Abundance Of Plant-parasitic Nematodes Research Articles

Fungal communities shift with plant parasitic nematode abundance in soils.

Fungal communities shift with plant parasitic nematode abundance in soils.

Cover crop functional types alter soil nematode community composition and structure in dryland crop-fallow rotations

Increasing dryland cropping intensity by integrating cover crops into crop-fallow rotations can add diversity and alter soil ecosystem functions, including improvements in soil nutrient and water retention and cycling, and suppression of soil-borne pests. However, the use of cover crops can also carry the risk of increasing the abundance of plant-parasitic nematodes that could undermine system productivity. Here, we examined how the integration of diverse cover crops of different functional groups: Poaceae [forage oat (Avena sativa L.)]; Brassicaceae [forage rape (Brassica napus L.)]; and Fabaceae [common vetch (Vicia sativa subsp. sativa L. and fababean (Vicia faba L.) in monocultures and mixtures into a dryland crop-fallow rotation altered soil nematode community composition and structure relative to conventional fallows. We found that cover crop mixtures had greater diversity and complexity of free-living nematodes, indicating enhanced cycling of energy and nutrients (enrichment index >50 %) compared to monocultures. Furthermore, using a structural equation modelling approach, we showed the abundance of free-living nematodes is driven primarily by cover crop residue quality (C:N ratio, and cellulose content) and marginally by cover crop quantity (biomass). The grass-legume mixture had the highest abundance of plant-parasitic nematodes (Pratylenchus neglectus and Merlinius brevidens) but also fostered robust soil food webs with complex soil nematode trophic interactions, indicating promotion of soil ecosystem functions related to N and C cycling and overall improvement in soil health. The results indicate bottom-up effects of cover crops on soil nematode communities are modulated by cover crop functional type and mixture composition. Consequently, cover crops with appropriate traits must be selected if soil health is to be improved via suppression of plant-parasitic nematodes, promotion of free-living nematodes, and enhancement of soil food web complexity.

Plant-parasitic nematode community and enzyme activities in soils under no-till soybean crops in Brazil

Soybean is Brazil's largest agricultural crop, grown across a variety of climates and soil conditions, and it is subjected to a large number of pests, including plant-parasitic nematodes. In general, the occurrence of plant-parasitic nematodes in soybean is influenced by various soil physicochemical properties, such as the pH, texture, and nutrient content. These soil properties may determine the nematodes community composition and affect soil quality and functioning, which can be monitored by analysing of soil enzyme activity. In this sense, the analysis of β-glucosidase and acid phosphatase enzymes can provide valuable information to assist decisions in the sustainable management of soybean cultivated soils in Brazil. In this study, we used 216 samples collected from no-till soybean fields across Brazil. The samples were used to investigate the influence of soil physical and chemical properties on the plant-parasitic nematode community and enzymatic activity. We identified seven genera of plant-parasitic nematodes including Meloidogyne, Pratylenchus, Heterodera, Rotylenchulus, Helicotylenchus, Scutellonema, and Xiphinema. Our results indicate that clay content and soil pH were the main properties modulating the plant-parasitic nematode community. We observed a higher abundance of plant-parasitic nematodes in highly acidic soils when compared to slightly acidic. In addition, soil organic matter content, available P, and pH were the main properties modulating microbial activity in the soil. No significant correlations were observed between enzymatic activity and nematode population density. This is the first study to provide insights into plant-parasitic nematode community composition and soil enzymes activity in soybean cultivated soils on a national scale in Brazil.

Distribution and Abundance of Nematodes in Horticultural Production in Paraguay

In Paraguay, there is no information describing the distribution and abundance of plant-parasitic nematodes and other free-living nematodes from vegetable farms. The objectives of this study were to determine the prevalence and abundance of plant-parasitic nematodes on vegetable farms, to evaluate the relationship between plant-parasitic nematodes and ecological diversity, and to evaluate the relationship between edaphic factors and nematode communities. Vegetable farms ( n = 217) across nine departments in Paraguay were included in this survey, and soil samples were collected between March and September 2021. More than 10 plant-parasitic nematode genera were identified in this survey and are presented as follows in decreasing order of prevalence: Helicotylenchus (0 to 2,000 nematodes/100 cm3 of soil), Meloidogyne (0 to 4,120), Criconemella (0 to 400), root-related genera in Tylenchidae (0 to 400), Pratylenchus (0 to 280), Tylenchorhynchus (0 to 200), Trichodorus (0 to 40), Rotylenchulus (0 to 1,800), Hoplolaimus (0 to 20), Xiphinema (0 to 80), Scutellonema (0 to 1,000), Criconema (0 to 24), and Hemicycliophora (0 to 20). Meloidogyne was the most abundant nematode on vegetable farms, highlighting the potential threat of this pathogen to horticultural production in Paraguay. Nematodes were separated into five trophic groups depending on their feeding habits. Diversity of trophic groups was estimated using Shannon's diversity index, which was inversely related to plant-parasitic nematodes. Additionally, the relationship between edaphic factors (physical-chemical soil properties) and nematode abundance was evaluated. Soil texture was significantly associated with nematode abundance. This study is a first step to aid local growers in developing sustainable and economic agricultural systems.

Plant-Soil Mediated Effects of Long-Term Warming on Soil Nematodes of Alpine Meadows on the Qinghai-Tibetan Plateau.

Global warming is one of the most pressing environmental issues today. Our study aimed to investigate how warming affected plant and soil nematode communities in alpine meadows on the Qinghai-Tibetan Plateau over the past seven years. An artificial warming experiment with different gradients was conducted from 2011 to 2018, including temperature increases of 0 °C (CK), 0.53 °C (A), 1.15 °C (B), 2.07 °C (C), and 2.17 °C (D), respectively. Cyperaceae plants were shown to be eliminated by increasing temperature, and plant community composition tended to cluster differently under different warming gradients. The number of nematodes decreased with the increase in soil depth, and the majority of them were observed in the topsoil layer. The individual densities of soil nematodes were 197 ind.·100 g-1 dry soil at 10-20 cm and 188 ind.·100 g-1 dry soil at 20-30 cm in the A treatment, which was significantly higher than the CK (53 and 67 ind.·100 g-1 dry soil) (p < 0.05). The lowest relative abundance of bacterivore nematodes (Ba) was 31.31% in treatment A and reached the highest of 47.14% under the warming gradient of D (p < 0.05). The abundance of plant parasitic nematodes (Pp) was significantly reduced to 26.03% by excessive warming (2.17 °C increase) in comparison to CK (41.65%). The soil nematode community had the highest diversity with a 0.53 °C increase in soil temperature; 1.15 °C warming gradients were lower, and nematode communities tended to be simplified (p < 0.05). All nematode channel ratio (NCR) values were above 0.5, indicating that warming did not change the decomposition pathway of soil organic matter dominated by the bacterial channels. The Wasilewska Index (WI) in the D treatment increased significantly compared to other treatments (p < 0.05), indicating that the mineralized pathway of the food web was primarily involved with Ba and fungivores nematodes (Fu), which is conducive to the growth of micro-biophagous nematodes. The plant parasite index (PPI) decreased significantly in the D treatment compared with other treatments (p < 0.05), indicating that a high warming gradient caused a reduction in the maturity of Pp nematodes. The maturity index (MI) increased in the D treatment compared with A, B, and C treatments, indicating that overheating affected the nematode community in the later stage of succession and caused the soil to be less disturbed. A partial least squares path model (PLSPM) showed that warming indirectly affects Fu and Pp diversity by directly impacting the plant community as well as indirectly affecting Ba by directly affecting soil properties. In conclusion, plant diversity and community composition profoundly affect the soil nematode communities, thus reflecting the dynamic processes and evolution of soil ecosystems.

Year-Long Assessment of Soil Nematode Diversity and Root Inhibition-Indicator Nematode Genera in Rice Fields.

Soil nematodes contribute to nutrient cycling. This year-long study aimed to investigate the changes in the diversity of soil nematodes during the spring, summer, and winter seasons in rice fields at 24 sites and to determine the indicator nematode genera that inhibit the roots of rice plants. A total of 216 soil samples were collected during three seasons, and the collection of 72 root samples was carried out during rice cropping. Forty-four soil nematode genera were identified. They exhibited significant changers in their abundance, which were dependent on the seasons and on soil characteristics. In particular, the abundance of plant-parasitic nematodes (PPNs) and free-living soil nematodes was 49% and 15% higher during the summer than during the spring and winter seasons, respectively. Soil characteristics, such as soil nitrogen (N) contents, carbon (C) contents, and soil moisture were significantly higher during the summer than in the spring and winter seasons, but soil pH was significantly lower during the summer than in the spring and winter seasons. Moreover, Hirschmanniella,Meloidogyne, and Heterodera emerged as good indicators for rice root inhibition, corroborating the frequency, density, and prominence value of PPNs of the sampled soil and rice roots. This study also indicated that free-living nematode genera, such as Rhabdolaimus, Diplogaster, and Rhabditis, might function as ecological indicators for soil health.

Occurrence, diversity and relative abundance of plant-parasitic nematodes: A survey of selected crop fields in Akure, Southwestern Nigeria

Occurrence, diversity and relative abundance of plant-parasitic nematodes: A survey of selected crop fields in Akure, Southwestern Nigeria

Organic substitutions improve soil quality and maize yield through increasing soil microbial diversity

Organic substitution is beneficial to sustainable agricultural development. In order to determine the proper fertilization strategy, it is necessary to evaluate the effects of partial substitution of nitrogen fertilizer with organic amendments on soil quality and crop yield, as well as their decisive factors. A five-year organic substitution field experiment was set up to investigate the effects of partial substitution of chemical fertilizer with stover, cattle manure and biochar on soil quality, soil microbial and nematode diversities and crop yield in a maize (Zea mays L.) field of Northeast China. Our results showed that organic substitutions increased soil quality and manure substitution increased maize yield through changing the composition and functional group of soil biota. Bacteria played important roles in determining the maize yield, but the beneficial effects were contingent on the different types of organic substitution. Stover substitution improved soil quality through increasing bacterial diversity but may lead to the competition of nitrogen between microorganisms and crops. Compared with conventional fertilization, manure substitution provided resources with suitable C/N ratio (6.82) and resulted in the higher maize yield, but the soil quality improvement was weaker under manure substitution than under stover substitution. Biochar substitution reduced the relative abundance of plant-parasitic nematodes but caused an increasing of potential pathogenic fungi for maize. Comprehensively, stover substitution is the most promising fertilization regime for maize in Northeast China from the perspective of soil quality and soil biodiversity.

Plant Parasitic Nematodes: A Review on Their Behaviour, Host Interaction, Management Approaches and Their Occurrence in Two Sites in the Republic of Ireland.

Plant parasitic nematodes are a major problem for growers worldwide, causing severe crop losses. Several conventional strategies, such as chemical nematicides and biofumigation, have been employed in the past to manage their infection in plants and spread in soils. However, the search for the most sustainable and environmentally safe practices is still ongoing. This review summarises information on plant parasitic nematodes, their distribution, and their interaction with their host plants, along with various approaches to manage their infestations. It also focuses on the application of microbial and fermentation-based bionematicides that have not only been successful in controlling nematode infection but have also led to plant growth promotion and proven to be environmentally safe. Studies with new information on the relative abundance of plant parasitic nematodes in two agricultural sites in the Republic of Ireland are also reported. This review, with the information it provides, will help to generate an up-to-date knowledge base on plant parasitic nematodes and their management practices.

Long-Term Giant Hogweed Invasion Contributes to the Structural Changes of Soil Nematofauna.

Heracleum mantegazzianum (giant hogweed) is the largest central European forb, naturalized or invasive in many European countries. The impacts of its colonization of native habitats on soil mesofauna groups are unfortunately obscure. This study assessed the effect of giant hogweed invasion on the communities of plants and soil nematodes in the riparian habitat. We found that invasion by H. mantegazzianum increased soil pH, decreased carbon and nitrogen content, reduced the number and coverage of the native plant species, and influenced nematode communities and their structures. Nematode species number was significantly lower in invaded than uninvaded plots, but nematode species diversity was not affected by invasion throughout the whole study. Total nematode abundance slightly increased under giant hogweed, while total nematode biomass did not differ between the invaded and uninvaded plots. The higher abundance of bacterivores and fungivores but lower number of omnivorous nematodes well represented the negative impact of giant hogweed invasion on soil food webs, supported by low values of all maturity indices or channel index. The hogweed invaded plots contained higher abundance of plant parasitic nematodes, mainly Paratylenchus microdorus. Our results thus indicate that invasion by H. mantegazzianum influences several nematode communities’ parameters while others remain unaffected by invasion.

Plant Parasitic Nematode Abundance and Diversity in Potato (Solanum tuberosum) Cultivation at Various Altitudes in Wonosobo and Banjarnegara

Plant-parasitic nematodes are one of the causes of yield loss in potato cultivation. Currently, information on the diversity, abundance, and dominance of potato parasitic nematode genera is not available. This research aimed to determine the pattern of distribution, abundance, and dominance of parasitic nematode genera on potato plant (Solanum tuberosum) in Wonosobo and Banjarnegara Districts at various altitudes i.e.: 1,250--1,500; 1,500--1,750; 1,750--2,000; and 2,000--2,250 meters above sea level (m.a.s.l.). Soil rhizosphere and root samples were collected, and nematodes were extracted using the Whitehead tray modification technique. The nematodes were adjusted with Formalin Acetic acid Alchohol (FAA), mounted, and identified based on morphological characters. The diversity index was determined to distinguish plant-parasitic nematode diversity. Six genera of potato plant-parasitic nematodes were found, namely Meloidogyne, Hirschmanniella, Globodera, Criconemoides, Helicotylenchus, and Xiphinema. The highest population of plant-parasitic nematodes was found at 1,250–1,500 m.a.s.l. from both root and soil samples. The nematode populations were 56.67 nematodes/5 g root and 103.33 nematodes/100 g of soil. The abundance of parasitic nematodes did not differ significantly among different altitudes in both districts. The dominant parasitic nematodes in soil samples were Meloidogyne with 16.78%, while Globodera was 13.98%. The Shannon-Wiener index implied that the diversity of parasitic nematodes of potato plants and stability of community in Wonosobo and Banjarnegara Districts were categorized as low.

Identification and Abundance of Plant-parasitic Nematodes Associated with Amenity Trees in the University of Port Harcourt, Rivers State, Nigeria

Plant-parasitic nematodes contribute to unnoticeable damages which lead to gradual decline in the values and eventually death of amenity trees. Identification of these nematode pests is vital for their effective management. Reconnaissance survey was carried out to identify amenity tree species present in the University of Port Harcourt (UNIPORT). Composite bulked soil and root samples (126) were collected from amenity trees in UNIPORT and nematode pests were extracted from samples using modified Baerman method. The nematode pests were identified and their populations determined using standard procedures. Relative importance value (RIV) and diversity indices were calculated with appropriate software. Data were processed using descriptive statistics and with analysis of variance. 38 tree species were identified in UNIPORT belonging to 20 families. Terminalia mantaly, Cocos nucifera and Terminalia catappa with RIVs of 15.1, 9.35, and 9.12 respectively were the three most important amenity trees in UNIPORT. Fifteen nematode pest genera; Helicotylenchus, Aporcelaimus, Tylenchulus, Meloidogyne, Scutelonema, Pratylenchus, Tylenchus, Rotylenchoides, Criconema, Hemicyliophora, Trichodorus, Mesodorylaimus, Heterodera, Paratylenchus and Longidorus were associated with 21 of the amenity trees. The three most important nematode pest genera were Helicotylenchus, Tylenchulus and Aporcelaimus with RIVs of 42%, 16% and 5.34%, respectively. Helicotylenchus (RIV 45.41%) and Tylenchulus (RIV 30%) were the most important plant-parasitic nematode genera in the soil and roots of amenity trees, respectively. Helicotylenchus, Tylenchulus and Aporcelaimus were the three most important plant-parasitic nematode genera associated with amenity trees in UNIPORT.
 Keywords: Amenity trees, Diversity indices, Identification, Nematode pests, Survey

An evaluation of selected chemical, biochemical, and biological parameters of soil enriched with vermicompost

The aim of this study was to assess the changes in chemical and microbial properties and enzymatic activity of soil enriched with vermicompost derived from household waste. The vermicompost was tested in the rhizosphere of Larix decidua seedlings cultivated in 10-L pots in: (i) nursery soil (as the control), (ii) soil with 10% v/v vermicompost, and (iii) with 20% v/v vermicompost. The impact of vermicompost was assessed in terms of soil C/N ratio; bacterial, fungal, and nematode counts; and enzymatic activity. It was found that vermicompost increased the C/N ratio from 21 to 32, as well as the content of nitrate from 78 to 134 mg kg−1, of ammonium from 14 to 139 mg kg−1, of phosphorus from 92 to 521 mg kg−1, and of potassium from 142 to 1912 mg kg−1, compared with the control soil. The abundance of beneficial bacteria was increased (from 8.61 × 107 to 37.9 × 107), along with decreases in microbiological ratios of fungi and bacteria (e.g. fungi/Bacillus from 0.18818 to 0.00425). A significant 2- to 4-fold increase was observed compared with the control in the number of beneficial nematodes belonging to bacterivorous, fungivorous, and predatory groups with no change in the abundance of plant-parasitic nematodes. Addition of vermicompost brought about a change in soil enzyme activity. Vermicompost reduced the activity of alkaline phosphatase only. Both doses of vermicompost led to an increase in the activity of acid phosphatase, inorganic pyrophosphatase, dehydrogenases, β-glucosidase, and urease. Only the higher dose had an effect on increasing the activity of o-diphenol oxidase and proteases. No significant change was observed for nitrate reductase. Also, the presence of antibiotics produced by bacteria was detected depending on the dose of vermicompost, e.g. iturin (ituC) and bacillomycin (bmyB) were found in soil with a dose of 20% v/v vermicompost. Overall, vermicompost produced from household waste can be an excellent organic fertilizer for larch forest nurseries.

Accurate evaluation of blackening disease in lotus (Nelumbo nucifera Gaertn.) using a quantitative PCR-based assay for Hirschmanniella diversa Sher and H. imamuri Sher

Blackening and deformation disease (called “kurokawa-senchu-byo” in Japanese) of lotus (Nelumbo nucifera Gaertn.) is a critical issue in lotus cultivation that is known to be caused by the plant-parasitic nematodes Hirschmanniella diversa Sher and H. imamuri Sher. To evaluate the extent of the disease, a damage index that classifies the nematode damage into five stages according to the surface condition of the lotus tubers has been proposed; however, this method requires considerable experience to perform an accurate evaluation. In this study, we quantified H. diversa and H. imamuri populations using a 5.8S ribosomal RNA (rRNA) gene/internal transcribed spacer (ITS) region-targeted quantitative PCR (qPCR) technique in lotus root and soil samples collected from 24 fields in Japan. We attempted to reveal the relationship between the damage index values and the abundance of lotus-parasitic nematodes based on the gene copy numbers of the 5.8S rRNA/ITS region in order to predict the in situ contamination level of lotus cultivation fields. Through the use of template DNA extracted from lotus roots, we successfully detected both H. diversa and H. imamuri at 6.8 ± 0.24 and 5.0 ± 0.32 log10 copies/g-fresh lotus root, respectively. Moreover, many large variations as well as samples in which Hirschmanniella spp. were not detected were observed in the soil samples, indicating that using lotus root-derived DNA could more precisely quantify the abundance of plant-parasitic nematodes in the lotus cultivation fields. Linear regression analyses showed a strong correlation between the density of H. diversa and the damage index values, while there was no significant correlation between the H. imamuri density and the damage index values. These results indicate that H. diversa, rather than H. imamuri, may act as a major causative agent of “kurokawa-senchu-byo” in lotus cultivated in Japan and that 6.4 log10 copies/g-fresh lotus root of H. diversa density represents an economic injury level (damage index = 2) for lotus cultivation.

Survey of Plant-Parasitic Nematodes Associated with Cotton in Nuh and Palwal Districts of Haryana

An extensive survey was conducted to assess the frequency and abundance of plant-parasitic nematodes associated with cotton (Gossypium hirsutum L.) in Haryana (Nuh and Palwal districts) during 2018-20. Based on incidence, population density and associated damage on affected crops, root-knot nematode (Meloidogyne incognita) was considered to be the most important parasite of the crops under local condition. During 2018-19, a total of 11 soil and root samples of cotton were collected from Nuh and Palwal districts. Out of these, eight were found infected with M. incognita with 72.0% frequency of occurrence. The results revealed that out of 7 samples (Nuh), five were found infested with M. incognita with 71.4% frequency of occurrence. In Palwal district, this nematode had 75.0% frequency of occurrence with density range of 60-300 j2 200-1 cc soil. During 2019-20, a total of 27 soil and root samples of cotton were collected from Nuh and Palwal districts. Out of these, 14 were found infected with M. incognita with 51.8% frequency of occurrence. The results revealed that out of 21 samples (Nuh), 12 were found infested with M. incognita with 57.1% frequency of occurrence and density range of 95-690 j2 200-1 cc soil. In Palwal district, this nematode had 33.3% frequency of occurrence (2 out of 6 samples) with density range of 135-435 j2 200-1 cc soil. Other plant parasitic nematodes which were found associated with the cotton belonged to Rotylenchulus reniformis, Hoplolaimus sp., Helicotylenchus sp. and Tylenchorhynchus sp.

The response of soil nematode fauna to climate drying and warming in Stipa breviflora desert steppe in Inner Mongolia, China

Global warming and drying are important environmental issues. Our study aimed to investigate how warming and precipitation changes affect soil nematode communities in an Inner Mongolian desert steppe for 10 years. Soil nematodes were extracted by the Baermann funnel method. Changes in the nematode communities under artificial warming and precipitation conditions were assayed by analyzing their abundance and ecological indices. Soil nematode abundance decreased significantly by 37.47% under artificial warming; however, there was no significant effect of warming on the nematode community diversity. As for precipitation experiment, the decreased precipitation eliminated some of non-dominant nematode genera, such as Pratylenchus, Helicotylenchus, and Aphelenchus. It caused not only a significant decrease (37.65%) in soil nematode abundance but also a more structured food web and shorter food chain. However, nematode faunal analysis indicated that the soil nematode community was more resistant to drought. Both soil nematode abundance and community diversity increased significantly as increase of precipitation. In particular, the abundance of plant parasitic nematodes increased by 46.69%, which may due to the increase in total nitrogen content in soil. Nematode faunal analysis showed that increased precipitation improved soil environment for the nematodes, and increased food web connectivity and food chain length. However, bacterivorous nematode abundance decreased by 74.39%, and the decomposition pathway of the nematode community had switched from the bacterial channel to the fungal channel. In the Inner Mongolian steppe, both climate drying and warming had negative impacts on soil nematode abundance; however, only drying affected nematode community diversity and food web structure and slowly changed nematode ecological functions. Increased precipitation may aid soil nematode community recovery.

Biochar addition combined with daily fertigation improves overall soil quality and enhances water-fertilizer productivity of cucumber in alkaline soils of a semi-arid region

Crop land degradation is a common phenomenon in most regions of the world, especially in arid and semi-arid regions. To mitigate cropland degradation and further enhance crop productivity, it is crucial to restore soil quality by utilizing efficient soil management practices. Although biochar has been widely used to improve soil conditions, the efficiency of biochar in enhancing crop productivity is often limited by inappropriate agricultural practices (e.g. irrigation and fertilization). Moreover, little information is available regarding the link among availability of water, biochar and productivity. In this study, we measured the effects of biochar addition, daily fertigation and their combination on overall soil quality, crop yield and water-fertilizer productivity in alkaline soils of a semi-arid region, over two years. To comprehensively evaluate soil quality, a wide range of soil physical, chemical, biological and ecological properties were measured and integrated into a soil quality index (SQI). The treatments evaluated were (i) untreated soils managed with traditional irrigation and fertilization (control), (ii) soils treated with biochar and managed with traditional irrigation and fertilization (B), (iii) untreated soils managed with daily fertigation (DF), and (iv) soils treated with biochar and managed with daily fertigation (B + DF). In general, biochar addition enhanced soil quality (expressed by SQI) mainly through increasing soil water content (SWC), available phosphorus (AP), the capacity of soil microbes to utilize miscellaneous (CSM-MI) and microbial biomass carbon (Cmic), and decreasing soil pH and plant-parasitic nematode abundance. Daily fertigation improved soil quality primarily by enhancing SWC, AP, CSM-MI and Cmic. The SQI exhibited strong positive correlations with both plant biomass and fruit yield. In addition, the treatment B + DF showed not only the highest SQI and fruit yield, but also the highest irrigation water-productivity (326.3 and 557.9 kg mm−1 in 2017 and 2018, respectively) and partial factor productivity for fertilizer in both years 2017 and 2018. Our results show that biochar addition combined with daily fertigation can improve overall soil quality, and further enhance cucumber yield and water-fertilizer productivity in alkaline soils.

Occurrence of vermiform plant-parasitic nematodes in North Dakota corn fields and impact of environmental and soil factors

Plant-parasitic nematodes (PPN) can negatively affect corn production. In this study, incidence and abundance of PPN were assessed in 300 corn fields across 20 counties in North Dakota during 2015 and 2016. Seventy-two percent of the fields were positive for PPN. The major genera identified were Helicotylenchus (incidence: 52%; mean density: 1513 nematodes kg−1 of soil; greatest density: 16 910 nematodes kg−1 of soil), Tylenchorhynchus (37%; 687; 9500), Paratylenchus (31%; 1484; 7800), Pratylenchus (20%; 399; 2125), Heterodera (9%; 555; 4500), Xiphinema (8%; 330; 900), Hoplolaimus (3%; 294; 500) and Paratrichodorus (1%; 124; 200). Neighbouring counties had greater similarity in PPN diversity than counties that are further apart, with western, north-eastern and south-eastern counties forming clusters of similar nematode occurrence and diversity. Canonical correspondence analysis was conducted to determine the association between incidence and abundance of these PPN populations and various soil edaphic and climatic factors. The analysis revealed that Hoplolaimus, Paratrichodorus, Paratylenchus and Pratylenchus were positively correlated with soil temperature, rainfall and per cent sand, while Helicotylenchus, Tylenchorhynchus and Xiphinema were positively correlated with pH, percent clay and percent organic matter. This is the first report of an extensive investigation of PPN communities in North Dakota corn fields. Research findings will be useful in future field experiments to determine the impact of PPN on corn in the Northern Great Plains.

Nematode Management in the Strawberry Fields of Southern Spain

(1) Background: Spain is the sixth strawberry producer in the world, with about 6500 ha producing more than 350,000 tons, and an annual commercial value about 390 million €. Stunted and dead strawberry plants are frequently associated with plant-parasitic nematodes, but nematode diseases have not been characterized to date in the country. (2) Methods: A poll on the perception of the impact of nematodes on strawberry production was carried out by face-to-face interviews with farm advisors. In addition, nematological field surveys were carried out at the end of the growing season in 2017 and 2018 to determine prevalence and abundance of plant-parasitic nematodes in strawberry crops. The host suitability to Meloidogyne hapla of seventeen strawberry cultivars and the tolerance limit to M. hapla at progressively higher initial population densities (Pi) were assessed in pot experiments in a growth chamber. Comparison of the relative efficacies of several soil disinfestation methods in controlling nematode populations (M. hapla and Pratylenchus penetrans) was carried out in experimental field trials for twelve consecutive years. (3) Results: Meloidogyne spp., Pratylenchus penetrans, and Hemicycliophora spp. were the main plant-parasitic nematodes in the strawberry fields in South Spain. Root-knot nematodes were found in 90% of the fields, being M. hapla the most prevalent species (71% of the fields). A tolerance limit of 0.2 M. hapla juveniles per g of soil was estimated for strawberry, and currently cropped strawberry cultivars did not show resistance to M. hapla. Nematode population densities were reduced by more than 70% by soil fumigation with 1,3-dichloropropene, dazomet, dimethyl-disulfide, and methyl iodide. The efficacy of metam-sodium in reducing nematode populations was about 50% and that of chloropicrin, furfural, and sodium-azide, less than 40%. Combination of solarization with organic manures (biosolarization) reduced soil nematode populations by 68–73%. (4) Conclusions: Plant-parasitic nematodes (Meloidogyne, Pratylenchus, and Hemicycliophora) are widely distributed in the strawberry fields of Southern Spain. Strawberry is a poor host for M. hapla with a tolerance limit of 0.2 J2 per g of soil, and low population increases in cropping cycles of 7–8 months. Strawberry cultivars show a range of susceptibility and tolerance to M. hapla, but no resistance is found. Nematodes are effectively controlled by chemical fumigation of soils, but soil biosolarization is equally effective, and therefore, can be proposed as a sustainable alternative for pathogen control in strawberry cultivation.

Distribution and community structure of plant-parasitic nematodes and their relationship with some soil properties in betel vine-growing regions of West Bengal, India

Summary The distribution and community structure of plant-parasitic nematodes associated with betel (Piper betle) vine and their relationship with soil chemical properties were investigated in four major growing regions of West Bengal, India. Ordinary kriging method was applied to infer the patterns of spatial distribution of major plant-parasitic nematodes across the growing regions. Meloidogyne and Rotylenchulus were found to be the most abundant genera in betel vine crops in all growing regions. Co-inertia analysis between soil properties and nematode abundance indicated that soil chemical characters significantly affect abundances of plant-parasitic nematodes. The type of betel vine crop (sweet and bitter) also has a significant effect on the abundance of plant-parasitic nematodes, with the highest abundance of Meloidogyne reported from the bitter type of betel crop. Spatial distribution depicted a higher abundance of Meloidogyne throughout the North Bengal growing region. Root-knot and reniform nematodes are two important plant-parasitic nematodes of betel vine that might cause economic yield loss to the growers in West Bengal.