Добірка наукової літератури з теми "Root-lesion nematodes (RLN)"

Apple replant disease (ARD) is a serious problem in fruit production, and none of the major clonal rootstocks are resistant to ARD. We have screened Malus domestica clones and species accessions from the USDA Malus Germplasm Repository at Geneva, N.Y., including M. angustifolia-2375.03 (MA), M. coronaria-2966.01 (MC), M. fusca-3031.01 (MF), M. ioensis-3059.01 (MI), M. sieversii-3530.01 (MS), and M. kirghisorum-3578.01 (MK), for resistance to ARD and root-lesion nematodes (RLN, Pratylenchus spp.), in a composite soil collected from 11 New York orchards with known ARD. Plant dry mass and height, root necrosis, and nematode populations in different apple species and clones were compared after 60 days growth in steam-pasteurized (PS), RLN-inoculated (IS), and naturally infested field (FS) soils with 1200 RLN per 100 cm3. More severe stunting, reduced plant dry mass, and root necrosis occurred in FS seedlings compared with those in PS, but M. angustifolia seedlings were substantially more resistant or tolerant to RLN and ARD than the other species tested. Plant dry mass ranked MK>MS>MA>MI>MF>MC, and these differences were significant at the 5% level. RLN root populations were negatively correlated with plant dry mass, and accounted for about 10% of its variation, with nematode populations in roots ranking MC>MF>MK>MI>MS>MA. Useful resistance to ARD and parasitic nematodes apparently exists within Malus germplasm collections, and can be identified by testing more genotypes, developing rapid resistance screening methods, and comparing RLN host preferences among Malus genotypes and various orchard cover crops.

The root lesion nematode (RLN) Pratylenchus penetrans is a migratory species that attacks a broad range of crops. After the RLN is initially attracted to host roots by root exudates and compounds, it releases secretions that are critical for successful parasitism. Among those secretions are nematode virulence factors or effectors that facilitate the entry and migration of nematodes through the roots and modulate plant immune defenses. The recognition of the effectors by host resistance proteins leads to effector-triggered immunity and incompatible plant–nematode interactions. Although many candidate effectors of the RLN and other plant-parasitic nematodes have been identified, the detailed mechanisms of their functions and particularly, their host targets remain largely unexplored. In this study, we sequenced and annotated genes encoding expansin-like proteins, which are major candidate effectors of P. penetrans. One of the genes, Pp-EXPB1, which was the most highly expressed during nematode infection in different plant species, was further functionally characterized via transient expression in the model plant Nicotiana benthamiana and global transcriptome profiling of gene expression changes triggered by this candidate effector in plants. As a result of this investigation, the biological roles of Pp-EXPB1 in nematode parasitism were proposed, the putative cellular targets of the proteins were identified, and the molecular mechanisms of plant responses to the nematode-secreted proteins were outlined.

The efficacy and phytotoxicity of postplant treatments to control root lesion nematodes [RLN (Pratylenchus penetrans)] and dagger nematodes [DN (Xiphinema bakeri)] in red raspberry (Rubus idaeus) were evaluated in four field studies, each conducted over 1 to 3 years. Spring spray applications of oxamyl or fosthiazate reduced RLN and DN population densities for up to 2 years, but fall oxamyl sprays and spring drip-applied oxamyl applications were not effective. Oxamyl application rate determined the duration of nematode suppression. Two spring applications of oxamyl at 2 lb/acre provided more than 2 years of suppression, while two spring applications of 0.8 lb/acre suppressed nematodes for only 1 year. Spring oxamyl applications reduced ‘Nootka’ fruit yield for one season, but did not affect ‘Willamette’ yield. Fall spray-applied fenamiphos, fall and spring spray-applied DiTera (a fermentation product of the fungus Myrothecium verrucaria), fall drip-applied 1,3-dichloropropene, and spring shallow-incorporated abyssinian mustard (Brassica carinata) seed meal suppressed RLN briefly (less than 6 months) or not at all.

The efficacy and phytotoxicity of postplant treatments to control root lesion nematodes [RLN (Pratylenchus penetrans)] and dagger nematodes [DN (Xiphinema bakeri)] in red raspberry (Rubus idaeus) were evaluated in four field studies, each conducted over 1 to 3 years. Spring spray applications of oxamyl or fosthiazate reduced RLN and DN population densities for up to 2 years, but fall oxamyl sprays and spring drip-applied oxamyl applications were not effective. Oxamyl application rate determined the duration of nematode suppression. Two spring applications of oxamyl at 2 lb/acre provided more than 2 years of suppression, while two spring applications of 0.8 lb/acre suppressed nematodes for only 1 year. Spring oxamyl applications reduced ‘Nootka’ fruit yield for one season, but did not affect ‘Willamette’ yield. Fall spray-applied fenamiphos, fall and spring spray-applied DiTera (a fermentation product of the fungus Myrothecium verrucaria), fall drip-applied 1,3-dichloropropene, and spring shallow-incorporated abyssinian mustard (Brassica carinata) seed meal suppressed RLN briefly (less than 6 months) or not at all.

Chickpea is a popular legume crop in Asia and Africa's semi-arid regions. Crop production gains, on the other hand, have been modest, owing to biotic and abiotic stressors. Among the different biotic stresses, nematodes portray serious threat to chickpea production and colossal losses have been reported due to stress-free infection by other pathogens on infection with root lesion nematode (RLN). The worldwide distribution of two major species of RLN namely P. thornei and P. neglectus made them a focus research area especially on management aspect. In dryland farming areas of southeastern Australia, the P. thornei alone can cause yield losses of up to 40% in cereals and legumes. Despite the fact that chickpea breeders have been working persistently to generate superior chickpea varieties with increased resilience or tolerance to biotic and abiotic challenges, contemporary biotechnology technologies can help to speed up this process. To incorporate these tools and/or accelerate breeding programmes, identification of RLN resistant source with its genetic factor is first step in developing improved cultivars. However, study of resistance screening methods for chickpea against RLN is limited and standardization of different factors for development of a stable screening methodology distinguishing various levels of resistance is the need of the hour in RLN research.

Plant-parasitic nematodes (PPNs) are highly damaging pests responsible for heavy losses in worldwide productivity in a significant number of important plant crops. Common pest management strategies rely on the use of synthetic chemical nematicides, which have led to serious concerns regarding their impacts on human health and the environment. Plant natural products, or phytochemicals, can provide a good source of agents for sustainable control of PPNs, due to their intrinsic characteristics such as higher biodegradability, generally low toxicity for mammals, and lower bioaccumulation in the environment. In this work, the nematicidal activity of 39 phytochemicals was determined against the root-lesion nematode (RLN) Pratylenchus penetrans using standard direct and indirect contact methodologies. Overall, the RLN was tolerant to the tested phytochemicals at the highest concentration, 2 mg/mL, seldom reaching full mortality. However, high activities were obtained for benzaldehyde, carvacrol, 3-octanol, and thymol, in comparison to other phytochemicals or the synthetic nematicide oxamyl. These phytochemicals were seen to damage nematode internal tissues but not its cuticle shape. Also, the environmental and (eco)toxicological parameters reported for these compounds suggest lower toxicity and higher safety of use than oxamyl. These compounds appear to be good candidates for the development of biopesticides for a more sustainable pest management strategy.

Apple replant disease (ARD) causes serious problems in most fruit-growing regions worldwide. It is associated with nematodes, fungi, bacteria, and other deleterious factors. Its symptoms range from severe stunting to death of replants in old orchards. We evaluated effects of antibacterial (cecropin-, attacin- and hen egg white lysozyme-encoding) and antifungal (chitinase-encoding) transgenics, obtained from the apple-rootstock breeding program at Geneva, N.Y., on ARD. Transgenics were tested in a composite soil collected from New York orchards with known replant problems. The ARD-infested field soil (FS) had ≈675 Pratylenchus penetrans (root-lesion nematodes, RLN) and ≈75 Xiphinema americanum (dagger nematodes) per liter pot; soil for controls was steam-pasteurized. Height, biomass, nematode vermiforms and eggs were recorded after ≈60 days under optimal growing conditions in the greenhouse. There was significant variation in growth and Pratylenchus counts among transgenics (P < 0.00), most of which were susceptible to ARD. However, endoparasitic RLN accounted for <50% of the variation in biomass, suggesting that other factors were important in affecting plants. Conversely, RLN significantly increased root necrosis (P < 0.00; R2 = 80%). Eggs were observed in diseased chitinase-encoding lines, probably because of low-gene expression. There was no significant difference in eggs among the lines (P ≤ 0.3). Apparently, good growth was inconsistent and due to confounding factors such as mild ARD. These results suggest that single-gene therapy and low-gene expression may not protect apple against ARD complex, instead gene-pyramiding and high-gene expression should be tested.

The root lesion nematode (RLN) species Pratylenchus thornei and P. neglectus are widely distributed within cropping regions of Australia and have been shown to limit grain production. Field experiments conducted to compare the performance of cultivars in the presence of RLNs investigate management options for growers by identifying cultivars with resistance, by limiting nematode reproduction, and tolerance, by yielding well in the presence of nematodes. A novel experimental design approach for RLN experiments is proposed where the observed RLN density, measured prior to sowing, is used to condition the randomization of cultivars to field plots. This approach ensured that all cultivars were exposed to consistent ranges of RLN in order to derive valid assessments of relative cultivar tolerance and resistance. Using data from a field experiment designed using the conditioned randomization approach and conducted in Formartin, Australia, the analysis of tolerance and resistance was undertaken in a linear mixed model framework. Yield response curves were derived using a random regression approach and curves modeling change in RLN densities between sowing and harvest were derived using splines to account for nonlinearity. Groups of cultivars sharing similar resistance levels could be identified. A comparison of slopes of yield response curves of cultivars belonging to the same resistance class identified differing tolerance levels for cultivars with equivalent exposures to both presowing and postharvest RLN densities. As such, the proposed design and analysis approach allowed tolerance to be assessed independently of resistance.

Plant parasitic nematodes are a major biotic cause of wheat-yield loss in temperate wheat-growing regions. A major strategy to develop resistance to root-lesion nematodes (RLNs) in wheat is to assess and then exploit their natural genetic variation. This study examines RLN (Pratylenchus thornei) resistance in 1 Middle Eastern landrace (AUS4930 7.2) and 1 synthetic hexaploid wheat, CROC_1/AE.SQUARROSA (224)//OPATA (CROC), using F2 and F9 populations generated by crossing AUS4930 7.2 and CROC with the susceptible cultivar Pastor, and inoculating these crosses with P. thornei in greenhouse trials. Wheat microsatellite markers linked to previously identified quantitative trait loci (QTLs) for resistance to P. thornei and P. neglectus were used to screen both populations. In the AUS4930 7.2 × Pastor population, resistance loci on chromosomes 1B, 2B, and 6D were detected. Similarly, in the CROC × Pastor population, 2 resistance loci, located on chromosomes 1B and 3B, were identified. Interestingly, a resistance locus located on chromosome 6D was not detected. More detailed mapping is required in these 2 populations, developed using new RLN resistance sources, to determine whether the QTLs identified on these chromosomes are the same, are allelic, or are linked to different resistance loci from those previously identified, and to determine whether these 2 sources contain other novel resistance loci.

Several nematode species can be found in different densities in almost any soil ecosystem, and their diversity in those ecosystems depends on numerous reasons, such as climatic conditions and host presence. Cereals are one of the main hosts of plant-parasitic nematodes (PPN), chiefly root-lesion nematodes (RLN, Pratylenchus spp.) and cereal cyst nematodes (CCN, Heterodera spp.). These nematodes are known as major parasites of the cereal crops; however, agricultural areas accommodate various nematodes showing biological variation. The diversity of parasitic nematodes on cereals in the Sakarya provinces of Türkiye, where cereals are intensively grown and located in the middle of two climatic zones, has not been well studied. Therefore, in this study, we aimed to determine the diversity, identification, and molecular phylogeny of PPNs in wheat-growing ecosystems in the Hendek, Pamukova, Geyve, Akyazı, and Central districts of Sakarya. The diversity of PPNs was calculated using the Shannon diversity index. Thirteen PPN genera were detected in 92% of soil samples. Heterodera filipjevi was identified in 24% of the soil samples using morphological, morphometrical, and molecular tools. In the morphological and molecular analyses, intraspecific polymorphism was observed in H. filipjevi populations. The result indicated that the high infestation rate of H. filipjevi was recorded from Geyve and Pamukova, followed by Hendek and Akyazı; however, a low infestation rate was detected in the Central district. The moderate value of the Shannon index of migratory nematode species was obtained in wheat fields as 2.31, whereas the value of evenness was 0.93, implying moderate diversity and high evenness of nematodes. This study is the first comprehensive report on H. filipjevi from wheat cropping areas in the Sakarya province. Intensified cereal cropping systems with/without non-cereal rotations increased the risk of plant-parasitic nematodes, especially RLNs and H. filipjevi infection of wheat production areas in the province.

A soja, o milho e o algodão são as culturas de enorme importância econômica no Brasil, pois juntas ocupam grande parte da área agrícola no país. Além disso, essas culturas são essenciais no fornecimento de alimento e fibras para uma crescente população mundial. Vários fatores podem afetar a produção das mesmas, sendo que os nematoides anualmente causam bilhões de dólares de perdas. As principais técnicas disponíveis para o manejo dos nematoides são rotação de culturas, cultivares resistentes e nematicidas químicos. Apesar de o controle químico ser uma ferramenta viável, há poucos nematicidas disponíveis no Brasil. Como inovação entre os nematicidas, o tioxazafen é uma nova molécula de amplo espectro, desenvolvida para aplicação via tratamento de sementes, para o controle de nematoides nas culturas do milho, da soja e do algodão. Portanto, seu desenvolvimento e posterior registro poderão fornecer uma nova alternativa ao manejo integrado de nematoides aos produtores brasileiros. Assim, esse trabalho teve como objetivos avaliar a eficácia do nematicida tioxazafen, por meio do tratamento de sementes, no controle de Heterodera glycines, Meloidogyne javanica e Pratylenchus brachyurus na soja; M. incognita e P. zeae no milho; e M. incognita no algodão. Além disso, foram avaliados possíveis efeitos fitotóxicos do tratamento de sementes com tioxazafen nas mesmas culturas. Ensaios de casa de vegetação foram conduzidos para avaliação do efeito do tratamento de sementes na população de nematoides, em plantas artificialmente infestadas, bem como na massa de raízes e parte aérea das plantas. O tioxazafen demonstrou supressão substancial na população de nematoides em todas as espécies testadas nas três culturas, com atividade igual ou maior que à referência comercial (imidacloprido + tiodicarbe). As melhores doses observadas foram de 0,250 mg de tioxazafen por semente no controle de M. javanica e de P. brachyurus em soja, 0,500 mg por semente no controle de H. glycines na soja e de M. incognita no milho, 0,750 mg por semente no controle de M. incognita no algodão e 1,000 mg por semente no controle de P. zeae no milho. As plantas tratadas com tioxazafen não exibiram sintomas de fitotoxidez e desenvolveram biomassa similar às plantas não tratadas. Esses resultados mostram o potencial do tioxazafen em se tornar um efetivo tratamento de sementes para controle dos principais nematoides da soja, do milho e do algodão no Brasil,com baixos riscos de fitotoxidez.
Corn, soybean and cotton crops are of great economic importance in Brazil. They together account for the greatest amount of planted area in country. These crops are essential for keeping and providing enough food and fiber for a growing world population. Many factors can affect the production of these crops, and the nematodes are among the most relevant, causing crop losses that reach into billions of dollars. The main techniques available for managing nematodes are crop rotation, resistant cultivars and chemical nematicides. Chemical control is one of the key tools, but there are only a few nematicides available in the Brazilian market. Tioxazafen is a novel nematicide for seed treatment designed to provide consistent broad-spectrum control of nematodes in corn, soy, and cotton. Therefore, the registration of this molecule will provide an important tool to Brazilian farmers that suffer losses due to nematodes. Thereby, the current trials aimed to evaluate the efficacy of tioxazafen through seed treatment to control Heterodera glycines, Meloidogyne javanica and Pratylenchus brachyurus in soybean; M. incognita and P. zeae in corn, and M. incognita in cotton. Furthermore, were evaluated if tioxazafen may cause phytotoxicity in these crops. Greenhouse experiments were carried out to evaluate the effects of seed treatments on nematode population densities, and plant shoot and root weight. Tioxazafen demonstrated substantial suppression of nematode population to all species tested in three crops, with activity equaled or exceeded commercial standard nematode seed treatments (imidacloprid + thiodicarb). The best rates observed were 0.250 mg of tioxazafen per seed to control de M. javanica and P. brachyurus in soybean, 0.500 mg per seed to control H. glycines in soybean and M. incognita in corn, 0.750 mg per seed to control M. incognita in cotton and 1.000 mg per seed to control lesion P. zeae in corn. Tioxazafen treated plants also did not exhibit phytotoxicity and grow equally to untreated plants. These results demonstrated the potential of tioxazafen for the control of the main nematodes in soybean, corn and cotton, without the risk of phytotoxicity.

Plant-parasitic nematodes are invasive pathogens that cause severe damage to crops. To minimise the infestation of plant-parasitic nematodes, appropriate identification techniques and accurate population estimation of plant-parasitic nematodes are necessary to employ optimal control strategies. Conventionally, nematodes are identified using a manual microscope, and their morphological features are investigated to discern nematode species and count their population in the sample. However, this process is laborious and time consuming with the increasing number of samples. Although several nematode identification techniques have been proposed such as morphological, and molecular methods, these methods require complicated high-cost equipment, nematologists, or microbiologists, and bioinformatic skills. This study investigated image processing methods using state-of-the-art computer vision and deep learning (YOLO, you look only once) models to detect and quantify plant-parasitic nematode juveniles and eggs. The novel computer vision algorithm implemented graph network-based skeleton analysis to identify unique features of nematode juveniles in microscopic images. A new feature was revealed from the middle and average width difference of nematode eggs using the medial axis transform. The extreme point method was implemented to detect the accurate length of nematode eggs. Subsequently, this study explored the novel application of mosaic augmentation to detect and count plant-parasitic nematodes using state-of-the-art YOLO models. The YOLOv5-608 model attained the highest accuracy in the detection and counting of nematodes, whereas YOLOv7-512 performed well in detecting overlapped nematodes. The deep learning-based decision support tool was developed to automate the detection and enumeration of plant-parasitic nematode, calculate its population in the microscopic images, and suggest suitable nematode management strategies.