Suppression Of Plant-parasitic Nematodes Research Articles

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.

Successional effects of cover cropping and deep tillage on suppression of plant-parasitic nematodes and soilborne fungal pathogens.

Cover crops can suppress soilborne nematodes and fungal pathogens by serving as a poor host to pathogens and producing allelopathic compounds. Yet, cultural practices can influence their effectiveness. Cover crop and weedy fallow rotations and their interactions with deep tillage were evaluated from 2019 to 2021 in a three-season vegetable cropping system (spring tomato, fall squash, and winter cabbage) for their suppressive effects on soilborne diseases. Experimental plots were arranged in a split-plot 2 × 4 factorial design in randomized complete blocks. Whole-plot tillage treatments were shallow-tilled or deep-tilled. Subplots had two factors of crop rotations: rotation type (cover crop [spring or fall sunn hemp or winter rye] or weedy fallow) and rotation season. Independent of tillage practice, sunn hemp and weedy fallow reduced population density and root galling severity of root-knot nematode (Meloidogyne incognita) for the first subsequent vegetable compared to the all-vegetable rotation (P < 0.05) but had little effect on fungal pathogens. Fall sunn hemp had higher plant biomass and reduced gall severity for the second subsequent vegetable. Spring and fall sunn hemp improved vegetable yields. Winter rye only reduced ring nematodes (Mesocriconema spp.) population density in the first subsequent vegetable. Deep tillage reduced incidence of fungal pathogens of Rhizoctonia solani and Sclerotinia sclerotiorum, and population density of stubby-root nematode (Nanidorus minor). Sunn hemp is effective in suppressing M. incognita, whereas deep tillage can be used to suppress R. solani, S. sclerotiorum, and N. minor in vegetable production systems. © 2023 Society of Chemical Industry.

The Short-Term Effects of Amendments on Nematode Communities and Diversity Patterns under the Cultivation of Miscanthus × giganteus 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.

A rapid bioassay for measuring nematode suppressive potential of anaerobic digestate

Summary Anaerobic digestate is a byproduct of anaerobic digestion of organic materials for biogas production. Land application of digestates may provide plant nutrition and suppression of plant-parasitic nematodes. The characteristics of digestates may vary by organic substrates and digestion conditions. To measure nematode-suppressive potential, the rigour and simplicity of a radish bioassay with Heterodera schachtii was expanded. In a three-factor factorial design, three incubation environments, two growth containers and two nematode life stages as inoculum were tested. Containers with 50 g of dry sandy loam soil were inoculated with 500 second-stage juveniles (J2) of H. schachtii or with cysts with equivalent hatchable J2. One seed of radish Raphanus sativus ‘Cherry Belle’ was planted into each container, and 1 ml of drench treatment was applied. After 64 degree days (4-5 days), roots were washed and stained with acid fuchsin for nematode counting. In three experiments, food waste digestate permeate suppressed nematode root penetration in the growth chamber, glasshouse and laboratory, in cups and tubes, and following inoculation with cysts and J2. However, root penetration by J2 was more greatly reduced after cyst inoculation than after J2 inoculation. Investigations in preserving nematode cysts showed that J2 within cysts remained viable after incubation in sandy loam soil at 23°C in sealed tubes in the laboratory for 35 days. Results of the radish assay predicted nematode-suppressive potential against Pratylenchus vulnus on peach rootstock ‘Nemaguard’ in a glasshouse experiment. In summary, a straightforward rapid bioassay for measuring nematode suppressiveness of organic liquids was developed for routine use.

Effects of biofumigant crop termination methods on suppression of plant-parasitic nematodes

Biofumigation is a soil sterilization technique using isothiocyanates (ITCs) generated from naturally occurring glucosinolates (GLs, thioglucosides) in members of Brassicaceae. Efficacy of biofumigation on plant-parasitic nematodes could be affected by the way biofumigant crops are terminated. The objective of this research was to determine biofumigant crop termination method suppressive to Meloidogyne spp. and Rotylenchulus reniformis on zucchini (Cucurbita pepo). Three field trials were conducted where ‘Sodbuster’ oil radish (OR; Raphanus sativus) and ‘Caliente 199’ brown mustard (MS; Brassica juncea) were grown as biofumigant crops and subjected to various termination methods. In the first trial (Trial I), OR and MS were each terminated by: 1) clipping off shoots at soil line and covering residues with woven weed mat in no-till (NT); 2) macerating shoots followed by tilling (MT); and 3) MT plus covering with black plastic (MTBP). In the second and third trials (Trials II and III), MS was terminated by: 1) NT; 2) MT; or 3) MTBP, in the same way, described in Trial I; 4) macerating shoots in no-till (MNT); 5) MNT plus covering residues with black plastic (NTBP); and tilling without prior tissue maceration (T). A bare ground (BG) control was included in each trial. Brown mustard MTBP suppressed soil populations of Meloidogyne spp. (Trial I-III) or R. reniformis (Trial I), reduced severity of root galls (Trial I-II) and increased zucchini canopy (Trials I and III) (P ≤ 0.05). None of the OR treatments suppressed Meloidogyne spp. and R. reniformis, but MT and MTBP reduced severity of root galls and increased zucchini canopy (Trial I). When soil glucose and sulfate were analyzed as indicators of biofumigation efficacy, sulfate depicted biofumigation efficacy in the order of MTBP > MT > T, higher than in no-till treatments (NT, MNT, and NTBP) and BG. A similar trend in the glucose was observed only when toluene (methylbenzene) was added immediately to soil samples to arrest microbial degradation of glucose. In summary, Meloidogyne spp. were sensitive to biofumigation than R. reniformis. Biofumigation effect was stronger with MS than OR, and MTBP was the most suppressive treatment on the targeted nematodes. Soil sulfate was more stable in the soil than glucose, thus a good indicator of biofumigation.

Nematode soil food webs in maize agro-ecosystems and their implication on plant-parasitic nematodes

Maize is the most important staple food crop consumed in Kenya and Africa. Plant-parasitic nematodes are a major constraint in maize production. On the other hand, free-living nematodes provide key ecological functions such as nutrient mineralization and pest suppression. The aim of this study was to assess the soil food web structure in maize agroecosystems in Kirinyaga County, Kenya in order to understand the potential role of predatory nematodes in suppresion of plant-parastic nematodes. Soil samples were collected from maize fields in Gichugu, Kirinyaga Central, Ndia and Mwea sub-counties in Kirinyaga County. Fifty nematode genera were identified across the sub-counties with Pratylenchus, Cephalobus, Heterocephalobus, Aphelenchus, Labronema and Nygolaimus being the most predominant genera in their respective feeding guilds. The highest enrichment index was recorded in Gichugu sub-county. Nematode functional metabolic footprints based on enrichment index and structure index characterized Mwea as a degraded ecosystem, while Gichugu, Kirinyaga Central and Ndia were structured. The plant-parasitic index was highest in Mwea sub-county although the differences between sub-counties were not statistically significant. Sub-counties which were characterized as structured had a low plant-parasitic index. Canonical correspondence analysis revealed a significant correlation between some soil physical properties, nematode indices and metabolic footprints. The results provide valuable information on soil food web structure and function in maize agro-ecosystems in Kirinyaga County, Kenya and they highlight the potential role of organic amendments in suppression of plant-parasitic nematodes in maize.

Exploring patterns of Camellia seed cake application in relation to plant growth, soil nematodes and microbial biomass

ABSTRACT The suppression of plant-parasitic nematodes is crucial for maintaining the worldwide development of the banana industry. In this study, different application patterns of Camellia seed cake previously reported to suppress root-knot nematode were conducted to manage pests and promote banana seedling growth. The results demonstrated seven days delay before transplanting was necessary after Camellia seed cake application. The dose 5 g/kg soil resulted in best plant growth promotion performance, which increased banana seedling height, stem diameter, shoot, and root fresh weight by upto 29%, 27%, 47%, and 21%, respectively. Plastic film mulching was beneficial when high amount (2%) of Camellia seed cake was added. The application of Camellia seed cake increased nutrient potassium amounts; the abundance of soil free-living nematodes, especially bacterivores; and the abundance of soil microbes and the soil catalase activity, while reduced plant-parasitic nematodes amounts. Further correlation analysis between the soil nematodes and microbial abundance showed that plant-parasite numbers had significant negative correlations with the bacterial biomass and a portion of the fungal biomass; bacterivores had significant positive correlations with the bacterial biomass; and omnivores had significant correlations with the bacterial biomass and fungal biomass. A fundamental challenge of root-knot nematode control is to sustain ecological services without losing biodiversity. This study provided an environmentally friendly strategy based on Camellia seed cake to regulate the soil health and quality.

Biochemical characteristics of cover crop litter affect the soil food web, organic matter decomposition, and regulation of plant-parasitic nematodes in a banana field soil

Suppression of plant-parasitic nematodes and decomposition of organic matter are important soil food web functions. The availability and nature of carbon substrates in soil drive the structure, dynamics, and activities of soil food webs and may alter the way they function in the ecosystem. In this study, we assessed the effects on nematode communities of incorporating litter from three cover crops with contrasting biochemical characteristics into soil taken from a banana field. The litter type influenced nematode taxa and functional guilds during the 90-day assay. The cellulose- and hemicellulose-rich litters of Crotalaria zanzibarica and Paspalum notatum induced similar nematode successions, causing bacterivorous and fungivorous nematode populations to increase early in the study period and promoting a fungal decomposition pathway at the end of the trial. These two litters were the most effective at decreasing the soil’s nematode infective potential with regard to major banana plant-parasitic nematodes, such as Pratylenchus coffeae, Helicotylenchus multicinctus, and Rotylenchulus reniformis. C. zanzibarica showed good potential as a green manure plant, as it increased the soil mineral nitrogen content during the 45 days following incorporation of litter. By contrast, litter from Acacia auriculiformis, which had high lignin content, induced immobilization of soil nitrogen and did not significantly increase microbivorous nematodes before day 45. This treatment failed to reduce the soil’s nematode infective potential for H. multicinctus and R. reniformis populations. Our study also showed that the dynamics of nitrogen mineralisation in soil were related to the C:N ratio of litters but not to the decomposition pathway. The biochemical characteristics of litters appear to be critical drivers of nematode ecological successions and decomposition pathways following plant litter amendments to soil taken from a banana field.

Modes of action associated with microbially inducedin plantasuppression of plant-parasitic nematodes

This article discusses the extensive research that has been conducted on the use of mutualistic bacterial and fungal endophytes for the biological control of plant-parasitic nematodes. This review deals in particular with the modes of action of multitrophic interactions involving endophytic bacteria or fungi that have biological control activity towards the root-knot nematode, Meloidogyne incognita, and the potato cyst nematode, Globodera pallida, on tomato or potato. The bacterial and fungal endophytes discussed here are those that: (1) have the ability to colonise the endorhiza at some point in their life-cycle; (2) can grow saprophytically in the soil or in the rhizosphere; and (3) have plant health promoting activity and antagonistic activity towards sedentary plant-parasitic nematodes.

Tropical soil microflora of spice-based cropping systems as potential antagonists of root-knot nematodes

Suppression of plant parasitic nematodes with nematode predators, parasites or antagonists is an eco-friendly approach than the toxic chemicals. In a study, soil borne fungi from the rhizosphere of major spice crops were collected from diverse cropping systems prevailing in three southern states of India. A series of in vitro studies were conducted using 73 freshly collected fungal isolates and 76 isolates obtained from other sources. Out of this 67 isolates were not parasitic on females of root-knot nematodes whereas 115 isolates, though colonized the egg masses, did not show any signs of parasitism on nematode eggs. Fifty-nine isolates showed 50–90% inhibition in egg hatch. Pochonia chlamydospora, Verticillium lecanii, Paecilomyces lilacinus, and few isolates of Trichoderma spp. showed >25% parasitism on root-knot nematode eggs. The most promising isolates in this study were one isolate each of Aspergillus (F.45), Fusarium (F.47), and Penicillium (F.59); three each isolates of Trichoderma (F.3, F.52, and F.60) and Pochonia (F.30 and Vc.3) Verticillium (Vl); and two isolates of fungi that could not be identified (F.28 and F.62). Parasitism by Aspergillus tamarii, Aspergillus ustus, Drechslera sp., Humicola sp., and Scopulariopsis sp. on root-knot nematode eggs or females, reported in the present study, are new reports.

Amendments of sugarcane trash induce suppressiveness to plant-parasitic nematodes in a sugarcane soil

In a field experiment at Bundaberg, Queensland, sugarcane trash was incorporated into soil with, or without, additional nitrogen supplied as either soybean residue or ammonium nitrate. The carbon inputs from plant material (lOtC/ha) were the same in all treatments, while both plus-nitrogen treatments received the same amount of nitrogen (210kgN/ha). Sugarcane was planted 23 weeks after amendments were incorporated, and 24 weeks later there were 95%fewer lesion nematodes (Pratylenchus zeae) in roots growing in amended soil than in roots from the unamended control. Populations of P. zeae and Tylenchorhynchus annulatus in amended soil were reduced by 85%and 71%, respectively. Bioassays in which forage sorghum was planted in soil collected during the experiment and inoculated with P. zeae indicated that amended soils were suppressive to the nematode at 20 weeks but not after 47 weeks. All amendments increased readily oxidisable carbon, microbial biomass, microbial activity and numbers of free-living nematodes, but had no effect on known predators of nematodes (i.e. dorylaimid and mononchid nematodes and three naturally occurring species of nematode-trapping fungi, Arthrobotrys conoides, A. thaumasium and Drechslerella dactyloides). However, an unidentified predatory fungus was found only in soil amended with sugarcane trash and was possibly involved in the suppression of plant-parasitic nematodes.

Suppression of plant-parasitic nematodes by application of live and dead infective juveniles of an entomopathogenic nematode, Steinernema carpocapsae, on boxwood (Buxus spp.)

Effects of live and dead (heat-killed) infective juveniles (IJs) of the entomopathogenic nematode Steinernema carpocapsae on nematodes associated with boxwood Buxus spp. were evaluated in field experiments during 1999 and 2000. Both living and dead IJs of S. carpocapsae were equally effective, causing more than 50% reduction in total populations of plant-parasitic nematodes relative to the control 15 and 30 days after treatment in both years. No significant differences were observed between reductions in populations of plant-parasitic nematodes following entomopathogenic nematode and chemical nematicide (ethoprop) treatments. In 2000, populations of Criconemella, Hoplolaimus, Longidorus, and Rotylenchus were significantly reduced in all treatments relative to the control 30 days after treatment. However, in 1999 these genera were unaffected by treatments even though total plant-parasitic nematode population was decreased. The population of Tylenchorynchus was significantly reduced in all treatments 30 days after treatment in 1999. Further, the population of Tylenchus was significantly reduced in ethoprop and dead S. carpocapsae treatments 15 days after treatment relative to the control whereas the population of Aphelenchoides was unaffected by these treatments in 1999. Live S. carpocapsae showed no significant effect on the population of both these genera either 15 or 30 days after treatment in 1999. No viable symbiotic bacteria were observed in the dead nematodes used in this study indicating that dead nematodes alone or dead nematodes in combination with dead symbiotic bacteria produced the suppressive effect. In contrast to the plant-parasitic nematodes, populations of non-stylet-bearing nematodes were not affected by the application of entomopathogenic nematodes. Although ethoprop reduced population of non-stylet-bearing nematodes relative to the untreated control 15 days after treatment in 2000, no significant differences were observed 30 days after treatment. These findings suggest that allelochemicals produced by dead or live nematodes and/or by their symbiotic bacteria may be selectively acting against plant-parasitic nematodes. Our results demonstrate that both live and dead infective juveniles of S. carpocapsae may provide a possible control strategy for plant-parasitic nematodes on boxwood.

Suppression of plant parasitic nematodes in pastoral soils amended with chitin

White clover and perennial ryegrass plants were grown in pots containing a sandy soil amended with chitin Soil nematode numbers were examined after 6 weeks of plant growth Amendment with chitin significantly reduced the abundance of Heterodera trifolii in white clover roots and Pratylenchus sp in perennial ryegrass roots Abundance of Paratrichodorus minor was significantly reduced by chitin amendment compared to unamended controls The total nematode fauna responded to chitin amendment with large increases in abundance

Suppression of plant parasitic nematodes in the chinampa agricultural soils

Soil from the chinampa agricultural system in the Valley of Mexico suppressed damage by plant-parasitic nematodes to tomatoes and beans in greenhouse and growth chamber trials. Sterilization of the chinampa soil resulted in a loss of the suppressive effect, thereby indicating that one or more biotic factors were responsible for the low incidence of nematode damage. Nine organisms were isolated from chinampa soil, which showed antinematodal properties in culture. Naturally occurring populations of plant-parasitic nematodes were of lower incidence in chinampa soil than in Chapingo soil.

Hardwood Bark as a Soil Amendment for Suppression of Plant Parasitic Nematodes on Container-grown Plants1

Abstract Hardwood bark as a soil amendment for container-grown plants suppressed several species of parasitic nematodes in greenhouse tests. Volumetric bark to soil ratios of 4:1, 2:1, 1:1 and 1:2 greatly reduced incidence of root-knot caused by Meloidogyne hapla Chitwood and M. incognita (Kofoid and White) Chitwood on tomato (Lycopersicon esculentum Mill.). A 2:1 bark to soil mixture inhibited galling by M. incognita and population development of Pratylenchus penetrans (Cobb) Filipjev and Schuurmans Stekhoven and Trichodorus christiei Allen on Forsythia intermedia Zabel.