Root-knot Nematode Species Research Articles

A southern root-knot nematode (Meloidogyne incognita) first reported on cucumber in Manipur

Root-knot nematode is one of the major pest of vegetable crops that produces root galls in the infected roots, seriously reducing the farmer’s produce. According to statistics, phyto-parasitic nematodes affect 12.3% of the world’s major crops each year, resulting in yield losses. Most common species of root-knot nematodes have been reported to be vulnerable to cucumber and they can reduce productivity by up to 60% in protected commercial farming. Till now, there was no report of root knot nematode affecting cucumber in the state of Manipur (India). In 2021, an extensive investigation was conducted in each block of Kakching district, Manipur to observe for the root-knot nematode (Meloidogyne spp.) infecting the cucumber crop of that area based on morphological characteristic symptoms of the infected plant. The root samples forming galls and soil were collected for confirmatory studies at the laboratory. For the first time, it was discovered during the study that the cucumber crop was infested by the Meloidogyne spp. showing the general symptoms like water and nutrient stress, yellowing of leaves, stunted growth, wilting of infested plants and patchiness of plants in the infested field, together with the typical symptoms of gall formation in the root system. According to morphological investigations, the southern root-knot nematode (M. incognita) was found to be responsible for the infestation of the cucumber plant sample taken from a farmer’s field in the Kakching district of Manipur.

Molecular diagnosis and differentiation of Meloidogyne arenaria, Meloidogyne javanica and Meloidogyne incognita using SNP-based KASP assays

Root-knot nematodes (RKNs) are one of the most economically important plant-parasitic nematodes in many crops. Meloidogyne arenaria, M. incognita and M. javanica are the most common species attacking tomato, pepper, eggplant, cucumber, melon, watermelon and zucchini, which have economic importance in vegetable growing areas. Thus, a rapid and accurate identification system is required for RKNs. In this study, Kompetitive Allele-Specific PCR (KASP) genotyping assays were developed to identify three common RKNs. The novel technique developed in this study utilized only two primers: one allele-specific forward primer and a reverse common primer. Meloidogyne arenaria, M. incognita and M. javanica were separated easily from each other and other RKN species. This is the first report on three species identified by the KASP assay. The results showed that the KASP assays are suitable for the high-throughput identification of these species. The developed system can be used to identify three RKN species in research, routine and quarantine laboratories.

Meloidogyne arenaria candidate effector MaMsp4 interacts with maize (Zea mays L.) proteins involved in host defense response and cell wall modifications

Background and aimsMeloidogyne arenaria is an economically important root-knot nematode species. Successful plant infection by nematode is facilitated by parasite effectors. This study aimed to characterize a candidate M. arenaria effector, indicate its molecular partners from maize, and analyze its role during infection.Material and methodsAt first, we performed EST database mining to find candidate effector protein from M. arenaria. The expression of its coding gene in nematode developmental stages was assessed using digital droplet PCR. Candidate effector molecular partners were determined using yeast two-hybrid screening of maize cDNA library and interactions were confirmed by co-immunoprecipitation after co-expression in Nicotiana benthamiana. Candidate effector and its molecular partners were GFP-fused and localization in N. benthamiana leaves was observed under confocal microscope. Then, expression level of genes encoding interacting proteins from maize was measured.ResultsMaMsp4 protein was evaluated as candidate effector in M. arenaria and the highest expression level of its coding gene was observed in stage J2. MaMsp4 maize molecular partners were indicated, interactions with beta-galactosidase 11, pectinesterase, S-adenosyl methionine decarboxylase 2, and ethanolamine-phosphate cytidylyltransferase were confirmed, and all proteins fused with GFP were detected in the apoplast and/or cytoplasm. Genes of beta-galactosidase 11 and pectinesterase, playing role in cell wall modifications, were overexpressed at 24 hpi followed by down-regulation at 7 dpi, while S-adenosyl methionine decarboxylase 2 and ethanolamine-phosphate cytidylyltransferase, involved in plant defense response, were suppressed at 7 dpi, without preceding up-regulation.ConclusionsWe have found that MaMsp4 interacts with plant proteins involved in plant cell wall modifications and defense mechanisms related to polyamines biosynthesis.

Distinct Genomic Loci Underlie Quantitative Resistance to Meloidogyne enterolobii Galling and Reproduction in Citrullus amarus.

Meloidogyne enterolobii is a virulent species of root-knot nematode that threatens watermelon (Citrullus lanatus) production in the southeastern United States. There are no known sources of root-knot nematode resistance in cultivated C. lanatus. Specific genotypes of a wild watermelon relative, C. amarus, are resistant against M. incognita but the genetics that underly this resistance are still unknown and it is not clear that this same resistance will be effective against M. enterolobii. To identify and characterize new sources of resistance to M. enterolobii, we screened 108 diverse C. amarus lines alongside a susceptible C. lanatus cultivar (Charleston Gray) for resistance against M. enterolobii. Different C. amarus genotypes ranged from resistant to susceptible for the three resistance phenotypes measured; mean percent root system galled ranged from 10 to 73%, mean egg mass counts ranged from 0.3 to 64.5, and mean eggs per gram of root ranged from 326 to 146,160. We used each of these three resistance phenotypes combined with whole-genome resequencing data to conduct a genome-wide association scan that identified significant associations between M. enterolobii resistance and 11 single-nucleotide polymorphisms (SNPs) within the C. amarus genome. Interestingly, SNPs associated with reduced galling and egg masses were located within a single quantitative trait locus (QTL) on chromosome Ca03, while reductions in nematode eggs per gram of root were associated with separate QTL on chromosomes Ca04 and Ca08. The results of this study suggest that multiple genes are involved with M. enterolobii resistance in C. amarus and the SNPs identified will assist with efforts to breed for M. enterolobii resistance in watermelon.

A novel soybean hairy root system for gene functional validation.

Agrobacterium rhizogenes-mediated transformation has long been explored as a versatile and reliable method for gene function validation in many plant species, including soybean (Glycine max). Likewise, detached-leaf assays have been widely used for rapid and mass screening of soybean genotypes for disease resistance. The present study combines these two methods to establish an efficient and practical system to generate transgenic soybean hairy roots from detached leaves and their subsequent culture under ex vitro conditions. We demonstrated that hairy roots derived from leaves of two (tropical and temperate) soybean cultivars could be successfully infected by economically important species of root-knot nematodes (Meloidogyne incognita and M. javanica). The established detached-leaf method was further explored for functional validation of two candidate genes encoding for cell wall modifying proteins (CWMPs) to promote resistance against M. incognita through distinct biotechnological strategies: the overexpression of a wild Arachis α-expansin transgene (AdEXPA24) and the dsRNA-mediated silencing of an endogenous soybean polygalacturonase gene (GmPG). AdEXPA24 overexpression in hairy roots of RKN-susceptible soybean cultivar significantly reduced nematode infection by approximately 47%, whereas GmPG downregulation caused an average decrease of 37%. This novel system of hairy root induction from detached leaves showed to be an efficient, practical, fast, and low-cost method suitable for high throughput in root analysis of candidate genes in soybean.

First Report of Meloidogyne enterolobii Yang & Eisenback, 1983 (Guava Root-knot Nematode) Infecting Guava (Psidium guajava) in Egypt.

Meloidogyne enterolobii Yang & Eisenback, 1983 (guava root-knot nematode) is an important disease in subtropical to tropical climate in several areas of the world (Subbotin et al., 2021). It is a highly polyphagous root-knot nematode species causing major damage to a range of economically important crops. The expansion of this species is increasing worldwide creating a potential problem to the maintenance of resistance genes to other major Meloidogyne species (Castagnone-Sereno and Castillo, 2020). Additionally, the diagnosis of M. enterolobii can be challenging due to morphological similarities with other root-knot nematode species (Castagnone-Sereno, 2012). In the African continent, it has been cited in several countries of Equatorial and South Africa (Subbotin et al., 2021), but not in North Africa. Two guava groves (at Bany Salama, Natrn vally, El Beheira governorate, 30.322043N, 30.518529E; and Izbat Al Halawijah, Monshaah Alaweyah, Abu El Matamir, El Beheira governorate 30.9398050N, 30.1484430E), in Egypt, were found with significant symptoms of tree decline and root galling damage. The presence of egg masses and females of root-knot nematodes were found inside the galls (Figure 1A, B). Nematodes were extracted from soil samples with levels of 12300 and 12600 second-stage juveniles (J2s)/250 g of soil using a modified Baerman method (Hooper, 1986), respectively. Nematode root density was 24367 eggs/g of root, using the protocol described in Hussey and Barker (1973) for Izbat Al Halawijah population. For morphological and morphometrical identification, J2s and females were fixed using a hot formalin solution (4% v/v). DNA was isolated from single J2s specimen for: i) testing multiplex specific-PCR assay for M. incognita, M. javanica and M. arenaria (Kiewnick et al., 2013), and ii) amplifying and sequencing of cytochrome oxidase subunit II (COII) and the 16S rRNA mitochondrial region using the primer pair C2F3 (5'-GGTCAATGTTCAGAAATTTGTGG-3') (Powers and Harris, 1993) and MRH106 (5'- AATTTCTAAAGACTTTTCTTAGT-3') (Stanton et al., 1997). Perineal patterns of females for Izbat Al Halawijah population were typical of the species (Fig. 1D), body size (L: 520-774 µm; W: 214-487 µm), stylet length (12.5-13.7 µm) and ratio from distance from anterior end to excretory pore and stylet length (4.2) in females (n = 18), fitting with original description and others (Subbotin et al., 2021). J2s from Izbat Al Halawijah population (n=13) (Fig. 1C, E-H) showed: body length (393.5-475 µm), stylet length (11.5-13.5), excretory pore to anterior end (89-95.5 µm), tail length (50.0-60.0 µm), tail hyaline region (12.0-21.0 µm), a ratio (24.2-32.5), b ratio (4.9-6.5), c ratio (7.3-8.6) and c' (5.0-6.4), also fitting with original description and others (Subbotin et al., 2021). Specific PCR did not amplify any band (Kiewnick et al., 2013). Four J2s individuals were sequenced for COII-16S rRNA region for each population showing M. enterolobii as unique species and without intraspecific variability. Two identical DNA fragments of 814 bp obtained for both populations (OP434400 and OP434401) were compared with those in GenBank. A BLAST search indicated the sequences were 100% identical to several sequences of M. enterolobii (MF467278 and KX823371). On the basis of these results, the root-knot nematodes isolated from these two guava groves in Egypt were confirmed as M. enterolobii. This is a well-known pathogen of guava, causing important losses in this crop (Castagnone-Sereno and Castillo, 2020) and it is regulated as quarantine nematode in the Mediterranean region (EPPO).

Identification and virulence of five isolates of root-knot nematode Meloidogyne floridensis on vegetables.

Meloidogyne floridensis is of particular concern because it reproduces on tomato, pepper, corn, and tobacco cultivars that have resistance to the common tropical root-knot nematode (RKN) species (i.e., M. incognita, M. arenaria, and M. javanica). During a survey of 436 randomly selected vegetable fields in Georgia in 2018, six M. floridensis infested fields were found and cultured from single egg-mass isolates on a susceptible tomato (cv. Rutgers), and speciated using molecular analyses. Five isolates of M. floridensis were identified from collard, cowpea, cucumber, watermelon, and tomato fields by DNA sequence-based identification targeting mitochondrial genes [cytochrome c oxidase subunit II, tRNAHis, large subunit rRNA, and NADH dehydrogenase subunit 5 gene]. Two greenhouse trials determined the host preference and reproduction level for each M. floridensis isolate. Evaluations were conducted on Rutgers tomato, a resistant tomato (cv. Skyway carrying the Mi-1.2 gene), and vegetable crops associated with the origin of M. floridensis populations. This study confirmed that most associated vegetables, except collards, were good hosts to M. floridensis, having a reproduction factor > 1. All isolates were able to reproduce aggressively on the resistant tomato. We found variations among M. floridensis isolates in pathogenicity and reproduction levels on the vegetable crops tested which should be considered when using or developing host resistance.

Meloidogyne Species (Root Knot Nematodes) Associated with Different Climatic Conditions of the Sorghum bicolor Production Sites in Telangana, India

Although crop damage due to nematodes in Telangana, Sorghum bicolor crops has been suspected and sampled occasionally and no study on Meloidogyne species (root-knot nematodes) associated with different climatic conditions of the soil has yet to be reported. In the present study, we report the Meloidogyne species associated with different climatic conditions (seasonal variations) and edaphic factors like soil moisture, soil pH, organic matter, sand, silt, clay, and soil types of the Sorghum bicolor crop production sites, which could be useful to get more knowledge and develop appropriate management strategies. A total of 60 rhizosphere soil samples along with roots were collected from 60 fields of 4 villages to provide comprehensive coverage of the S. bicolor production sites in four agro-climatic districts of Telangana. An aliquot from each of the 60 composite soil samples was processed for estimation of the soil conditions like moisture, organic content, pH, sand, silt, and clay. Subsequently, nematodes were isolated by Baermann funnel and Cobb's method, identified by root dissection, and verified using a microscope. Out of 60 soil samples, 21.2% of Meloidogyne-like species were observed at 5.0-7.5% of soil moisture, 27.3% at 17.5-20% of soil organic matter, 30.3% at pH between 7.0 and 7.5, 51.5% at 15-20% of silt, 36.4% at 20 to 25% of the rhizosphere clay and 45.5% of Meloidogyne-like species at 50-55% of rhizosphere sand. The distributions of other root-knot nematode species between different soil types were statistically significant (p-value = 0.039). The distributions of Meloidogyne-like species between different soils were statistically insignificant (p-value = 0.212). However, the infested roots were often carved in the shape of a hook, horseshoe, or a complete spiral without excessive proliferation of secondary roots which was common in Meloidogyne-like species. The results of this study can be used as an advisory to the farmers who intend to take only a particular variety of crops in their field but were unaware of the damage that was happening underground due to biotic and abiotic factors.

Occurrence and Distribution of Root-Knot Nematodes in Kiwifruit Orchard

The study was conducted to investigate the infestation and distribution of plant-parasitic nematodes on kiwi orchards in Korea. Plant parasitic nematodes genus and densities were investigated at a total of 102 sites in Jeollanam-do, Gyeongsangnam-do, and Jeju-do, which are the main production areas of domestic kiwi orchards. Plant parasitic nematodes detected were of 9 genera, including root-knot nematodes (Meloidogyne spp.), spiral nematodes (Helicotylenchus spp.), and needle nematodes (Paratylenchus spp.), and 56% of the 102 plantations were infected with root-knot nematodes. Root-knot nematodes were found to be the most important plant parasitic nematode in domestic kiwi orchards. The average density of root-knot nematodes is 97 per 300 cm<sup>3</sup> soil, and there is concern about the kiwi yield reduction. As a result of identifying the root-knot nematode species: M. arenaria, M. hapla, M. incognita, and M. javanica. Among them, M. arenaria is the most dominant. As the plant parasitic nematode infection route in fruit trees is often spread through the transplantation of infected seedlings, attention should be paid to the production of nematode-free plants during the production and supply of kiwifruit plants.

Comparative phylogenetic analysis of vitellogenin in species of cyst and root-knot nematodes

Summary Plant-parasitic nematodes (PPN) are an economically important group of crop pests and are oviparous animals; all nutrients required to develop and ensure the survival of their unhatched progeny need to be deposited within the egg, including proteins. The most abundant protein deposited is vitellin, formed of a precursor protein vitellogenin, which has roles in transporting lipids, providing amino acids and influencing post-embryonic development. The genes encoding vitellogenin have been well studied in Caenorhabditis elegans, but little is known about vitellogenin in PPN. Using the vitellogenin gene sequences from C. elegans, homologous sequences in the genomes of some economically important cyst and root-knot nematodes were identified and hypothetical vitellogenin genes were predicted. Protein domains were then determined. Sequences were aligned using MUSCLE and then used to construct phylogenetic trees using the maximum likelihood method. With the availability of genomic data and use of online local alignment tools, the vitellogenin encoding genes from C. elegans could be aligned to PPN genomes. All predicted genes contained the same protein domains as C. elegans; Vitellogenin_N, vitellogenin open beta-sheet and von Willebrand factor domain type D. The constructed phylogenetic tree clustered the species into four groups: root-knot nematodes, two cyst nematode groups and Caenorhabditis species. By determining the hypothetical vitellogenin genes in PPN and inferring their relationships, this could form a potential basis to understand further the role of vitellogenin in cyst and root-knot nematodes.

A New Root-Knot Nematode species, Meloidogyne karsseni n. sp. (Nematoda: Meloidogynidae), From Mexico and a Taxonomic Update on M. paranaensis From Guatemala.

A new root-knot nematode (RKN) species, Meloidogyne karsseni n. sp., associated with sweet pepper from Mexico, and a population of M. paranaensis from Guatemala, are described using data from morphological, biochemical (isozyme enzymes), molecular, and phylogenetic analyses. Meloidogyne karsseni n. sp. can be morphologically diagnosed using the combined features of the second-stage juveniles, viz. body length (345 to 422 μm), a conical rounded head region, a post-labial annule lacking transverse striation, a thin stylet 11 to 12 μm long, rounded to oval and backwardly sloping knobs, dorsal gland orifice (DGO) at 5.2 to 6.0 μm from the knobs, a hemizonid just above the secretory-excretory (SE) pore, a tapering tail with finely rounded terminus and one or two very weak constrictions at hyaline tail tip; the female characters viz. oval-to-rounded perineal pattern with coarse striation on lateral sides around the anus, low dorsal arch with finer striations, and distinctly visible lateral lines; and the male characteristics viz. a rounded and continuous head, a post-labial annule without transverse striations, a robust stylet 20 to 24 μm long, rounded-to-oval and slightly backwardly sloping knobs, and a DGO at 2.4 to 2.9 μm from the knobs. In all the studied males of M. paranaensis, a characteristic sclerotization around the duct of SE-pore was also observed for the first time. Sequences of 18S, D2-D3 of 28S, and ITS of rDNA, and cox1 of mtDNA were generated for the two species, and in the phylogenetic trees based on these genes, both species appeared in the tropical RKN species complex clade.

First Report of Direct Damage Caused by the Stubby-Root Nematode, Nanidorus minor, to Strawberry (Fragaria x ananassa), in Florida.

In 2019-2022, declining symptoms were observed in two commercial strawberry farms in Hillsborough County, Florida. The fields in the two farms consisted of raised beds covered by plastic mulch. Both were fumigated with a mixture of 1,3-dichloropropene (40%) + chloropicrin (60%) before planting. Samples collected from large patches with declining plants were infested with stubby-root nematodes. No sting and root-knot nematode species were detected. The results of morphological and molecular analyses indicated that the stubby-root nematode populations were representative of the species Nanidorus minor. The two cultivars 'Florida Brilliance' and 'Florida Sensation' in the two fields included plants with stubby root symptoms showing a reduction in the size of the root system and arrested growth and elongation of the feeder roots on the first strawberry crop. The nematode population densities in the two fields increased at the end of strawberry season and averaged 66 and 96 specimens in 200 cm3 soil. In one of the fields, a second strawberry crop was established as in the previous year using the same practices (fumigation and raised beds covered with plastic). However, in this field the population of N. minor declined and did not reach damaging levels at the end of the season on the second strawberry crop. The factors causing the decline of the nematode population were not elucidated. This is the first report of a direct damaging effect of N. minor to strawberry.

First report of Meloidogyne hapla infecting Salvia miltiorrhiza in Shaanxi, China.

Salvia miltiorrhiza is a perennial herbaceous plant for traditional Chinese medicine. It has been extensively applied for many hundred years to treat various diseases (Su et al. 2015). It is also a kind of important cash crop that is widely cultivated in southern Shaanxi province. In June of 2021, in a field in Luonan County, Shaanxi Province, some S. miltiorrhiza plants with stunting and leaf wilting symptoms were observed. The diseased plants exhibited a large number of globular galling on the secondary and tertiary roots. The symptoms were typical of infection by root-knot nematodes. Population densities of second-stage juveniles (J2s) ranged from 330 to 650 per 100 cm3. To identify the species of the root-knot nematodes, J2s and males were collected from the soil in the root zone, and females were isolated from diseased roots. The perineal patterns of females (n = 12) were round-shaped, with low dorsal arches, obvious lateral lines, and characteristic small punctations near anus. Morphological measurements of females (n = 20) included body length (L) = 565.25 ± 33.9 (503.35 - 632.47) μm, body width (BW) = 420.00 ± 21.28 (378.27 - 452.51) μm, stylet = 11.11 ± 0.73 (10.05-12.29) μm, dorsal pharyngeal gland orifice to stylet base (DGO) = 4.69 ± 0.45 (3.82-5.32) μm, vulval slit length = 21.1 ± 1.33 (18.38-22.96) μm, and vulval slit to anus distance = 15.76 ± 1.24 (13.38-17.45) μm. The morphological characters of males (n = 7): L = 1098.14 ± 82.99 (962.83-1193.87) μm, BW = 28.44 ± 1.18 (26.59-29.83) μm, stylet = 18.27 ± 0.97 (16.57-19.28) μm, DGO = 4.89 ± 0.62 (3.82-5.68) μm, and spicule length = 24.04 ± 1.80 (21.30-26.71) μm. The key morphometrics of J2s: L = 380.24 ± 18.24 (354.43-423.13) μm, BW = 13.94 ± 0.70 (12.88-15.34) μm, stylet = 11.82 ± 0.49 (10.96-12.61) μm, DGO = 3.68 ± 0.42 (3.09-4.56) μm, tail length = 55.42 ± 5.81 (46.97-67.03) μm, and hyaline tail terminus = 13.79 ± 1.24 (12.0-16.51) μm. These morphological characteristics are consistent with Meloidogyne hapla as described by Whitehead (1968). Ten individual females were transferred to ten different tubes for DNA extraction. The DNA extraction followed the method described by Htay et al. (2016). The species-specific primers JMV1 (5'-GGATGGCGTGCTTTCAAC-3') and JMV (5'-AAAAATCCCCTCGAAAAATCCACC-3') were used for the identification of M. hapla (Adam et al. 2007). A single 440 bp fragment was amplified by this pair of primers, confirming their identities as M. hapla. To confirm species identification, the ITS region was amplified using the primers 18S/26S (5'-TTGATTACGTCCCTGCCCTTT-3'/5'-TTTCACTCGCCGTTACTAAGG-3') (Vrain et al. 1992). The sequence from the ITS region was 768 bp (GenBank Accession No. OM049198) and was 100% identical to the sequences of M. hapla (GenBank Accession Nos. MT249016 and KJ572385). The mitochondrial DNA (mtDNA) region between COII and the lRNA gene was amplified using primers C2F3 (5'-GGTCAATGTTCAGAAATTTGTGG-3') and 1108 (5'-TACCTTTGACCAATCACGCT-3') (Powers and Harris, 1993). A fragment of 529 bp was obtained and the sequence (GenBank Accession No. OM055828) was 100% identical to the known sequence of M. hapla from Taiwan (GenBank Accession No. KJ598134). An infection test was conducted in greenhouse conditions. Six 2-month-old S. miltiorrhiza plants were individually maintained in 12-cm diameter, 10-cm deep plastic pots containing sterilized soil and each plant was inoculated with 3000 J2s hatched from egg masses of collected M. hapla samples. Two non-inoculated S. miltiorrhiza plants served as negative controls. After 60 days, inoculated plants exhibited galled roots similar to those observed in the field. Many galls (61.33 ± 8.52) and egg masses (26.17 ± 4.79) were found on each root system. The nematode reproduction factor (RF = final population/initial population) was 4.5. No symptoms were observed in control plants. The nematode was reisolated from root tissue and identified to be M. hapla with its sequence-specific primers JMV1/JMV. These results confirmed that the nematode population could infect S. miltiorrhiza. To our knowledge, this is the first time of natural infection of S. miltiorrhiza with M. hapla in China. Including S. miltiorrhiza, the medicinal ingredients of many traditional Chinese herbal medicines were extracted from the roots of the plants. The infection of root-knot nematode will cause a serious decline in the quality of Chinese medicinal materials. Therefore, it is necessary to identify the species of root-knot nematode in different Chinese herbal medicines.

Meloidogyne enterolobii risk to agriculture, its present status and future prospective for management.

Meloidogyne enterolobii, commonly known as guava root-knot nematode, poses risk due to its widespread distribution and extensive host range. This species is recognized as the most virulent root-knot nematode (RKN) species because it can emerge and breed in plants that have resistance to other tropical RKNs. They cause chlorosis, stunting, and yield reductions in host plants by producing many root galls. It is extremely challenging for farmers to diagnose due to the symptoms' resemblance to nutritional inadequacies. This pathogen has recently been considered a significant worldwide threat to agricultural production. It is particularly challenging to diagnose a M. enterolobii due to the similarities between this species and other RKN species. Identified using traditional morphological and molecular techniques, which is a crucial first in integrated management. Chemical control, biological control, the adoption of resistant cultivars, and cultural control have all been developed and effectively utilized to combat root-knot nematodes in the past. The object of this study was to get about the geographical distribution, host plants, symptoms, identification, and control techniques of M. enterolobii and recommend future initiatives to progress its management.

Species of Root-Knot Nematodes (Meloidogyne spp.) Infecting Soybean in Different Localities of Egypt and Rating of its Local Genotypes for their Resistance to Meloidogyne incognita

Species of Root-Knot Nematodes (Meloidogyne spp.) Infecting Soybean in Different Localities of Egypt and Rating of its Local Genotypes for their Resistance to Meloidogyne incognita

Frequency of Occurrence of Heterodera glycines Types, Meloidogyne spp., and Eight Other Nematode Taxa Associated with Soybeans in Georgia

Soybean fields in Georgia were surveyed for plant-parasitic nematodes (PPNs) during the 2021 growing season. The frequency and population density of 10 PPN taxa were determined in 144 soil samples collected from soybean fields in 31 Georgia counties. Between one and six PPN taxa were identified in 97% of the soil samples, with >50% of samples harboring four or more taxa. The spiral nematode ( Helicotylenchus spp.) was the most prevalent (85%), followed by lesion ( Pratylenchus spp., 71%), stubby root (Trichodoridae, 69%), ring (Criconematidae, 54%), root-knot ( Meloidogyne spp., 49%), stunt ( Tylenchorhynchus spp., 11%), reniform ( Rotylenchulus spp., 8%), cyst (Heteroderidae, 8%), dagger ( Xiphinema spp., 4%), and lance ( Hoplolaimus spp., 2%). Fourteen soil samples from nine Georgia counties were confirmed to have the soybean cyst nematode (SCN), Heterodera glycines (HG), based on morphological identification, molecular identification, and evidence of reproduction on soybean. HG type tests determined the virulence of each SCN population on resistant soybean. All SCN populations tested were able to reproduce at a female index ≥ 10% on PI 88788. HG type 1.2.- was the most frequent (57%), followed by HG type 2.- (29%) and HG type 1.2.3.- (14%). Meloidogyne incognita was the most frequently identified species of root-knot nematode (80%), followed by M. arenaria (28%) and M. javanica (6%). Our survey results serve to raise awareness of PPNs among Georgia soybean producers to inform future management decisions and improve information available to soybean breeders in their efforts to incorporate multiple nematode resistance into improved soybean cultivars.

Molecular determination of root-knot nematode species, Meloidogyne spp. Goeldi, 1892 (Tylenchida: Meloidogynidae) infesting weeds in kiwifruit orchards in Türkiye

In this investigation, the species of root-knot nematodes (RKNs) infesting weeds in kiwifruit orchards were investigated in the Ordu Province, Türkiye. A survey was conducted in 2018 and roots of weeds with RKN infestations were found in kiwifruit orchards. The infested weed samples were collected from 27 kiwifruit fruit orchards located in the Ordu Province. Identification of RKNs was performed using the molecular method based on mitochondrial DNA (mtDNA). The mtDNA region between the cytochrome oxidase II and the large subunit ribosomal RNA was amplified using two pairs of primers TRNAH/MRH106 and MORF/MTHIS. Species-specific primers previously described were used to confirm Meloidogyne species as the last step. Meloidogyne incognita (Kofoid & White, 1919), Meloidogyne arenaria (Neal, 1889) and Meloidogyne hapla (Chitwood, 1949) (Tylenchida: Meloidogynidae) were identified from fifteen weed species (2 unidentified) in eight families. Meloidogyne incognita was the most frequent species with 74.1% of the samples infested, followed by M. hapla at 22.2% and M. arenaria at 3.7%. In this study found Erigeron canadensis L. (Asterales: Asteraceae), Mercurialis annua L. (Malpighiales: Euphorbiaceae), Oxalis pes-caprae L. (Oxalidales: Oxalidaceae), Clinopodium nepeta (L.) Kuntze (Lamiales: Lamiaceae), Fumaria officinalis L. (Ranunculales: Papaveraceae) and Lycopus spp. (Lamiales: Lamiaceae) to be previously unrecorded hosts of M. incognita and Sigesbeckia orientalis L. (Asterales: Asteraceae) and Lythrum spp. (Myrtales: Lythraceae) a host of M. hapla.

Identification of the root-knot nematode species associated with Carica papaya

Abstract. Plena SNG, Indarti S, Widiastuti A, Putra NS. 2022. Identification of the root-knot nematode species associated with Carica papaya.Biodiversitas 23: 6212-6217. Root-knot nematodes (Meloidogyne spp.) are important economic pests causing low production and yield losses in horticultural crops. Meloidogyne spp. is widespread and regarded as a major pest since they are found all over the world in a variety of geographic locations, most frequently found in tropical and subtropical climate zones. They are obligate parasites that feed on various plants, including papaya and other horticultural plants. They are root-galling in host plants. Many species of root-knot nematodes may be found in a suitable environment. Therefore, accurate identification of the root-knot nematode species in papaya plants is important for developing and applying control and management measures. Surveys and sampling of nematodes on papaya plants were performed at the Agrotechnology Innovation Center, Universitas Gadjah Mada, the Special Region of Yogyakarta, Indonesia, and its surroundings. Identification was performed both morphologically (based on the perineal pattern of female nematodes) and molecularly (using root-knot nematode species-specific primers). The results revealed that the species of root-knot nematode associated with papaya plants was Meloidogyne javanica based on the perineal pattern of female nematodes, specifically the lateral lines. This finding was also supported by the results of the DNA amplification at 670-bp product using specific primers for M. javanica (FJav/RJav). Consequently, plant protection efforts will need to focus on minimizing M. javanica damage in papaya cultivation.

Molecular Characterization and Virus-Induced Gene Silencing of a Collagen Gene, Me-col-1, in Root-Knot Nematode Meloidogyne enterolobii.

Meloidogyne enterolobii, a highly pathogenic root-knot nematode species, causes serious damage to agricultural production worldwide. Collagen is an important part of the nematode epidermis, which is crucial for nematode shape maintenance, motility, and reproduction. In this study, we report that a novel collagen gene, Me-col-1, from the highly pathogenic root-knot nematode species Meloidogyne enterolobi was required for the egg formation of this pathogen. Me-col-1 encodes a protein with the size of 35 kDa, which is closely related to collagen found in other nematodes. Real-time PCR assays showed that the expression of Me-col-1 was highest in eggs and lowest in pre-parasitic second-stage juveniles (preJ2). Interestingly, knockdown of Me-col-1 did not compromise the survival rate of preJ2 but significantly reduced the egg production and consequentially caused 35.79% lower multiplication rate (Pf/Pi) compared with control. Our study provides valuable information for better understanding the function of collagen genes in the nematode life cycle, which can be used in the development of effective approaches for nematode control.

The FMRFamide-like peptide FLP-1 modulates larval development by regulating the production and secretion of the insulin-like peptide DAF-28 in Caenorhabditis elegans.

The FMRFamide-like peptides (FLPs) are conserved in both free-living and parasitic nematodes. This molecular genetic study verified the relevance of the flp-1 gene, which is conserved in many nematode species, to the larval development of the free-living soil nematode Caenorhabditis elegans. Using C. elegans as a model, we found that: (1) FLP-1 suppressed larval development, resulting in diapause; (2) the secretion of FLP-1, which is produced in AVK head neurons, was suppressed by the presence of food (Escherichia coli) as an environmental factor to continue larval development; (3) the FLP-1 reduced the production and secretion of DAF-28, which is produced in ASI head neurons and is the predominant insulin-like peptide (INS) present. FLP-1 is conserved in many species of plant-parasitic root-knot nematodes that cause severe damage to crops. Therefore, our findings may provide insight into the development of new nematicides that can disturb their infection and development.