Nematode Population Densities Research Articles

Unmanned Aerial Vehicle (UAV) for Detection and Prediction of Damage Caused by Potato Cyst Nematode G. pallida on Selected Potato Cultivars

High population densities of the potato cyst nematodes (PCN) Globodera pallida and G. rostochiensis cause substantial yield losses to potato production (Solanum tuberosum) due to the delay caused to tuber formation by the retardation of plant growth. It requires meticulous estimation of the population densities by using soil sampling and applying the right combination of nematode management to deal with the PCN problem. This study aims to assess the use of an unmanned vehicle (UAV) in detecting and estimating the effect of ranges of densities of a PCN, G. pallida, on four cultivated potato cultivars with resistance to PCN in a naturally infested potato field in The Netherlands. First, the initial population density (Pi) of G. pallida was estimated by using an intensive sampling method of collecting about 1.5 kg of soil per m2 from the center of each 3 × 5 m plot. At harvest, the fresh tuber yield of the potato cultivars (Avarna, Fontane, Sarion, and Serresta) were assessed. The Seinhorst yield loss model was used to investigate the relationship between Pi and fresh tuber yield. Secondly, the spatial data of UAV with optical and thermal sensors were analyzed to find any relationship between Pi and UAV indices. By using the classical yield loss model, all four cultivars were found to be affected by Pi with a relative minimum fresh tuber yield m, which ranged from 0.26 to 0.40. The maximum fresh tuber yield varied from 49.48 to 80.36 tons (ha)−1. The density at which the fresh tuber yield started to deteriorate was in the range of 0.62–2.16 eggs (g dry soil)−1. A regression was observed between Pi, and all UAV indices in a similar pattern to that of the fresh tuber yield by using the Seinhorst yield loss model, except for the cultivar Avarna for the two UAV indices (NDRE and NDVI). Unlike the tolerance limit, the relative minimum values of the UAV indices—except the chlorophyll index—differ when compared among each other and when compared with that of the fresh tuber yield within the same cultivar. This indicates that all indices can be useful for detection and decision making for statutory purposes but not for estimating damage (except the chlorophyll index).

First Report of Direct Damage Caused by the Stubby-Root Nematode, Nanidorus minor, to Strawberry (Fragaria x ananassa), in Florida.

In 2019-2022, declining symptoms were observed in two commercial strawberry farms in Hillsborough County, Florida. The fields in the two farms consisted of raised beds covered by plastic mulch. Both were fumigated with a mixture of 1,3-dichloropropene (40%) + chloropicrin (60%) before planting. Samples collected from large patches with declining plants were infested with stubby-root nematodes. No sting and root-knot nematode species were detected. The results of morphological and molecular analyses indicated that the stubby-root nematode populations were representative of the species Nanidorus minor. The two cultivars 'Florida Brilliance' and 'Florida Sensation' in the two fields included plants with stubby root symptoms showing a reduction in the size of the root system and arrested growth and elongation of the feeder roots on the first strawberry crop. The nematode population densities in the two fields increased at the end of strawberry season and averaged 66 and 96 specimens in 200 cm3 soil. In one of the fields, a second strawberry crop was established as in the previous year using the same practices (fumigation and raised beds covered with plastic). However, in this field the population of N. minor declined and did not reach damaging levels at the end of the season on the second strawberry crop. The factors causing the decline of the nematode population were not elucidated. This is the first report of a direct damaging effect of N. minor to strawberry.

Control of Meloidogyne javanica with Pleurotus djamor spent mushroom substrate

BackgroundThe interest in the development of products that cause less damage to the environment associated with the loss of efficiency of chemical nematicides for the control management of nematodes is growing. Thus, the adoption of biological control or the use of biopesticides are excellent options for these products like those based on chemical compounds, such as commercial pesticides and anthelmintic (AH) drugs. Spent mushroom substrate (SMS), a product of the mushroom production industry, has great potential for biological control due to its high levels of mycelium, residual enzymes, high humidity and unique microbiota that may contain other nematode antagonists. For this reason, this study aimed to evaluate the potential of spent mushroom substrate (SMS) from Pleurotus djamor cultivation in the control of Meloidogyne javanica in lettuce and assess its effects on plant resistance enzymes and soil biological activity.ResultsSMS reduced by 98.68% the nematode reproduction, and a plateau was reached at SMS concentrations above 15%. For the population density of nematode (nematode g-1 root), this reduction was 99,75%. Higher concentrations of SMS caused phytotoxicity in lettuce, with reduction of vegetative variables, chlorophyll content and nitrogen balance in the leaves; however, SMS increased the anthocyanin content. Guaiacol peroxidase activity was the highest in treatments containing 0% and 30% SMS and phenylalanine ammonia-lyase activity was the highest in the 60% SMS treatment, suggesting induction of resistance to M. javanica. The maximum soil basal respiration was estimated to be achieved with 25.75% SMS, whereas the maximum soil metabolic quotient was estimated to be achieved with 8.8% SMS. Soil biomass carbon increased with increasing SMS proportion.ConclusionsSpent substrate from P. djamor cultivation incorporated in soil at proportions of 15, 30, 45 and 60% is efficient in controlling M. javanica in lettuce.Graphical

Evaluation of the mechanism of action of Bacillus spp. to manage Meloidogyne incognita with split root assay, RT-qPCR and qPCR.

The goal of this research is to determine the mechanism of action of two Bacillus spp. that can manage Meloidogyne incognita population density in cotton. The overall objectives are 1) determine the efficacy and direct antagonistic capabilities of the Bacillus spp. and 2) determine the systemic capabilities of the Bacillus spp. The greenhouse in planta assay indicated B. amyloliquefaciens QST713 and B. firmus I-1582 could manage M. incognita similarly to the chemical standard fluopyram. An in vitro assay determined that B. firmus I-1582 and its extracted metabolites were able to directly manage M. incognita second stage juveniles by increasing mortality rate above 75%. A split root assay, used to determine systemic capabilities of the bacteria, indicated B. amyloliquefaciens QST713 and B. firmus I-1582 could indirectly decrease the nematode population density. Another species, B. mojavensis strain 2, also demonstrated systemic capabilities but was not a successful biological control agent because it supported a high population density in greenhouse in planta assay and in the split root assay. A RT-qPCR assay was used to confirm any systemic activity observed in the split root assay. At 24 hours both B. amyloliquefaciens QST713 and B. firmus I-1582 upregulated one gene involved in the initial stages of JA synthesis pathway but not another gene involved in the later stages of JA synthesis. These results point to a JA intermediate molecule, most likely OPDA, stimulated by the bacteria rather than JA in a short-term systemic response. After 1 week, the Bacillus spp. stimulated a SA-responsive defense related gene. The long-term systemic response to the Bacillus spp. indicates salicylic acid also plays a role in defense conferred by these bacteria. The final assay was a qPCR to determine the concentration of the bacteria on the cotton roots after 24 days. Bacillus amyloliquefaciens QST713 and B. firmus I-43 1582 were able to colonize the root successfully, with the concentration after 24 days not significantly differing from the concentration at inoculation. This study identifies two bacteria that work via systemic resistance and will help aid in implementing these species in an integrated management system.

Sampling Depth and Crop Growth Stage affect Estimates of the Population Density of Lesion Nematodes (Pratylenchus spp.) in Corn Fields in Ohio.

The effects of sampling depth and crop growth stage on the population density of lesion nematodes were investigated in three commercial fields in Wayne and Fulton counties, Ohio during the 2016 and 2017 growing seasons. Soil samples were collected at five growth stages by removing 15 soil cores to a depth of 70 cm from each of 25 plots per field-year. Cores were divided into seven 10-cm sections from each of which nematodes were extracted from the soil and root fractions. Pratylenchus crenatus and P. thornei were detected in approximately 84 and 78% of the samples collected in Wayne and Fulton counties, respectively. Depth significantly affected total population density of both species as well as densities in the soil and root factions in all field-years, but the effects of growth stage and its interaction with depth varied with field-year. In most cases, mean population densities were higher from 10 to 40 cm soil depth than at the reference 40-50 cm depth, and lower from 50 to 70 cm. There were quadratic relationships between population density (on the log link scale) and depth, with the highest peaks in estimated predicted densities generally occurring between 20 and 40 cm, depending on crop growth stage and growing conditions. These findings suggest that the standard practice of sampling between growth stages V3 and V6 to a depth of 45 to 50 cm and using the entire core for extraction and enumeration could lead to underestimation of population densities of P. crenatus and P. thornei.

Effect of Different Rates, Application Timing, and Combination of Nonfumigant Nematicides in Control of Meloidogyne incognita in Watermelon

The use of plasticulture systems, which consist of raised beds, plastic mulch, and drip irrigation, for watermelon production has increased in the Southern United States in recent decades. The root-knot nematode (RKN), Meloidogyne incognita, is a significant pathogen of watermelon production in plasticulture systems and can cause varying levels of yield loss depending on the nematode population density if not properly controlled. A few new nonfumigant nematicides (fluensulfone, fluazaindolizine, and fluopyram) have emerged in the last decade to help manage RKNs. A 2-year field study was conducted to examine the impact of different rates, application timing (i.e., days before transplanting, at transplanting, and days after transplanting), and combinations of these new nematicides and an older one (oxamyl) in control of RKN in watermelon cultivar Fascination. The nematicide treatments, except for a single-time application of oxamyl in 2019 and 2020, significantly reduced root galling compared with the untreated check. Similarly, all treatments, except a single application of oxamyl in 2020, resulted in a lower soil population level of M. incognita than the untreated check. All nematicide treatments, except a single application of fluensulfone and a two-time application of fluopyram at a half-recommended rate, increased fruit yields when compared with the untreated check. Overall, the drip application of new chemistries, known as 3-F nematicides, has been shown to be a useful option for RKN management in watermelon. At-planting application of fluazaindolizine or fluopyram and two-time applications of oxamyl based on the manufacturer's recommended rate show potential to prevent crop loss.

A Survey of Soybean Cyst Nematode Population Densities and Phenotypes in Illinois: 2018 and 2020

In Illinois, soybean cyst nematode (SCN; Heterodera glycines) has been estimated to cause over $15 million in losses as recently as 2021. In addition, populations of SCN insensitive to PI 88788-derived resistance, the most commonly used SCN resistance source in commercially available soybeans, continues to increase in soybean production areas in the United States. Despite this, awareness of this pathogen and its current status in the state is relatively lacking. A survey was conducted in 2018 and 2020 to assess the presence, population level, and virulence phenotypes in Illinois soybean fields. Soil samples were collected and processed for SCN eggs after harvest each year, and samples with sufficient numbers of SCN eggs were virulence tested using the Hg type test. A total of 95 samples were collected, representing 46 counties. Eighty-seven percent of fields sampled contained SCN eggs, with 38% containing population densities over 2,000 eggs/100 cm3. All samples included in the Hg type test had a female index > 10 on indicator line PI 88788, indicating insensitivity to this resistance source. Extrapolated across soybean production acres, these data indicate that approximately 4.4 million acres of soybeans contain levels of SCN requiring SCN management, and over 54% of acres using cultivars derived from PI 88788 are not fully protected from this pathogen.

Inducing Systemic Acquired Resistance (SAR) Against Root-knot Nematode Meloidogyne Javanica and Evaluation of Biochemical Changes in Cucumber Root.

For inducing systemic acquired resistance (SAR), Salicylic acid (SA), Ascorbic acid (AA), and silicon (Si) were applied on shoots, roots, and both of them simultaneously. Results showed that all treatments reduced the number of galls, root gall index, number of egg mass/root system, number of nematodes/root system, number of eggs/root system, number of nematodes/pot soil, the final population density of nematodes, and rate of reproduction. Treatments also increased growth criteria, including chlorophyll, shoot fresh weight, root fresh weight, shoots dry weight, root dry weight, shoots length, and root length. SA foliar and root application decreased infection criteria and increased total phenol, peroxidase, and phenol oxidase activities. Ascorbic acid and silicon increased total phenol, peroxidase, and phenol oxidase activities.

Population Density of Free-Living Nematodes and their Relationships with Some Soil Physicochemical Properties of Alfalfa

The present study was conducted to evaluate the soil’s suitability for the alfalfa crop in Nomal Valley, Gilgit Baltistan (GB), using a variety of physicochemical parameters and free-living soil nematodes as indicators. Ten soil samples from different sites (A1-A10) of the valley were collected in zip-lock plastic bags to test for free-living soil nematodes and physicochemical characteristics. Each sample’s free-living nematodes were extracted using the modified Baermann funnel method and counted using a compound microscope (at 40 and 100X). About 100 nematodes were identified from each sample to the family level. Based on feeding behavior, nematodes were divided into groups. Nematode population densities ranged from 102 to 507. The most prevalent feeding group members were bacterivores, while predators were the least common. Cephalobidae was the most frequently occurring family, which indicates soil’s fertility. Various physiochemical parameters, including soil temperature, pH, electrical conductivity (EC), moisture, bulk density, and texture, were also measured. The ranges for the selected soil parameters were as follows: pH 7.20-7.80, EC 68-252 mS/m, bulk density 0.91-1.37g/cm2, and soil temperature 22-30 ℃. All sites had slit loam soil texture except A-5, which had sandy loam.

Pochonia chlamydosporia Is the Most Prevalent Fungal Species Responsible for Meloidogyne Suppression in Sustainable Vegetable Production Systems

The fluctuations in Meloidogyne densities and fungal egg parasitism were determined from February 2015 to July 2016 in four vegetable production sites conducted under organic production and two sides conducted under integrated standards. At each site, the soil nematode densities at transplanting and at the end of the crops, the galling index, the number of eggs in roots, and the percentage of fungal egg parasitism were determined, and the fungal species were identified. In addition, two pot experiments were conducted with soil taken from each site in February 2015 and 2016 to assess the fungal egg parasitism comparing non-sterile and sterile soil from each site. In field conditions, the nematode population densities in the soil decreased along the crop rotations. The maximum number of eggs per plant was recorded in the spring–summer crops. Egg parasitism ranged from 11.2 to 55% in the organic sites and from 0.8 to 16.5% in the integrated production sites. Pochonia chlamydosporia was the only fungal species isolated in five of the six sites. In both pot experiments, the number of eggs per plant was lower in non-sterile than in sterile soils, except for the M10.45 site, where fungal egg parasites were not recovered. P. chlamydosporia was the only fungal species isolated, ranging between 11 and 74%. Therefore, P. chlamidosporia was the most prevalent fungal species related to Meloidogyne suppression.

Response of sugarcane aphid (Melanaphis sacchari) to interactive effects of soil drenched triterpenoid phytonematicides in sweet sorghum (Sorghum bicolor)

Triterpenoid phytonematicides, namely, Nemarioc-AL, Nemafric-BL and Mordica, when drench-applied each consistently suppressed root-knot nematode population densities, with limited information on whether the products could induce any systemic effects that would suppress sugarcane aphid population densities and reproductive potential. The objective of the study was therefore to determine the interactive effects of soil-drenched triterpenoid phytonematicides on aphid population densities and their reproductive factors. A 2× 2× 2 factorial experiment was laid out in a randomised complete block design with six replications during 2020-21 and 2021-22 growing seasons in Limpopo Province, South Africa. Each sweet sorghum seedling was infested with 5 adult M. sacchari, with appropriate treatment combinations drench-applied weekly. At 150 days after infestation, treatments had highly significant effects on aphid population densities and reproductive factors. Relative to untreated control, the second order interaction and the three first order interactions reduced aphid population densities by 92, 75, 79 and 80%, respectively. In conclusion, soil-drenched triterpenoid phytonematicides induced systemic effects in sweet sorghum, which significantly suppressed population densities of M. sacchari.

Host Suitability of Cover Crops to the Root-Lesion Nematode Pratylenchus penetrans Associated with Potato.

Nonhost or poor host cover crops can provide an alternative method for nematode management. A total of 25 cover crop species/cultivars, along with three controls were evaluated in greenhouse experiments for their host suitability to the root-lesion nematode Pratylenchus penetrans. Trials were conducted in a completely randomized design using nematode-infested soil and terminated 3 months after planting. Nematodes were extracted from the roots and soil of each crop to determine their final population densities, reproductive factor (Rf = final population density/initial population density), and distributions in the soil and root habitats. Reproductive factor was used to categorize the host suitability of crops. Faba bean cv. Petite produced the greatest nematode population density in all trials, whereas only alfalfa cv. Bullseye constantly demonstrated the poor host ability to P. penetrans. Annual ryegrass, winter rye cv. ND Dylan, and white proso millet also showed poor hosts in most trials. Five cover crops consistently maintained the population throughout the experiments, with Rf values less than 2, and the remaining tested cover crops were suitable hosts for P. penetrans. The majority of the tested cover crops had less than or equal to 30% of the final population residing in the roots after three months of growth in all the trials. This research helps us gain the knowledge on cover crops and P. penetrans interaction and will be useful for potato growers to select better cover crops and avoid susceptible hosts to manage P. penetrans in infested fields to minimize potato yield losses.

Parasitic Nematodes of Plant Persimmon (Diospyros Kaki, l.) Rhizosphere in District Swat, Kp Pakistan

Purpose: Different species of plant parasitic nematodes of persimmon (Diospyros kaki, L.) were identified from various localities of District Swat KPK Pakistan namely Chail, Madyan, Piya, Jare, Chikrai, Thesil, Fateh pur, Baghdheri, Naway kalay, Shin, Pirpatay, Sambat and Gurra. Methods: Soil samples were collected from the bases of persimmon trees along with rhizospheres that show stunted growth. The collected samples were then processed by using modified Bearmann funnel technique. Nematode specimens isolated in cavity block were killed by heat and treated with TAF (Triethylamine formaldehyde) solution. Findings and Practical implication: After 24 hours, the specimens were transferred to 1.25 % glycerin with trace amount of picric acid for staining of nematodes. Nine different species of nematodes were reported from these localities were Tylenchus spp, Psilenchus spp, Meloidogyne larvae, Aphelenchus spp, Tylenchus juveniles, Filenchus spp, Pratylenchus spp, Helicotylenchus pseudorobustus and Helicotylenchus dihystera. Helicotylenchus species were more common in the collected samples. Conclusion: It is concluded from analysis of soil samples that plant parasitic nematodes associated with persimmon cause economic loss in district swat. Persimmon plants show stunted and retarded growth in soil which has high nematode population density. Keywords: Nematodes, Persimmon, Swat, Diospyros kaki, Triethylamine formaldehyde.

Effect of interaction between Meloidogyne incognita and Cowpea mild mottle virus on soybean

The study investigated the effects of the interaction between Meloidogyne incognita and Cowpea mild mottle virus on soybean cultivars. Two weeks after planting, treatments were applied to the plants in both the screenhouse and field trials as listed; single inoculation of 5,000 eggs of M. incognita on roots of soybean seedlings, single inoculation of leaves of soybean seedlings with CPMMV sap, mixed inoculation 5,000 eggs of M. incognita on roots of soybean seedlings 2 days before inoculating leaves with CPMMV sap, mixed inoculation of leaves of soybean seedlings with crude CPMMV sap 2 days before inoculating plant roots with 5,000 eggs of M. incognita, simultaneous inoculation of leaves of soybean seedlings with crude CPMMV sap and plant roots with 5,000 eggs of M. incognita, and uninoculated plants (control). Data were collected on plant height, number of leaves showing symptoms, grain weight and nematode populations. The results showed that combined inoculations of CPMMV and M. incognita reduced the population density of the nematode and increased the growth and grain yields of M. incognita infected soybean cultivars. It also revealed that plants inoculated with the nematode at 2 days before the virus was inoculated significantly reduced growth and yields of soybean and increased nematode population densities compared to single infections and other combined infections.

Diversity and temporal distribution of Fusarium oxysporum f. sp. vasinfectum races and genotypes as influenced by Gossypium cultivar.

This study assess the population diversity and temporal variability of caused by Fusarium oxysporum f. sp. vasinfectum (FOV) races/genotypes infecting cotton cultivars with either FOV or Meloidogyne incognita resistance. All plants sampled demonstrated typical symptoms of FOV including wilting, chlorosis and necrosis of the leaves, and discoloration of the vascular tissue in the stem. A diverse population of FOV was characterized. Eight races/genotypes of FOV were collected throughout the three site years. FOV race 1 was the most predominant in all tests (AUDPC=101.1); statistically higher numbers of isolates from LA-108 (AUDPC=59.9), race 8 (AUDPC=47.5), and race 2 (AUDPC=38.6) were also found compared to other races and genotypes collected. FOV race 1, race 2, race 8, and 108 were the most virulent races identified. The genotypes MDS-12, LA-110, and LA-127/140 were found in all tests but at a low incidence, and LA-112 was only found in trace amounts. MDS-12, LA-110, LA-112, and LA-127/140 produced less disease pressure. FOV race 4 which is highly virulent and present in California and Texas was not found in Alabama. A positive correlation was observed between the accumulation of growing degree days and FOV race 1, race 2, race 8, LA-108, and LA-110. Later symptom expression influenced by seasonal heat partially mitigates damage allowing cotton to produce bolls though they may be reduced in number and lint quality. Plant resistance to the FOV as expressed in these cultivars appears to provide better protection than M. incognita resistance. PhytoGen 72, which is resistant to FOV races/genotypes had low levels of FOV infection even though it sustained a high level of M. incognita root population density. The M. incognita resistant cultivars Deltapine 1558NR B2RF and PhytoGen 480 W3FE supported a lower nematode population density, however, FOV disease incidence was not reduced. FOV races/genotypes did not vary significantly between the nematode resistant and nematode susceptible cultivars.

Impact of Pratylenchus penetrans on Soybean Grown in Wisconsin, U.S.A.

Models were developed to quantify the impact of Pratylenchus penetrans to the early season growth and yield of soybean in field and greenhouse environments and to estimate yield loss because of P. penetrans in Wisconsin. There was a negative linear relationship between initial nematode population densities (Pi) and shoot and total plant weight at V2 and yield, pod number, seed number, and seed mass at harvest in the field. Relative yield loss, modeled for the second year of the field experiment, suggested a loss of 4.5% for yield and between 2.4 and 2.8% for yield components at the mean field Pi value. Negative linear relationships were demonstrated for the relative loss in those variables as well as for harvest index and shoot, root, and total plant weight at harvest in the greenhouse. Stress imposed by P. penetrans began within 2 weeks after planting and continued through harvest. Estimates of the percent loss attributed to each nematode Pi value were 0.020% for yield, 0.015% for pod number, and 0.017% for seed number. Pratylenchus spp. was the most widely prevalent pest nematode among samples submitted to a statewide nematode testing program. Molecular identification of a subset of 63 samples suggested 15% were infested with P. penetrans at a mean Pi value of 197 P. penetrans per 100 cm3 soil. Yield loss because of P. penetrans, estimated from prevalence data and our empirical greenhouse model, ranged from 0.23 to 2.76% among Wisconsin's agricultural districts. The cumulative impact for all Pratylenchus spp. is likely much greater, given this loss estimate does not account for the monoecious species present in 79% of the samples.

Population Development of the Root-Lesion Nematode Pratylenchus dakotaensis on Soybean Cultivars.

Two greenhouse experiments were conducted with the new species of root-lesion nematode, Pratylenchus dakotaensis, discovered in North Dakota, USA in 2017 and named in 2021. Experiment 1 was conducted to ascertain resistance levels of soybean (Glycine max [L.] Merr.) cultivars to the new species P. dakotaensis and Experiment 2 was conducted to evaluate the population levels of P. dakotaensis in roots versus soil. A total of 20 soybean cultivars, and the positive control, cultivar Barnes, accompanying a nonplanted control, were evaluated in both experiments; they each had five replicates and the experiments were repeated. Among the 20 soybean cultivars evaluated, a cultivar with the ID# 13 consistently produced the greatest population densities of P. dakotaensis across all the experiments and therefore it was selected as the susceptible check. The ratio of the final nematode population density of a test cultivar relative to the final population density of the susceptible check was used to scale resistance rating. Combined results of all the trials indicated that seven of the cultivars were moderately resistant, nine of the cultivars plus 'Barnes' were moderately susceptible, and four of the cultivars were susceptible. However, none of the cultivars tested were classified as resistant. Analysis of P. dakotaensis population levels revealed that ≥50% of the population resided in the root habitat and the remaining nematodes were recovered from soil at 9 weeks after planting for a majority of the cultivars tested. These results provide an insight into the virulence of P. dakotaensis on commercial soybean cultivars.

Plant parasitic nematodes and disease severity of common bean lines evaluated for reaction to root knot nematodes infestation

Plant parasitic nematodes are important pests in crop production in sub-Saharan Africa. The objective of this study was to identify the occurrence of nematodes associated with common bean (Phaseolus vulgaris L.) and evaluate breeding lines for their reaction to Meloidogyne spp. in Ghana. Common bean rhizosphere soil was sampled and processed using Modified Baermann Tray method. Five nematode genera, namely Meloidogyne, Pratylenchus, Rotylenchulus, Helicotylenchus and Trichodorus were extracted. The first four genera listed above were prevalent across locations, with Trichodorus present in 30% of the fields sampled. The highest nematode population density of 319 juveniles per 200 cubic centimeter of soil was recorded for Meloidogyne spp. compared to 45 juveniles per 200 cubic centimeter, for Trichodorus. Twelve breeding lines were evaluated by inoculating roots of two-weeks-old plants with 2000 infective-stage juveniles of Meloidogyne sp. Reactions of test lines to Meldogyne sp. infection were assessed by determining the number of egg masses and galling index (GI) on roots. Reproduction index (RI) was used to classify test lines as resistant or susceptible. Significant differences (P < 0.05) were observed in the number of eggs, GI and RI among lines tested. No resistant line was identified; however, lines SEF 47, BFS 35 and BFS 60 were moderately resistant, with RI of 13.1, 17.4 and 23.7%, respectively. Line SEF 60, although classified as slightly resistant, recorded a 100 seed weight of 26.0 g, which was 60% higher than line SEF 53 with seed weight of 16.2 g. Moderately resistant common bean lines identified could be used in common bean improvement programmes to develop elite cultivars tolerant to root knot nematodes.

Efficacy of Seed Priming With Cucurbitacin Phytonematicides Against Meloidogyne incognita on Pea

The cost and environment concerns of existing drench-application technologies of cucurbitacin phytonematicides resulted in conceptualization of the priming-and-drying (PAD) technology of seeds with hypogeal germination. The preliminary observations suggested that the PAD technology improved seed germination, plant growth, and vigor in pea (Pisum sativa), with limited information on suppression of root-knot (Meloidogyne species) nematodes. Post-soaking pea seeds in geometric concentrations of Nemarioc-AL and Nemafric-BL phytonematicides, seedlings were raised in greenhouse and on microplot experiments during 2019 and validated in 2020. At 60 days after inoculation with 300 eggs + second-stage juveniles (J2) of M. incognita seasonal data were pooled. Gall rating, eggs in root, and J2 in root vs. Nemarioc-AL phyto nematicide in greenhouse and on microplot exhibited negative quadratic relations, with models explained by 80–85% and 89–94% associations, respectively. Similarly, for the respective sites negative quadratic models for nematode variables vs. Nemafric-BL phytonematicide were explained by 82–93% and 90–94% associations, respectively. In conclusion, pea seed remnants belowground gradually released cucurbitacins into the rhizosphere throughout the growing period, thereby suppressing nematode population densities, and therefore, the PAD technology has the potential for assessment in a large-scale application of cucurbitacin phytonematicides for pea 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