D.Permanent resistance to all soil-borne pathogens
Correct Answer: Stunting
Explanation:
Damaged roots cannot support normal growth, so affected plants often become stunted.
Incorrect! Try again.
15Nematode damage in a field often appears in which pattern?
Impact on crop yield
Easy
A.Uniform rows
B.Perfect circles
C.Irregular patches
D.A single straight line across every type of soil
Correct Answer: Irregular patches
Explanation:
Nematodes are usually unevenly distributed in soil, so crop damage commonly appears in irregular patches.
Incorrect! Try again.
16How can nematode infection affect the market quality of root and tuber crops?
Impact on quality
Easy
A.By creating an additional protective skin around every harvested root
B.By producing uniform shapes
C.By improving storage life
D.By causing lesions and deformities
Correct Answer: By causing lesions and deformities
Explanation:
Lesions, galls, and deformities reduce the visual quality and market value of roots and tubers.
Incorrect! Try again.
17Which quality characteristic may decline when nematodes attack harvested plant parts?
Impact on quality
Easy
A.Soil depth
B.Rainfall
C.Appearance
D.Length of daylight
Correct Answer: Appearance
Explanation:
Nematode damage can produce visible spots, cracks, galls, or deformities that lower product appearance.
Incorrect! Try again.
18Nematode-created wounds may reduce crop quality because they can provide entry points for what?
Impact on quality
Easy
A.Other pathogens
B.Beneficial insects that pollinate flowers throughout the season
C.Sunlight
D.Mineral fertilizers
Correct Answer: Other pathogens
Explanation:
Wounds caused by nematode feeding can allow fungi and bacteria to enter plant tissues and cause additional damage.
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19What is the main purpose of plant quarantine in relation to nematodes?
Impact on international trade
Easy
A.To prevent pest movement between regions
B.To guarantee that every shipment contains the same crop variety
C.To increase the weight of exported produce
D.To improve the flavor of imported crops
Correct Answer: To prevent pest movement between regions
Explanation:
Plant quarantine helps prevent harmful nematodes from entering or spreading into new regions through traded materials.
Incorrect! Try again.
20Which traded material is most likely to carry plant-parasitic nematodes to a new country?
Impact on international trade
Easy
A.Clean glass containers
B.Infested planting material
C.Processed plastic packaging manufactured without soil contact
D.Sealed metal tools
Correct Answer: Infested planting material
Explanation:
Planting material with infected roots, tubers, bulbs, or adhering soil can transport nematodes across borders.
Incorrect! Try again.
21A historian finds an eighteenth-century report describing worms recovered from abnormal wheat seeds called "ear-cockles." Which scientist is most closely associated with this early observation?
History of phytonematology
Medium
A.Nathan A. Cobb
B.Hermann Schacht
C.Miles Joseph Berkeley
D.John Needham
Correct Answer: John Needham
Explanation:
John Needham reported nematodes in wheat seed galls in 1743. The organism was later recognized as the seed-gall nematode, Anguina tritici.
Incorrect! Try again.
22Which sequence correctly orders these developments from earliest to most recent?
Needham described wheat seed-gall nematodes in 1743, Berkeley linked nematodes with root knots in 1855, and Cobb advanced systematic nematology mainly in the late nineteenth and early twentieth centuries.
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23A survey detects nematodes in agricultural soil, freshwater sediment, marine sediment, and plant tissue. What is the best conclusion from these findings?
Habitat and diversity
Medium
A.All nematodes detected are plant parasites
B.Nematodes occupy highly diverse ecological habitats
C.Marine nematodes originated recently from farmland
D.Nematodes survive only where crops are cultivated
Correct Answer: Nematodes occupy highly diverse ecological habitats
Explanation:
Nematodes occur in terrestrial, freshwater, marine, and host-associated habitats. Only a fraction of their diversity consists of plant-parasitic species.
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24A nematode remains outside the root but inserts its stylet into epidermal cells to feed. How should its parasitic habit be classified?
Habitat and diversity
Medium
A.Migratory ectoparasite
B.Sedentary endoparasite
C.Migratory endoparasite
D.Sedentary ectoparasite
Correct Answer: Migratory ectoparasite
Explanation:
An ectoparasite feeds while remaining outside plant tissue. If it moves between feeding sites instead of establishing a permanent feeding position, it is migratory.
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25Two soil samples contain equal total numbers of nematodes. Sample X contains bacterivores, fungivores, predators, omnivores, and plant parasites, while Sample Y is dominated by one plant-parasitic species. Which interpretation is most appropriate?
Habitat and diversity
Medium
A.Neither sample contains a nematode community
B.Sample X has greater trophic diversity
C.Both samples have identical community structure
D.Sample Y has greater trophic diversity
Correct Answer: Sample X has greater trophic diversity
Explanation:
Trophic diversity reflects the range of feeding groups, not merely total abundance. Sample X includes more functional feeding groups than Sample Y.
Incorrect! Try again.
26A historical account describes a 1901 report of root-knot nematodes damaging tea in southern India. Why is this report important to Indian nematology?
Evolution of nematode research in India and globally
Medium
A.It was an early documented plant-nematode report from India
B.It introduced electron microscopy into Indian laboratories
C.It established the first global nematode quarantine agreement
D.It demonstrated that all tea decline was nematode-induced
Correct Answer: It was an early documented plant-nematode report from India
Explanation:
E. A. Barber's report of root-knot nematodes on tea in 1901 is recognized as an early milestone in the development of plant nematology in India.
Incorrect! Try again.
27A laboratory replaces identification based only on body measurements with an approach combining morphology, host response, and DNA markers. Which research trend does this represent?
Evolution of nematode research in India and globally
Medium
Correct Answer: Development toward integrative nematode diagnostics
Explanation:
Modern diagnostics integrate morphology, biological information, and molecular markers. This improves discrimination among closely related or morphologically similar species.
Incorrect! Try again.
28Why did the establishment of specialized nematology divisions, professional societies, and coordinated surveys accelerate nematode research in India?
Evolution of nematode research in India and globally
Medium
A.They organized expertise, training, and regional data collection
B.They made all nematode species easy to identify visually
C.They transferred plant protection entirely to quarantine agencies
D.They eliminated the need for field-based crop experiments
Correct Answer: They organized expertise, training, and regional data collection
Explanation:
Specialized institutions and professional networks strengthened training, diagnostics, surveys, and collaborative research across crops and regions.
Incorrect! Try again.
29A field has a plant-parasitic nematode population below the economic threshold. Which decision is generally most appropriate?
Economic importance of nematodes
Medium
A.Assume the population cannot increase during the season
B.Monitor the population and avoid unnecessary treatment
C.Apply the most expensive nematicide immediately
D.Destroy the crop before symptoms become visible
Correct Answer: Monitor the population and avoid unnecessary treatment
Explanation:
Below the economic threshold, expected damage may not justify control costs. Monitoring is still necessary because populations can increase under favorable conditions.
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30A nematode causes moderate root injury but also creates infection sites for a soil-borne fungus. Which estimate best represents its economic importance?
Economic importance of nematodes
Medium
A.Combined direct damage and disease-complex losses
B.Direct root damage without secondary disease losses
C.Visible shoot symptoms without production losses
D.Control expenditure without any crop value
Correct Answer: Combined direct damage and disease-complex losses
Explanation:
The economic effect includes direct feeding injury and indirect losses caused by interactions with other pathogens in a disease complex.
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31A treatment costs $120 per hectare and is expected to prevent a crop loss worth $300 per hectare. Ignoring other costs, what is the economically rational decision?
Economic importance of nematodes
Medium
A.Reject the treatment because the expected net benefit is negative
B.Apply the treatment because the expected net benefit is $180
C.Apply the treatment because the expected net benefit is $300
D.Reject the treatment because the expected net benefit is $120
Correct Answer: Apply the treatment because the expected net benefit is $180
Explanation:
The expected net benefit is $300 - $120 = $180 per hectare, so the treatment is economically justified under the stated assumptions.
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32A nematode-free plot yields 8 tonnes per hectare, while an infested plot yields 6 tonnes per hectare under otherwise similar conditions. What is the estimated percentage yield loss?
Impact on crop yield
Medium
A.
B.
C.
D.
Correct Answer:
Explanation:
Percentage loss is .
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33Two fields contain the same initial root-knot nematode density. One is planted with a susceptible cultivar and the other with a resistant cultivar. Which outcome is most likely?
Impact on crop yield
Medium
A.Both cultivars will show equal reproduction and equal yield loss
B.Neither cultivar will be affected because initial densities are equal
C.The susceptible cultivar will support more reproduction and greater yield loss
D.The resistant cultivar will support more reproduction and greater yield loss
Correct Answer: The susceptible cultivar will support more reproduction and greater yield loss
Explanation:
A susceptible cultivar permits greater nematode development and reproduction, usually increasing root damage and yield loss relative to a resistant cultivar.
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34A crop infested early in the season suffers greater yield loss than a crop infested shortly before harvest. What best explains this difference?
Impact on crop yield
Medium
A.Early infection disrupts growth during more developmental stages
B.Late infection always kills nematodes before they reproduce
C.Early infection prevents all other pathogens from entering roots
D.Late infection permanently increases the crop's genetic resistance
Correct Answer: Early infection disrupts growth during more developmental stages
Explanation:
Early infection affects water and nutrient uptake over a longer period and interferes with establishment and development during yield-forming stages.
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35A potato crop produces nearly normal total biomass, but tubers have lesions and surface blemishes caused by nematodes. What is the most likely economic consequence?
Impact on quality
Medium
A.Reduced market grade despite limited biomass loss
B.Higher seed value because lesions indicate maturity
C.Increased market grade because biomass is unchanged
D.No economic loss unless every tuber is destroyed
Correct Answer: Reduced market grade despite limited biomass loss
Explanation:
Nematodes can reduce appearance and market grade even when total yield changes little. Quality loss can therefore cause substantial economic damage.
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36A seed-gall nematode replaces normal wheat grains with dark galls. Which quality component is affected most directly?
Impact on quality
Medium
A.Physical purity and acceptability of the grain lot
B.Flowering duration of the processed wheat flour
C.Rooting depth of grain during warehouse storage
D.Photosynthetic rate of the harvested grain lot
Correct Answer: Physical purity and acceptability of the grain lot
Explanation:
Seed galls contaminate harvested grain and reduce its physical purity, grading, processing suitability, and acceptability for seed or food use.
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37A root nematode reduces nutrient uptake in a fruit crop, producing smaller fruits with uneven ripening. Why is this classified as a quality impact?
Impact on quality
Medium
A.It increases the number of export certificates
B.It guarantees a longer postharvest storage life
C.It lowers size uniformity and market grade
D.It changes only the soil texture around roots
Correct Answer: It lowers size uniformity and market grade
Explanation:
Fruit size, uniformity, and ripening are important quality attributes. Their deterioration can reduce market grade even if some harvestable yield remains.
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38An importing country requires a shipment of planting material to be certified free from a regulated nematode. What is the main purpose of this requirement?
Impact on international trade
Medium
A.To guarantee that the crop has the highest possible yield
B.To ensure that all nonparasitic nematodes are removed
C.To determine the fertilizer requirement of the importing farm
D.To prevent introduction and establishment of the regulated pest
Correct Answer: To prevent introduction and establishment of the regulated pest
Explanation:
Phytosanitary certification reduces the risk that regulated nematodes will enter, establish, and spread through traded planting material.
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39A quarantine nematode is detected in one consignment of seed potatoes at an international port. Which immediate action is most consistent with phytosanitary practice?
Impact on international trade
Medium
A.Release the consignment because symptoms are not yet visible
B.Mix the consignment with uninfested lots to reduce prevalence
C.Send the consignment directly to farms for field confirmation
D.Hold the consignment and apply the prescribed regulatory measure
Correct Answer: Hold the consignment and apply the prescribed regulatory measure
Explanation:
A consignment containing a regulated pest is normally detained while authorities confirm the finding and order treatment, re-export, destruction, or another prescribed measure.
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40Why can a nematode with limited visible effects in the exporting country still cause rejection of a shipment by another country?
Impact on international trade
Medium
A.Its detection proves that every item in the shipment is damaged
B.Its trade status depends only on symptoms in the exporting country
C.Its presence matters only when commodity prices are decreasing
D.Its quarantine status depends on risk to the importing country
Correct Answer: Its quarantine status depends on risk to the importing country
Explanation:
Quarantine decisions are based on the likelihood and consequences of pest introduction in the importing country, not solely on visible damage in the country of origin.
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41Which observation most directly established that some nematodes were causal agents of plant disease rather than merely secondary inhabitants of damaged tissue?
B.Their repeated recovery from decaying plant organs
C.Their successful transmission causing symptoms in healthy plants
D.Their association with visible root lesions
Correct Answer: Their successful transmission causing symptoms in healthy plants
Explanation:
Reproduction of symptoms after transmission to healthy plants provides stronger causal evidence than simple association or repeated isolation.
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42Why was the discovery of the wheat seed-gall nematode historically important to plant nematology?
History of phytonematology
Hard
A.It established nematodes as exclusive vectors of viruses
B.It linked a microscopic animal with a seed-borne crop disease
C.It demonstrated that nematodes developed only in roots
D.It proved that all nematodes required living hosts
Correct Answer: It linked a microscopic animal with a seed-borne crop disease
Explanation:
The wheat seed-gall nematode demonstrated that nematodes could survive in seed-associated structures and cause economically important disease.
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43A historical account describes a nematode species by its host-associated symptoms but without microscopy, morphology, or infection tests. What is the most defensible interpretation?
History of phytonematology
Hard
A.It is evidence of obligate parasitism
B.It is proof of a virus interaction
C.It is a confirmed species record
D.It is a provisional disease observation
Correct Answer: It is a provisional disease observation
Explanation:
Symptoms alone can document an observation, but species confirmation requires diagnostic evidence such as morphology, molecular data, or validated pathogenicity tests.
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44A soil sample contains abundant nematodes, but only a small fraction are plant parasites. Which conclusion is most scientifically justified?
Habitat and diversity
Hard
A.The community includes multiple functional feeding groups
B.The nonparasitic forms are accidental soil contaminants
C.Most nematodes are feeding directly on crop roots
D.The crop is experiencing severe nematode damage
Correct Answer: The community includes multiple functional feeding groups
Explanation:
Soil nematode communities commonly include bacterial feeders, fungal feeders, predators, omnivores, and plant parasites.
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45Which ecological feature best explains why plant-parasitic nematode populations can remain undetected in a field despite causing later crop losses?
Habitat and diversity
Hard
A.Their populations may be spatially aggregated
B.Their hosts are uniformly distributed
C.Their eggs always hatch immediately
D.Their feeding occurs only after harvest
Correct Answer: Their populations may be spatially aggregated
Explanation:
Patchy distribution can make limited soil sampling unrepresentative, allowing damaging populations to escape detection.
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46A nematode is recovered from a plant but is absent from surrounding bulk soil. Which explanation is most consistent with nematode ecology?
Habitat and diversity
Hard
A.It must be a free-living bacterial feeder
B.It necessarily originated from irrigation water
C.It cannot complete any developmental stage
D.It may occupy a protected endophytic habitat
Correct Answer: It may occupy a protected endophytic habitat
Explanation:
Some nematodes live within roots, stems, bulbs, seeds, or other plant tissues, so bulk-soil sampling may miss them.
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47Which development most changed modern nematode diagnosis from morphology-centered identification toward an integrative approach?
Evolution of nematode research in India and globally
Hard
A.Combining morphology, morphometrics, and molecular markers
B.Using host symptoms as the primary taxonomic character
C.Replacing field surveys with greenhouse observations
D.Classifying species only by their geographic origin
Correct Answer: Combining morphology, morphometrics, and molecular markers
Explanation:
Integrative taxonomy resolves cryptic species and strengthens identifications by combining independent lines of evidence.
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48Why did the expansion of intensive agriculture increase the strategic importance of nematology in India and worldwide?
Evolution of nematode research in India and globally
Hard
A.It increased repeated cultivation of susceptible hosts
B.It eliminated nematode survival between crop cycles
C.It made nematode damage independent of soil conditions
D.It reduced host continuity across production systems
Correct Answer: It increased repeated cultivation of susceptible hosts
Explanation:
Monoculture, short rotations, and intensive production can amplify nematode populations and increase selection pressure on management practices.
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49A research program shifts from identifying individual nematode species to studying suppressive soils, host resistance, and cropping systems. What does this shift represent?
Evolution of nematode research in India and globally
Hard
A.A rejection of epidemiology in favor of morphology
B.A move from descriptive taxonomy toward systems-based management
C.A return from molecular biology to symptom classification
D.A replacement of field research by laboratory culture
Correct Answer: A move from descriptive taxonomy toward systems-based management
Explanation:
Modern nematology integrates biology, ecology, agronomy, economics, and molecular tools to manage nematodes within production systems.
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50Which research strategy would best distinguish a genuinely emerging nematode problem from improved detection of a long-established species?
Evolution of nematode research in India and globally
Hard
A.Compare damage estimates without accounting for host area
B.Use only recent symptom reports from commercial fields
C.Infer emergence from the first published species name
D.Compare historical samples using standardized detection methods
Correct Answer: Compare historical samples using standardized detection methods
Explanation:
Apparent emergence can result from better sampling or diagnostics; comparable historical and current methods help separate real expansion from improved detection.
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51Why can a nematode with modest average yield effects still be economically important at regional scale?
Economic importance of nematodes
Hard
A.Nematodes cause identical damage in every field
B.Regional production is unaffected by crop price
C.Small losses multiplied across extensive acreage can be substantial
Correct Answer: Small losses multiplied across extensive acreage can be substantial
Explanation:
Economic importance depends on affected area, crop value, management costs, and market effects, not only on percentage loss in individual fields.
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52Which factor would most likely cause the economic threshold for nematode management to be lower in one crop than another?
Economic importance of nematodes
Hard
A.The crop is grown in a field with greater soil depth
B.The crop has a lower market value
C.The crop has high value and limited damage tolerance
D.The crop tolerates root injury more effectively
Correct Answer: The crop has high value and limited damage tolerance
Explanation:
High crop value and low tolerance mean that relatively small nematode populations can justify management expenditures.
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53A nematode management practice increases yield but also raises production costs and reduces marketable quality. Which measure best evaluates its economic success?
Economic importance of nematodes
Hard
A.Net return from marketable yield
B.Nematode population decline alone
C.Number of nematodes killed per gram of soil
D.Gross yield increase alone
Correct Answer: Net return from marketable yield
Explanation:
Economic evaluation should account for marketable output, product value, treatment costs, and quality-related price differences.
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54Two fields have the same final nematode density, but one shows greater yield loss. Which explanation is most plausible?
Impact on crop yield
Hard
A.Nematodes affect yield only through direct tissue consumption
B.The fields necessarily have identical damage histories
C.The crops may differ in host susceptibility and stress exposure
D.Final density always predicts loss better than initial density
Correct Answer: The crops may differ in host susceptibility and stress exposure
Explanation:
Yield response depends on host genotype, nematode species, initial inoculum, soil conditions, crop stage, and interacting stresses.
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55Why may early nematode infection reduce yield even when plants show no obvious above-ground symptoms?
B.Root damage can reduce water and nutrient acquisition before canopy symptoms appear
C.Nematodes remain inactive until seed maturation
D.Yield formation is unrelated to root system function
Correct Answer: Root damage can reduce water and nutrient acquisition before canopy symptoms appear
Explanation:
Subclinical root injury can impair resource uptake and reproductive development before visible wilting, chlorosis, or stunting develops.
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56A resistant cultivar maintains yield in a nematode-infested field but supports a gradual increase in nematode density. What is the principal long-term concern?
Impact on crop yield
Hard
A.Yield stability proves population suppression
B.The cultivar may be tolerant but not resistant
C.Nematode density is irrelevant when symptoms are absent
D.The cultivar must be immune to all nematodes
Correct Answer: The cultivar may be tolerant but not resistant
Explanation:
Tolerance limits yield loss without necessarily reducing nematode reproduction, allowing population buildup and risk to later susceptible crops.
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57Which outcome best illustrates a nematode effect on crop quality rather than merely on yield quantity?
Impact on quality
Hard
A.Root length increases without yield change
B.Tubers develop internal discoloration and reduced market grade
C.Fewer plants emerge per unit area
D.Field size decreases after land preparation
Correct Answer: Tubers develop internal discoloration and reduced market grade
Explanation:
Quality effects alter appearance, composition, processing performance, storability, or grade even when total harvested mass is not greatly reduced.
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58A nematode infestation causes uneven fruit size but little change in total fruit weight. Which interpretation is most appropriate?
Impact on quality
Hard
A.Quality and grade losses may occur despite stable aggregate yield
B.The nematode has increased crop uniformity
C.The symptom proves that the nematode is nonparasitic
D.There is no economic impact because total weight is stable
Correct Answer: Quality and grade losses may occur despite stable aggregate yield
Explanation:
Market returns often depend on size uniformity and grade, so quality penalties can occur without a major reduction in total weight.
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59Why can the detection of a regulated plant-parasitic nematode affect international trade even when the shipment shows no visible crop damage?
Impact on international trade
Hard
A.Trade restrictions apply only to nematodes that reduce grain weight
B.Asymptomatic shipments are automatically considered pathogen-free
C.Quarantine decisions are based only on visible symptoms
D.The organism may threaten crops in the importing region
Correct Answer: The organism may threaten crops in the importing region
Explanation:
Quarantine systems address potential establishment and spread, and regulated nematodes may be present without visible symptoms.
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60A country requires soil-free planting material because a nematode survives in root-associated soil. What risk is the measure primarily intended to reduce?
Impact on international trade
Hard
A.Transmission through contaminated soil attached to commodities
B.Loss of nematode diversity in the exporting country
C.Improvement of crop quality through soil removal
D.Mutation of nematodes during long-distance transport
Correct Answer: Transmission through contaminated soil attached to commodities
Explanation:
Soil adhering to roots, machinery, or planting material can carry nematodes and facilitate their movement across borders.
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