Genera Of Plant Parasitic Nematodes Research Articles

Nematode community structure in sugarcane fields under continuous vinasse fertigation

Sugarcane vinasse is a residue from ethanol production, which has high content of nutrients and organic matter, improving chemical, physical and biological changes in the soil. This study evaluated nematode community structure, food web, metabolic footprint, and soil quality in sugarcane fields under continuous vinasse fertigation. Soil samples were collected from four sugarcane fields in Pernambuco State, Brazil, under continuous vinasse fertigation for nematode identification at the genus (plant parasites) and family (free-living) level, physical and chemical analyses of the soil. Nine genera of plant-parasitic nematodes and five families of free-living nematodes were identified in sugarcane fields. Plant-parasitic nematodes were dominant, except in the field with five years of continuous vinasse application. The genera Mesocriconema, Meloidogyne, Helicotylenchus and Pratylenchus were frequent in all fields. Predators and fungivores nematodes were few abundant, although, according to the soil food web, all sugarcane fields were low to moderately disturbed environments. A positive correlation was observed between the microbial respiration and Rhabdtidae in fields with five years of vinasse application, and between the electrical conductivity of the soil and Meloidogyne in fields without vinasse application. We highlight those alterations in the structure and composition of the nematode community, and soil characteristics that can occur due to vinasse fertigation in sugarcane fields.

Identification of Plant Parasitic Nematodes Associated with Citrus in Dibrugarh District

The present investigation was carried out to determine the occurrence and distribution of plant parasitic nematodes associated with citrus plants of different citrus orchards in Dibrugarh district. A total of 149 soil and root samples were collected randomly from the rhizosphere of citrus plants from the twenty four different citrus orchards of seven blocks from Dibrugarh district. Eight genera of plant parasitic nematodes were found to be associated with citrus plants of Dibrugarh district. Genera of plant parasitic nematodes recorded were namely Tylenchulus, Hoplolaimus, Helicotylenchus, Tylenchorhynchus, Meloidogyne, Xiphinema, Paratylenchus and also nematodes genera found under criconematids. Among them Hoplolaimus sp., Helicotylenchus sp., Tylenchorhynchus sp. and T. semipenetrans were found to be present in most of the samples. Community analysis of plant parasitic nematodes revealed that the genus Hoplolaimus ranked first in relative frequency, absolute frequency, absolute density, relative density and prominence value. Genus Helicotylenchus ranked second in absolute density, relative density and prominence value and genus Tylenchorhynchus ranked third in case of absolute density absolute frequency and prominence value. Results shown that Tylenchulus semipenetrans ranked second in absolute frequency and relative frequency and fourth in prominence value.

Drivers of plant parasitic nematode community structures associated with tobacco‐growing areas in southern Brazil

AbstractTobacco (Nicotiana tabacum L.) is one of the most important crops in southern Brazil, but little is known about the distribution and diversity of plant parasitic nematodes (PPNs). We surveyed the occurrence and diversity of PPNs in 36 tobacco‐growing areas in southern Brazil as well as evaluated their relationship with 19 bioclimatic variables. For these purposes, extracted nematodes (from soil and roots) were identified based on morphological and biochemical traits and estimates of incidence and abundance were obtained, which were used to compute diversity indices. Furthermore, the relationship between taxa and diversity and the influence of bioclimatic variables were studied using principal component analysis (PCA) and generalized linear models (GLMs), respectively. We observed diversity across the sampled sites, with values varying from 0.03 to 1.22 and from 0.05 to 0.76 according to the Shannon‐Wiener and Pielou's evenness indices, respectively. Seven genera of PPNs (Meloidogyne, Helicotylenchus, Tylenchus, Xiphinema, Pratylenchus, Paratylenchus and Mesocriconema) were identified, highlighting taxa with high incidence and abundance, such as Meloidogyne (100%; 1800 to 41,850 specimens/250 cm3), Helicotylenchus (100%; 50 to 9850 specimens/250 cm3), and Pratylenchus (86.1%; 50 to 1950 specimens/250 cm3). The PCA disclosed the major roles of Meloidogyne, Tylenchus, and Helicotylenchus in the structure of the PPN communities and their interplays. Among root‐knot nematodes, Meloidogyne javanica, M. arenaria and M. incognita were the predominant species. Using GLMs, we found that average annual temperature and annual precipitation strongly influenced the abundance of PPNs as well as the diversity indices (p < .01), with negative and/or positive interactions. Collectively, our findings fill gaps in knowledge about the current impact of PPNs and provide insights into future scenarios, including for other host crops.

Prevalence, Spatial Distribution, and Population Density of Plant-Parasitic Nematodes in Vegetable Fields of North Carolina, South Carolina, and Tennessee Counties

Plant-parasitic nematodes are a diverse group of soilborne plant pathogens that limit the yield of numerous vegetable crops globally. Few studies have investigated nematode populations affecting vegetable crops in Tennessee and North and South Carolina. Between December 2020 and October 2022, vegetable fields in selected counties of these states were sampled for plant-parasitic nematodes. Data on the prevalence, spatial distribution, and population density of seven genera of plant-parasitic nematodes, identified via morphology, were collected. Root-knot nematodes were identified in 60% of the fields sampled, with population densities ranging from 10 to 10,400 nematodes per 500 cm3 of soil. Detection rates of other genera as percentages of total fields sampled were: spiral (42%), stubby root (32%), stunt (21%), ring (13%), and lesion (8%) nematodes. Out of eight crops sampled, fields either currently or formerly planted to tomato or pepper were the most frequently sampled in the survey (77% of total fields). This is the first survey to collect data on populations of plant-parasitic nematodes in this region, and the results highlight the need for continued surveillance and study of their impact in vegetable production.

Ecological Interaction in the Proliferation of Phytoparasitic Nematodes in Coffee var. Typica

Phytoparasitic nematodes are a common problem in coffee production worldwide. In Peru, the proliferation of phytoparasitic nematodes in Coffea arabica L. var. Typica has negative impacts on coffee production and huge economic losses. The objective of this study was to determine the ecological interactions that influence the proliferation of phytoparasitic nematodes in C. arabica var. Typica in Quillabamba, Cusco, Peru. The density of phytoparasitic nematodes in the soil and root was evaluated using the modified Baermann channel method. Identification of genera and species of phytoparasitic nematodes was carried out in the different samples, based on descriptions and taxonomic keys. Physical and chemical parameters of the soil were evaluated. Principal component analysis (PCA) and a correlation network were employed to distribute the different species of nematodes. The variables soil texture, organic matter, pH, altitude, temperature and humidity were used. During the sampling, several genera of plant-parasitic nematodes were identified in addition to various categories of nematodes. Meloidogyne exigua, Pratylenchus coffeae, Allotrichodorus longispiculis and Helicotylenchus longicaudatus are among the specific species of nematodes identified. The genus with the highest incidence was Meloidogyne spp. with 77.3% in soil and 96% in roots, reaching an average density of 340 nematodes in 100 g of soil and 368 nematodes in 1 g of roots. The PCA results show that 63.7% of the variability of the data is retained in the first two components. PCA shows that the sampled areas were differentiated and grouped with the evaluated characteristics, while the nematodes overlap in the representation of the analysis, thus making it difficult to select them. Pearson’s correlation showed a negative correlation between altitude and soil nematode density (−0.22), suggesting that conditions at higher altitudes may be more unfavorable for nematode growth. In addition, a positive correlation was found between soil pH and organic matter (0.93, p < 0.001) and may influence nematode density. The factors that influence the density of nematodes in the soil and plant roots are multiple and complex, and their understanding is essential for the success of coffee production. The finding of the current study may be useful in the development of sustainable strategies for managing nematodes in coffee network production.

Aphelenchoides varicaudatus (Nematoda: Aphelenchoididae) and Helicotylenchus erythrinae (Nematoda: Hoplolaimidae) from Garlic Plantation in Magelang, Central Java, Indonesia.

There were two most found genera of plant parasitic nematodes from garlic plantation in Magelang, Central Java, Indonesia which suffered losses due to bulb rot, Aphelenchoides and Helicotylenchus. Polymerase Chain Reaction (PCR) was conducted using a pair of universal nematode primer (D2A/D3B) to determine the Aphelenchoides and Helicotylenchus species from those host. Both genera were amplified at ~780 bp. The Blast-N results for the Aphelenchoides showed high identity to Aphelenchoides varicaudatus from Yunnan China (HQ283353) with 99.47 % identity, while the Helicotylenchus showed 95.22 % identity to Helicotylenchus erythrinae from Colombia (MT321739). From morphological and molecular data, we confirm that the Aphelenchoides species is A. varicaudatus. Based on female morphological character, Helicotylenchus species refers to H. erythrinae. Which is also supported by its nucleotide alignment which has same region character as H. erythrinae (MT321739). This is the first report of molecular characterization of H. erythrinae in Indonesia.

Prevalence of major parasitic nematodes associated with tomatoes (Solanum lycopersicum L.) in two districts of Jimma, Ethiopia

This study assessed the diversity of plant parasitic nematodes associated with tomatoes in two major tomato producing districts. A total of 40 composite soil and root samples were collected, and extracted nematodes were identified morphologically to a genus level, however, Meloidogyne arenaria was identified based on molecular methods. Accordingly, eight plant parasitic nematode genera were identified, including Meloidogyne, Pratylenchus, Helicotylenchus, Scutellonema, Rotylenchulus, Criconema, Paratylenchus, and Globodera. The highest prominence value was recorded for Meloidogyne and the lowest being for Paratylenchus. In terms of Meloidogyne infestation, the highest mean root knot incidence was in the Dedo district, specifically at the Babo peasant association, where Meloidogyne could be considered a major threat to tomato production. The study further indicated that Meloidogyne density was higher in soil with a pH between 6.4 and 7.4, and an altitude above 1800 m. This result implies the need for immediate attention and implementation of feasible management strategies to reduce the damage caused by Meloidogyne sp.

Effect of Compost Along with Bio Agents on Root Knot Nematode (Meloidogyne spp.) in Okra (Abelmoschus esculentus L., Walp)

Okra [Abelmoschus esculentus L., Moench] a native of South-Africa and commonly known as ‘Bhindi’ is an annual malvaceous vegetable crop, especially grown in tropical and subtropical climates. It is also called “perfect villager’s vegetable”. Root-knot nematodes are considered among the top five major plant pathogens and the first among the ten most important genera of plant parasitic nematodes in the world. Amongst nematodes, root-knot nematode (Meloidogyne incognita and Meloidogyne javanica) causes severe damage to okra. Trichoderma viride, Pseudomonas fluorescene and Rhizobium were tested under field conditions during Rabi 2020-2021 for their efficacy against the Root knot nematode and growth & nematode population.

Molecular investigation of proteinase inhibitor (PI) gene in tomato plants induced by Meloidogyne species

BackgroundThe plant parasitic nematode genus Meloidogyne parasitize almost all flowering crops. Plants respond with a variety of morphological and molecular mechanisms to reduce the effects of pathogens. Proteinase inhibitors (PI), a special group of plant proteins which are small proteins, involve in protective role in the plants attacked by microorganisms. Still, the plant response using PI against nematodes has not been well understood. Therefore, this study was aimed to determine the expression of proteinase inhibitor I (PI-I) gene subsequent the infection of M. incognita, M. javanica, and M. chitwoodi in tomato plants post nematode infections. Molecular methods were used to determine the PI gene expressions at different days post nematode infections in host tissues. ResultsResults revealed that the population of M. incognita species reached the highest level of nematode population followed by M. javanica and M. chitwoodi, respectively. All Meloidogyne species induced expression of PI-I gene reached at the utmost level at 3 days post infection (dpi) in host tissues. Relative gene expression level was sharply dropped at 7 dpi, 14 dpi, and 21 dpi in M. incognita induced gene expression in host tissues. Similar results were observed in host tissues after infection of M. javanica and M. chitwoodi. ConclusionsThe commonalities of plant response across a diverse Meloidogyne species interaction and the expression of PI gene may be related to plant defense system. Increased level of PI gene expressions in early infection days in host tissues induced by parasitic nematodes may share resemblances to the mechanisms of resistance on biotrophic interactions.

'Candidatus Xiphinematincola pachtaicus' gen. nov., sp. nov., an endosymbiotic bacterium associated with nematode species of the genus Xiphinema (Nematoda, Longidoridae).

An intracellular bacterium, strain IAST, was observed to infect several species of the plant-parasitic nematode genus Xiphinema (Xiphinema astaregiense, Xiphinema incertum, Xiphinema madeirense, Xiphinema pachtaicum, Xiphinema parapachydermum and Xiphinema vallense). The bacterium could not be recovered on axenic medium. The 16S rRNA gene sequence of IAST was found to be new, being related to the family Burkholderiaceae, class Betaproteobacteria. Fungal endosymbionts Mycoavidus cysteinexigens B1-EBT (92.9 % sequence identity) and ‘Candidatus Glomeribacter gigasporarum’ BEG34 (89.8 % identity) are the closest taxa and form a separate phylogenetic clade inside Burkholderiaceae. Other genes (atpD, lepA and recA) also separated this species from its closest relatives using a multilocus sequence analysis approach. These genes were obtained using a partial genome of this bacterium. The localization of the bacterium (via light and fluorescence in situ hybridization microscopy) is in the X. pachtaicum females clustered around the developing oocytes, primarily found embedded inside the epithelial wall cells of the ovaries, from where they are dispersed in the intestine. Transmission electron microscopy (TEM) observations supported the presence of bacteria inside the nematode body, where they occupy ovaries and occur inside the intestinal epithelium. Ultrastructural analysis of the bacterium showed cells that appear as mostly irregular, slightly curved rods with rounded ends, 0.8–1.2 µm wide and 2.5–6.0 µm long, possessing a typical Gram-negative cell wall. The peptidoglycan layer is, however, evident only occasionally and not detectable by TEM in most cells. Another irregularly occurring shell surrounding the endosymbiont cells or the cell clusters was also revealed, probably originating from the host cell membrane. Flagella or spore-like cells do not occur and the nucleoid is diffusely distributed throughout the cell. This endosymbiont is transmitted vertically through nematode generations. These results support the proposal of IAST as a new species, although its obligate intracellular and obligate endosymbiont nature prevented isolation of a definitive type strain. Strain IAST is therefore proposed as representing ‘Candidatus Xiphinematincola pachtaicus’ gen. nov., sp. nov.

Spatial distribution and community analysis of plant-parasitic nematodes associated with rice (Oryza sativa L.) in Benue State, Nigeria

Plant-parasitic nematodes (PPNs), also known as phyto-parasitic or plant-destructive nematodes are microscopic, translucent, bilaterally symmetrical, pseudocoelomic, multicellular worm-like organisms which feed on plant root mostly, and seldom on other vegetative parts. Although these PPNs have been reported to constitute threat to rice production, documentation of their spatial distribution and densities in major rice-producing areas of Benue state, Nigeria is absent. Using multi-stage sampling procedure, surveillance for PPNs, their densities and community analyses were conducted in six major rice-producing local government areas (LGAs) of Benue. The LGAs included Agatu, Apa, Gwer West, Guma, Kwande and Makurdi LGAs and a total of 108 samples were collected comprising 54 soil and 54 root samples. Nine plant-parasitic nematode genera which included Criconemoides, Tylenchorhynchus, Trichodorus, Hirschmanniella, Xiphinema, Helicotylenchus, Scutellonema, Pratylenchus and Meloidogyne were recovered. In order of ranking, Meloidogyne sp., P. zeae and H. oryzeae had the highest population densities across all LGAs included in the study. The highest density of PPN was recorded in Kwande (ca. 133 PPNs/10mL of nematode suspension) while lowest population density was recorded in Makurdi (ca. 77 PPNs/10mL of suspension). Although Meloidogyne sp. recorded the highest average population density in all LGA except in Gwer West LGA where H. oryzae recorded the highest average population density of approximately 13 PPNs/10mL of suspension. Community analysis also revealed that Meloidogyne sp. was the most spatially distributed PPN closely followed by P. zeae and H. oryzae with prominence values of 37.78, 21.84 and 20.91, respectively. However, in the soil, the highest prominence value was recorded in H. oryzae making it the most spatially distributed PPN in the soil.

NEMATODE PARASITES OF WATERLEAF (Talinum triangulare) IN OBIO-AKPOR AND IKWERRE LOCAL GOVERNMENT AREAS OF RIVERS STATE, NIGERIA

Waterleaf, Talinum triangulare is cultivated in home gardens and fields to improve nutritional quality for the family and a source of livelihood for farmers. However, the role of T. triangulare is often counteracted by plant-parasitic nematodes (PPNs). Effective management of PPNs will depend on the identification and determination of their population and distribution. A survey was conducted in two Local Government Areas (LGAs), Ikwerre and Obio-Akpor of Rivers State to identify plant-parasitic nematodes associated with waterleaf. Multistage random sampling technique was employed in the collection of 60 bulked soil and root samples across six waterleaf monoculture farming communities. The nematodes were extracted, identified and their population determined using standard procedures. Occurrences, relative importance values (RIV) and diversity indices were determined. Other data were analysed using descriptive statistics and analysis of variance. Six plant-parasitic nematodes genera were encountered in this study, Helicotylenchus, Pratylenchus, Paratylenchus, Meloidogyne, Scutellonema and Tylenchulus. Pratylenchus and Helicotylenchus were the most frequently occurring nematode pest genera with equal relative frequency of occurrence of 38.89%. Pratylenchus species with RIV of 61.34% was the most important nematode pest associated with waterleaf across the six farm communities. The dominance index of 0.71 for the nematode genera showed that some nematode species dominated others. Alakahia farms had the highest population of plant-parasitic nematodes (2,780) across the six farm communities, whereas Omagwa farms had the lowest (250). The study showed that nematode pests are associated with waterleaf and could be contributing to yield losses in this crop

Distribution of plant-parasitic nematodes and comparative effects of fadama (hydromorphic) fields and upland fields on plant-parasitic nematodes and free-living nematodes on three indigenous vegetables commonly grown in Osun State Nigeria

Surveys were conducted in 2016 and 2017 to investigate the distribution of plant-parasitic nematodes and the effects of fadama fields and upland fields on plant-parasitic and free-living nematodes. A total of 84 soil samples were collected from seven Local Government Areas visited in Osun State. Soil samples were collected from two fadama fields and two upland fields in all the LGAs visited. Nematodes were extracted, counted and identified under a compound microscope according to the morphological characteristics of the nematodes. The results showed that sixteen genera of plant-parasitic nematodes were found associated with Solanum macrocarpon, Amaranthus cruentus and Telfairia occidentalis. Meloidogyne\\ Helicotylenchus and Rotylenchulus were the most abundant nematodes associated with the vegetables. Fadama fields significantly had lower populations of plant-parasitic nematodes and higher populations of free-living nematodes in comparison with upland fields in fields sown to the vegetables. Farmers are advised to take full advantage of fadama fields in vegetable production.

Survey of Parasitic Nematode Genera Associated with Grapevine Roots in Sweida Governorate, Syria

Al-Halabi, S.M. and K. Al-Assas. 2021. Survey of Parasitic Nematode Genera Associated with Grapevine Roots in Sweida Governorate, Syria. Arab Journal of Plant Protection, 39(1): 14-21. The aim of this investigation was to survey the nematodes genera associated with the grapevine roots in Sweida Governorate, Syria. Samples were collected from vineyards of several main regions known for grape production (Massad, Al-Raha, Al-Kafer, Risas, Al-Quraya, Kanawat, and Ain Al-Arab in Dahr El-Jabal). The survey results confirmed the occurrence of the following plant-parasitic nematodes genera: Xiphinema, Meloidogyne, Pratylenchus, Paratylenchus, Helicotylenchus, Tylenchorynchus, Tylenchus and Ditylenchus in all investigated regions with high absolute frequency of 72.13, 73.77, 93.44, 96.72, 90.16, 93.44, 90.16 and 88.44%, respectively. The only exception was the genus Longidorus, which was limited with an absolute occurrence of 37.70%. Furthermore, this is the first record of these genera in Sweida Governorate. The results also revealed the presence of other genera of fungivore nematodes Aphelenchus and Aphelenchoides in all examined sites with 100% frequency. Keywords: Survey, classification, grapevine, nematodes, rhizosphere, Sweida, Syria

Distribution and population density of plant parasitic nematodes on cereal production areas of Isparta and Burdur Provinces of Turkey

Plant parasitic nematodes were systematically surveyed in cereal production areas of Isparta and Burdur Provinces of Turkey in 2016-2017. Nine plant parasitic nematode genera were identified in Isparta and Burdur [Ditylenchus (23%), Geocenamus (20%), Helicotylenchus (33%), Heterodera (<1%), Meloidogyne (3%), Pratylenchus (76%), Pratylenchoides (52%), Paratylenchus (41%) and Tylenchus (18%)]. Pratylenchus spp. was found in 82% and 68% of samples, and Pratylenchoides spp. in 55% and 63% samples in Isparta and Burdur Province, respectively. The densities of Pratylenchus and Pratylenchoides species were higher in Isparta than in Burdur, and were often over the threshold for economic damage. As a result of morphological diagnostic studies, Pratylenchus crenatus Loof, 1960, Pratylenchus neglectus (Rensch, 1924) Filipjev & Schuurmans-Stekhoven, 1941, Pratylenchus penetrans (Cobb, 1917) Filipjev & Schuurmans-Stekhoven, 1941, Pratylenchus thornei Sher & Allen, 1953 (Tylenchida: Pratylenchidae), Pratylenchoides alkani Yüksel, 1977, Pratylenchoides crenicauda Winslow, 1958, Pratylenchoides erzurumensis Yüksel, 1977, Pratylenchoides leiocauda Sher, 1970, Pratylenchoides ritteri Sher, 1970 and Pratylenchoides variabilis Sher, 1970 (Tylenchida: Merliniidae) were identified. Pratylenchoides alkani, P. erzurumensis, P. neglectus and P. thornei were the most common species in wheat and barley fields in Burdur and Isparta Provinces.

The host status of glyphosate-tolerant soybean genotypes to Meloidogyne incognita and Pratylenchus infection

The host status of South African adapted, genetically modified (GM) glyphosate-tolerant soybean genotypes to root-knot (field and glasshouse) and lesion (field) nematodes were assessed. Analyses of root and soil samples of 29 genotypes (collected from seven production areas during the 2014/15 season) enabled the identification of nine plant-parasitic nematode genera and 10 species. Predominant endoparasitic genera in root samples were Meloidogyne (Meloidogyne incognita and M. javanica) and Pratylenchus (Pratylenchus brachyurus, P. zeae and P. teres). Rotylenchulus parvus was the predominant semi-endoparasite in soil, followed by Scutellonema brachyurus and Helicotylenchus sp. Only ‘PAN 1583 R’ and ‘PAN 1521 R’ maintained less than 10% of the Meloidogyne spp. densities present in roots of the most susceptible genotype, while all genotypes were susceptible to the Pratylenchus spp. The host status of 36 soybean genotypes to M. incognita infection, evaluated in two follow-up glasshouse experiments terminated 56 days after inoculation of ca. 1000 M. incognita eggs and second-stage juveniles (J2) per seedling, varied substantially for final population density (Pf), reproduction factor (Rf) and relative percentage susceptibility (%S). Only ‘PRF-GCI7’ and the resistant reference ‘LS 5995’ had Rfs < 1 for both experiments, despite higher minimum and maximum temperatures recorded for the second experiment. Continuous evaluation of soybean genotypes for their host status to predominant nematode pests and their use to reduce densities of such species in producer’s fields are crucial to enable sustainable crop production, and contribute towards food provision and security.

Identification and Abundance of Plant-parasitic Nematodes Associated with Amenity Trees in the University of Port Harcourt, Rivers State, Nigeria

Plant-parasitic nematodes contribute to unnoticeable damages which lead to gradual decline in the values and eventually death of amenity trees. Identification of these nematode pests is vital for their effective management. Reconnaissance survey was carried out to identify amenity tree species present in the University of Port Harcourt (UNIPORT). Composite bulked soil and root samples (126) were collected from amenity trees in UNIPORT and nematode pests were extracted from samples using modified Baerman method. The nematode pests were identified and their populations determined using standard procedures. Relative importance value (RIV) and diversity indices were calculated with appropriate software. Data were processed using descriptive statistics and with analysis of variance. 38 tree species were identified in UNIPORT belonging to 20 families. Terminalia mantaly, Cocos nucifera and Terminalia catappa with RIVs of 15.1, 9.35, and 9.12 respectively were the three most important amenity trees in UNIPORT. Fifteen nematode pest genera; Helicotylenchus, Aporcelaimus, Tylenchulus, Meloidogyne, Scutelonema, Pratylenchus, Tylenchus, Rotylenchoides, Criconema, Hemicyliophora, Trichodorus, Mesodorylaimus, Heterodera, Paratylenchus and Longidorus were associated with 21 of the amenity trees. The three most important nematode pest genera were Helicotylenchus, Tylenchulus and Aporcelaimus with RIVs of 42%, 16% and 5.34%, respectively. Helicotylenchus (RIV 45.41%) and Tylenchulus (RIV 30%) were the most important plant-parasitic nematode genera in the soil and roots of amenity trees, respectively. Helicotylenchus, Tylenchulus and Aporcelaimus were the three most important plant-parasitic nematode genera associated with amenity trees in UNIPORT.&#x0D; Keywords: Amenity trees, Diversity indices, Identification, Nematode pests, Survey

Distribution of Cyst Nematodes in Gilgit-Baltistan, Pakistan

| Cyst nematode, the Heterodera Schmidt (1871) is one of the most widely distributed and economically important plant parasitic nematode genus. During the present investigation of plant-parasitic nematode fauna from Gilgit-Baltistan, Pakistan, four cyst nematode species viz., Heterodera avenae Wollenweber, 1924; H. mani Mathews,1971; H. schachtii Schmidt, 1871 and H. zeae Koshy, Swarup and Sethi, 1971 were detected from all four districts.

Phytonematodes Associating Wheat in North Eastern Egypt and Pathogenicity of Heterodera avenae on Certain Cereal Cultivars

A survey of plant-parasitic nematodes (PPNs) associating wheat in Ismailia governorate, northeastern Egypt was carried-out during 2016/2017 and 2017/2018 growing seasons. Results showed that seven PPNs genera and/or species were found associating wheat roots. These genera and/or species, in descending order of frequency, were: Tylenchorhynchus spp. (14%), Helicotylenchus spp. (10%), Heterodera avenae (8%), Ditylenchus spp. (5%), Meloidogyne javanica (4%), Pratylenchus spp. and Xiphinema spp. (3%, each). Two screening pot experiments, in two consecutive growing seasons (2017/17 and 2017/18) were carried out to determine the host suitability of 15 Egyptian cereal cultivars including bread wheat (Triticum aestivum), barley (Hordeum vulgare) and oat (Avena sativa) to the cereal cyst nematode, Heterodera avenae, under greenhouse conditions. Results of both experiments were very similar and showed that oat cv. Baladi and wheat cv. Giza 171 were highly susceptible, while wheat cvs. Masr 1, Masr 2, Masr 3, Sakha 95, Seds 1, Seds 12, and Shandawel 1 were susceptible. However, barley cvs. Giza 135, Giza 123, Giza 124, and Giza 125 were found to be moderately resistant to the tested nematode. H. avenae suppressed (P ≤ 0.05) the dry weights of roots, shoots and spikes of the inoculated plants, compared to the non-inoculated checks. Another greenhouse pot experiment was carried out during the wheat-growing season 2018/2019 to determine the effect of different initial population densities (Pi) of H. avenae on the growth parameters of wheat cv. Giza 171 and on nematode reproduction. Results showed that as the nematode Pi increased, both the wheat growth parameters and the nematode reproduction factor (Rf) were decreased (P ≤ 0.05).

PLANT PARASITIC NEMATODES ASSOCIATED WITH Annona squamosa L.

The current study was conducted from December 2018 to January 2019 to identify plant-parasitic nematodes (PPNs) associated with A. squamosa in Rizal Province, Philippines. A total of 10 soil and root samples were collected from the surveyed plants. Nematodes from the collected soil samples were extracted using the modified Baermann tray method while root nematodes were extracted using H2O2 incubation. Results of the study revealed the presence of Meloidogyne, Rotylenchulus, and Criconemoides PPNs genera from the roots and soil samples. The study revealed that the number of nematodes associated with A. squamosa is not enough to cause infestation and damage. Further, various environmental factors such as moisture and potassium content of the soil, temperature, and pH make the conditions unfavorable for the proliferation of plant-parasitic nematodes in the study area.