properties with potential for a biological nematicide. [ABSTRACT FROM AUTHOR]

[Objective] This study analyzed the distribution of root-knot nematodes (RKNs) in rice producing areas in northern China to provide strategies for nematode control. [Method] In spring of 2020 and 2021, 1 032 soil samples were collected from continuous paddy fields, surrounding field ridges and dry croplands from 13 provinces (municipality/autonomous region)in northern China, including Henan, Shandong, Ningxia, Beijing, Jilin, Heilongjiang, Xinjiang, Gansu, Hebei, Liaoning, Shanxi, Shaanxi and Inner Mongolia. Each soil sample was mixed with autosaved sand and divided into three sub-samples, and rice and omato were used as baiting plants to form galls, which were checked after 50 d. Perineal patterns were made on selected adult females to generate morphological features and 6 pairs of specific primers were used o identify the RKN species as molecular tools. [Result] A total of 11 9 soil samples were able to form root galls on baiting roots of rice or tomato. The overall relevance ratio was 11.53% and Ningxia had the highest relevance ratio of 33.33%. In identified samples, Meloidogyne graminicola was the dominant species with relevance ratio of 96.83%. The relevance ratios of M. arenaria, M. hapla, M. incognita, M. enterolobii and M.javanica were 84.1 3 %, 52.38%, 31.75 %, 15.87 % and 3.1 7 %, respectively. The ratios of PCR detected soil samples infested by 1, 2, 3, 4, 5 and 6 of RKN species were 11.11 %, 28.57%, 28.57%, 28.57 %, 3.1 8 % and 0 %, respectively. The mixture of M. graminicola, M. incognita, M. arenaria and M. hapla had the highest infection ration of 23.81 %, followed by M. graminicola and M. arenaria mixture (22.22%) and M. graminicola, M. arenaria and M. hapla mixture (15.87%), while those of other mixtures were below 10.00%. [Conclusion] RKNs were widely distributed in paddy fields and surrounding environment in northern China, among which M. graminicola was the dominant species. M. enterolobii had also spread and adapted to low temperature from south to north. Strengthening the study of RKNs adaptability and formulating corresponding control measures are suggested. [ABSTRACT FROM AUTHOR]

The most important root-knot nematodes specific for potatoes crops in Europe are Meloidogyne chitwoodi and M. fallax which are regulated as Union quarantine pests, according to Commission Implementing Regulation Annex II B of EU Reg. 2019/2072). A monitoring program is ongoing for detection and identification of quarantine and regulated non quarantine pests with economic importance for Solanum tuberosum in Romania. One of the goals of this program is to have a clear situation of nematodes which can occur in order to establish the status of them in Romania and their distribution. In the literature there is mentioned also another root-knot nematode species which can be present on potato, namely Meloidogyne hapla. Official surveys are based on taking sample consists of soil and potatoes tubers. For extraction of juvenile nematodes (J2) from soil samples were used Oostenbrink elutriator and Baermann funnel and for females from potato tubers samples by enzymatic digestion of potato peels. The identification of Meloidogyne species was done by morphological and molecular methods. It was the first record of M. hapla on Solanum tuberosum in Romania. [ABSTRACT FROM AUTHOR]

Citrus plants are host to several plant parasitic nematodes (PPNs), which are microscopic organisms. Among PPNs, the citrus root nematode, T. semipenetrans (Cobb 1913) (Tylenchida: Tylenchulidae), causes significant damage to citrus plantations worldwide. Understanding citrus nematode populations, precise identification, host preference among citrus species, and damage threshold are crucial to control T. semipenetrans. The minutiae of citrus plant–nematode interactions, nematode density and molecular nematode identification are not well understood. In this study, nematode species and density in citrus orchards, host specialization, molecular and morphological characteristics of nematodes were assessed.Molecular and morphological methods, host–nematode interactions, host (citrus species) preference, damage economic threshold (ET), and economic injury level (EIL) were determined using laboratory methods and field sampling. Citrus plantations in different provinces in the Mediterranean region of Turkey were investigated.Nematode species were identified molecularly and morphologically. ITS sequences revealed that samples were infected by citrus root nematode T. semipenetrans. The lowest nematode density was in C. reticulata in Mersin (53 2nd stage juveniles (J2s) 100 g−1 soil), while the highest density was from Hatay in C. sinensis (12173 J2s 100 g−1 soil). Highest citrus nematode population density was on roots of C. reticulata, followed by C. sinensis, C. limon, and C. paradisi.The citrus nematode is more common than was thought and population fluctuations change according to specific citrus species. Environmental conditions, host and ecological factors, such as temperature, soil pH, and soil nutrients, might influence nematode populations in citrus orchards. Investigating nematode density in diverse soil ecologies and the responses of different resistant/tolerant citrus species and cultivars to nematode populations is essential in future studies. [ABSTRACT FROM AUTHOR]

Samanea saman (Jacq.) Merr., commonly known as rain tree, is a crucial shade tree with traditional medicinal properties. In our study, 50 soil samples were collected around the rhizosphere of rain tree in Bangkok, Pathum Thani, Uttaradit, Khon Kaen and Ubon Ratchathani Provinces in Thailand. Meloidogyne populations were only found in soil samples from Mueang district, Khon Kaen Province and a 30‐year‐old rain tree exhibited root gall symptoms caused by root‐knot nematodes (Meloidogyne) on its adventitious roots. The species of the nematodes were identified based on its morphological and molecular characteristics. The results demonstrated that the perineal patterns and morphometrics of the nematodes were highly similar to the original description of M. enterolobii, except for a squarish dorsal arch and two faint lateral lines. During the molecular analysis, nematode DNA was extracted and amplified using three primer sets, C2F3/1108, D2A/D3B and MK7F/MK7R SCAR primer, to generate polymerase chain reaction (PCR) products of 700, 750 and 520 bp, respectively. The polygenetic tree of the two markers displayed similarity among the COII and the 16S rRNA gene in mitochondria and the D2/D3 region in 28S rRNA. Therefore, the nematodes were identified as M. enterolobii Yang and Eisenback, 1983. This study reports a new host record of M. enterolobii on rain tree. [ABSTRACT FROM AUTHOR]

Considered one of the most devastating plant parasitic nematodes worldwide, Meloidogyne spp. (commonly known as the root-knot nematodes (RKNs)) are obligate sedentary endoparasites that establish in the roots, causing hyperplasia and hypertrophy of surrounding cells, triggering the formation of galls. These galls will affect root development and physiology, leading to substantial yield losses. During 2017–2022, an extensive survey of Meloidogyne species was undertaken in Portugal (mainland and islands). A total of 1,071 samples were collected by the National Plant Protection Organization (DGAV) and private farmers from different regions of the country and were analysed at the Laboratory of Nematology (NemaINIAV). Samples in which the presence of Meloidogyne sp. was detected were used to perform bioassays to obtain females and juveniles for further studies. Since the accurate identification of RKNs is an important aspect of crop management, morphological and biochemical characterisation was performed. The most common morphological features were observed, showing consistency with previous descriptions of the genus. The biochemical identification using the esterase (EST) phenotype revealed the phenotypes of Meloidogyne arenaria, M enterolobi, M. hispanica, M. hapla, M. incognita, M javanica, and M. luci. Meloidogyne incognita and M. javanica were found to be the most prevalent species in the different regions followed by M. arenaria and M. hapla. This is the first distribution report performed in Portugal on RKNs, contributing to the development of management strategies and to updated information on the status of these pests in Europe. [ABSTRACT FROM AUTHOR]

Root‐knot nematodes (RKNs), belonging to genus Meloidogyne, cause economically damage on turfgrasses areas worldwide. Many RKN species have been identified in studies conducted in golf courses around the world. However, no study has been carried out on RKNs in golf fields so far in Türkiye. In this study, root and soil samples were taken from different golf courses in Antalya which has the biggest golf areas of Türkiye. Meloidogyne graminis (Sledge & Golden, 1964) Whitehead, 1968 was identified in six of forty‐five samples by using species‐specific primers. In addition, SRAP primers were used to investigate polymorphism among M. graminis populations and other RKN species. The number of average polymorphic fragments per primer was 10.18. The mean polymorphism information content and coph.corr (r) value is.88 and.88, respectively. Phylogenetic analysis showed that M. graminis populations grouped different distant to other trophic and temperate RKNs. This is the first report on presence of M. graminis in Türkiye. [ABSTRACT FROM AUTHOR]

Root‐knot nematodes (Meloidogyne spp.) are the major group of plant parasitic nematodes impeding the cultivation of fruiting Solanaceous vegetable crops i.e., tomato, pepper, and eggplant worldwide. In the last two decades, significant progress has been achieved in the development of management strategies, however, the management of root-knot nematodes is still a serious concern due to their wide diversity of species and host range. Host plant resistance is the most viable and eco-friendly strategy. The knowledge of the available genetic resources of the cultivated and their related wild species with resistance to root-knot nematodes, gene action, and available molecular markers associated with resistance is crucial for breeding resistant/tolerant varieties/hybrids. With advances in next-generation sequencing technologies, fine mapping and the development of precise markers will aid in accelerated marker-assisted breeding. Recently grafting, which explores resistant rootstocks for managing root-knot nematodes has also been shown to be highly promising in Solanaceous vegetable crops. The current review highlights the present understanding of root-knot nematodes, resistant genetic resources, breeding of rootstocks, and advancements made in traditional and marker-assisted breeding for root-knot nematode resistance in tomato, pepper, and eggplant globally. [ABSTRACT FROM AUTHOR]

Guava is a nutritious and profitable high-yield crop. Guava root-knot nematode (GRKN), M. enterolobii Yang & Eisenback, 1983 (= M. mayaguensis Rammah & Hirschmann, 1988), cause detrimental damage in guava orchards in more than 15 countries. Fifteen guava orchards in Homestead, Florida, were randomly sampled to check for potential plant-parasitic nematode damage to the trees. The guava RKN, M. enterolobii, was detected in 80% of the sampled orchards, causing damage to white and pink guava. Morphological and molecular analyses confirmed the identification of nematode species, and the host pathogenicity test showed the guava's susceptibility to M. enetrolobii. [ABSTRACT FROM AUTHOR]

Root-knot nematodes (RKNs) are important nematode pests, causing huge economic losses on vegetable crops worldwide. A decline in the yield of Swiss chard (Beta vulgaris L.) which was associated with RKNs was observed on an organic vegetable farm in the Western Cape Province of South Africa. Nematodes were extracted from galled plant roots and identified using molecular tools. PCR-based Sequence Characterised Amplified Region (SCAR) primers was used to confirm the specie of the RKN associated with the infected plants. Thereafter, a pot assay was conducted to determine the response of artificially infected Swiss chard plants to varying concentrations of bio-synthesized silver nanoparticle Ag-NP (1 μg/mL, 2 μg/mL, and 3 μg/mL) under controlled conditions. The results of the study showed that Swiss chard is highly susceptible to M. javanica with an egg-laying-female index of >5 in all infected plants. Significantly lower values (at P=0.05) in egg masses (EM), juveniles (J2s), and reproduction factor (RF) of nematodes were recorded on plants treated with 3 μg/mL, indicating a potential for nematode control. A negative correlation was also observed in the number of egg masses, J2s, and RF of the nematodes with increasing concentrations of the Ag-NP. This study confirms that Swiss chard is highly susceptible to M. javanica and demonstrates the potential nematicidal property of Ag-NP in controlling the nematode pest of Swiss chard. [ABSTRACT FROM AUTHOR]

A rotation sequence of ungrafted and grafted tomato-melon-pepperwatermelon on resistant rootstocks 'Brigeor', Cucumis metuliferus, 'Oscos' and Citrullus amarus, respectively, was carried out in a plastic greenhouse, ending with a susceptible or resistant tomato crop. The rotation was conducted in plots infested by an avirulent (Avi) or a partially virulent (Vi) Meloidogyne incognita population to the Mi1.2 gene. At the beginning of the study, the reproduction index (RI, relative reproduction in the resistant respect susceptible tomato) of Avi and Vi populations was 1.3% and 21.6%, respectively. Soil nematode density at transplanting (Pi) and at the end (Pf) of each crop, disease severity and crop yield were determined. Moreover, the putative virulence selection and fitness cost were determined at the end of each crop in pot tests. In addition, a histopathological study was carried out 15 days after nematode inoculation in pot test. The volume and number of nuclei per giant cell (GC) and the number of GC, their volume and the number of nuclei per feeding site in susceptible watermelon and pepper were compared with C. amarus and resistant pepper. At the beginning of the study, the Pi of Avi and Vi plots did not differ between susceptible and resistant germplasm. At the end of the rotation, the Pf of Avi was 1.2 the Pi in susceptible and 0.06 in resistant, the cumulative yield of grafted crops was 1.82 times higher than that of the ungrafted susceptible ones, and the RI in resistant tomato less than 10% irrespective of the rotation sequence. Concerning the Vi, Pf was below the detection level at the end of the rotation in resistant and 3 times Pi in the susceptible. The cumulative yield of grafted crops was 2.83 times higher than that of the ungrafted and the RI in resistant tomato was 7.6%, losing the population's virulence. In the histopathological study, no differences in number of GC per feeding site were observed in watermelon compared to C. amarus, but they were more voluminous and contained higher number of nuclei per GC and per feeding site. Regarding pepper, Avi population did not penetrate resistant rootstock. [ABSTRACT FROM AUTHOR]

Copyright of Nematropica is the property of Organization of Nematologists of Tropical America and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Nematropica is the property of Organization of Nematologists of Tropical America and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Since the first detection of Meloidogyne graminicola in Piedmont, North Italy, in 2016, further inspections for the presence of the rice root‐knot nematode were carried out in rice fields of neighboring regions, in accordance with the Italian NPPO (National Plant Protection Organization) to support the official phytosanitary measures, to enable the early detection of the rice pest, and to prevent its spread within the national territory. In 2018, surveys of rice fields in Lombardy region revealed a new occurrence of M. graminicola. In the present study, we confirmed the identification of the rice nematode in Lombardy using the ribosomal ITS region and the mitochondrial COI and COII genes. The sequences and phylogenetic analyses revealed that Lombardy M. graminicola population grouped in all trees in the main cluster containing Meloidogyne species belonging to graminis group, but always in a different subgroup compared to the Piedmont population of M. graminicola. These results clearly suggest that the two Italian populations have been recently and independently introduced and confirm that the geographic origin is not the main factor leading to M. graminicola population variability. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of Pesticide Science / Nongyaoxue Xuebao is the property of Chinese Journal of Pesticide Science and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Summary: The rice root-knot nematode, Meloidogyne graminicola , is a serious pathogen of rice production worldwide. In Vietnam, scientific information on the rice root-knot nematode is limited. In this circumstance, our study aimed to investigate the characteristics of M. graminicola from rice fields in southern Vietnam and to evaluate the reaction of 20 rice varieties to this soil-borne pathogen in a glasshouse experiment. Ten populations of root-knot nematode collected from rice fields at different geographical regions in the Mekong Delta were identified as M. graminicola based on the perineal configuration of females and species-specific molecular markers. The morphological, morphometric and molecular characteristics of ten nematode isolates were defined, and the variations observed between these isolates were not significantly different. The pathogenicity of these isolates was examined in the susceptible Indica rice, Oryza sativa 'IR64', with a reproduction factor ranging from 18.1 to 37.8. Of the 20 Indica rice varieties tested in response to the nematode population MG-PN08, the 'Tetep' variety showed moderate resistance to the nematode (reproductive factor = 11.7; galling index = 2.4), while others were ranked at levels ranging from moderately susceptible to highly susceptible. The life cycle of M. graminicola in 'Tetep' root is 28 days compared to 21 in 'IR64'. 'Tetep'-nematode interaction at the histological and molecular levels needs further investigation to develop new rice varieties resistant to rice root-knot nematode. [ABSTRACT FROM AUTHOR]

Summary: Crop damage inflicted by Meloidogyne enterolobii justifies an updated literature review focusing on recent discoveries about its identification, biology and management. Since its description in 1983, M. enterolobii has become a pest of great concern, particularly due to its virulence, which renders controlling this nematode pest a challenge. The global distribution of M. enteroblii is summarised, with emphasis placed on limited research done for the species in sub-Saharan Africa where food production and security is threatened by root-knot nematode parasitism. Novel advances in methods used to detect M. enterolobii are touched upon, especially the improvement in advanced molecular techniques that complements shortcomings in morphology and morphometic approaches. Despite these exciting developments, the employment of effective management strategies to combat the species remains problematic. Future research on various aspects of M. enterolobii is crucial, with focus to be placed on the use of available resources to contain damage caused by this species. [ABSTRACT FROM AUTHOR]

Summary: Meloidogyne hapla and Pratylenchus penetrans are important plant-parasitic nematodes affecting potato in New York and the Northeastern United States, yet little is known of their spatial patterns and spatiotemporal dynamics. Spatial patterns of M. hapla and Pratylenchus spp. were quantified using semivariogram analysis and Spatial Analysis by Distance IndicEs (SADIE). Nematode populations were assessed within each of three commercial potato fields in 2016 and 2017, with fields sampled on two occasions in-season. Semivariogram analysis and ordinary kriging indicated initial population densities to be spatially dependent over an average range of 110 m for M. hapla and 147 m for Pratylenchus spp. SADIE indicated Pratylenchus spp. to be significantly aggregated in nearly all fields (10 of 12 samplings, I a = 1.367 to 2.113). Meloidogyne hapla populations were aggregated in only three of 12 samplings ( I a = 1.318 to 1.738). Spatiotemporal analysis using the association function of SADIE indicated a strong and significant association between initial and final population densities of M. hapla and Pratylenchus spp. within fields. This information is fundamental for the development of enhanced sampling protocols for estimation of plant-parasitic nematodes and evaluating the feasibility of site-specific nematicide application in New York potato fields. [ABSTRACT FROM AUTHOR]

This study aims to identify the root-knot nematode (RKN) at seven olive plantations in Rajasthan (India), and understand the possible spread of RKN and its bacterial parasite, Pasteuria penetrans through olive planting material (OPM). We identified the RKN as Meloidogyne javanica based on perineal pattern morphology and species-specific SCAR marker. RKN was prevalent at all the locations with high natural incidence (50–90%) of P. penetrans in the females dissected from unstained roots. An artificial exposure of air-dried soil of seven locations to healthy juvenile (J2) of M. javanica showed that the trend was consistent with the natural population. We conclude that root hardening media comprising of dried river sand and nematode-infested soil mixed at the secondary site (Jaipur) in India possibly resulted in M. javanica infection of OPM along with P. penetrans. Our study suggests that P. penetrans proliferated to suppressive levels and kept the nematode population below damaging levels. [ABSTRACT FROM AUTHOR]

Summary: Little information is available for nematode pests associated with watermelon in sub-Saharan Africa (SSA). This study recorded the abundance and prevalence of plant-parasitic nematodes from 25 localities across south-west Nigeria during 2016/2017. Of the 11 nematode species identified, those belonging to Meloidogyne spp. were predominant according to Prominence Values, followed by Helicotylenchus dihystera , Pratylenchus zeae and Scutellonema bradys. Morphological and molecular analyses revealed the identity of four species of root-knot nematodes: Meloidogyne enterolobii , M. incognita , M. javanica and M. arenaria (in descending order of abundance and occurrence). Meloidogyne arenaria is reported for the first time from south-west Nigeria, while S. bradys and Xiphinema nigeriense are first reports for watermelon. Significant associations were observed between the frequency of occurrence of the predominant nematode species and soil properties as well as rainfall. Results provide baseline information on the nematode pest occurrence on watermelon in Nigeria and in a wider context for SSA. [ABSTRACT FROM AUTHOR]

Root-lesion nematodes (Pratylenchus spp.) are among the most important nematode pests on grapevine along with root-knot, dagger, and ring nematodes. In 2019, two samples of both soil and roots were collected from a vineyard in Delano, Kern County, California and submitted to the United States Department of Agriculture, ARS, Mycology and Nematology Genetic Diversity and Biology Laboratory, Beltsville, MD, for identification purposes. Females and juveniles of Pratylenchus sp. were recovered from the root and soil samples using the sugar centrifugal flotation and Baermann funnel extraction methods. Both morphological observations and molecular analysis of internal transcribed spacer (ITS), 28S large subunit ribosomal DNA, and mitochondrial cytochrome oxidase (COI) sequences indicated that the specimens recovered from the soil and roots were Pratylenchus hippeastri. To the best of the authors’ knowledge, this is the first report of P. hippeastri from California including the first record of this species on grapevine and the second state record in North America. Damages caused by nematodes cannot be overemphasized, although economic importance of P. hippeastri has never been established. Hence, there is an urgent need to investigate the economic impact of this nematode in vineyards in California State in order to develop sustainable management strategies. [ABSTRACT FROM AUTHOR]

In order to investigate different species of root-knot nematodes associated with vegetable production in southern regions of Iran, 37 populations of the most predominant species, Meloidogyne javanica, were recovered. Morphological and morphometric studies were carried on the characters of females, males, J2s and perineal patterns. Species-specific Sequence Characterized Amplified Region (SCAR) primers confirmed morphological studies, and all these populations produced specific band in 670 bp using Fjav and Rjav primers. Genetic diversity of different populations was studied by Inter Simple Sequence Repeats (ISSR) and Random Amplified Polymorphic DNA (RAPD) markers implementing 10 primers for each approach. Results revealed a relatively low genetic diversity (the percentage of polymorphic bands were 19.08 and 24.60 for ISSR and RAPD, respectively). The analyses of molecular variance indicated that the variation resulted from genotypic variations within region and variances among regions are 81% and 19% for RAPD, and 86% and 14% for ISSR, respectively. On the other hand, FST and Nm values are 0.140 and 1.535 for ISSR while these values are 0.188 and 1.079 for RAPD. So it can be concluded that there is a great deal of gene flow between populations due to the movement of plant material contaminated with nematodes, which results in high mixing between populations. ISSR and RAPD datasets failed to group populations according to their geographic region. There were no pathotypes or other intraspecific biological entities observed in the species. [ABSTRACT FROM AUTHOR]

China is one of the largest producers of mulberry in the world. With the development of the sericulture industry, several pests and diseases have occurred in rapid succession, chief among which is the root-knot nematode disease affecting mulberry. According to the China cocoon and silk exchange, cocoon prices have doubled since the beginning of 2009 and rose to 92,700 yuan ($135,770) per tonne in mid-April 2010. According to customs statistics, in the first eight months of 2011, China’s silk merchandise exports amounted to 2.39 billion yuan. In this study, sequencing of the rDNA-ITS and D2-D3 region of the 28S rRNA gene was combined with root-knot nematode morphological characteristics to identify the root-knot nematode infecting mulberry in the Guangdong, Guangxi, and Hunan provinces of China. This resulted in the identification of Meloidogyne enterolobii as the causal species of root-knot nematode infections in these regions. Importantly, the morphological data agreed completely with our molecular phenotyping efforts, indicating that rDNA sequencing could provide a more clear-cut and less labor-intensive means of characterizing root-knot nematode infections in the future. The differences between this study and the previous studies were discussed, as well as the damage degree, host species and influence scope of M. enterolobii. [ABSTRACT FROM AUTHOR]

The root-knot nematode species Meloidogyne daklakensis n. sp. was discovered on the roots of Robusta coffee (Coffea canephora Pierre ex A. Froehner) in Dak Lak Province, Vietnam. This species is characterized by the females having rounded or oval perineal patterns, smooth, regular, continuous striae, and reduced lateral lines. The dorsal arch is low, rounded and encloses a quite distinct vulva and tail tip. The stylet is normally straight with well-developed and posteriorly sloped knobs. The males have a rounded cap that extends posteriorly into the lip region. The procorpus is outlined distinctly, and is three times longer than the metacorpus. The metacorpus is ovoid, with a strong valve apparatus. The species closely resembles M. marylandi , M. naasi, M. ovalis, M. panyuensis, M. lopezi, M. mali and M. baetica in the perineal pattern of the females, and the morphology of the males and the second-stage juveniles. Nonetheless, it can be differentiated from other species by a combination of morphometric, morphological and molecular characteristics. Phylogenetic analysis was conducted based on the internal transcribed spacer (ITS) and 28S rDNA as well as the region between the cytochrome c oxidase I (COI) and cytochrome c oxidase II (COII) mitochondrial genes. Herein, this nematode is described, illustrated, and designated as a new species, Meloidogyne daklakensis sp. n., based on morphometric, morphological and molecular analyses. [ABSTRACT FROM AUTHOR]

Cultivated Cretan mountain tea or Malotira ( Sideritis syriaca L.) was found to be infected by Meloidogyne hapla and Meloidogyne javanica in the island of Crete. The authors provide the first molecular characterization of M. hapla in Greece and the first report of Cretan mountain tea or Malotira as a host of Meloidogyne species worldwide. In addition, Meloidogyne hispanica was found infecting aloe (Andros island) and corn (Drama, North Greece) consisting the first reports of natural infection of these plants by M. hispanica in Europe. Furthermore, infection of corn by M. incognita and soybean by M. javanica (Drama, North Greece) are reported for the first time in Greece. Integrative taxonomical approach based on perineal pattern and EP/st ratio, as well as the region of the mitochondrial genome between the cytochrome oxidase subunit II ( coxII) and 16S rRNA mitochondrial DNA (mtDNA) genes was used to differentiate Meloidogyne species. [ABSTRACT FROM AUTHOR]

Wheat (Triticum spp.) is highly susceptible to the root lesion nematode, Pratylenchus thornei, which causes excessive amounts of crop losses each year. In this research, we investigated the cumulative effect of the biocontrol agent Purpureocillium lilacinum (syn: Paecilomyces lilacinus) against P. thornei. Three doses of P. lilacinum (106, 107 and 108 conidia cultures mL-1) with one dose of 400 P. thornei individuals (adults and juveniles) mL-1 were applied in 100 cm3 soil under greenhouse conditions. The number of nematodes in the soil and root in addition to total nematode in soil+root were determined. Moreover, different plant parameters such as the plant height, plant fresh and dry weight, root fresh and dry weight were evaluated. Applications with the higher dose of bio-agents (100 cm3 P. thornei infested soil with 108 conidia culture of P. lilacinum mL-1) exhibited maximal enhancement in dry and fresh weight of shoot and reduced P. thornei population. As a consequence, P. lilacinum individually was highly effective in enhancing different plant parameters and suppressing P. thornei reproduction. Overall, present findings suggest that the exploitation of the biocontrol agent P. lilacinum could be helpful for effective management of the root lesion nematode P. thornei. [ABSTRACT FROM AUTHOR]

Neem is a perennial plant of family Meliaceae grown very commonly in India. During a survey in Rajasthan, India; a population of root-knot nematode was found in association with tender neem plants causing yellowing, stunting, and heavy root galling. Inspection of the perineal pattern morphology of the adult females, extracted from the galled roots, primarily led to identification of the species as Meloidogyne indica. Further, detailed morphological and morphometric illustrations of second-stage juveniles, males and females were carried out by light compound and scanning electron microscopy. Gross morphology and measurements were found consistent with the original description of M. indica infecting citrus by Whitehead (1968). The neem population was found to infect and reproduce on citrus. Additionally, evolutionary relationship was deduced by Maximum likelihood method using ITS rRNA, D2D3 expansion segment of 28S rRNA and mitochondrial COI sequences. Phylogenetic analyses based on these sequences showed sufficient divergence of M. indica to be differentiated as a unique species under the genus Meloidogyne. [ABSTRACT FROM AUTHOR]

Root-knot nematodes of the genus Meloidogyne are recognised worldwide as a major production constraint in crops of primary economic importance. Knowledge of their diversity and prevalence, as well as the major environmental and agronomical cues for understanding their distribution in specific areas is of vital importance for designing control measures to reduce significant damage. We provide the first detailed information on the diversity, distribution and levels of Meloidogyne species infecting wild and cultivated olive soils in a wide-region in southern Spain that included 499 sampling sites. Overall Meloidogyne spp. were found in 6.6% of sampled olive plants, with 6.6% and 6.5% for cultivated and wild olive, respectively. We identified five previously described Meloidogyne spp. (Meloidogyne arenaria, M. baetica, M. hapla, M. incognita, M. javanica) and one new species (Meloidogyne oleae sp. nov.) which, characterized using integrative taxonomy, increases the known biodiversity of Meloidogyne spp. affecting olive. Meloidogyne arenaria and M. incognita were only found infecting cultivated olive varieties, while, M. baetica was only found infecting wild olive. Three major parameters drive the distribution of Meloidogyne spp. in cultivated olives in southern Spain, cover vegetation on alley, irrigation and soil texture, but different species respond differently to them. In particular the presence of M. incognita is highly correlated with sandy loamy soils, the presence of M. javanica with irrigated soils and cover vegetation, while the presence of M. arenaria is correlated with the absence of cover vegetation on alley and absence of irrigation. These parameters likely influence the selection of each particular Meloidogyne species from a major dispersal source, such as the rooted plantlets used to establish the orchards. [ABSTRACT FROM AUTHOR]

Plant-parasitic nematodes of the genus Meloidogyne, known as root-knot nematodes (RKN), have an important economic impact on golf course turfgrasses. The most prevalent RKN species associated with grasses are M. chitwoodi, M. graminicola, M. graminis, M. incognita, M. marylandi, M. microtyla, M. minor, M. naasi and M. sasseri. In 2010, slight thickening of the roots and RKN females with unusual features were observed in turfgrass roots on golf courses in Araras, São Paulo state, Brazil. This population (MgARA) was maintained in the lab and studied including morphological, morphometrical, biochemical and molecular markers. Morphology and morphometry were variable and not useful for identification, although perineal pattern morphology showed highly similarity with M. graminis description. Concerning to biochemical characterisation, the esterase phenotype Mg1, characterised by a very slow and fainter band, was detected in some protein homogenates. Regarding to molecular analysis, D2-D3 region of 28S rDNA gene and cytochrome oxidase subunit II region from mitochondrial DNA were amplified by PCR and sequenced. Phylogenetic analysis revealed that the Brazilian isolate, found associated with turfgrass, grouped with M. graminis isolates (98–99% bootstrap; variation of 8–11 and 0–24 bp, respectively), close to M. marylandi, supporting its identification as M. graminis. This is the first report of M. graminis on golf courses in Brazil. [ABSTRACT FROM AUTHOR]

High infection rates of roots of wild kiwifruit (Actinidia chinensis Planch) and soil infestation by a root-knot nematode were found in Anshun, GuiZhou Province, China. Morphology, esterase phenotype and molecular analyses confirmed that this nematode was different from previously described root-knot nematodes. In this report, the species is described, illustrated and named Meloidogyne aberrans sp. nov. The new species has a unique combination of characters. A prominent posterior protuberance, round and faint perineal pattern and a medium-length stylet (13.6–15.5 μm) characterized the females. Second-stage juveniles (J2) were characterized by a smooth lip region with distinctly protruded medial lips and a depression in outline at the oral aperture, a relatively long stylet (15.9–16.8 μm), four incisures in the lateral field and a very short, even poorly defined, hyaline tail terminus (2.2–5.5 μm). More incisures (11–15) existed in the lateral field of males, and the stylet and spicules of males were 18.2–19.6 μm and 22.7–36.8 μm long respectively. Egg masses were typically produced within the roots of kiwifruit. The new species had a rare Est phenotype, S2. Phylogenetic trees inferred from SSU, LSU D2D3, ITS, and partial coxII-16S rRNA revealed that M. aberrans sp. nov. was within the Meloidogyne clade and was distinguished from all described root-knot nematodes. Moreover, from histopathological observations, M. aberrans sp. nov. induced the formation of multinucleate giant cells. [ABSTRACT FROM AUTHOR]

The type population of Meloidogyne brasiliensis is synonymised under M. ethiopica based on morphological and morphometric similarities, as well as through biochemical, molecular and phylogenetic studies. Meloidogyne ethiopica was first described in 1968 in Tanzania using specimens from a single egg mass culture on tomato and re-described in 2004 using an isolate from Brazil. Meloidogyne brasiliensis was described in 2002 in Brazil based on specimens collected from tomato (type population) and pea. Morphological and morphometric studies of their descriptions showed important similarities in major characters as well as some general variability in others. Characterisation of esterase isozyme phenotypes of three populations of M. ethiopica from Brazil, Chile and Kenya, and two M. brasiliensis populations, resulted in only one esterase pattern (E3), a phenotype already known for M. ethiopica. In PCR assays, the species-specific 350 bp SCAR marker developed for M. ethiopica was amplified from the M. brasiliensis populations tested. In phylogenetic analyses based either on sequences of the ITS1-5.8S-ITS2 and D2-D3 (28S) rRNA regions or on RAPD and AFLP data, the populations of both species clustered together with a strong bootstrap support. Altogether, these results provide congruent evidence that M. brasiliensis is not a valid species but rather a junior synonym of M. ethiopica. [ABSTRACT FROM AUTHOR]

Copyright of Nematropica is the property of Organization of Nematologists of Tropical America and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Root-knot nematodes (RKN) are important plant pathogens affecting rice in South-East Asia and southern Brazil in irrigated rice fields. In order to investigate the specific diversity of RKN associated with irrigated rice in southern Brazil, Meloidogyne spp. from Rio Grande do Sul (RS) and Santa Catarina (SC) States were characterised biochemically by esterase (Est) and malate dehydrogenase (Mdh) phenotypes. Fifty-six Meloidogyne spp. populations were detected in 48% of rice samples, and a total of five esterase phenotypes were identified, four of which presented as drawn-out bands in different positions. In RS State, M. graminicola (Est VS1), Meloidogyne sp. 2 (Est R2) and Meloidogyne sp. 3 (Est R3) were identified, which corresponded to ca 80, 40 and 10% of samples, respectively. In SC State, M. graminicola, M. javanica (Est J3), Meloidogyne sp. 1 (Est R1), Meloidogyne sp. 2 and Meloidogyne sp. 3 accounted for ca 93.75, 12.50, 62.50, 12.25 and 6.25% of samples, respectively. The esterase phenotypes R1, R2 and R3 are new, never having been detected on rice before. Meloidogyne javanica showed a N1 Mdh phenotype (Rm: 1.0), while four other populations exhibited a N1a (Rm: 1.4) phenotype. All populations were tested with two SCAR markers specific to M. graminicola, which confirmed that, but no specificity was obtained with both markers in relation to the atypical populations analysed. Sequencing and phylogenetic analyses of internal transcribed spacer-rRNA (ITS) were performed to infer the phylogenetic relationship of these atypical Meloidogyne spp. populations. Meloidogyne sp. 1 grouped with the mitotic parthenogenetic species, while the two others (Meloidogyne sp. 2 and sp. 3) clustered with M. graminicola and other meiotic parthenogenetic species. Taken together, these data highlight the unprecedented specific diversity of RKN associated with irrigated rice in southern Brazil. Further morphological and phylogenetic studies involving these atypical isolates will be carried out to identify this complex of species. [ABSTRACT FROM AUTHOR]

In 2018 to 2019, soil and root samples from some declining peach orchards were collected in Edgefield County, South Carolina, USA. Excavated roots of Guardian® peach (Prunus persica) rootstock showed strong gall symptoms. Extracted root-knot nematodes (RKN) were identified by both morphological and molecular methods as M. floridensis. This is the first detection of the peach RKN in South Carolina and the third state in the USA after Florida and California. [ABSTRACT FROM AUTHOR]

I.42II.43III.44IV.47V.49VI.50VII.50VIII.50IX.5252References52 Summary: Root‐knot nematodes (RKNs) Meloidogyne spp. cause major damage to cultivated woody plants. Among them, Prunus, grapevine and coffee are the crops most infested by worldwide polyphagous species and species with a more limited distribution and/or narrower host range. The identification and characterization of natural sources of resistance are important steps to develop RKN control strategies. In woody crops, resistant rootstocks genetically different from the scion of agronomical interest may be engineered. We describe herein the interactions between RKNs and different woody crops, and highlight the plant species in which resistance and corresponding resistance (R) genes have been discovered. Even though grapevine and, to a lesser extent, coffee have a history of rootstock selection for RKN resistance, few cases of resistance have been documented. By contrast, in Prunus, R genes with different spectra have been mapped in plums, peach and almond and can be pyramided for durable resistance in interspecific rootstocks. We particularly discuss here the Ma Toll/interleukin‐1 receptor‐like‐nucleotide binding‐leucine‐rich repeat gene from Myrobalan plum, one of the longest plant R genes cloned to date, due to its unique biological and structural properties. RKN R genes in Prunus will enable us to carry out molecular studies aimed at improving our knowledge of plant immunity in woody plants. [ABSTRACT FROM AUTHOR]

Meloidogyne enterolobii (Me) is an emerging root-knot nematode (RKN) and the most important worldwide for its high aggressiveness and increasing geographical distribution. In Mexico only in watermelon and tomato has been reported. Here we report the presence of this nematode in Jalapeño pepper collected in the state of Sinaloa. The morphological and morphometric characteristics of the second-stage juveniles and adult females were similar to those described for Me. DNA sequencing and alignment analysis (BLAST/GenBank) showed that the SCAR and rDNA IGS2 fragments had a 99 % of identity, with Me DNA sequences present in the database. The results obtained indicate that the RKN detected corresponds to M. enterolobii. To our knowledge, this is the first report of this nematode in chilli pepper in this region of Mexico, considered of major economic importance for the variety of vegetables grown and the extension of the area sown. [ABSTRACT FROM AUTHOR]

Since weeds serve as hosts for nematode pests, the host status of 20 weed species (commonly occurring in fields of developing farmers) toMeloidogyne incognitaandM. javanica, respectively, were investigated. Greenhouse studies showed that seven weed species had Rf values >1 for both nematode species indicating susceptibility, while 13 had Rf values ≤ 1 indicating resistance. Greenhouse results showed thatHibiscus trionumandAmaranthus tricolorwere identified as the most susceptible andChenopodium carinatumandDatura feroxthe poorest hosts forM. incognitaandM. javanica. For field experiments at Kuruman,Solanum retroflexumwas the most susceptible weed to aM. javanicapopulation, while the same was evident forH. trionumat Nelspruit, where a mixed population ofM. incognitaandM. javanicaoccurred and at Potchefstroom, where a population ofM. incognitawas present. Results from this study indicated that certain weed species are highly susceptible to root-knot nematodes and should be removed timely and effectively to prevent population level increases of root-knot nematode pests in the fields of farmers. [ABSTRACT FROM AUTHOR]

Published data on the presence or absence of phasmids in males of Heteroderidae species are compiled and critically reviewed. Based mainly on results of previous SEM studies and complemented by light microscopy using DIC optics, the conclusion is drawn that male phasmids appear to be absent in all species of the genera assigned to the subfamilies Heteroderinae and Ataloderinae, but present and often distinct in theMeloidoderinae genera Cryphodera and Meloidodera. The presence of male phasmids is considered as ancestral, and loss of phasmids as a derived character. [ABSTRACT FROM AUTHOR]

Root-knot nematodes ( Meloidogyne incognita and M. javanica) were found infecting cultivated aloe ( Aloe vera) plants on the island of Crete, Greece. The infected plants showed reddish brownish leaf discolouration associated with poor plant growth, and roots with dark necrotic areas and irregular thickening but without the typical root-knot nematode galls. Females and egg masses were embedded deeply inside the root. Nematodes were identified using PCR assays either of females, juveniles and males directly obtained from aloe roots and surrounding soil, or of females generated by culturing the nematodes from the aloe on potted tomato plants. Histopathological studies showed female and juvenile bodies and feeding sites surrounded by darkened cells, suggesting the presence of phenolic contents at high levels. Transverse and longitudinal sections confirmed that this reaction was not related to a hypersensitive response because the feeding site was established, but that giant cell formation was accompanied by phenolic compound accumulation. Egg masses isolated from aloe roots were placed in water but juveniles did not hatch. Inspection under the light microscope showed different levels of darkening, with the majority of eggs undeveloped or degenerated. Additionally, PCR reactions which were successful for females failed in these egg masses, suggesting DNA degradation or presence of inhibitory compounds. These results indicate a possible plant defence mechanism impairing viability and development of eggs which are laid inside the aloe roots. It is suggested that the females either produced detoxification enzymes or expressed higher tolerance levels to toxic compounds and thus their development was not impaired. [ABSTRACT FROM AUTHOR]

Root-knot nematodes ( Meloidogyne spp.) are important pests of numerous crops worldwide. Some members of this genus have a quarantine status, and accurate species identification is required to prevent further spreading. DNA barcoding is a method for organism identification in non-complex DNA backgrounds based on informative motifs in short DNA stretches (≈600 bp). As part of the EU 7th Framework project QBOL, 15 Meloidogyne species were chosen to compare the resolutions offered by two typical DNA barcoding loci, COI and COII, with the distinguishing signals produced by two ribosomal DNA genes (small and large subunit rDNA; SSU ≈ 1,700 and LSU ≈ 3,400 bp). None of the four markers distinguished between the tropical species Meloidogyne incognita, M. javanica and M. arenaria. Taking P ID (Liberal) values ≥0.93 as a measure for species delimitation, the four mtDNA and rDNA markers performed well for the tropical Meloidogyne species complex, M. enterolobii, M. hapla, and M. maritima. Within cluster III A (Holterman et al. Phytopathology, 99, 227-235, ), SSU rDNA did not offer resolution at species level. Both mtDNA loci COI and COII did, whereas for LSU rDNA a longer fragment (≥700 bp) is required. The high level of mitochondrial heteroplasmy recently reported for M. chitwoodi (Humphreys-Pereira and Elling Nematology, 15, 315-327, ) was not found in the populations under investigation, suggesting this could be a regional phenomenon. For identification of RKNs, we suggest the combined use of SSU rDNA with one of three other markers presented here. [ABSTRACT FROM AUTHOR]

Copyright of Nematropica is the property of Organization of Nematologists of Tropical America and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)