Plant-parasitic Nematode Populations Research Articles

Influence of the Environment and Vegetable Cropping Systems on Plant-Parasitic Nematode Communities in Southern Georgia

Plant-parasitic nematodes (PPN) limit yields of vegetable production in the United States. During the spring and fall cropping seasons of 2018, 436 fields in bare ground and plastic bed cropping systems were randomly sampled from 29 counties in southern Georgia. The incidence (%), mean relative abundance, and maximum relative abundance (nematodes per 100 cm3 of soil) of the 10 different PPN genera detected in 32 vegetable crops in bare ground and plastic bed cropping systems include Meloidogyne spp. (67.3%; mean, 292; maximum, 14,144), Nanidorus spp. (49.4%; mean, 6; maximum, 136), Mesocriconema spp. (39.6%; mean, 17; maximum, 340), Helicotylenchus spp. (31.6%; mean, 20; maximum, 1152), Pratylenchus spp. (20.1%; mean, 2; maximum, 398), Rotylenchulus spp. (5.9%; mean, 1; maximum, 116), Hoplolaimus spp. (12.6%; mean, 1; maximum, 78), Heterodera spp. (2.3%; mean, <1; maximum, 60), Tylenchorhynchus spp. (0.9%; mean, <1; maximum, 12), and Xiphinema spp. (0.2%; mean, <1; maximum, 2). A nonmetric multidimensional scaling analysis indicated that most environmental and geological factors (i.e., longitude, precipitation, soil moisture, sand and silt content, and soil electrical conductivity) had no apparent relationship with nematode counts, except for latitude, soil pH, and temperature. The multirank permutation procedure followed by indicator species analysis and nonparametric Kruskal-Wallis analysis of variance indicated that Meloidogyne spp. are the predominant PPN associated with plastic beds in the south region sampled. The south region consisted mainly of commercial fields that rotated multiple vegetables crops through the same plastic beds. All other PPNs were associated with bare ground beds in the north region that are commonly rotated with row crops. This study validates that Meloidogyne spp. are the most important PPN in vegetable fields of southern Georgia and suggests that cropping systems have a greater effect on PPN population dynamics than the environment.

Root colonization and growth promotion of cover crops by Pochonia chlamydosporia

Several plants are used as cover crops in the no-tillage system in order to improve the physical, chemical and biological characteristics of the soil. The fungus Pochonia chlamydosporia (Goddard) Zare and Gams 2001, a biological control agent of plant parasitic nematodes (PPNs), is capable of promoting plant growth and adding it to the cover crop can increase the biomass of these plants and reduce the population level of nematodes in the soil. The objective of this work was to evaluate the ability of P. chlamydosporia to colonize soil and roots of the cover crops Pennisetum glaucum (L.) R. Br. (ADR 300, ADR 500 and ADRG 9050 cultivars), Urochloa ruziziensis (R. Germ. & Evrard) Crins, Crotalaria spectabilis Röth and Stylosanthes sp. and to promote the growth of these plants. P. chlamydosporia colonized the root systems of all the evaluated cover crops. Chlamydospores, conidia and hyphae were easily observed within the cells of plant roots. P. chlamydosporia increased the height of the shoots of all plants, except U. ruziziensis. The fungus also increased the total weight of the dry plant of cultivars ADR 300 and ADR 500 of P. glaucum, U. ruziziensis and C. spectabilis in 29, 17, 16 and 30%, respectively. The root volume of P. glaucum (ADR 300), U. ruziziensis and C. spectabilis were also increased in 66, 88 and 64%, respectively, in the presence of P. chlamydosporia. Higher numbers of colony forming units (CFU) of P. chlamydosporia g−1 of soil were detected in the presence of cultivars ADR 300 and ADR 500 of P. glaucum at the 12.5 cm soil depths (12.5, 25.0, 37.5 and 50.0 cm), highlighting the 12.5 cm depth with 10,684 CFU of P. chlamydosporia g−1 of soil. This is the first report of the colonization of cover crops roots by P. chlamydosporia and its resulting plant growth promotion effect, as well as the formation of chlamydospores of P. chlamydosporia inside their root cells. The application of P. chlamydosporia in the cover crop increases the biomass of crops that will be used as green manure and guarantee a greater establishment of the fungus in the area, consequently reducing even more the populations of PPNs in the soil.

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.

NEMATODE PARASITES OF WATERLEAF (Talinum triangulare) IN OBIO-AKPOR AND IKWERRE LOCAL GOVERNMENT AREAS OF RIVERS STATE, NIGERIA

Waterleaf, Talinum triangulare is cultivated in home gardens and fields to improve nutritional quality for the family and a source of livelihood for farmers. However, the role of T. triangulare is often counteracted by plant-parasitic nematodes (PPNs). Effective management of PPNs will depend on the identification and determination of their population and distribution. A survey was conducted in two Local Government Areas (LGAs), Ikwerre and Obio-Akpor of Rivers State to identify plant-parasitic nematodes associated with waterleaf. Multistage random sampling technique was employed in the collection of 60 bulked soil and root samples across six waterleaf monoculture farming communities. The nematodes were extracted, identified and their population determined using standard procedures. Occurrences, relative importance values (RIV) and diversity indices were determined. Other data were analysed using descriptive statistics and analysis of variance. Six plant-parasitic nematodes genera were encountered in this study, Helicotylenchus, Pratylenchus, Paratylenchus, Meloidogyne, Scutellonema and Tylenchulus. Pratylenchus and Helicotylenchus were the most frequently occurring nematode pest genera with equal relative frequency of occurrence of 38.89%. Pratylenchus species with RIV of 61.34% was the most important nematode pest associated with waterleaf across the six farm communities. The dominance index of 0.71 for the nematode genera showed that some nematode species dominated others. Alakahia farms had the highest population of plant-parasitic nematodes (2,780) across the six farm communities, whereas Omagwa farms had the lowest (250). The study showed that nematode pests are associated with waterleaf and could be contributing to yield losses in this crop

Distribution of plant-parasitic nematodes and comparative effects of fadama (hydromorphic) fields and upland fields on plant-parasitic nematodes and free-living nematodes on three indigenous vegetables commonly grown in Osun State Nigeria

Surveys were conducted in 2016 and 2017 to investigate the distribution of plant-parasitic nematodes and the effects of fadama fields and upland fields on plant-parasitic and free-living nematodes. A total of 84 soil samples were collected from seven Local Government Areas visited in Osun State. Soil samples were collected from two fadama fields and two upland fields in all the LGAs visited. Nematodes were extracted, counted and identified under a compound microscope according to the morphological characteristics of the nematodes. The results showed that sixteen genera of plant-parasitic nematodes were found associated with Solanum macrocarpon, Amaranthus cruentus and Telfairia occidentalis. Meloidogyne\\ Helicotylenchus and Rotylenchulus were the most abundant nematodes associated with the vegetables. Fadama fields significantly had lower populations of plant-parasitic nematodes and higher populations of free-living nematodes in comparison with upland fields in fields sown to the vegetables. Farmers are advised to take full advantage of fadama fields in vegetable production.

Nematicide Effects on Arthropods in Bermudagrass

In turfgrass systems, nematicides are a valuable tool for managing plant-parasitic nematode populations, but few studies have examined non-target nematicide effects on arthropods. Our study evaluated effects of turfgrass nematicide formulations of abamectin (Divanem SC), fluopyram (Indemnify), furfural (MultiGuard Protect EC), and fluensulfone (Nimitz Pro G) on arthropod populations in bermudagrass (Cynodon spp.; Poaceae). A randomized block design was used with 5 replications of the 4 nematicide treatments and an untreated control. Plots were 6 m2 with 0.6 m untreated borders between adjacent plots. Data were collected from 1.5 m2 subplots located in the center of the treatment plots. Nematicides were applied at labeled rates every 4 wk as a summer treatment program from 7 Jun to 30 Aug 2016 and from 24 Apr to 18 Jul 2017 at the University of Florida Plant Science Research and Education Unit in Citra, Florida, USA. Samples were collected before treatment and at 2 d, 14 d, 56 d, and 238 d after the final treatment. Data from each nematicide treatment were compared to the untreated data at each sample date using analysis of covariance with initial population counts serving as the covariate. Abamectin treatments significantly increased fungivore mite abundance relative to the untreated control at 2 sampling dates in 2016 and 3 sampling dates in 2017. Abamectin also decreased collembolan abundance significantly at 2 sampling dates in 2017. Fluopyram increased predatory mite abundance significantly at 3 sampling dates in 2016; decreased collembolan abundance significantly at 4 sampling dates in 2017; and significantly increased phytophagous insect abundance at 2 dates in 2017. Furfural and fluensulfone had low impacts on arthropod abundance. The results of this study suggest nematicides can impact arthropods in bermudagrass, which could affect organic matter decomposition and nutrient cycling processes.

Soil nutrient and nematode community changes in response to hardwood charcoal application

ABSTRACT A one-time, large application of biochar (charcoal) could increase soil carbon (C) content and improve overall soil quality. It is known that nematodes have effects on soil organic matter and nutrient cycling and are plant diseases; moreover, nematodes affect nutrient mobilization in C-rich soil conditions; however, information is scant on the effect of biochar addition on nematode communities. Therefore, the objective of this field study was to evaluate the influence of sugar maple hardwood biochar on soil nematode communities and assess the relation among soil nematode communities and soil nutrient concentrations. Nematode communities were sampled and identified in soils without biochar application and soil amended with an application of 8% by weight (equivalent to 160 Mg ha−1). The application of 8% biochar did not change the abundance of nematodes but affected some nematode communities. Compared to the unamended soil, biochar-amended soil had lower plant-parasitic nematode populations and higher abundance of predatory nematodes. The Shannon diversity index (H’) was lower, and the maturity index (MI) was higher with a mean value of 2.38 with biochar addition compared to 2.21 in unamended plots. Higher soil acidity and addition of substantial amounts of magnesium, calcium, potassium, and manganese in the biochar-amended soils were recorded after biochar application.

Evaluation of a new chemical nematicide, fluazaindolizine (ReklemelTM active), for plant-parasitic nematode management in bermudagrass.

Plant-parasitic nematodes are a major pest of turfgrass in the United States, yet there are few options for successful management. Most current management strategies rely on the use of a limited number of chemical nematicides, so finding a new management option for nematode suppression would be extremely valuable for turfgrass managers. The aim of this study is to evaluate a new nematicide, fluazaindolizine (Reklemel™ active), for its ability to reduce plant-parasitic nematode population density and improve turfgrass quality. Separate research trials were conducted on bermudagrass infested with Belonolaimus longicaudatus and Meloidogyne incognita in greenhouse, microplot, and field settings over 2018 and 2019. Both greenhouse evaluations demonstrated multiple rates of fluazaindolizine reduced B. longicaudatus population density, and one of the two M. incognita trials showed multiple rates of fluazaindolizine reduced nematode population density. Fluazaindolizine was also effective at reducing population density of both B. longicaudatus and M. incognita in microplot settings for both 2018 and 2019, and a significant improvement in turf quality was observed for both visual turfgrass ratings and NDVI. Field trials demonstrated a significant reduction for both B. longicaudatus and M. incognita population density by multiple rates of fluazaindolizine, but no significant differences in turf quality ratings were observed. Overall, fluazaindolizine shows promise as a chemical nematicide for plant-parasitic nematode management on turfgrass.

PERCEPTION OF HORTICULTURISTS ON NEMATODE PESTS OF ORNAMENTAL PLANTS AND THE LIKELIHOOD OF SOIL AS PRIMARY SOURCE OF INFECTION

Nematode pests contribute significantly to poor growth and losses in ornamental plants. However, majority of ornamental garden operators have little or no knowledge of these nematode pests. This study assesses the perception of horticulturists on plant-parasitic nematodes (PPNs) of ornamental plants in Port Harcourt metropolis. A total of 23 ornamental gardens were randomly chosen and visited. Structured questionnaire was randomly administered directly to all operators in collection of data and options were given in code to rank the results. A total of fifty-three soil samples were collected from all the gardens visited. Nematode pests were extracted from the samples using standard procedures. Data were processed using descriptive statistics, diversity indices, relative importance value (RIV) and analysis of variance. The results showed that 95.7% of the horticulturists were male, 78.2% were youth, while 100.0% of the ornamental garden owners had no knowledge of nematode pests attacking ornamental plants. Four nematode pest genera, Meloidogyne, Pratylenchus, Tylenchulus and Helicotylenchus were found in the soil being used for propagation by these horticulturists. However, Meloidogyne species with the RIV of 40.45% were the most important genus and the most frequently encountered nematode pest (relative frequency of occurrence of 19.35%). Hilltop horticultural garden had the highest mean population of PPNs, but not significantly more than PPNs in other gardens. The study revealed that nematode pests are one of the major bio constraints to ornamental plants and that soil if not treated could be a primary source of nematode infection.

DISTRIBUTION AND POPULATION DENSITIES OF PLANT-PARASITIC NEMATODES ASSOCIATED WITH GINGER (ZINGIBER OFFICINALE) IN KADUNA STATE, NIGERIA

Ginger (Zingiber officinale) is an important cash crop in Nigeria. In spite of the economic importance of plant-parasitic nematodes reported on ginger, little or no information is available as regards plant-parasitic nematodes diversity and abundance on ginger in Nigeria. This work was conducted in 2018 to identify plant-parasitic nematodes associated with ginger in Kaduna state and to determine their population densities. Three Local Government Areas (LGA) were visited and between 12 to 16 ginger farms were sampled per LGA. A total of 42 soil samples was collected at a depth of 0 - 30 cm of the plant rhizosphere. Plant-parasitic nematodes were extracted from the soil using modified sieving and decanting method. Identification to genera level was done using identification keys viewing with dissecting microscope at X40 magnification. Nineteen (19) genera of plant-parasitic nematodes were identified, with 12 genera occurring in all LGA(s). Scutellonema (113.33), Meloidogyne (110), and Pratylenchus (93.33) were the most abundant per 100 ml of soil when locations are combined. Plant-parasitic nematodes population average was 870-950 per 100 ml of soil. All locations showed a high percentage similarity of plant-parasitic nematodes diversity and were statistically similar. This high diversity and population abundance can be among the reasons for the low productivity of ginger in Nigeria. It is therefore important to educate farmers on the economic importance of plant-parasitic nematodes on ginger and its management. Further research using the most occurring genera to establish the threshold population densities capable of causing economic yield loss needs to be conducted

Popular Biofortified Cassava Cultivars Are Heavily Impacted by Plant Parasitic Nematodes, Especially Meloidogyne Spp.

The development of new biofortified cassava cultivars, with higher micronutrient contents, offers great potential to enhance food and nutrition security prospects. Among the various constraints affecting cassava production are plant parasitic nematodes (PPN), especially root-knot nematodes. In this study, six popular biofortified cultivars were field-evaluated for their response to PPN in Nigeria. A field naturally infested with a diversity of PPN but dominated by root-knot nematodes was used. Application of the nematicide carbofuran significantly reduced PPN densities, and at harvest, no root galling damage was observed, compared with untreated plots, which had heavy galling damage. Plant height, stem girth, plant weight, marketable storage root number and weight were significantly lower for most cultivars in untreated plots. Percentage yield losses in the range of 21.3–63.7% were recorded from two separate trials conducted for 12 months each. Lower total carotenoid and dry matter contents were associated with higher PPN densities in some biofortified cultivars, resulting in a loss of as much as 63% of total carotenoid and 52% of dry matter contents. The number and weight of rotted storage roots were significantly greater in untreated plots across cultivars, reducing in-field and post-harvest storability. This study demonstrates that natural field populations of PPN can substantially affect yield, quality and nutritional value of released biofortified cassava cultivars.

Significant genetic differences among Heterodera schachtii populations within and among sugar beet production areas

Summary Characterising the non-neutral genetic variation within and among populations of plant-parasitic nematodes is essential to determine factors shaping the population genetic structure. This study describes the genetic variation of the parasitism gene vap1 within and among geographic populations of the beet cyst nematode Heterodera schachtii. Forty populations of H. schachtii were sampled at four spatial scales: 695 km, 49 km, 3.1 km and 0.24 km. DGGE fingerprinting showed significant differences in vap1 patterns among populations. High similarity of vap1 patterns appeared between geographically close populations, and occasionally among distant populations. Analysis of spatially sampled populations within fields revealed an effect of tillage direction on the vap1 similarity for two of four studied fields. Overall, geographic distance and similarity of vap1 patterns of H. schachtii populations were negatively correlated. In conclusion, the population genetic structure was shaped by the interplay between the genetic adaptation and the passive transport of this nematode.

Plant health evaluations of Belonolaimus longicaudatus and Meloidogyne incognita colonized bermudagrass using remote sensing

The objective of this study was to evaluate the ability of an unmanned aerial system (UAS) equipped with a multispectral sensor to track plant health in the presence of plant-parasitic nematodes in conjunction with nematicide applications. Four nematicides were evaluated for their ability to suppress Belonolaimus longicaudatus and Meloidogyne incognita in microplots, and three nematicides were evaluated on a golf course for their ability to suppress multiple plant-parasitic nematode genera. Visual ratings, Normalized Difference Vegetation Index (NDVI), and Normalized Difference RedEdge Index (NDRE) were reported throughout the trial to assess plant health. B. longicaudatus and M. incognita population density was significantly lowered by nematicide treatments in microplots and correlated with visual ratings, NDVI, and NDRE plant health ratings. On the golf course, all nematicides reduced total plant-parasitic nematode population density at 28, 56, and 84 days after treatment (DAT). Visual turf quality ratings, NDVI, and NDRE were positively correlated with lower nematode population density in the majority of evaluation dates. In the microplot and golf course settings, the parameters evaluated for plant health were correlated with plant-parasitic nematode population density: visual ratings, NDVI, and NDRE improved as nematode population density declined. These results show that remote sensing has the potential to be a beneficial tool for assessing plant-parasitic nematode infected bermudagrass.

Plant-parasitic nematodes associated with the root zone of hop cultivars planted in a Florida field soil.

In early 2016, hop plants were introduced into Florida. By late 2016, the hop plants were showing stunted growth and were heavily parasitized by Meloidogyne javanica. In this study, we determined host susceptibility of 14 hop cultivars to M. javanica in a greenhouse experiment and monitored population development of plant-parasitic nematode species in the root zone of 17 hop cultivars planted in three newly established hop yards in Florida. Plant-parasitic nematodes in the rooting zone soil of field grown hop plants included M. javanica, Pratylenchus brachyurus, Paratrichodorus minor, Belonolaimus longicaudatus, Xiphinema setariae/vulgare complex, Mesocriconema xenoplax, and Helicotylenchus dihystera; however, soil population densities of P. minor, B. longicaudatus, X. setariae/vulgare complex, M. xenoplax, and H. dihystera remained low through the study. Root galling, M. javanica egg production, and soil population densities of M. javanica were consistently large on the ‘Canadian Red Vine’, ‘Centennial’, ‘Chinook’, and ‘Comet’ cultivars, and small on the ‘Galena’ and ‘Triple Perle’ cultivars. No differences were observed in soil population densities of P. brachyurus among hop cultivars. Overall, our study provides the first report of plant-parasitic nematode population development in the root zone on hop cultivars planted in Florida.

Study of PH and Electrical Conductivity in Soil of Barnala District (Punjab, India): Deleterious Effects on Human Lives

The purpose of this study was to determine the pH and electrical conductivity in soil of different villages of barnala district (Punjab,India ) and their harmful effects on human health. Samples of soil were collected from agricultural fields of four different villages of barnala region such as Rure ke kalan, Gunas, Handiaya and cheema from five different layers(0-10 cm; 10-20 cm; 20-30 cm; 30-40 cm and 40-50 cm depth).There are three industrial sites in barnala district and these four villages are located near to these industial sites. In this study, adverse effect of different industries on fields of these four villages were investigated. Handiaya village has high values of pH and electrical conductivity while Gunas and Cheema villages have lowest value of electrical conductivity and pH respectively. when textile effluent reaches the soil or underground water it causes bad effect on human health such as people may suffer from alkalosis which is due to high pH and can lead to arrhythmia which means irregular heartbeat. Alkalosis can induce a coma, it may cause seizures and malfunctioning of kidneys. Due to large value of Electrical conductivity activity of soil micro-organism declines so, the important microbial processes, such as nitrogen cycling, production of nitrous and other N oxide gases, respiration, and decomposition; populations of plant-parasitic nematodes can increase; and increased nitrogen losses.

Effects of Cover Cropping on Microbial Communities Associated with Heterodera schachtii and Nematode Virulence

Nematode-resistant cover crops can suppress populations of plant-parasitic nematodes. Samples of a loamy and a sandy loam soil were collected from two sugar beet fields in Lower Saxonia, northern Germany (“Jeinsen” and “Gross Munzel”) to measure the effects of cover cropping on the population genetic structure and infectivity of Heterodera schachtii as well as the composition of soil microbial communities. These fields allowed for a comparison of cover cropping with Brassica species resistant to Heterodera schachtii to fallow. In a series of radish bioassays with H. schachtii populations from Jeinsen and Gross Munzel, ratios of second-stage juveniles in roots per eggs in soil were higher in soil from under Brassica cropping than from under fallow. In denaturing gradient gelelectrophoresis, profiles of the parasitism gene vap1 differed between Brassica and fallow treatments in both populations. At Gross Munzel, microbes of soils and within nematode cysts differed between Brassica and fallow areas. Specifically, the frequency and occurrence of isolates of Pochonia chlamydosporia and Exophiala salmonis were lower within the cysts from Brassica than from fallow treatments. Overall, cover cropping with resistant Brassica species affected the bacteria and fungi infecting the cysts and subsequently, the infectivity of the H. schachtii population. Cover crop effects on nematode virulence (vap1 gene) and microbial colonization of the cysts could affect long-term nematode population dynamics.

Antagonistic role of the microbiome from a Meloidogyne hapla-suppressive soil against species of plant-parasitic nematodes with different life strategies

Summary In certain soils populations of plant-parasitic nematodes (PPN) decline. Understanding this effect may open up environmentally friendly management options. We identified such a suppressive soil containing virtually no PPN. Inoculated Meloidogyne hapla declined in this soil more than in a control soil and reproduction on tomato was reduced. The extracted soil microbiome alone decreased root invasion of second-stage juveniles (J2) and progeny as well as the native soil. We tested the antagonistic potential against PPN that differ in life strategies. The microbiome was most suppressive against two populations of M. hapla and one population of Pratylenchus neglectus, and least suppressive against M. incognita and the ectoparasite Hemicycliophora conida. In a split-root system with M. hapla, plant-mediated but not direct effects of the microbiome significantly reduced root invasion of J2, while direct exposure of M. hapla to the microbiome significantly affected reproduction. Overall, both plant-mediated and direct effects of the microbiome were responsible for the soil suppressiveness against M. hapla.

Deletion of the Nonribosomal Peptide Synthetase Gene nps1 in the Fungus Clonostachys rosea Attenuates Antagonism and Biocontrol of Plant Pathogenic Fusarium and Nematodes.

Secondary metabolites produced by biological control agents may influence the outcome of their interactions with plant pathogenic microorganisms and plants. In the present study, we investigated the role of the nonribosomal peptide synthetase gene nps1 expressed by the biocontrol fungus Clonostachys rosea. A gene expression analysis showed that nps1 was induced during confrontations with the plant pathogenic fungus Botrytis cinerea. Gene deletion strains of nps1 displayed increased growth rates and conidiation. However, the nematicidal activity of culture filtrates from C. rosea Δnps1 strains was significantly weaker than that from wild-type filtrates (P ≤ 0.001); after 24 h of incubation with culture filtrates from nps1 deletion strains, only 13 to 33% of a mixed community of nematodes were dead compared with 42% of nematodes incubated with wild-type culture filtrates. The Δnps1 strains also showed reduced biocontrol efficacy during pot experiments, thus failing to protect wheat seedlings from foot rot disease caused by the plant pathogenic fungus Fusarium graminearum. Furthermore, C. rosea Δnps1 strains were not able to reduce populations of plant-parasitic nematodes in soil or in roots of wheat as efficiently as the wild-type strain. Both C. rosea wild-type and Δnps1 strains increased the dry shoot weight and shoot length of wheat by 20 and 13%, respectively. We showed that NPS1, a putative nonribosomal peptide synthetase encoded by nps1, is a biocontrol factor, presumably by producing a hitherto unknown nonribosomal peptide compound with antifungal and nematicidal properties that contributes to the biocontrol properties of C. rosea.

Worldwide YS groups/organizations. Different boarding models

Predatory nematodes play an important role in maintaining the population of plant parasitic nematodes and other soil biota in soil ecosystem. Based on feeding apparatus and feeding methods, predatory nematodes can be categorized in four major groups viz., mononchids, diplogasterids, dorylaimids and aphelenchids. This review examines predatory attributes of these groups. Biocontrol potential, factors affecting efficacy, biology, culturing and survival of predatory nematodes are also discussed here. The authors have analyzed the research status on predatory nematodes vis-a-vis plant parasitic and entomopathogenic nematodes and suggested future line of work for their utilization against plant parasitic nematodes.

In vitro nematicidal activity of natural and semisynthetic cadinenes from Heterotheca inuloides against the plant-parasitic nematode Nacobbus aberrans (Tylenchida: Pratylenchidae).

Nacobbus aberrans (Tylenchida: Pratylenchidae) is one of the main plant-parasitic nematodes species that affects crops in Mexico, generating substantial economic losses. Traditionally, the control of the nematodes is carried out using chemical products; however, research efforts are presently focused on the search for new methods for the control of this pest. Natural products derived from plants are an alternative for the control of populations of plant-parasitic nematodes. The genus Heterotheca (Asteraceae) is characterized by containing sesquiterpenes with cadinane skeleton, and some species of this genus exert nematicidal activity. We determined the effects of selected Heterotheca inuloides plant metabolites and some semisynthetic derivatives on the hatching of eggs isolated from the gelatinous matrix and infective second-stage juveniles (J2) of the false root-knot nematode N. aberrans using an in vitro experimental model. Among the evaluated compounds, nematodes were more susceptible to hydroxylated and quinone compounds, whereas the remaining compounds showed moderate or no activity. The presence of the hydroxyl group is essential for nematicidal potential, with changes at the hydroxyl group modifying the nematicidal activity. Flowers of Heterotheca inuloides contain bioactive compounds that showed nematicidal activity against N. aberrans. Here we report the nematicidal activities of cadinenes isolated from the flowers of H. inuloides and their semisynthetic derivatives against the false root-knot nematode N. aberrans. © 2018 Society of Chemical Industry.