Characterization of finger millet extracts and evaluation of their nematicidal efficacy and plant growth promotion potential.

Plant-parasitic nematodes pose a significant threat to finger millet crops, potentially causing yield reduction of up to 70%. Extracts derived from finger millet varieties contain potent bioactive compounds that can mitigate nematode damage and promote plant growth. This study aimed at isolating and characterizing bioactive compounds from the finger millet varieties Ikhulule, Okhale-1, and U-15; evaluating the impact of Ikhulule and U-15 extracts on the mortality of the root lesion nematode Pratylenchus vandenbergae; assessing the growth promotion effects of Ikhulule and U-15 extracts on the finger millet variety Okhale-1; and determining the efficacy of these extracts in managing plant-parasitic nematodes under greenhouse conditions. Extracts were obtained from both leaves and roots and tested in vitro for nematode mortality and in vivo for growth promotion and nematode control. The results showed that finger millet extracts exhibited strong nematicidal properties in vitro, achieving a mortality rate of up to 98% against P. vandenbergae nematodes. Applying these extracts to finger millet shoots significantly reduced nematode populations in both soil and roots and decreased the reproductive factor to below one (1), indicating an effective nematode control. The study attributes the enhanced nematicidal effects of finger millet extracts to their bioactive compounds, particularly dodecanoic acid, phytol, 1,1,4a-trimethyl-6-decahydro naphthalene, 2,3-dihydro-benzofuran, 2-methoxy-4-vinylphenol and ethyl ester, and hexadecanoic acid. These findings suggest that finger millet-derived extracts offer a natural solution for nematode management and broader agronomic benefits, ultimately contributing to overall plant health and productivity.

Distribution, morphological and molecular characterization of root-lesion nematodes (Pratylenchus spp.) (Tylenchida: Pratylenchidae) in maize (Zea mays L.) (Poales: Poaceae) in Türkiye.

BACKGROUND: Root-lesion nematodes (RLN) are the most economically important pathogenic nematodes attacking maize. Significant economic losses due to lesion nematodes have been reported in maize producing countries in the world. METHODS AND RESULTS: This study was conducted to determine the distribution and identity of root-lesion nematodes (Pratylenchus spp.) (Tylenchida: Hoplolaimidae) in maize (Zea mays L.) (Poales: Poaceae) fields of the Black Sea region of Türkiye. For this purpose, 39 locations were surveyed and soil samples were taken from 17 regional provinces. Nematodes were extracted using the modified Baerman funnel technique. The species were identified based on sequences of the Internal Transcribed Spacer (ITS) region of ribosomal DNA, as well as morphological characters and morphometrics. In addition, species identifications were confirmed using species-specific primers in the D3 expansion region of 26 S rDNA. At the end of the study, 51.3% of the maize production areas sampled in the region were infected with root-lesion nematode species. Pratylenchus agilis, P. mediterraneus, P. neglectus, P. penetrans, P. thornei, and P. vulnus were identified, and were present in 25%, 5%, 25%, 10%, 15%, and 20% of samples, respectively. To our knowledge, this is the first report of P. agilis in Türkiye. CONCLUSION: The present study concluded that the molecular analysis of Pratylenchus sequences based on the ITS and D3 region of ribosomal RNA genes allowed the identification of six root lesion nematode species. This study is of great importance in terms of adding additional species to the root-lesion nematode fauna in Turkey and will provide data for future research on the management of these nematodes.

Detection of Resistance, Susceptibility, Tolerance, and Virulence in Plant-Nematode Interactions: Part II: Migratory and Semi-endoparasitic Nematodes.

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.

The Fight against Plant-Parasitic Nematodes: Current Status of Bacterial and Fungal Biocontrol Agents.

Plant-parasitic nematodes (PPNs) are among the most notorious and underrated threats to food security and plant health worldwide, compromising crop yields and causing billions of dollars of losses annually. Chemical control strategies rely heavily on synthetic chemical nematicides to reduce PPN population densities, but their use is being progressively restricted due to environmental and human health concerns, so alternative control methods are urgently needed. Here, we review the potential of bacterial and fungal agents to suppress the most important PPNs, namely Aphelenchoides besseyi, Bursaphelenchus xylophilus, Ditylenchus dipsaci, Globodera spp., Heterodera spp., Meloidogyne spp., Nacobbus aberrans, Pratylenchus spp., Radopholus similis, Rotylenchulus reniformis, and Xiphinema index.

Effect of Biofumigation on Population Densities of Pratylenchus spp. and Verticillium spp. and Potato Yield in Eastern Canada.

Biofumigation has been proposed as an alternative to soil fumigation to manage soil-borne diseases including potato early dying disease complex (PED). This study examined the potential of using brown mustard (Mustard juncea) biofumigation to manage PED under rain-fed potato production in New Brunswick, Canada in two trials between 2017 and 2020 in comparison with chloropicrin fumigation and a conventional barley rotation. Biofumigation increased yield in one trial, but not in a second trial where the potato crop experienced severe drought, whereas chloropicrin fumigation increased yield in both trials. Biofumigation was effective in suppressing root-lesion nematode (RLN, Pratylenchus spp.) counts in both trials, but was ineffective in suppressing V. dahliae population density. Chloropicrin fumigation was effective in suppressing RLN counts and V. dahliae population density only in the hill where injected, but the effect was short-lived as the population density of V. dahliae in the hill increased to the level of the control in one potato growing season. Biofumigation may be an alternative to chloropicrin fumigation in managing PED, particularly in fields with high RLN population but relatively low Verticillium population density. However, neither biofumigation nor fumigation used alone may be sustainable in the short-term potato rotations commonly used in New Brunswick, and additional beneficial practices are required to sustain productivity in the long-term.

La biofumigación se ha propuesto como una alternativa a la fumigación del suelo para manejar las enfermedades transmitidas por el suelo, incluido el complejo de enfermedades de muerte prematura de la papa (PED). Este estudio examinó el potencial del uso de la biofumigación de mostaza marrón (Mustard juncea) para manejar la PED bajo la producción de papa de secano en New Brunswick, Canadá, en dos ensayos entre 2017 y 2020 en comparación con la fumigación con cloropicrina y una rotación de cebada convencional. La biofumigación aumentó el rendimiento en un ensayo, pero no en un segundo ensayo en el que el cultivo de papa experimentó una sequía severa, mientras que la fumigación con cloropicrina aumentó el rendimiento en ambos ensayos. La biofumigación fue efectiva para suprimir los conteos del nematodo lesionador de la raíz (RLN, Pratylenchus spp.) en ambos ensayos, pero fue ineficaz para suprimir la densidad de población de V. dahliae. La fumigación con cloropicrina fue efectiva para suprimir los conteos de RLN y la densidad de población de V. dahliae solo en el lomo del surco donde se inyectó, pero el efecto fue de corta duración ya que la densidad de población de V. dahliae en el surco aumentó al nivel del testigo en un ciclo de cultivo de papa. La biofumigación puede ser una alternativa a la fumigación con cloropicrina en el manejo de la PED, particularmente en campos con alta población de RLN pero densidad de población de Verticillium relativamente baja. Sin embargo, ni la biofumigación ni la fumigación utilizadas por sí solas pueden ser sustentables en las rotaciones de papa a corto plazo comúnmente utilizadas en New Brunswick, y se requieren prácticas benéficas adicionales para mantener la productividad a largo plazo.

Improving Soil Quality and Potato Productivity with Manure and High-Residue Cover Crops in Eastern Canada.

Under intensive low residue agricultural systems, such as those involving potato (Solanum tuberosum L.)-based systems, stagnant crop yields and declining soil health and environmental quality are common issues. This study evaluated the effects of pen-pack cow (Bos Taurus) manure application (20 Mg·ha-1) and cover crops on nitrate dynamics and soil N supply capacity, subsequent potato yield, selected soil properties, and soil-borne disease. Eight cover crops were tested and included grasses, legumes, or a mixture of legumes and grasses, with red clover (Trifolium pratense L.) used as a control. Forage pearl millet (Pennisetum glaucum L.) was associated with highest dry matter. On average, red clover had 88% higher total N accumulation than the treatments mixing grasses and legumes, and the former was associated with higher soil nitrate in fall before residue incorporation and overwinter, but this was not translated into increased potato yields. Pearl millet and sorghum sudangrass (Sorghum bicolor × sorghum bicolor var. Sudanese) were associated with lower soil nitrate in comparison to red clover while being associated with higher total potato yield and lower numerical value of root-lesion nematodes (Pratylenchus penetrans), although this was not statistically significant at 5% probability level. Manure incorporation increased total and marketable yield by 28% and 26%, respectively, and increased soil N supply capacity by an average of 44%. Carbon dioxide released after a short incubation as a proxy of soil microbial respiration increased by an average of 27% with manure application. Our study quantified the positive effect of manure application and high-residue cover crops on soil quality and potato yield for the province of Prince Edward Island.

Evaluation of root-lesion nematode (Pratylenchus zeae) resistance assays for sugarcane accession lines.

No sugarcane cultivar is resistant to root-lesion (Pratylenchus zeae) nematode in Australia. Sugar Research Australia commenced a research project to evaluate new sets of accession lines derived from introgression breeding between wild relatives of sugarcane and commercial parents. No established method of assessment was available for comparing the resistance of sugarcane in the glasshouse. This study aimed to determine the most suitable assessment method for comparing resistance in accession lines. Two resistance parameters were measured, (i) number of nematodes per plant, and (ii) number of nematodes per g of roots. Nine screening trials were conducted from 2011 to 2020. Resistance parameter number of nematodes/plant had less variations within trials compared to nematodes/g roots, although both parameters were equally repeatable. Number of nematodes/g of root were negatively correlated (r = ‒0.29 to ‒0.86, p ≤ 0.001) with root biomass in all nine trials, and with shoot biomass in three out of seven trials (r = ‒0.23 to ‒0.31, p ≤ 0.05). In contrast, the number of nematodes per plant were positively correlated with shoot biomass (r = 0.25-0.53, p ≤ 0.05) in three out of seven trials and with root biomass (r = 0.17-0.27, p ≤ 00.05) in three out of nine trials. These results clearly indicated that nematodes per g root is related to reduction in root biomass and shoot biomass.

Molecular and Morphological Characterization of The Root -lesion Nematode, Pratylenchus Neglectus, on Corn from Henan Province of China.

Root-lesion nematodes, Pratylenchus spp., are economically important pathogens because of their detrimental and economic impact on a wide range of crops. In August 2018, two samples of both roots and rhizosphere soil were collected from a corn field in Liangyuanqu of Shangqiu city, Henan Province, China. Root-lesion nematodes were recovered from the roots and soil samples using the modified Baermann funnel extraction method. Both the morphological characters and molecular analysis of the internal transcribed spacer (ITS) and D2-D3 expansion region of 28S ribosomal RNA sequences confirmed that the root-lesion nematode population collected from corn in this study was P. neglectus. Phylogenetic analyses showed that this isolate formed a highly supported clade with other P. neglectus isolates. To the best of our knowledge, this is the first report of P. neglectus on corn in Henan Province of China. This study reports the first partial sequences of 28S D2-D3 region of P. neglectus on corn in China. Due to the great harmfulness of root-lesion nematodes to corn, care should be taken to prevent the spread of P. neglectus to other regions in China. At the same time, further study on the biological characteristics of P. neglectus is needed, which will be helpful to develop corresponding management and control strategies.

Phytonematodes infesting common bean fields in Brazil, and pathogenicity tests with Pratylenchus brachyurus

Phytonematodes are among the main pathogens of the common bean. In general, control practices that aim to control these pathogens have not been regularly adopted in Brazil. The objectives of the present study were to evaluate the occurrence of phytonematodes in dry bean fields in Paraná and São Paulo states and estimate the pathogenicity of Pratylenchus brachyurus to dry bean in glasshouse experiments. Root and soil were sampled for nematode extraction, identification and estimation of population density. Four glasshouse experiments with different initial population densities were carried out to evaluate the effect of P. brachyurus on the growth of dry bean plants. Six species of phytonematodes were detected, namely Helicotylenchus dihystera, P. brachyurus, Pratylenchus crenatus, Meloidogyne javanica, Meloidogyne incognita and Rotylenchulus sp. The spiral nematode H. dihystera was found in all samples and was the most abundant species in both states. The lesion nematode P. brachyurus was also frequent, reaching 94% in Paraná and 100% in São Paulo. The root-knot nematodes and Rotylenchulus sp. were reported only in São Paulo fields (45% and 18% frequency, respectively), and P. crenatus only in Paraná (12%). The most abundant nematode in the soil was H. dihystera, and in roots was P. crenatus. It was demonstrated that densities of 6.66 specimens of P. brachyurus per cm3 of soil provoke visible and measurable root decay. In conclusion, survey data showed low phytonematode densities and pathogenicity tests demonstrated that densities above 6.67 specimens of P. brachyurus per cm3 of soil cause damage to the dry bean roots.

A new esophageal gland transcriptome reveals signatures of large scale de novo effector birth in the root lesion nematode Pratylenchus penetrans.

BACKGROUND: The root lesion nematode Pratylenchus penetrans is a migratory plant-parasitic nematode responsible for economically important losses in a wide number of crops. Despite the importance of P. penetrans, the molecular mechanisms employed by this nematode to promote virulence remain largely unknown. RESULTS: Here we generated a new and comprehensive esophageal glands-specific transcriptome library for P. penetrans. In-depth analysis of this transcriptome enabled a robust identification of a catalogue of 30 new candidate effector genes, which were experimentally validated in the esophageal glands by in situ hybridization. We further validated the expression of a multifaceted network of candidate effectors during the interaction with different plants. To advance our understanding of the "effectorome" of P. penetrans, we adopted a phylogenetic approach and compared the expanded effector repertoire of P. penetrans to the genome/transcriptome of other nematode species with similar or contrasting parasitism strategies. Our data allowed us to infer plausible evolutionary histories that shaped the effector repertoire of P. penetrans, as well as other close and distant plant-parasitic nematodes. Two remarkable trends were apparent: 1) large scale effector birth in the Pratylenchidae in general and P. penetrans in particular, and 2) large scale effector death in sedentary (endo) plant-parasitic nematodes. CONCLUSIONS: Our study doubles the number of validated Pratylenchus penetrans effectors reported in the literature. The dramatic effector gene gain in P. penetrans could be related to the remarkable ability of this nematode to parasitize a large number of plants. Our data provide valuable insights into nematode parasitism and contribute towards basic understating of the adaptation of P. penetrans and other root lesion nematodes to specific host plants.

A Systematic Review of the Effects of Arbuscular Mycorrhizal Fungi on Root-Lesion Nematodes, Pratylenchus spp.

Root-lesion nematodes (Pratylenchus spp.) and arbuscular mycorrhizal fungi (AMF) occupy the same ecological niche in the phytobiome of many agriculturally important crops. Arbuscular mycorrhizal fungi can enhance the resistance or tolerance of a plant to Pratylenchus and previous studies have been undertaken to investigate the relationship between these organisms. A restructuring of the AMF phylum Glomeromycota has reallocated the species into genera according to molecular analysis. A systematic review of the literature was synthesized to assess the interaction between Pratylenchus spp. and AMF using the revised classification. Plants inoculated with AMF generally exhibited greater tolerance as demonstrated by increased biomass under Pratylenchus pressure. Species of AMF from the order Diversisporales tended to increase Pratylenchus population densities compared to those from the order Glomerales. Species from the genera Funneliformis and Glomus had a reductive effect on Pratylenchus population densities. The interaction between AMF and Pratylenchus spp. showed variation in responses as a result of cultivar, crop species, and AMF species. Putative mechanisms involved in these interactions are discussed.

Morphological and molecular characterization of Pratylenchus species from Yam (Dioscorea spp.) in West Africa.

The root-lesion nematodes (RLN), Pratylenchus spp., are among the major plant-parasitic nematodes affecting yam (Dioscorea spp.) production in West Africa. The distribution and diversity of RLN species associated with yam was investigated through a soil and tuber survey of the main producing areas in Nigeria and Ghana. Pratylenchus spp. were detected in the yam rhizosphere in 59% of 81 soil samples from Ghana and 39% of 114 soil samples from Nigeria. Pratylenchus spp. were detected in 24 of 400 tubers examined, in combination with root-knot nematodes (Meloidogyne spp.) and their associated damage of galls and crazy roots (79%), and with yam nematode (Scutellonema bradys) and their associated damage of dry rot (17%), although no specific additional symptoms were observed for Pratylenchus spp. Species of Pratylenchus were identified by their morphological features and by sequences of the D2-D3 region of the 28 S rDNA gene and the mitochondrial cytochrome oxidase I gene (COI). Pratylenchus brachyurus was the most frequent RLN species in both the rhizosphere and tubers of yam. Pratylenchus hexincisus was recovered from one tuber collected in Nigeria. While further investigations are required to establish the host status of yam for this nematode, this appears to be the first record of P. hexincisus on yam. The present taxonomical status of P. scribneri and P. hexincisus is discussed.

Resistance of Wheat Genotypes to Root-Lesion Nematode (Pratylenchus thornei) Can be Used to Predict Final Nematode Population Densities, Crop Greenness, and Grain Yield in the Field.

The root-lesion nematode Pratylenchus thornei is a major pathogen of wheat (Triticum aestivum) in many regions globally. Resistance of wheat genotypes to P. thornei can be determined from final nematode population densities in glasshouse experiments but combining results across multiple experiments presents challenges. Here, we use a factor analytic method for multiexperiment analysis of final population densities of P. thornei for 1,096 unique wheat genotypes in 22 glasshouse experiments. The resistance to P. thornei of the genotypes was effectively represented by a two-factor model with rotation of the axes to a principal components solution. Principal axes 1 and 2 (PA1 and PA2) accounted for 79 and 11% of the genetic variance, respectively, over all experiments. Final population densities of P. thornei as empirical best linear unbiased predictors (PA[1+2]-eBLUPs) from the combined glasshouse experiments were highly predictive (P < 0.001) of final nematode population densities in the soil profile, crop canopy greenness (normalized difference vegetation index), and grain yield of wheat genotypes in P. thornei-infested fields in the Australian subtropical grain region. Nine categories of resistance ratings for wheat genotypes from resistant to very susceptible were based on subdivision of the range of PA(1+2)-eBLUPs for use in growers' sowing guides. Nine genotypes were nominated as references for future resistance experiments. Most (62%) Australian wheat genotypes were in the most susceptible three categories (susceptible, susceptible to very susceptible, and very susceptible). However, resistant germplasm characterized in this study could be used in plant breeding to considerably improve the overall resistance of Australian wheat crops.

Resistance to Plant-Parasitic Nematodes in Chickpea: Current Status and Future Perspectives.

Plant-parasitic nematodes constrain chickpea (Cicer arietinum) production, with annual yield losses estimated to be 14% of total global production. Nematode species causing significant economic damage in chickpea include root-knot nematodes (Meloidogyne artiella, M. incognita, and M. javanica), cyst nematode (Heterodera ciceri), and root-lesion nematode (Pratylenchus thornei). Reduced functionality of roots from nematode infestation leads to water stress and nutrient deficiency, which in turn lead to poor plant growth and reduced yield. Integration of resistant crops with appropriate agronomic practices is recognized as the safest and most practical, economic and effective control strategy for plant-parasitic nematodes. However, breeding for resistance to plant-parasitic nematodes has numerous challenges that originate from the narrow genetic diversity of the C. arietinum cultigen. While levels of resistance to M. artiella, H. ciceri, and P. thornei have been identified in wild Cicer species that are superior to resistance levels in the C. arietinum cultigen, barriers to interspecific hybridization restrict the use of these crop wild relatives, as sources of nematode resistance. Wild Cicer species of the primary genepool, C. reticulatum and C. echinospermum, are the only species that have been used to introgress resistance genes into the C. arietinum cultigen. The availability of genomic resources, including genome sequence and re-sequence information, the chickpea reference set and mini-core collections, and new wild Cicer collections, provide unprecedented opportunities for chickpea improvement. This review surveys progress in the identification of novel genetic sources of nematode resistance in international germplasm collections and recommends genome-assisted breeding strategies to accelerate introgression of nematode resistance into elite chickpea cultivars.

Status of Pratylenchus coffeae in banana-growing areas of Tanzania.

Pratylenchus coffeae is among the plant parasitic nematodes contributing to yield losses of banana. To determine the status of P. coffeae, a survey was conducted in banana-growing regions of Tanzania and samples collected. The results indicated that in 2015 there was an increase in total counts of P. coffeae extracted from roots compared to that reported in 1999 in Unguja West, North and South. Moreover, we noted its presence for the first time in mainland Tanzania. Generally, the densities of P. coffeae were high on banana roots collected at 500-1000 m above sea level. This information on the status of P. coffeae is important in planning management of nematodes in Tanzania.

Serendipitous identification of Pratylenchus curvicauda from the grainbelt of Western Australia.

A Pratylenchus species identified during a survey of Pratylenchus quasitereoides incidence at four locations of the grainbelt of Western Australia is described. Morphological and morphometric features indicated the previously undescribed morphotypes in nematode mixtures encountered were conspecific to P. curvicauda, and were clearly distinguishable from nine common Pratylenchus spp. Typical features of P. curvicauda were its body length (415-540 µm), which was curved to a c-shaped with a maximum body diameter of 20 µm, and the nature of its tail; 34 µm long, 2.8 µm wide at the anus and a typical ventrally arcuate with a round terminus. Sequenced for the first time, the sequences of the partial 18S-ITS1-5.8S-ITS2-partial 28S (80 clones, 14 individual nematodes) and the 28S-D3 (17 clones) regions of the rDNA of P. curvicauda had overall mean distances of 0.013 and 0.085, respectively. Phylogenetic analyses with sequences of both segments of the rDNA clearly showed the P. curvicauda isolates as monophyletic, distinct from ca 40 Pratylenchus species. Notably, it was distinct from Pratylenchus species present in Australia including P. quasitereoides and a Western Australia isolate of P. thornei. Further research into the biology of P. curvicauda is needed to facilitate development of strategies for its management, if it is an important pest.

Molecular characterization and species delimiting of plant-parasitic nematodes of the genus Pratylenchus from the penetrans group (Nematoda: Pratylenchidae).

Root-lesion nematodes of the genus Pratylenchus are an important pest parasitizing a wide range of vascular plants including several economically important crops. However, morphological diagnosis of the more than 100 species is problematic due to the low number of diagnostic features, high morphological plasticity and incomplete taxonomic descriptions. In order to employ barcoding based diagnostics, a link between morphology and species specific sequences has to be established. In this study, we reconstructed a multi-gene phylogeny of the Penetrans group using nuclear ribosomal and mitochondrial gene sequences. A combination of this phylogenetic framework with molecular species delineation analysis, population genetics, morphometric information and sequences from type location material allowed us to establish the species boundaries within the Penetrans group and as such clarify long-standing controversies about the taxonomic status of P. penetrans, P. fallax and P. convallariae. Our study also reveals a remarkable amount of cryptic biodiversity within the genus Pratylenchus confirming that identification on morphology alone can be inconclusive in this taxonomically confusing genus.

Óleo essencial das folhas e frutos de Schinus terebinthifolius raddi no controle de Pratylenchus zeae / Essential oil from the leaves and fruits of Schinus terebinthifolius raddi in the control of pratylenchus zeae / Aceite esencial de las hojas y frutos de Schinus terebinthifolius raddi en el control de pratylenchus zeae

Os óleos essenciais (OEs) são metabólitos secundários que podem apresentar potencial no controle alternativo de nematoides. Assim objetivou-se testar o OE de pimenta rosa no controle de P. zeae em condições in vitro e na cultura do milho. O OE foi extraído por hidrodestilação, utilizando massa fresca das folhas e frutos maduros. O experimento in vitro foi instalado em arranjo fatorial 8x2, sendo oito concentrações (0,00, 7,80, 15,00, 31,00, 62,00, 125,00, 250,00 e 500,00 µg mL-1) e OE das folhas e dos frutos. As unidades experimentais foram tubos de ensaio com capacidade para 5mL, contendo 1 mL de cada concentração, e 1mL de suspensão de 50 nematoides. Decorrido 48 horas avaliou-se a porcentagem de mortalidade. O experimento em casa de vegetação foi instalado em arranjo fatorial 5x2, sendo cinco concentrações (0,00, 7,8, 15,0, 31,0 e 62,0 µg mL-1) e OEs (Folhas e frutos). As unidades experimentais constituíram-se por vasos com capacidade para 1,5 kg, os quais foram inoculados com 2000 e 1800 nematoides e semeados com sementes de milho tratadas com as concentrações dos OEs. Os OEs e as concentrações avaliadas apresentaram porcentagem de mortalidade em condições in vitro e reduziram a população de P. zeae, em casa de vegetação, o OE dos frutos promoveu maior mortalidade nos testes in vitro. Sendo assim os OEs demonstraram potencial no controle de fitonematoide, porém, há a necessidade de estudos a aplicabilidade dos mesmos.(AU)

Essential oils (EOs) are secondary metabolites that may present potential for an alternative control of nematodes. The purpose of this study was to test the EO of pink peppercorn in the control of P. zeae under in-vitro conditions and in the maize crop. Essential Oil was extracted by hydro-distillation using fresh leaf mass and mature fruits. The in-vitro experiment was installed in an 8x2 factorial arrangement, with eight concentrations (0.00, 7.8, 15.0, 31.0, 62.0, 125.0, 250.0 and 500.0 µg mL-1) and EO from leaves and fruits. The experimental units were 5-mL test tubes containing 1 mL of each concentration and 1 mL of suspension of 50 nematodes. The mortality percentage was evaluated after 48 hours. The greenhouse experiment was installed in a 5x2 factorial arrangement, with five concentrations (0.00, 7.8, 15.0, 31.0 and 62.0 µg mL-1) and EOs (leaves and fruits). The experimental units consisted of 1.5-kg capacity vases, which were inoculated with 2000 and 1800 nematodes, and seeded with corn seeds treated with EO concentrations. The EOs and concentrations evaluated presented a mortality percentage under the in-vitro conditions and reduced the P. zeae population in the greenhouse, while the EO from the fruits promoted higher mortality in the in-vitro tests. Therefore, EOs have shown potential in the control of phytonematodes, but further studies are required for their applicability.(AU)

Los aceites esenciales (OEs) son metabolitos secundarios que pueden presentar potencial en el control alternativo de nematodos. Así se objetivó probar el OE de pimienta rosa en el control de P. zeae en condiciones in vitro y en el cultivo del maíz. El OE fue extraído por hidrodestilación utilizando masa fresca de las hojas y frutos maduros. El experimento in vitro fue instalado en un arreglo factorial 8x2, siendo ocho concentraciones (0,00, 7,80, 15,00, 31,00, 62,00, 125,00, 250,00 y 500,00 µg mL-1) y OE de las hojas y de los frutos. Las unidades experimentales fueron tubos de ensayo con capacidad para 5 mL, conteniendo 1 mL de cada concentración, y 1 mL de suspensión de 50 nematodos. Después de 48 horas se evaluó el porcentaje de mortalidad. El experimento en casa de vegetación fue instalado en arreglo factorial 5x2, siendo cinco concentraciones (0,00, 7,8, 15,0, 31,0 y 62,0 µg mL-1) y OEs (Hojas y frutos). Las unidades experimentales se constituyeron por floreras con capacidad para 1,5 kg, los cuales fueron inoculados con 2000 y 1800 nematodos y sembrados con semillas de maíz tratadas con las concentraciones de los OEs. Los OEs y las concentraciones evaluadas presentaron un porcentaje de mortalidad en condiciones in vitro y redujeron la población de P. zeae, en casa de vegetación, el OE de los frutos promovió mayor mortalidad en las pruebas in vitro. Así los OE demostraron potencial en el control de fitonematodos, sin embargo, hay la necesidad de estudios a la aplicabilidad de los mismos.(AU)

Morphometric and molecular characterization of populations of Pratylenchus kumamotoensis and P. pseudocoffeae (Nematoda, Pratylenchidae) newly recorded in Korea.

At least 70 species of root-lesion nematodes, Pratylenchus spp., have been identified worldwide, many of which are serious pests of various agricultural crop plants. In Korea, only 14 species have been recorded in vegetable and fruit fields. Here, we report two new records of root-lesion nematode species in Korea based on morphometric and molecular methods. Soil samples were collected from chrysanthemum cultivars in various regions. Morphometric diagnosis showed that two new records for Korea: Pratylenchus kumamotoensis in Chilgok County and Pratylenchus pseudocoffeae in Geumsan County. In addition, molecular diagnosis using the two sequences of the internal transcribed spacer (ITS) and the D2-D3 region of ribosomal DNA showed that these two species were most similar with those from Japan, Costa Rica and USA. The similarities of the ITS and D2-D3 sequences were 99.85 and 99.74%, respectively, for Pratylenchus kumamotoensis and 99.99 with Costa Rica populations and 99.86% with USA populations, respectively, for Pratylenchus pseudocoffeae. To our knowledge, this is the first report of two species in Korea.

Plant-Parasitic Nematodes Infecting Grapevine in Southern Spain and Susceptible Reaction to Root-Knot Nematodes of Rootstocks Reported as Moderately Resistant.

Incidence and nematode population densities of plant-parasitic nematodes were determined in 64 samples of soil and grapevine roots collected from commercial vineyards in southern Spain between October 2003 and May 2005. In addition, a histopathological study was done of root-stock roots naturally infected by root-knot nematodes (Meloidogyne spp.). Nematodes infecting the rootstocks were identified according to conventional procedures, and the Meloidogyne spp. were furthermore identified by sequence characterized amplified region-polymerase chain reaction (SCAR-PCR) and isozyme esterase analyses. The most important plant-parasitic nematodes detected, in order of decreasing frequency of total soil infestation and root infection (percentage of samples), were Mesocriconema xenoplax (34.4%), Meloidogyne incognita (26.6%), Meloidogyne javanica (14.1%), Xiphinema index (12.5%), Xiphinema italiae (10.9%), Pratylenchus vulnus (6.3%), and Meloidogyne arenaria (1.6%). No disease symptoms were observed on aboveground plant parts of the infected grapevines, except for plants in some fields where soil was infested with the virus-vector nematodes X. index and X. italiae. Those grapevines showed a yellow mosaic pattern in leaves early in the growing season and the internode shortening characteristic of infections by Grapevine fanleaf virus. Rootstocks infected by root-knot nematodes (Meloidogyne spp.) showed distorted feeder roots and large- to moderate-sized root galls, present either singly or in clusters. Histopathology of galled roots showed a typical susceptible response to infection by root-knot nematodes: cellular alterations were induced in the cortex, endodermis, pericycle, and vascular system, including giant-cell formation and severe distortion of vascular tissues. Most Meloidogyne egg masses ocurred on the surface of the galled root tissues, a position that could facilitate dispersion of the nematode eggs and juveniles and the occurrence of secondary infections. Some of the grapevine rootstocks surveyed in this study (Paulsen 1103, Richter 110, Rupestris du Lot, and SO4) had previously been reported to be resistant to Meloidogyne spp.; however, the population densities of these nematodes found in soil and roots sampled in the present study, as well as the compatible host-parasite relationship revealed by histopathology, indicate a susceptible response to Meloidogyne spp. from southern Spain.