The Influence of Selected Abiotic Factors on the Occurrence of Entomopathogenic Nematodes (Steinernematidae, Heterorhabditidae) in Soil

Original research confirms a significant impact of abiotic factors, such as soil type and physicochemical properties, on the biological activity and infectivity of entomopathogenic nematodes from the Steinernematidae and Heterorhabditidae families. Nematodes were found to prefer sandy loam soils; however, the highest species diversity was found in sandy soils. Some species of nematodes were associated with a specific type of soil. For example, Steinernema silvaticum and Heterorhabditis bacteriophora were found only in sands, and H. megidis predominantly in clay. Nematodes were found in soils of varying pH levels, although individual species preferred a certain degree of acidity. S. bicornutum and H. megidis were found only in alkaline soils, while others, such as S. silvaticum, only in acidic environments (pH<4.5)

Populations of parasitic nematodes colonizing Jerusalem artichoke (Helianthus tuberosus L.)

The populations of parasitic nematodes colonizing the rhizosphere of Helianthus tuberosus L. grown in Polish plantations were studied in the summer of 2016 and the spring of 2017. A total of 35 nematode species were identified: Paratrichodorus pachydermus, Trichodorus cylindricus, T. viruliferus, Longidorus attenuatus, L. elongatus, L. leptocephalus, Criconema annuliferum, Criconemoides informis, Mesocriconema rusticum, M. solivagum, M. xenoplax, Paratylenchus nanus, P. neoamblycephalus, P. projectus, Bitylenchus dubius, B. maximus, Merlinius brevidens, M. nothus, Scutylenchus quadrifer, S. tartuensis, Helicotylenchus digonicus, H. pseudorobustus, H. vulgaris, Rotylenchus pumilus, R. robustus, Pratylenchus crenatus, P. fallax, P. neglectus, Hirschmanniella gracilis, Aphelenchoides fragariae, Aphelenchus avenae, A. eremitus, Ditylenchus dipsaci, and D. medicaginis. Aphelenchoides fragariae and Ditylenchus dipsaci could be foliar pathogens of H. tuberosus L. This is the first study to demonstrate the presence of A. fragariae on the leaves of the Jerusalem artichoke in Poland. The frequencies of occurrence and population densities of the 35 nematode species were determined

Distinguishing Cyst Nematode Species Using Image Textures and Artificial Neural Networks

Cyst nematodes are plant parasitic nematodes infecting crops, causing extensive crop damage and annual losses, and affecting food production. The precise species identification is significant to initiate their control. The repeatable, less expensive, and less laborious distinguishing cyst nematode species using image processing and artificial intelligence can be advantageous. The objective of this study was to distinguish cyst nematodes belonging to the species Globodera pallida, Globodera rostochiensis, and Heterodera schachtii based on image parameters using artificial neural networks (ANN). The application of parameters selected from a set of 2172 textures of images in color channels L, a, b, X, Y, Z, R, G, B, V, U, and S to build classification models using a narrow neural network, medium neural network, wide neural network, trilayered neural network, WiSARD, multilayer perceptron, and RBF network is a great novelty of the present study. Algorithms allowed for distinguishing cyst nematode species with an average accuracy reaching 89.67% for a model developed using WiSARD. The highest correctness was obtained for H. schachtii and this species was distinguished from each other with the highest accuracy of 95–98% depending on the classifier. Whereas the highest number of misclassified cases occurred between G. pallida, G. rostochiensis belonging to the same genus Globodera. The developed procedure involving image parameters and artificial neural networks can be useful for non-destructive and objective distinguishing cyst nematode species

Influence of <i>Eisenia fetida</i> on the Nematode Populations during Vermicomposting Process

Vermicomposting stands as a sustainable and environmentally friendly waste management practice, leveraging the metabolic prowess of earthworms to facilitate the decomposition of organic matter into nutrient-rich compost. The aim of this experiment was to study the influence of Eisenia fetida on the density and the tropic structure of a nematode community during the vermicomposting process over a period of 3 months. Sewage sludge and green waste served as composting substrates. Overall, six compost variants were prepared consisting of three variants incorporating E. fetida and three control variants lacking E. fetida. Throughout the investigation, samples were gathered on a monthly basis, with each variant undergoing three repetitions. The aim was to isolate nematodes, determine the population density of the five trophic groups, and identify the dominant community. The anaysis was conducted employing both microscopic examination and molecular metabarcoding (NGS). It was shown that the bacterial-feeding community maintained dominance. The introduction of E. fetida into the compost led to a significant rise in the abundance of Diplogasteridae. In the variant without E. fetida, the amount of Diplodasteridae exceeded 0.1% only after the 30th (C3) or the 60th (C1, C2) day of composting, while in the compost with E. fetida, they were present in large amounts (ranging from 11.0% to 28.0%) already on the 30th day of composting. The introduction of Eisenia fetida also led to a notable reduction in H. gingivalis with significant implications for mitigating the risk of halicephalobiosis. The introduction of E. fetida resulted in reducing H. gingivalis to levels below 0.1% in all compost variants

Description of Pratylenchoides ojcowensis sp. nov. (Nematoda: Merlinidae) from Polish Jurassic Highland

Winiszewska, Grażyna, Dobosz, Renata, Malewski, Tadeusz, Skwiercz, Andrzej (2020): Description of Pratylenchoides ojcowensis sp. nov. (Nematoda: Merlinidae) from Polish Jurassic Highland. Zootaxa 4742 (1): 117-128, DOI: 10.11646/zootaxa.4742.1.

Can Nematode Communities Work as an Indicator of Soil Health in a Multiyear <i>Miscanthus × Giganteus</i> Plantation Growing in Lead-Contaminated Soil?

Analysis of the nematode community has been considered a key indicator of soil health. In this study, the assessment of nematodes was performed two times during the third growing season in soil contaminated by chemical elements where Miscanthus × giganteus was cultivated in the years 2019–2022. A morphological approach was used to identify the nematode communities that showed sensitivity to the level of soil contamination. In contrast, the value of M × g dry biomass was a more conservative indicator and displayed only a small yield, which decreased (3.6%) at the highest level of soil contamination by lead to 290.5 ± 75.4 µg/g. Principal component analysis revealed four trends associated with the coherent variability of contamination in soil and various organs of M × g. The variability of elements was reflected by the first three principal components and did not affect the nematode community. The variability of lead concentration was associated with principal component 4, which was the largest driver of changes in the nematode community. The trophic structure of the nematode communities was the most sensitive to soil contamination by lead. A decrease in the Structural Index was the general indicator in the transformation of the nematode community structure due to increasing levels of soil contamination

Plant parasitic nematodes in the soil and roots of Winter wheat grown in crop rotation and long – term monoculture

The species structure of plant parasitic nematode populations from the rhizosphere of winter wheat grown with crop rotation or in 48-year-old monoculture was analyzed and compared. Dominating species: Bitylenchus dubius, Merlinius microdorus, Paratylenchus neglectus and Heterodera avenae, in monoculture plots, had higher populations than in crop rotation plots. Heterodera avenae eggs and larvae were infected by pathogenic fungi in 68% of the monoculture crops (vs. 65–66% of the cysts from crop rotation), 12–20% of Paratylenchus sp. specimens were colonized by bacteria, mainly by Bacillus penetrans. This study shows nematological changes occurring in long-term wheat breeding, thus providing additional information necessary to fight dangerous viral vectors of the examined cereal

Nicienie w glebie i korzeniach jęczmienia jarego uprawianego w płodozmianie i monokulturze długookresowej

Background. Species structure of plant parasitic nematode populations from the rhizosphere of spring barley grown in an 18-year-old crop rotation and in a 48-year-old monoculture were analyzed and compared. Material and methods. Plots were established in fields of spring barley grown in an 18-year-old crop rotation and in a 48-year-old monoculture. Four $1 m^2$ plots were located in each corner of each field. Four soil samples from each $1 m^2$ plot were taken by a pedestrian cane of a $3 cm$ section at a depth of $40 cm$ in the vicinity of the barley roots at start (BBCH 09) and a day after harvest (BBCH 99). Each soil sample weighed 1 kg and contained 50 g of fresh roots and spikes. The sample from each of the four $1 m^2$ plots was a replicate (and at the same time, the combination of the soil + roots + stems), hence the isolated nematode from each part of the sample was a set of nematodes associated with the host on $1 m^2$. Results. Populations of dominating species such as Bitylenchus dubius, Merlinius microdorus, Pratylenchus neglectus and Heterodera avenae became higher in the monoculture than in the crop rotation. H. avenae eggs and larvae were infected by pathogenic fungi in 50% of samples from the monoculture (vs. 60% of the cysts from the crop rotation), and 18–35% of Pratylenchus specimens were colonized by bacteria, mainly by Bacillus penetrans. Conclusion. The results illustrated nematological changes occurring in long-term cropping systems and provided additional information necessary to fight dangerous viral vectors for the examined cereal.W pracy przedstawiono wyniki badań struktury gatunków pasożytniczych populacji nicieni roślinnych z ryzosfery jęczmienia jarego uprawianego w 18-letnim płodozmianie i 48-letniej monokulturze. W każdym rogu obu pól znajdowały się cztery poletka o powierzchni $1 m^2$. Cztery próbki gleby z każdego poletka pobrano laską glebową o przekroju $3 cm$ na głębokości $40 cm$ w pobliżu korzeni jęczmienia na początku (BBCH 09) i dzień po zbiorach (BBCH 99). Każda próbka gleby ważyła 1 kg, z czego 50 g stanowiły świeże korzenie i kłosy. Każda próbka, z której wyizolowano nicienie, stanowi połączenie powtórzeń każdego wariantu doświadczenia (połączenie gleba + korzenie + łodygi). Populacje gatunków dominujących, takich jak Bitylenchus dubius, Merlinius microdorus, Pratylenchus neglectus i Heterodera avenae, są znacznie wyższe w monokulturze niż w płodozmianie. Jaja i larwy gatunku H. avenae zostały zainfekowane chorobotwórczymi grzybami w 60% próbek pochodzących z monokultury jęczmienia (w porównaniu z płodozmianem, którego infekcja dotyczyła 50% cyst). Z kolei bakterie, głównie Bacillus penetrans, skolonizowały nicienie z rodzaju Pratylenchus, co stanowiło przedział 18–35% pobranych próbek. Uzyskane wyniki obrazują zmiany nematologiczne zachodzące w długotrwałych systemach uprawy jęczmienia jarego. Dostarczają one dodatkowych informacji niezbędnych do podjęcia odpowiednich działań w celu zwalczania niebezpiecznych wektorów wirusowych dla badanego zboża

The Short-Term Effects of Amendments on Nematode Communities and Diversity Patterns under the Cultivation of <i>Miscanthus × giganteus</i> on Marginal Land

The short-term effects of soil amendments on the structure, diversity and function of a nematode community of Miscanthus × giganteus was investigated. Crop was cultivated on marginal, nutrient-poor land amended with biochar in single and double doses (BD1 and BD2), biogas digestate (D), sewage sludge (SS), and hemicellulose waste (HW). Sampling was done after planting, in the middle and end of vegetation; morphology-based approach was used. 28 nematode taxa were identified, including 5 bacterivores genera, 4 fungivores genera, 5 herbivores genera (11 species), 2 omnivores genera, 5 predators genera. The general linear models, correspondence analysis and clustering were applied for evaluation. The total abundance of nematode taxa Filenchus, Dorylaimus, Cephalobus, Panagrolaimus, Aphelenchus, and Ditylenchus was depended on the sampling time and amendments. The incorporation of amendments affected nematode food web and resulted in suppression of plant-parasitic nematodes (PPNs). It was revealed that community structure was more mature for SS, less stable for D and had inconclusive effects for BD1, BD2, and HW. Using amendments ensured pest control benefits which is important given concern that PPNs can inflict crop damage during increased cultivation of M × g. Further research is needed to examine amendments which can minimise PPNs without reducing populations of nitrogen-fixing bacterivores and fungivores