Nematode Densities Research Articles

Screening for resistance and susceptibility in some beetroot cultivars to root-knot nematode, Meloidogyne javanica

Aim: The present study was conducted to identify the resistance and susceptibility of beetroot cultivars against root-knot nematode, Meloidogyne javanica. Methodology: In this study, seven beetroot cultivars were screened against the root-knot nematode, Meloidogyne javanica, at the inoculum level of 1500 second-stage juveniles (J2s) per pot. Five replications of each cultivar of beetroot were used for screening and kept in a completely randomized design (CRD) at 25 ± 2 °C under greenhouse conditions. The data were subjected to ANOVA using SPSS-17 statistical software (SPSS Inc., Chicago, IL, USA). According to Duncan’s Multiple Range Test, the mean values were statistically compared and separated at P ≤ 0.05. Results: The results revealed that all seven cultivars of beetroot showed varying degrees of resistance and susceptibility to M. javanica. Among all the cultivars, three were moderately resistant, i.e., CG, DDR and Red Ace with the minimum number of galls (4.0, 8.0 and 7.0), and two were moderately susceptible, i.e., Atlas and Red Queen (28 and 22). Red Ruby (84) was found susceptible and Red Express was highly susceptible with the maximum galls (126). None of the cultivars were found to be highly resistant or immune. Interpretation: A positive and significant correlation was found between the number of galls and per cent reduction in plant growth parameters. From the results, it can be recommended that the use of resistant cultivars is an environment-friendly approach that can be used to manage the nematode density below the economic threshold level.

Mixed planting reduces the shaping ability of legume cover crop on soil microbial community structure

Cover crop species and management are the key factors for reaping maximum benefits. Current studies lack a comprehensive assessment of the effects of cover crop species and planting patterns on soil properties, plant properties, and rhizosphere microbial communities at the full-blooming stage. A field experiment was conducted for 8 years (2011–2018) in Tianjin (fluvo-aquic soil) in China to compare various cover crops (hairy vetch, February orchid and rye) under different planting patterns (monoculture or mixed culture) in terms of cover crop biomass, soil physicochemical and biological properties, and rhizosphere microbial communities through high-throughput sequencing. The following groups were established: CK (winter fallow; the control), FO (February orchid monoculture), RY (rye monoculture), HV (hairy vetch monoculture), FOHV (February orchid–hairy vetch mixed culture), and RYHV (rye–hairy vetch mixed culture). RY had the highest biomass and nitrogen (N) uptake, and HV had the lowest biomass and highest N content. Mixed culture produced biomass higher in amount than the average biomass of monocultures of each individual species. RYHV showed a higher amount of biomass and uptake of nutrients, especially N. Cover crop planting significantly increased soil organic matter content (22.45 %–33.22 %), N levels (78.28 %–412.04 %), and available phosphate (9.70 %–45.03 %) and potassium (20.71 %–56.62 %) levels, but no significant differences in soil pH and total phosphorus content were found among the treatments. FO and HV treatments showed higher increments in soil biological properties: soil microbial biomass C (Cmic) and soil microbial biomass N (Nmic) and nematode density than the RY treatment. Mixed planting further promoted these properties, and FOHV treatment showed the highest values, which indicated improved soil properties. HV treatment significantly reduced bacterial and fungal diversity and the number of operational taxonomic units. These effects can be alleviated by mixed planting with FO and RY. Principal component analysis showed that the bacterial and fungal communities in the control were distinct from those in the cover crop treatments, and the difference was the greatest in the HV treatment. However, mixed planting with FO and RY reduced this difference between HV and CK. Structural equation model integration and analysis confirmed that the bacterial community was primarily regulated by soil physicochemical properties, whereas the fungal community was primarily regulated by plant properties. Soil biological properties affected bacterial and fungal communities, and mixed planting alleviated the impact of hairy vetch on soil microbial communities.

The Effect of Different Irrigation Types on Distribution and Population Densities of Citrus Nematode [Tylenchulus semipenetrans (Cobb, 1913) (Tylenchida: Tylenchulidae)] in Citrus Orchards in Adana and Mersin Provinces

The Effect of Different Irrigation Types on Distribution and Population Densities of Citrus Nematode [Tylenchulus semipenetrans (Cobb, 1913) (Tylenchida: Tylenchulidae)] in Citrus Orchards in Adana and Mersin Provinces

Plant Parasitic Nematodes Associated with Okra in the Forest Savanna Transition and Semi-Deciduous Forest Agro-Ecologies of Ghana

Okra is an important vegetable crop in Ghana. Plant-parasitic nematodes infect okra, reducing the quality and quantity of fresh immature and dry fruits. This study was carried out to determine diversity, density and distribution of plant parasitic nematodes attacking okra in the Forest savanna transition and Semi-deciduous forest agro-ecologies of Ghana. In each agro-ecology, soils from okra rhizosphere were sampled from 15 farms for plant-parasitic nematodes assessment. Nematodes were extracted using the modified Baermann nematodes extraction method. Six nematode genera were identified; Meloidogyne, Pratylenchus, Xiphinema, Helicotylenchus, Rotylenchulus and Scutellonema. Meloidogyne occurred with 64.9% relative abundance and 100% frequency. Rotylenchulus, Pratylenchus, and Helicotylencus nematodes also occurred with 100% frequency. Xiphinema were the least abundant (0.05%) and the least frequent (15%). The findings have shown that a large number of nematodes exist on okra plants and therefore there is the need for educational campaigns to be stepped up by Agricultural Extension Services of the Ministry of Food and Agriculture on plant parasitic nematode infections in okra production.

Frequency Occurrence and Population Density of Plant-Parasitic Nematodes Associated with Solanaceous Plantations Grown in Dakahlia Governorate

Frequency Occurrence and Population Density of Plant-Parasitic Nematodes Associated with Solanaceous Plantations Grown in Dakahlia Governorate

Free-living marine nematodes community structure in the conservation area (Chaojing Park) and its adjacent area of Keelung, Taiwan.

Studies conducted in the same seas or even study sites nearby each other, showed very different community structure, implying the patchiness of free-living marine nematodes which may be related to the sedimentary environment such as sediment type and food availability of the study area. This study was motivated by the concerns about the impacts of high level of anthropogenic activities on Chaojing Park (gazetted as Wanghaixiang’s Chao-Jing Bay Resource Conservation Area (WCJBRA) in 2016). The present study provides baseline knowledge of free-living marine nematode community structure in WCJBRA and identify potential marine nematodes as bioindicators to indicate possible impacts of the anthropogenic activities to the Chaojing Park. A total of 15 stations were selected in the subtidal zones of WCJBRA and its adjacent area. Marine nematode sample collection was carried out on the 13th and 14th of September 2019 using SCUBA diving technique. Results showed positive correlation between nematode density and medium sand (500μm-1.0mm). Presence of certain species such as Daptonema sp., Pomponema sp. and Innocuonema sp. indicates presence of disturbances in S12 and S13. Several species also showed potential to be introduced as indicator for healthy environment subjected to further studies on nematode-pollutants relationship, particularly on autecology as per se. Higher species diversity, H’ index of S1-S8 and S11 was categorised as Good Condition; followed by station with moderate species diversity index (S9, S10, S14 –Moderate Condition) zone; and lastly S12, S13 and S15 (Poor Condition).

Strategy of Nematophagous Fungi in Determining the Activity of Plant Parasitic Nematodes and Their Prospective Role in Sustainable Agriculture.

In this review, we supply a framework for the importance of nematophagous fungi (nematophagous fungi [NF]) and their role in agricultural ecosystems. We characterize the taxonomy, diversity, ecology, and type of NF, depending on their interaction with plant-parasitic nematodes (PPNs). We described potential mechanisms of NF in the control of PPNs, the efficiency and methods of utilization, and the use of nematicides in sustainable agriculture. We explain the utilization of NF in nanotechnology as a new approach. NF are significant in the soil for having the effective potential for use in sustainable agriculture. These types of fungi belong to wide taxa groups, such as Ascomycota, Basidiomycota, and other groups. Diverse NF are available in different kinds of soil, especially in soils that contain high densities of nematodes. There is a relationship between the environment of nematodes and NF. NF can be divided into two types according to the mechanisms that affect nematodes. These types are divided into direct or indirect effects. The direct effects include the following: ectoparasites, endoparasites, cyst, or egg parasites producing toxins, and attack tools as special devices. However, the indirect effect comprises two groups: paralyzing toxins and the effect on the life cycle of nematodes. We explained the molecular mechanisms for determining the suitable conditions in brief and clarified the potential for increasing the efficacy of NF to highly impact sustainable agriculture in two ways: directly and indirectly.

Kök Lezyon Nematodlarının (Pratylenchus thornei (Sher et Allen) Pratylenchus neglectus (Rensch) Filipjev & Schuurmans Stekhoven (Tylenchida: Pratylenchidae) ve Soğan-sak Nematodu Ditylenchus dipsaci (Kühn, 1857) (Tyleneida) 'nın Nohut Yetiştirme Alanlarında Dikey Dağılımı

Investigation of the vertical distribution of three plant-parasitic nematodes was conducted in two southeastern (Şanlıurfa) and central Anatolia (Ankara) Turkey chickpea fields during 2015/2016 and 2016/2017 growing season. Twelve accessions of wild Cicer species representing three Cicer species (Cicer reticulatum L. and C. echinospermum L.) were used in the experiments for it. Soil samples were collected around the plant roots at a 10-20 cm and 20-30 cm depth by using an auger at each site. Maximum population densities of the root-lesion nematodes (Pratylenchus thornei (Sher et Allen) and (Pratylenchus neglectus (Rensch) Filipjev & Schuurmans) were observed at the depth of 20-30 cm, pod filling stage, and harvest time on most sampling. Also, the population density of root-lesion nematodes at the depths of 20-30 cm was observed as higher than Ditylenchus dipsaci (Kühn, 1857) (Tylenchida: Anguinidae) in the chickpea field. Population density of root-lesion nematodes was positively correlated with the contents of depth, site, time sampling, species chickpea, and there was determined significant difference between soil depth and population density of nematodes in both sites statistically.

Assessing Direct and Residual Effects of Cover Crops on the Soybean Cyst Nematode, Heterodera glycines.

Greenhouse experiments were conducted to determine if cover crops directly decrease population densities of the soybean cyst nematode (SCN), Heterodera glycines, and/or have residual effects on reproduction of the nematode on soybean (Glycine max). Population densities of SCN were not significantly decreased by nine cover crop plants or three cover crop mixes compared with a non-planted soil control in a repeated 60-day-long greenhouse experiment. When susceptible soybeans were grown in the soils after cover crop growth, fewer SCN females formed after three annual ryegrass (Lolium multiflorum) cultivars (Bounty, King, and RootMax), the Daikon radish (Raphanus sativus var. longipinnatus) cultivar CCS779, Kodiak mustard (Brassica juncea), and a mix containing cereal rye, crimson clover (Trifolium incarnatum), plus Daikon radish (cultivars not stated) compared with following the non-planted control. In another repeated experiment, cover crops were grown for 56 days in SCN-infested soil in the greenhouse then exposed to Iowa winter conditions for 28 days to simulate winter termination of the plants. One treatment, a cover crop mix containing 'Bounty' annual ryegrass plus 'Enricher' Daikon radish, had a decrease in SCN population density greater than the non-planted control at the end of the experiment. Significantly fewer SCN females formed on soybeans grown after several cover crops, including the three annual ryegrass cultivars that had the suppressive residual effects in the first experiment. In summary, there were no cover crop treatments that consistently decreased SCN population densities across experiments, and only one cover crop treatment in one experiment significantly reduced SCN population densities more than a non-planted soil control. However, there was a somewhat consistent, adverse, residual effect of cover crops on reproduction of SCN on susceptible soybeans after growth of multiple cover crops.

Interaction effect of Root Lesion Nematodes and Fusarium culmorum Sacc. on disease complex in some wheat cultivars

The study was conducted to assess a possible interaction between fungal pathogen of Fusarium culmorum Sacc. and Root lesion nematodes at sequentially and simultaneously inoculation. Fusarium culmorum spore suspension effect evaluated on plant disease severity and nematode density on moderate resistant wheat line to F. culmorum (2-49) and susceptible wheat variety (İkizce) under controlled condition. The disease severity was higher on İkizce cv. than 2-49. This indicates that there is a considerable important pathogen resistance. Simultaneous and sequential inoculation of Pratylenchus thornei and F. culmorum reduced the final nematode density and reproduction rate more than inoculation with only nematode on İkizce cv. The simultaneously P. penetrans and F.culmorum inoculation (N+F) affected the positively of final density on İkizce cv. The N+ F treatment affected the positively of P. neglectus density on İkizce cv., whereas negative effect was found in pre or post inoculation of F. culmorum treatments. No synergistic interactions were detected on 2-49 when plants were co-infected by the root lesion nematode and fungus. It was determined that P. thornei had a positive effect on disease severity when it entered the plant simultaneously and before the F. culmorum on İkizce cv.. The disease severity decreased in F. culmorum was applied four weeks after the P. neglectus treatment on 2-49 wheat line and İkizce cv. In the interaction with F. culmorum on İkizce cv., differences were determined between the species of root lesion nematodes.

First Report of Meloidogyne enterolobii Infecting Cassava (Manihot esculenta) Resulting in Root Galling Damage in Africa.

Meloidogyne enterolobii is a highly polyphagous tropical species of root knot nematode. It has been recorded to be causing major damage to a range of economically important crops and is increasingly recorded from new locations. The morphological similarity and overlap of characteristics with other commonly occurring species, especially M. incognita, has confused its diagnosis using morphometrics. Cassava (Manihot esculenta) is an important crop across the tropics, including Africa, where it is among the most important root and tuber crop for food security. Cassava can be heavily infected by root knot nematodes, which can incur heavy production losses. The main species known to affect cassava are M. incognita and M. javanica (Coyne and Affokpon, 2018). With the exception of one report of M. enterolobii morphologically identified from cassava roots during a survey in Brazil (Rosa et al., 2014), there is no record with molecular confirmation of it infecting the crop. In the absence of any molecular or isozyme confirmation, diagnosis of M. enterolobii is difficult to determine. In the current study, the species responsible for substantial galling damage (Fig. 1A) on several cassava roots growing in Ibadan, Nigeria (7°22'39″ N; 3°54'21″ E) were diagnosed. DNA isolated from juveniles recovered using a modified Baermann method (Hooper, 1986) from these roots was used for PCR amplification of the mitochondrial Nad5 using primer pair, NAD5F2 (5'-TATTTTTTGTTTGAGATATATTAG-3') and NAD5R1 (5'-CGTGAATCTTGATTTTCCATTTTT-3'). The 515 bp PCR DNA product was sequenced on both strands (GenBank Accession No. MW965454) and found to be 100% identical to M. enterolobii with those in the DNA sequence database (KU372358, KU372359) (Janssen et al., 2016; Kolombia et al., 2017). In addition, M. incognita was also recovered from the galled roots and identified using the same primers (GenBank Accession No. MW965455) indicating a combined species infection (Fig. 2). Cultures of M. enterolobii, developed from single egg masses were maintained on tomato plants and used to assess infection on cassava in 10 L pots filled with steam sterilized loam soil in the screenhouse. Cassava cv. IITA-TMS-IBA070593 cuttings planted in June, 2018 and repeated in April, 2019 were inoculated with 1,000 juveniles per pot at three weeks after planting, and then maintained for four months before quantifying the nematode densities in both roots and soil. Nematode reproduction factor (RF), calculated from total nematode densities (n=8) from soil and roots was as high as 44.3, compared to uninoculated controls. Molecular diagnostics of M. enterolobii, as above, confirms unequivocally the host status of cassava to this nematode. This study reports for the first time the infection of cassava by M. enterolobii under field conditions in Africa and for the first time demonstrates the host suitability of cassava to this nematode (Fig. 1B). M. enterolobii is among the most commonly occurring root-knot nematode species in West Africa (dos Santos et al., 2019). It is therefore anticipated that M. enterolobii has long been infecting, especially in West Africa, but has been overlooked due to its morphological similarity with M. incognita. Given the high reproductive ability of M. enterolobii on cassava and its highly aggressive nature on a range of crops, it is likely that it is causing, or will result in, high levels of losses on cassava in Africa.

Differential Impact of the Pinewood Nematode on Pinus Species Under Drought Conditions

The pinewood nematode (PWN), Bursaphelenchus xylophilus, responsible for the pine wilt disease (PWD), is a major threat to pine forests worldwide. Since forest mortality due to PWN might be exacerbated by climate, the concerns regarding PWD in the Mediterranean region are further emphasized by the projected scenarios of more drought events and higher temperatures. In this context, it is essential to better understand the pine species vulnerability to PWN under these conditions. To achieve that, physiological responses and wilting symptoms were monitored in artificially inoculated Pinus pinaster (P. pinaster), Pinus pinea (P. pinea), and Pinus radiata (P. radiata) saplings under controlled temperature (25/30°C) and water availability (watered/water stressed). The results obtained showed that the impact of PWN is species-dependent, being infected P. pinaster and P. radiata more prone to physiological and morphological damage than P. pinea. For the more susceptible species (P. pinaster and P. radiata), the presence of the nematode was the main driver of photosynthetic responses, regardless of their temperature or water regime conditions. Nevertheless, water potential was revealed to be highly affected by the synergy of PWN and the studied abiotic conditions, with higher temperatures (P. pinaster) or water limitation (P. radiata) increasing the impact of nematodes on trees’ water status. Furthermore, water limitation had an influence on nematodes density and its allocation on trees’ structures, with P. pinaster revealing the highest nematode abundance and inner dispersion. In inoculated P. pinea individuals, nematodes’ population decreased significantly, emphasizing this species resistance to PWN. Our findings revealed a synergistic impact of PWN infection and stressful environmental conditions, particularly on the water status of P. pinaster and P. radiata, triggering disease symptoms and mortality of these species. Our results suggest that predicted drought conditions might facilitate proliferation and exacerbate the impact of PWN on these two species, through xylem cavitation, leading to strong changes in pine forests of the Mediterranean regions.

Diversity of plant parasitic nematodes characterized from fields of the French national monitoring programme for the Columbia root-knot nematode.

Plant parasitic nematodes are highly abundant in all agrosystems and some species can have a major impact on crop yields. To avoid the use of chemical agents and to find alternative methods to manage these pests, research studies have mainly focused on plant resistance genes and biocontrol methods involving host plants or natural enemies. A specific alternative method may consist in supporting non-damaging indigenous species that could compete with damaging introduced species to decrease and keep their abundance at low level. For this purpose, knowledge about the biodiversity, structure and functioning of these indigenous communities is needed in order to carry out better risk assessments and to develop possible future management strategies. Here, we investigated 35 root crop fields in eight regions over two consecutive years. The aims were to describe plant parasitic nematode diversity and to assess the potential effects of cultivation practices and environmental variables on communities. Community biodiversity included 10 taxa of plant parasitic nematodes. Despite no significant abundance variations between the two sampling years, structures of communities varied among the different regions. Metadata collected for the past six years, characterizing the cultural practices and soils properties, made it possible to evaluate the impact of these variables both on the whole community and on each taxon separately. Our results suggest that, at a large scale, many variables drive the structuration of the communities. Soil variables, but also rainfall, explain the population density variations among the geographical areas. The effect of the variables differed among the taxa, but fields with few herbicide applications and being pH neutral with low heavy metal and nitrogen concentrations had the highest plant parasitic nematode densities. We discuss how these variables can affect nematode communities either directly or indirectly. These types of studies can help to better understand the variables driving the nematode communities structuration in order to support the abundance of indigenous non-damaging communities that could compete with the invasive species.

Soil Sterilization Eliminates Beneficial Microbes That Provide Natural Pest Suppression Ecosystem Services Against Radopholus similis and Fusarium Oxysporum V5w2 in the Endosphere and Rhizosphere of Tissue Culture Banana Plants

Endosphere and rhizosphere microbes offer plant growth promotion and pest suppression ecosystem services in banana-based agroecosystems. Interest has been growing towards the use of such beneficial microbes in protecting vulnerable tissue culture banana plants against pathogens such as Radopholus similis and Fusarium oxysporum. A screenhouse experiment with potted tissue culture banana plants was conducted using sterile and non-sterile soil to investigate the effect of soil biota on R. similis and F. oxysporum strain V5w2. Plants grown in non-sterile soil had lower damage and R. similis density in roots and rhizosphere, while most plant growth-related parameters including root freshweight, shoot freshweight, total freshweight, plant height, and leaf size were larger compared to those from sterile soil. Shoot dryweight and Mg content were higher in plants from sterile soil, while their leaves developed discolored margins. R. similis-inoculated plants in sterile soil were smaller, had more dead roots, higher nematode density, and produced fewer and smaller leaves, than those from non-sterile soil. For all plant growth-related parameters, nematode density and root damage, no differences were recorded between controls and F. oxysporum V5w2-inoculated plants; and no differences between those inoculated with R. similis only and the ones co-inoculated with the nematode and F. oxysporum V5w2. Banana roots inoculated with F. oxysporum V5w2 were lighter in color than those without the fungus. Independent or combined inoculation of banana plants with F. oxysporum V5w2 and R. similis resulted in lower optical density of root extracts. In vitro assays indicated the presence of Fusarium spp. and other root endophytic microbes that interacted antagonistically with the inoculated strain of F. oxysporum V5w2. It is concluded that, soil sterilization eliminates beneficial microbes that provide natural pest suppression ecosystem services against R. similis and F. oxysporum in the endosphere and rhizosphere of tissue culture banana plants. I recommend the integration of microbiome conservation into tissue culture technology through the proposed “Tissue Culture Microbiome Conservation Technology.”

Soil Microbes Determine Outcomes of Pathogenic Interactions Between Radopholus similis and Fusarium oxysporum V5w2 in Tissue Culture Banana Rhizospheres Starved of Nitrogen, Phosphorus, and Potassium

The contributions of soil biota toward outcomes of pathogenic interactions between Radopholus similis and Fusarium oxysporum V5w2 in tissue culture banana plants starved of nitrogen (N), phosphorus (P), and potassium (K) were investigated. The study was based on three screenhouse factorial experiments (2 × 2 × 2) comprising of potted banana plants with or without R. similis, with or without F. oxysporum V5w2, and either grown in sterile or non-sterile soil. All plants in each of the three experiments received nutrient solutions that were deficient in N, P, or K, respectively. In all the three nutritional regimes, plants inoculated with R. similis were heavily colonized by the nematode with high percentage dead roots and necrosis, while their root biomasses were low. N-starved plants co-inoculated with R. similis and F. oxysporum V5w2 had lower percentage dead roots and tended to have numerically lower nematode density compared to those treated with R. similis only, especially in non-sterile soil. N-starved plants inoculated with R. similis had higher shoot dry weight, were taller with more leaves that were larger, compared to those not inoculated with the nematode. Plants grown in non-sterile soil had lower percentage dead roots, necrosis and R. similis density than those from sterile soil, regardless of the nutrient regime. N-starved plants from non-sterile soil were shorter with smaller leaves having decreased chlorophyll content and lower biomass, compared to those from sterile soil. By contrast, P and K starved plants from non-sterile soil were taller with larger leaves and more biomass, compared to those from sterile soil. Roots inoculated with R. similis had higher endophytic colonization by Fusarium spp., especially when co-inoculated with F. oxysporum V5w2 and grown in sterile soil among the N and K-starved plants. In conclusion, pathogenic interactions between R. similis and F. oxysporum V5w2 are predominantly suppressed by a complex of soil microbes that exert plant growth promoting effects in tissue culture banana plants through N, P, and K dependent processes. Nitrogen is the most important limiting factor in rhizosphere interactions between banana roots, beneficial microbes and the pathogens. Soil sterilization and the stringent aseptic tissue culture techniques still require the development of alternative innovative ways of conserving microbial services for sustainable agriculture.

What is the Optimal Way to Assess Meloidogyne Spp. Reproduction in Greenhouse Pot Experiments?

Often research efforts that address both the practical concerns of managing Meloidogyne spp. and understanding their basic biology involve greenhouse reproduction assays. However, there is little consensus in regards to what parameters should be used to conduct greenhouse assays. The goal of this research was to evaluate how pot size, Meloidogyne spp. inoculation life stage, inoculation density, and time of assay impacted final reproduction factor (RF = initial nematode density/final nematode density) values. In experiments with M. incognita, the factor of the pot size mattered, with higher RF values in pots containing 500 g soil vs. pots with 100 g soil; larger pots containing 3,000 g soil did not have RF values different from the aforementioned sizes. Inoculating with M. incognita J2 resulted in RF values on average of >2 fold higher then when inoculating with eggs at comparable densities. Inoculation density of M. incognita did not have an impact on final M. incognita RF values. In experiments that considered time of assay, three species were evaluated: M. incognita, M. chitwoodi, and M. hapla. There was no difference in M. incognita RF values when assays were conducted for 5 wk, 6 wk, 7 wk, and 8 wk. However, a longer assay time resulted in higher RF values for M. hapla and M. chitwoodi, with at least a 7 week assay required. In conclusion, a moderate pot size (500 g of soil) inoculated with M. incognita J2 resulted in maximum RF values. The length of the assay required will depend on the Meloidogyne spp. in question, with longer duration assays required for M. hapla and M. chitwoodi than for M. incognita.

Endophytic Non-Pathogenic Fusarium oxysporum-Derived Dual Benefit for Nematode Management and Improved Banana (Musa spp.) Productivity

The banana weevil (Cosmopolites sordidus) and the burrowing nematode Radopholus similis represent two of the most important pests of bananas. Previously, colonization of banana plants by the non-pathogenic Fusarium oxysporum (isolate V5w2) and the entomopathogenic Beauveria bassiana (isolate WA) have been shown to increase host resistance to various banana pests and diseases. However, there is limited data on how the combined inoculation of these isolates would affect field performance of bananas. In this study, the fungal endophytes were inoculated separately and in combination. Tissue cultured plantlets of cooking banana cultivar Mbwazirume and dessert banana cultivar Grande Naine were inoculated by root drenching with a suspension of 1.0 × 107 spores mL−1 of the endophytes on three occasions, separated 4 weeks apart, before transplanting into the field. Each plantlet was further inoculated with 1800 nematodes, composed primarily of R. similis. Inoculation of banana plants with the fungal endophytes significantly reduced nematode densities by >34%. Similarly, plant toppling was lower in the endophyte-enhanced plants (<16.5%) compared with the control (23.3%). We also observed improved yield of the first crop cycle in the endophyte-enhanced plants, which yielded >11 t ha−1 year−1 versus 9 t ha−1 year−1 achieved in the non-inoculated plants. These findings demonstrate the benefits of fungal endophytes in improving the yield of both cooking and dessert bananas via suppression of nematode densities and nematode-related damage.

Impact of caterpillars and plant-parasitic nematodes on Chinese tallow tree are more strongly affected by nematode density than by caterpillar identity

Impact of caterpillars and plant-parasitic nematodes on Chinese tallow tree are more strongly affected by nematode density than by caterpillar identity

Biofertilizers in the control of Pratylenchus brachyurus in soybean crop

Nematodes are of great importance in soybean cultivation, especially the Pratylenchus brachyurus known as root lesion nematode. Its attack on plant roots causes less efficiency in the absorption of water and nutrients, in addition to damaging the plant's development. There is still no fully efficient method to control this phytopathogen, however, some products are available on the market, including biological control. Thus, the aim of this study was to evaluate commercial biological products in the efficiency of reducing the nematode population in soybean crop in Goiás, Brazil. The design was completely randomized in a 2x4 factorial scheme, the first factor being two soybean genotypes (Brasmax Bônus and Nidera NS 8383) and the second factor the treatments consisting of different dosages in an association of three commercial products: No-Estio®, Bio-fertility® and Radic®. The treatments used were: T1 control - without application of the products; T2 half the recommended dose; T3 the recommended dose and T4 a dose and a half that recommended by the manufacturer. Plant evaluation was carried out after 75 days of nematode inoculation. The results obtained showed that both cultivars hosted P. brachyurus, however, the treatments using the products had a lower population density of this nematode. It was concluded that the two soybean cultivars are hosts of Pratylenchus brachyurus. The agronomic character plant height was more affected when there was no application by the biological method. The association of No-Estio®, Bio-fertility® and Radic® products reduced the population density of nematodes in infected plants.

Abundance of mites, but not of collembolans or nematodes, is reduced by restoration of a Pinus ponderosa forest with thinning, mastication, and prescribed fire

Thinning, mastication, and prescribed fire are restoration treatments frequently employed in unnaturally dense second-growth Pinus ponderosa forests of the Western United States. Although a goal of these treatments is to restore ecosystem structure and function, little information is available regarding treatment effects on soil micro- and mesofauna, which comprise the overwhelming majority of metazoan forest inhabitants and occupy key positions in soil food webs. We quantified nematodes, mites, and collembolans in soil and litter habitats within untreated control, thinned (comprising thinning and masticating wood), and burned (comprising thinning and masticating, followed by broadcast burn) in P. ponderosa forest management units at Valles Caldera National Preserve in New Mexico, USA. We linked patterns in animal abundance to resource and habitat characteristics, hypothesizing that resources and available habitat for many taxa would increase with thinning and decrease with burning. Two years after thinning, densities of collembolans and nematodes in the thinned unit were higher than in the untreated control unit, but one year post-fire, their densities in the burned unit were similar to those of the untreated control unit. Mite abundance, however, was not elevated in the thinned unit and was lower in the burned unit. Although faunal communities were highly heterogeneous, a significant proportion of the variance in faunal abundances was explained by easily and inexpensively measured habitat and resource characteristics: bulk density, soil organic matter (SOM), pH, grass cover, and litter cover and depth. These findings demonstrate the abiotic and biotic factors that structure faunal habitats so that forest managers have a more complete understanding of the impacts of forest restoration treatments.