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In the process of infecting plants, plant parasitic nematodes release a series of proteins that play an essential role in the successful infection and pathogenesis of plant cells and tissues through stylets or body walls. In this study, based on transcriptome data, a chorismate mutase gene of Radopholus similis (RsCM) was identified and cloned, which is a single copy gene specifically expressed in the oesophageal gland and highly expressed in juveniles and females. Transient expression of RsCM in tobacco leaves showed that it was localised in the cytoplasm and nucleus of tobacco leaf cells, which inhibited the pattern-triggered immunity (PTI) induced by flg22, including callose deposition and defence gene expression, and cell death induced by immune elicitors BAX, but could not inhibit cell death induced by immune elicitors Gpa2/RBP-1. The RNA interference (RNAi) transgenic tomato of RsCM obviously inhibited the infection, pathogenicity, and reproduction of R. similis. However, the resistance of the overexpression transgenic tomato of RsCM to R. similis infection was significantly reduced, and the expression levels of two salicylic acid (SA) pathway genes (PR1 and PR5) in roots infected by the nematode were significantly down-regulated, which indicated that RsCM might be involved in the inhibition of SA pathway. The results of this study demonstrate that RsCM suppresses the host immune system and might be a new target for the control of R. similis, which also provides new data for the function and mechanism of CM genes of migratory parasitic plant nematodes.

Plant pathogenic nematodes pose a significant threat to banana production, causing symptoms such as root lesions, stunted growth, and reduced yield. A comprehensive study in Bangladesh's Sylhet district aimed to assess nematode infestations in banana fields, involving interviews with farmers, soil sample collection, and microscopic examination. Results revealed the presence of multiple nematode species, with Helicotylenchus spp. being the most abundant. PCR analysis confirmed R. similis infestation in 35% of fields, highlighting its prevalence. Monoculture practices were observed among farmers, exacerbating nematode infestation risks. Limited communication between farmers and agricultural offices contributes to unawareness of nematode infestations. Country-wide studies and improved communication are crucial for implementing effective nematode mitigation strategies and safeguarding banana yield. [ABSTRACT FROM AUTHOR]

Plantain is one of the major staples contributing to food security and income generation in West and Central Africa. Local cultivars in Cameroon are susceptible to pests and diseases causing severe losses in plantain production. This study aimed at evaluating the agronomic performance and producer’s perception of plantain hybrids in the humid forest of Cameroon. Field trials were established in a completely randomized block design with eight genotypes and three replicates. Data on pest and disease as well as farmer perception were collected over two growing cycles. These genotypes included seven improved and one local genotype (check). Improved genotypes were highly tolerant to the Black Sigatoka disease compared to local plantain. While root necrosis index was above 50% in local varieties, indices below 25% were recorded in hybrids. Weevil severity in local was higher (55.0 ± 5.2%) compared to 21.0 ± 4.6% to 28.5 ± 3.2% in improved plantains. Average bunch weight was higher for FHIA 21 with 17.9 ± 0.7 kg in the first and 19.7 ± 0.3 kg for the second cycle, while those of the local Ebang were 9.6 ± 0.5 kg and 12.8 ± 0.9 kg, respectively. FHIA 21 and CRBP 568 were the preferred varieties by farmers (68.8% and 56.3% acceptance) from an agronomic perspective. The consumers’ preferences for all the genotypes varied with types of cooking. The implications of these findings for adoption by farmers and consumers as well as for the promotion of the plantain sector in central Africa are discussed.

Radopholus similis (Cobb 1893) (Rhabditida, Pratylenchidae) is a common and destructive pest that causes significant yield losses in Cavendish bananas. The repeated use of synthetic pesticides to control this nematode has raised concerns about toxicity to users and the environment. An alternative approach to managing this harmful species involves the use of nontoxic plant-derived extracts that enhance protection against various biological constraints. In this study, aqueous extract from the leaves and stems of Eupatorium odoratum Linn. (EAEO) was used to control R. similis in banana roots under in vitro and on-plant conditions. Through direct contact and penetration experiments on roots, as well as on-plant trials, concentrations of 12500, 6250, 3120, 1560, and 780 mg DW·L−1 EAEO were used to evaluate nematode mortality rates, infection levels in root segments (in vitro experiment), root infection, root necrosis index, shoot and root fresh weight, and growth parameters such as stem length, diameter, leaf number, and leaf surface area (on-plant experiment). The results showed that the nematode mortality rate due to EAEO ranged from 35.3% to 90.1%, which is statistically significant compared to the mortality rate in the control treatment (16%). Significant nematode inhibition was observed in banana roots infected with R. similis and exposed to EAEO for 48 h. There were no statistically significant differences in root infection, root necrosis, and plant fresh weight between plants treated with fenamiphos and EAEO. Maximum effectiveness was observed at the 12500 mg DW·L−1 EAEO concentration. These findings provide valuable insights into the nematicidal metabolites of EAEO against R. similis. Thus, the potential of EAEO as a biocontrol agent against R. similis has been demonstrated. For future research, investigations will be extended to elucidate the mechanisms of action of the essential compounds in EAEO against nematodes, determine the optimal EAEO dosage for nematode control without harm to banana plants and the environment, assess the long-term effects of EAEO on banana plants and the environment, explore the ecological impact of EAEO use in agricultural ecosystems, study the effectiveness of EAEO on various plant species, and consider the development of commercial products or formulations based on EAEO.

Summary: Turmeric (Curcuma longa) is a major spice of Indian origin. Turmeric is commonly used in Ayurvedic and Siddha medicine, and also in Indian cuisine. India produces nearly 1.2 million tonnes (Mt) of turmeric annually and is one of the world's largest producers. Turmeric production is limited by a number of biotic and abiotic factors. Among the biotic factors, plant-parasitic nematodes (PPN) are important. They include Meloidogyne spp., Pratylenchus spp., Radopholus similis and Rotylenchulus reniformis. However, the information about the distribution, density and prominence of plant-parasitic nematodes and their interrelation with soil types is very scarce. Hence, the present comprehensive nematode survey was undertaken in the major turmeric-producing states of India: Tamil Nadu, Andhra Pradesh, Telangana and Odisha. The results indicated that Meloidogyne spp., R. reniformis , Pratylenchus spp., R. similis , Hoplolaimus spp., Helicotylenchus spp. and Tylenchorhynchus spp. were associated with turmeric. The most abundant nematodes were Meloidogyne spp. (115 individuals (100 cm3 soil)−1), followed by R. reniformis (68 (100 cm3 soil)−1) and Pratylenchus spp. (50 (100 cm3 soil)−1). The frequency of occurrence ranged from 0 to 60%, with Meloidogyne spp. (60%) and R. reniformis (51%) being the most common. Meloidogyne spp. (38%) and Pratylenchus spp. (19%) were the most prominent nematodes in plant samples. Overall, Meloidogyne spp. followed by Pratylenchus spp., R. reniformis and R. similis were the key nematodes associated with the turmeric crop in all the four states. Further, we have identified hotspot areas for the plant-parasitic nematodes, namely: Meloidogyne spp. (16), Pratylenchus spp. (16), R. reniformis (20), and R. similis (5) on the basis of the economic threshold level. The interrelationship of soil type and nematode distribution was also investigated. [ABSTRACT FROM AUTHOR]

The effect of Radopholus similis, Pratylenchus araucensis, Meloidogyne spp., and their interaction was evaluated in seedlings of Musa AAB ‘Dominico Hartón’. The study was conducted in a nursery in Palestina, Caldas department, Colombia. Forty-day-old plantain seedlings were infected separately with 750, 1,500, 2,250 and 3,000 of each species of nematodes/plant. Two experiments were conducted to evaluate the damage of R. similis, P. araucensis, Meloidogyne spp. and the mixture of 750 R. similis + 750 P. araucensis + 750 Meloidogyne spp. compared with the mixture of different proportions (1,500, 2,250 and 3,000 of each species of nematodes). Noninfected plants were included as a control treatment, for a total of 17 treatments in a randomized complete block design with ten replications. Twelve weeks after inoculation, all nematodes, both alone and in combination, reduced (p < 0.05) plantain dry root and shoot weight. In two experiments, R. similis, P. araucensis, and Meloidogyne spp. alone, each with a population density of 3,000, reduced (p < 0.05) root dry weight by 32.5%, 9.5% and 49%, respectively, and decreased (p < 0.05) shoot dry weight by 21.5%, 23%, and 31.5%, respectively, compared to the control. The interaction of nematodes with the lowest population decreased root (33%) and shoot (21%) weight. We conclude that the growth of ‘Dominico Hartón’ seedlings was affected by plant-parasitic nematodes, but the greatest damage occurred with concomitant nematode infection.

Se evaluó el efecto de Fosfito de potasio, Fosetil-Al, Acibenzolar-s-metil, Ácido DL-3-aminobutírico y lixiviados de raquis de plátano, en la reducción de nematodos fitoparásitos en suelo y raíces de plántulas de plátano Dominico-Hartón y FHIA-21. El diseño experimental fue de bloques al azar con siete tratamientos, ocho plántulas por tratamiento, y cuatro repeticiones, incluyendo dos testigos: absoluto y relativo. Se registró la brotación, altura de plántulas, longitud de raíces, materia seca de raíces y nematodos fitoparásitos en 100 g de raíces y suelo. En todos los tratamientos ocurrió el 100% de brotación. La altura de plántulas y longitud de raíces no fue afectada negativamente por la aplicación de los inductores de resistencia, excepto en las tratadas con lixiviados de raquis que presentaron síntomas de fitotoxicidad. La materia seca de raíces aumentó a través del tiempo en los tratamientos con inductores y disminuyó en los testigos. La aplicación de los inductores de resistencia redujo significativamente las poblaciones de nematodos fitoparásitos en raíces de Dominico-Hartón entre 61 y 91% y en FHIA-21 entre 51 y 85%. En suelo la reducción en Dominico-Hartón osciló entre 42 y 78% y en FHIA-21 entre 38 y 72%. En ambos materiales de plátano, se registró Radopholus similis, Helicotylenchus spp. y Meloidogyne spp.

The burrowing nematode Radopholus similis is considered a major problem of intensive banana cultivation. It can cause extensive root damage resulting in the toppling disease of banana, which means that plants fall to the ground. Soaking R. similis in double-stranded (ds) RNA of the nematode genes Rps13, chitin synthase (Chs-2), Unc-87, Pat-10 or beta-1,4-endoglucanase (Eng1a) suppressed reproduction on carrot discs, from 2.8-fold (Chs-2) to 7-fold (Rps13). The East African Highland Banana cultivar Nakitembe was then transformed with constructs for expression of dsRNA against the same genes, and for each construct, 30 independent transformants were tested with nematode infection. Four months after transfer from in vitro culture to the greenhouse, the banana plants were transferred to a screenhouse and inoculated with 2000 nematodes per plant, and thirteen weeks later, they were analyzed for several parameters including plant growth, root necrosis and final nematode population. Plants with dsRNA constructs against the nematode genes were on average showing lower nematode multiplication and root damage than the nontransformed controls or the banana plants expressing dsRNA against the nonendogenous gene. In conclusion, RNAi seems to efficiently protect banana against damage caused by R. similis, opening perspectives to control this pest. [ABSTRACT FROM AUTHOR]

ABSTRACTPlantain is one of the major staples contributing to food security and income generation in West and Central Africa. Local cultivars in Cameroon are susceptible to pests and diseases causing severe losses in plantain production. This study aimed at evaluating the agronomic performance and producer’s perception of plantain hybrids in the humid forest of Cameroon. Field trials were established in a completely randomized block design with eight genotypes and three replicates. Data on pest and disease as well as farmer perception were collected over two growing cycles. These genotypes included seven improved and one local genotype (check). Improved genotypes were highly tolerant to the Black Sigatoka disease compared to local plantain. While root necrosis index was above 50% in local varieties, indices below 25% were recorded in hybrids. Weevil severity in local was higher (55.0 ± 5.2%) compared to 21.0 ± 4.6% to 28.5 ± 3.2% in improved plantains. Average bunch weight was higher for FHIA 21 with 17.9 ± 0.7 kg in the first and 19.7 ± 0.3 kg for the second cycle, while those of the local Ebang were 9.6 ± 0.5 kg and 12.8 ± 0.9 kg, respectively. FHIA 21 and CRBP 568 were the preferred varieties by farmers (68.8% and 56.3% acceptance) from an agronomic perspective. The consumers’ preferences for all the genotypes varied with types of cooking. The implications of these findings for adoption by farmers and consumers as well as for the promotion of the plantain sector in central Africa are discussed.

Summary: The root-burrowing nematode, Radopholus similis , is reputedly the most damaging nematode pest of banana and responsible for major production losses. In this study, the endophytic potential of 13 fungal isolates was assessed for the management of R. similis in East African Highland bananas ('Ng'ombe'). All isolates successfully colonised tissue-cultured banana roots, with isolates from Trichoderma , Fusarium and Hypocrea producing the highest (⩾49.1%) and Beauveria isolates the lowest (⩽14.4%) colonisation. The fungal endophytes T. asperellum (ICIPE 700) and H. lixii (ICIPE 697) were the most effective in reducing R. similis densities (>81%) relative to the non-inoculated control. However, the combined inoculation of ICIPE 700 and ICIPE 697 led to greater suppression of R. similis (>21%) relative to individual inoculation. Suppression of R. similis following inoculation of banana roots with ICIPE 700 and/or ICIPE 697 was associated with the significant upregulation of the defence-related gene PR-1 , the cell signalling gene calmodulin Ca 2+ and the cell-wall-strengthening gene β-1 , 3-glucan synthase. This study demonstrates the potential for nematode management in bananas with fungal endophytes, especially using the isolates ICIPE 700 and ICIPE 697 when combined. [ABSTRACT FROM AUTHOR]

Rhizobacteria has shown promising results in managing nematodes and improving the root system of banana plants. However, their effects on commercial banana plants in different generations remain unclear. In this study performed under field experiment, we evaluated the effect of three types (injection, edaphic and foliar) of a local rhizobacterial consortium application on the system root, nematode populations, and their damage in the third-generation plants. Only mother and daughter plants were treated twice with the rhizobacteria. Plants not treated with rhizobacteria constituted the control treatment. Our results show that rhizobacteria affect different underground tissues and nematodes in third-generation banana plants. Helicotylenchus spp., Meloidogyne spp., Pratylenchus spp., Radopholus similis, and Rhabditis spp. were the nematodes found in banana roots. R. similis population and the damage in the root system of banana plants were reduced significantly by the rhizobacteria edaphic application. The application of rhizobacteria could be a sustainable management strategy over time to improve the root system and suppress nematodes, and their damage in commercial banana plants.

Fitonematoda merupakan salah satu penyebab penyakit pada tanaman kopi robusta dan arabika. Penelitian ini bertujuan menganalisis komunitas fitonematoda pada kopi robusta dan arabika serta distribusinya pada kondisi kesehatan pertanaman yang berbeda. Lokasi pengambilan sampel berada di Kebun Percobaan Sumber Asin (Desa Krajan, Kecamatan Sumbermanjing, Kabupaten Malang), Blawan (Desa Sempol, Kecamatan Sempol, Kabupaten Bondowoso), dan Kalisat Jampit (Desa Kalisat, Kecamayan Ijen, kabupaten Bondowoso) Provinsi Jawa Timur. Sampel akar dan tanah diambil pada tanaman bergejala penyakit, tanaman di antara tanaman sakit dan sehat, dan tanaman sehat. Ekstraksi nematoda dari sampel akar dilakukan dengan metode pengabutan (mist chamber) dan sampel tanah dengan flotasi sentrifugasi. Peubah yang diamati ialah nilai prominensi (NP) dan proporsi sebaran fitonematoda penting. Fitonematoda yang diperoleh pada kopi robusta ialah Pratylenchus coffeae, Rotylenchulus reniformis, Meloidogyne spp., dan Hemicriconemoides cocophillus. Fitonematoda yang diperoleh pada kopi arabika ialah Radopholus similis, Meloidogyne spp., Paratylenchus sp., Criconemoides sp., dan Helicotylenchus sp. Fitonematoda didominasi oleh spesies P. coffeae dan R. reniformis pada kopi robusta serta R. similis dan Meloidogyne spp. pada kopi arabika. Terdapat perbedaan nilai prominensi pada masing-masing fitonematoda yang ditemukan. Nilai prominensi fitonematoda tertinggi dari ekstraksi perakaran kopi robusta terdapat pada P. coffeae, yaitu sebesar 295.83, sedangkan pada perakaran kopi arabika terdapat pada R. similis sebesar 259.16. Secara umum, pada spesies tersebut terjadi peningkatan populasi dari tanaman sehat ke tanaman bergejala penyakit.

Radopholus similis (Cobb 1893) Thorne (1949) is a destructive migratory endoparasitic plant nematode. In this study, the pathogenic process of R. similis infection in Nicotiana benthamiana (tobacco) was studied using quartz sand culture in laboratory. The results showed that R. similis mainly parasitised the root cortex, leading to cortical cell decomposition and tissue decay. We optimised the inoculation conditions to establish a method for determining the pathogenicity of R. similis as follows: (1) a glass culture tube was filled with quartz sand (about 1/3 of the height) and sterilised twice; (2) 20-day-old N. benthamiana seedlings were transplanted into test tubes and cultivated for 10 days at (25±1)°C; (3) R. similis female nematodes were inoculated in the root rhizosphere at a rate of 150 nematodes per plant; (4) the number of nematodes, disease severity, and growth of the plant at 30 days post-inoculation (dpi) were determined. The pathogenicity of eight R. similis populations from different hosts was determined, which proved the feasibility of this method.

The burrowing nematode Radopholus similis is considered a major problem of intensive banana cultivation. It can cause extensive root damage resulting in the toppling disease of banana, which means that plants fall to the ground. Soaking R. similis in double-stranded (ds) RNA of the nematode genes Rps13, chitin synthase (Chs-2), Unc-87, Pat-10 or beta-1,4-endoglucanase (Eng1a) suppressed reproduction on carrot discs, from 2.8-fold (Chs-2) to 7-fold (Rps13). The East African Highland Banana cultivar Nakitembe was then transformed with constructs for expression of dsRNA against the same genes, and for each construct, 30 independent transformants were tested with nematode infection. Four months after transfer from in vitro culture to the greenhouse, the banana plants were transferred to a screenhouse and inoculated with 2000 nematodes per plant, and thirteen weeks later, they were analyzed for several parameters including plant growth, root necrosis and final nematode population. Plants with dsRNA constructs against the nematode genes were on average showing lower nematode multiplication and root damage than the nontransformed controls or the banana plants expressing dsRNA against the nonendogenous gene. In conclusion, RNAi seems to efficiently protect banana against damage caused by R. similis, opening perspectives to control this pest.

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The contributions of soil biota toward outcomes of pathogenic interactions between Radopholus similis and Fusarium oxysporum V5w2 in tissue culture banana plants starved of nitrogen (N), phosphorus (P), and potassium (K) were investigated. The study was based on three screenhouse factorial experiments (2 × 2 × 2) comprising of potted banana plants with or without R. similis, with or without F. oxysporum V5w2, and either grown in sterile or non-sterile soil. All plants in each of the three experiments received nutrient solutions that were deficient in N, P, or K, respectively. In all the three nutritional regimes, plants inoculated with R. similis were heavily colonized by the nematode with high percentage dead roots and necrosis, while their root biomasses were low. N-starved plants co-inoculated with R. similis and F. oxysporum V5w2 had lower percentage dead roots and tended to have numerically lower nematode density compared to those treated with R. similis only, especially in non-sterile soil. N-starved plants inoculated with R. similis had higher shoot dry weight, were taller with more leaves that were larger, compared to those not inoculated with the nematode. Plants grown in non-sterile soil had lower percentage dead roots, necrosis and R. similis density than those from sterile soil, regardless of the nutrient regime. N-starved plants from non-sterile soil were shorter with smaller leaves having decreased chlorophyll content and lower biomass, compared to those from sterile soil. By contrast, P and K starved plants from non-sterile soil were taller with larger leaves and more biomass, compared to those from sterile soil. Roots inoculated with R. similis had higher endophytic colonization by Fusarium spp., especially when co-inoculated with F. oxysporum V5w2 and grown in sterile soil among the N and K-starved plants. In conclusion, pathogenic interactions between R. similis and F. oxysporum V5w2 are predominantly suppressed by a complex of soil microbes that exert plant growth promoting effects in tissue culture banana plants through N, P, and K dependent processes. Nitrogen is the most important limiting factor in rhizosphere interactions between banana roots, beneficial microbes and the pathogens. Soil sterilization and the stringent aseptic tissue culture techniques still require the development of alternative innovative ways of conserving microbial services for sustainable agriculture.

Endosphere and rhizosphere microbes offer plant growth promotion and pest suppression ecosystem services in banana-based agroecosystems. Interest has been growing towards the use of such beneficial microbes in protecting vulnerable tissue culture banana plants against pathogens such as Radopholus similis and Fusarium oxysporum. A screenhouse experiment with potted tissue culture banana plants was conducted using sterile and non-sterile soil to investigate the effect of soil biota on R. similis and F. oxysporum strain V5w2. Plants grown in non-sterile soil had lower damage and R. similis density in roots and rhizosphere, while most plant growth-related parameters including root freshweight, shoot freshweight, total freshweight, plant height, and leaf size were larger compared to those from sterile soil. Shoot dryweight and Mg content were higher in plants from sterile soil, while their leaves developed discolored margins. R. similis-inoculated plants in sterile soil were smaller, had more dead roots, higher nematode density, and produced fewer and smaller leaves, than those from non-sterile soil. For all plant growth-related parameters, nematode density and root damage, no differences were recorded between controls and F. oxysporum V5w2-inoculated plants; and no differences between those inoculated with R. similis only and the ones co-inoculated with the nematode and F. oxysporum V5w2. Banana roots inoculated with F. oxysporum V5w2 were lighter in color than those without the fungus. Independent or combined inoculation of banana plants with F. oxysporum V5w2 and R. similis resulted in lower optical density of root extracts. In vitro assays indicated the presence of Fusarium spp. and other root endophytic microbes that interacted antagonistically with the inoculated strain of F. oxysporum V5w2. It is concluded that, soil sterilization eliminates beneficial microbes that provide natural pest suppression ecosystem services against R. similis and F. oxysporum in the endosphere and rhizosphere of tissue culture banana plants. I recommend the integration of microbiome conservation into tissue culture technology through the proposed “Tissue Culture Microbiome Conservation Technology.”

Burrowing nematode (Radopholus similis) causes severe stunting and yield reduction in anthurium (Anthurium andraeanum) cut flower production. Two field trials were conducted at commercial grower farms to test the efficacy of fluopyram or fluopyram + trifloxystrobin for managing burrowing nematodes. Nematode population densities in roots and cinder media were evaluated during the trial in addition to cut flower yield and canopy cover. In the first trial, the nematode population in roots was reduced by 57% after two applications of fluopyram 3 months apart. As plant health improved, the increasing anthurium root weight supported higher nematode populations. After 14 months, fluopyram-treated plots had 43% more green canopy cover and a 53% increase in flower production compared with the untreated control plots. At a second location, population densities of burrowing nematode were reduced in roots after one application of fluopyram + trifloxystrobin and remained low with quarterly applications. Nematode populations were initially reduced in fluopyram-treated plots followed by a resurgence as demonstrated in the other trial. Ten months after the initial treatment, flower yield was greater in fluopyram + trifloxystrobin-treated plots with more large and extra-large flowers produced. Canopy cover was 45% and 22% greater with fluopyram + trifloxystrobin and fluopyram applications, respectively. Fluopyram shows potential for management of burrowing nematodes in anthurium by improving plant vigor and cut flower production.

Fusarium oxysporum V5w2 is a fungal agent, which was originally intended for biological control of the root pathogenic nematode Radopholus similis among other banana pests. Information on some of its actual effects on banana plants and pests has been scarce. A study was conducted to assess the effects of F. oxysporum V5w2 and mulch on R. similis and banana plants in the field. The experiment was a 3-factor (2 × 2 × 2) complete randomized block design with or without F. oxysporum V5w2, R. similis or mulch. Root damage was higher when plants were inoculated with R. similis compared to non-inoculated plants, while plant height, leaf size, bunch size and banana yields were lower in R. similis-inoculated plants. Plant growth and bunch size were greater in mulched than in non-mulched plots, with banana yields on mulched plots increasing by 131% to reach 37 tonnes per hectare. F. oxysporum V5w2-inoculated plants were shorter, with fewer leaves that were smaller, and had shorter duration to harvest than non-inoculated ones. When R. similis-inoculated mulched plants received F. oxysporum V5w2 inoculum, plant toppling-over occurred less frequently compared to plants that were not inoculated with the fungus, probably because the plants were smaller in size during growth. The benefits of mulching in banana production were evident, while the claimed enhancing effect of inoculating tissue culture plants with F. oxysporum V5w2 as a biological control agent could not be verified. I conclude by suggesting that, the use of F. oxysporum V5w2 as a biological control agent of R. similis and other pests should be reconsidered, because this fungal strain has the potential of invading xylem vessels and becoming pathogenic to banana plants.

The effects of nematicide rotation on banana (Musa AAA cv. Williams) root weight, root nematode control, and crop yield were compared in a commercial banana plantation in Ecuador, testing six treatments in a randomized complete block design with six replicates. Treatments consisted of two, three and four different nematicide cycles per year plus the untreated control. Regarding the untreated plants and averaging the 24 root nematode samplings after treatment application, the nematicide applications reduced significantly R. similis (P

Radopholus similis is an economically important pest of both banana and citrus in tropical regions. Here we present draft genomes from two populations of R. similis from Costa Rica that were created and assembled using short read libraries from Illumina HiSeq technology.

Nonpathogenic strains of Fusarium oxysporum are promising weapons in the endophytic biological control warfare against various banana pests, especially the banana weevil Cosmopolites sordidus and the root endoparasitic nematodes Pratylenchus goodeyi and Radopholus similis. The fungal endophytes are reintroduced into tissue culture banana plants to restore resistance against the pests, in the innovative ‘endophyte-enhanced tissue culture banana technology’. The strain Fusarium oxysporum V5w2 is said to have shown great potential for development into a biopesticide for suppression of the banana pests. Various studies have evaluated F. oxysporum V5w2 with mixed findings, which have brought up a stalemate in consensus towards transfer of the endophyte technology to farmers. This article brings into perspective variations in research findings that are associated with endophytic control of C. sordidus and R. similis using F. oxysporum V5w2 in tissue culture banana. Emphasis is laid on understanding the basis of research that informed the transfer of F. oxysporum V5w2-enhanced tissue culture banana plants to farmers in East Africa. The objective of this article is to unlock the biotechnological stalemate on endophytic control of C. sordidus and R. similis using F. oxysporum V5w2 in tissue culture banana. It is concluded that, F. oxysporum V5w2 still remains an unidentified rhizosphere root-invading plant growth suppressive (pathogenic) endophytic microbe, which should not be registered as a biopesticide or transferred to banana farmers in East Africa and elsewhere around the world. An open debate through reliable channels of scientific communication is encouraged.

Radopholus similis (Cobb) Thorne (Tylenchida: Pratylenchidae) and Meloidogyne incognita Kofoid and White (Tylenchida: Meloidogynidae) are agriculturally important migratory endoparasitic and sedentary endoparasitic plant nematodes, respectively. In this study, the effects of prey density, starvation time, and temperature on the number of R. similis consumed by a population of Neoseiulus barkeri Hughes (Acari: Phytoseiidae) isolated from the soil were studied in the laboratory. Moreover, the efficiencies of the control of R. similis in the Anthurium andraeanum Linden rhizosphere and of M. incognita in the tomato rhizosphere by mites were tested using potted plant experiments. At prey densities ranging from 100 to 500, the nematode consumption rate increased with the increasing density. With 500 nematodes per arena, the consumption rate of a female N. barkeri starved for 96 h was highest (218 nematodes) at 25°C among starvation treatments, and the maximum consumption rate of a female mite starved for 24 h was 152 nematodes at 28°C in temperature treatments. The addition of N. barkeri reduced the number of R. similis in the rhizosphere of potted anthurium and of M. incognita in the rhizosphere of potted tomato plants. Releasing 400 N. barkeri in the rhizosphere of each pot was optimum for controlling R. similis and M. incognita, and decreased the number of R. similis, root knots, and egg mass by 62.0%, 66.7%, and 69.7%, respectively. Therefore, the use of N. barkeri could be an effective biological method for the control of plant parasitic nematodes. [ABSTRACT FROM AUTHOR]

Six candidate reference genes were chosen from the transcriptome database of Radopholus similis using the bioinformatics method, including four conventional reference genes (actin, Eukaryotic translation initiation factor 5A (eIF5A), Tubulin alpha (a-tubulin), ubiquitin (UBI)) and two new candidate reference genes (Ribosomal protein S21 (Rps21) and Serine/threonine protein phosphatase PP1-β catalytic subunit (β-PP1)). In addition, a traditional reference gene 18S ribosomal RNA (18S rRNA) obtained from NCBI databases was also added to the analysis. Real-time PCR was used to detect the expression of seven candidate reference genes in six populations of R. similis and four developmental stages (female, male, larva and egg) of a population. The stability of the expression of candidate genes was evaluated by three software programs, BestKeeper, geNorm and NormFinder. The results showed that eIF5A is the most suitable reference gene for gene functional research of different populations, while both Rps21 and eIF5A are the most suitable reference genes for different developmental stages of a population. Therefore, eIF5A is the best reference gene for studying R. similis. However, one defect of this study is that only seven candidate reference genes were analyzed; ideally, more genes should be tested.

This chapter is a continuation of Chap. 3 . Initially, protocols for the screening of several host plants to their major migratory and semi-endoparasitic nematodes are presented. Then the problems related to assessment of tolerance to these nematodes are described, followed by the determination of nematode races. The main plant-nematode interactions considered are annuals and perennials to Pratylenchus spp.; banana to Radopholus similis; potato to Nacobbus aberrans; several crop plants, including onion, alfalfa, clovers, and potato, to Ditylenchus dipsaci; broad bean to D. giga; potato and sweet potato to D. destructor; peanut to D. africanus; rice to D. angustus and Aphelenchoides besseyi; wheat to Anguina tritici; different plants to Rotylenchulus reniformis; and citrus to Tylenchulus semipenetrans. Schemes to identify races or biotypes are only presented for D. dipsaci and T. semipenetrans. The occurrence of pathotypes in other nematode species is also discussed. Finally, comments are made on ectoparasitic nematodes., (© 2024. The Author(s), under exclusive license to Springer Science+Business Media, LLC, part of Springer Nature.)

Radopholus similis is a migratory endoparasitic nematode that is extremely harmful to host plants. Venom allergen-like proteins (VAPs) are members of the cysteine-rich secretory protein family that are widely present in plants and animals. In this study, we cloned a VAP gene from R. similis, designated as RsVAP. RsVAP contains an open reading frame of 1089 bp encoding 362 amino acids. RsVAP is specifically expressed in the esophageal gland, and the expression levels of RsVAP are significantly higher in juveniles than in other life stages of R. similis. This expression pattern of RsVAP was consistent with the biological characteristics of juveniles of R. similis, which have the ability of infection and are the main infection stages of R. similis. The pathogenicity and reproduction rate of R. similis in tomato was significantly attenuated after RsVAP was silenced. In tobacco leaves transiently expressing RsVAP, the pathogen-associated molecular pattern-triggered immunity (PTI) induced by a bacterial flagellin fragment (flg22) was inhibited, while the cell death induced by two sets of immune elicitors (BAX and Gpa2/RBP-1) was repressed. The RsVAP-interacting, ras-related protein RABA1d (LeRabA1d) was identified in tomato hosts by yeast two-hybrid and co-immunoprecipitation assays. RsVAP may interact with LeRabA1d to affect the host defense response, which in turn facilitates nematode infection. This study provides the first evidence for the inhibition of plant defense response by a VAP from migratory plant-parasitic nematodes, and, for the first time, the target protein of R. similis in its host was identified.

Ginger is an important commercial crop with global trade of 1.3 million tonnes, worth US$1038 million in 2016, but is impacted by several soil borne diseases including plant-parasitic nematodes. Radopholus similis, the burrowing nematode, has been recorded as a persistent problem in Fijian ginger production, but has not been recorded on ginger in Australia. The objective of this study was to establish if differences in the pathogenicity of R. similis on ginger exist between isolates from Fiji and Australia. Four Australian and two Fijian isolates of R. similis were compared in the glasshouse for their impacts on plant growth and multiplication on ginger and banana. Harvest and plant assessments were conducted over a 10-week interval, beginning 12 weeks post-inoculation. All isolates of R. similis were able to multiply on ginger, but the two Fijian isolates reduced above and below-ground ginger growth and caused significantly greater (P = 0.05) damage to rhizomes than the four Australian isolates. In contrast, the Fijian isolates did not multiply on banana or have any damaging effects, whereas, the Australian isolates multiplied and caused damage on this host. Thus, R. similis isolates from Fiji and Australia differed in pathogenicity on ginger and banana, indicating pathotype differences between isolates. Given the pathogenic variability observed in this study, care should be taken when soil and plant material (e.g. fresh rhizomes) are transferred between Fiji and Australia to avoid the potential introduction of infected material that could be used for plant propagation. [ABSTRACT FROM AUTHOR]

The burrowing nematode, Radopholus similis, is an obligate migratory endoparasite. Currently detection of this nematode is carried out mostly by physically extracting them from soil and then observing under a light microscope. To identify this nematode, a thorough knowledge about their morphological features is quite indispensable. Developing a DNA based detection technique makes it more convenient and accurate in detection. Though PCR based methods have been reported by earlier workers, developing a real-time PCR based method will enable estimating their population in field samples. In this study, real-time PCR primers were designed using the DNA sequences from the ITS region of R. similis. It can detect R. similis up to the limit of 100 fg µL-1 DNA. The real-time PCR based detection serves as an efficient tool for the detection and estimation of this nematode from soil samples. [ABSTRACT FROM AUTHOR]

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An analysis of the plant-parasitic nematodes found on the banana (Musa AAA) plantations in the provinces of Cañar, El Oro, Guayas, Los Rios and Santo Domingo of Ecuador from 2008 to 2014 was carried out. The nematode extraction was done from 25 g of fresh roots that were macerated in a blender and from which nematodes were recovered in a 0.025 mm (No. 500) mesh sieve. The data were subjected to frequency analysis in PC-SAS and the absolute frequency was calculated for each individual genus. Four plant parasitic nematodes were detected and, based on their frequencies and population densities, the nematode genera in decreasing order was: Radopholus similis > Helicotylenchus spp. > Meloidogyne spp. > Pratylenchus spp. Radopholus similis was the most abundant nematode, accounting for 49 to 66% of the overall root population, followed by Helicotylenchus spp. with 29 to 45% of the population throughout the different analyzed years. From a total of 13,773 root samples, 96% contained R. similis, 91% Helicotylenchus spp., 35% Meloidogyne spp., and 25% Pratylenchus spp. and, when all of the nematodes that were present were pooled (total nematodes), 99.9% of the samples had nematodes. A large number of samples with a nematode population above the economic threshold suggested by Agrocalidad, INIAP and Anemagro (2,500-3,000 nematodes/100 g of roots) was observed in all of the years, the months and the five sampled provinces. The statistical differences (P

Radopholus similis also known as the burrowing nematode is a devastating pest of banana (Musa spp.) and many economically important crops and ornamentals. In this publication, we present the genome assembly of R. similis.

All the root inhabiting migratory endoparasitic nematode populations of Radopholus procured from banana crop of Vellayani, Thiruvananthapuram, Kerala were identified as Radopholus similis. Heat killed females were straight to slightly ventrally curved posteriorly. Female's head was low, rounded, continuous or slightly setoff with the body contour. Females were 500-660 μm long and were comparatively longer than males. Males had button shaped head set off by a constriction; female with three to five lip annuli, four crenate and areolated lateral incisures, stylet 14-18 μm long with rounded knobs, vulva postequatorial (58%), sometimes with slight protuberant lips, ovary paired and equally developed, oesophageal gland overlapped the intestine dorsally, tail elongate-conoid with narrowly rounded terminus. The stylet length (μm), width of stylet knob (μm), distance of excretory pore from anterior end (μm), distance from head to basal bulb (μm), lateral field structure, shape of stylet knob, head region, position of phasmid, tail shape with its terminus, morphometric values like m%, o% and v% and a, c and c' ratios of females were stable (CV<12%) features. There is an existence of intra-specific variability in the morphological and morphometric features of R. similis. The main morphological diversity was observed with P% of male and female, b ratio of female and stylet length, distance of DEGO from stylet base, o% and T% of male. All the root inhabiting migratory endoparasitic nematode populations of Radopholus Thorne, 1949 procured from banana of Vellayani, Thiruvananthapuram, Kerala were identified as Radopholus similis (Cobb, 1893) Thorne, 1949. A high degree of intra-specific morphometric variability was observed with regard to the total body length (μm), body width (μm), stylet length (μm), distance of dosrsal oesophageal gland orifice (DEGO) from stylet base (μm), number of lip annuli, lip height (μm), distance from head to basal bulb (μm), distance of anus from anterior end (μm), tail length (μm), anal body width (μm), distance of phasmid from tail terminus (μm), number of lateral lines, width of lateral field (μm), b ratio and P % among females of R. similis. Morphometric features like m%, o% and v% of females of R. similis showed least variability. These can be considered as the stable morphometric characters for discrimination of females of R. similis. Ratios like 'a' and 'c' of females of R. similis were found moderately variable. The morphometric feature and of male i.e. distance from head to basal bulb (μm) was found least variable; while number of lip annuli and spicule length (μm) were moderately variable. [ABSTRACT FROM AUTHOR]

Sunn hemp, Crotalaria juncea, foliage (SH) has been documented as a soil amending material for controlling multiple plant-parasitic nematodes such as root-knot nematodes, Meloidogyne spp., and burrowing nematode, Radopholus similis, and enhancing beneficial free-living nematodes. In Hawai.i the macadamia nut, Macadamia integrifolia, husk (MN) as a mulch and soil amending material is used in areas with macadamia orchards. MN compost improves soil health in sub-tropical horticulture by increasing microbial activity, water holding capacity, pH, carbon, and nitrogen. SH and MN amendments were compared to non-amended soil (CC) to determine effects on Meloidogyne, R. similis, and beneficial nematodes through two laboratory experiments. In both experiments, banana orchard soil infested with R. similis and Meloidogyne were sampled. In both experiments, SH consistently showed the highest number of beneficial nematodes (P.0.05) and the lowest populations of R. similis. The effects of SH on Meloidogyne were not observed in Experiment-I. However, in Experiment-II, no Meloidogyne were found in SH. Compared to CC and SH, MN did not increase beneficial nematode numbers (P.0.05), nor reduce R. similis and Meloidogyne populations (P . 0.05). Researchers and Hawaiian farms should compare the effects of SH and MN on Meloidogyne and R. similis and beneficial nematodes under field conditions. [ABSTRACT FROM AUTHOR]