Unit 4: Symptomatology and Disease Interaction - Practice Quiz

1 What does the term symptom mean in plant nematology?

2 Which root symptom is most commonly associated with root-knot nematodes?

3 Which is a common above-ground symptom of nematode damage?

4 Nematode-damaged plants often occur in irregular patches in a field because nematodes are usually:

5 How can nematode feeding increase the entry of other plant pathogens?

6 A disease involving a nematode and another pathogen is commonly called a:

7 What does it mean when nematodes predispose a plant to disease?

8 What is a likely result when a nematode and another pathogen act synergistically?

9 Which fungal disease is commonly intensified by root-knot nematode infection?

10 Why can root-lesion nematodes favor infection by soil-borne fungi?

11 In a nematode-fungus disease complex, the fungus usually enters the plant through:

12 Which nematode genus is well known for interacting with Fusarium wilt fungi?

13 How do plant-parasitic nematodes commonly assist bacterial infection?

14 Root-knot nematodes may increase the severity of bacterial wilt caused by:

15 The wheat seed-gall nematode Anguina tritici is associated with which bacterial disease?

16 In tundu disease of wheat, Anguina tritici mainly helps the bacterium by acting as a:

17 What role do some plant-parasitic nematodes play in viral diseases?

18 Which nematode genus is commonly called a dagger nematode and can transmit plant viruses?

19 Which group of nematodes is known for transmitting tobacco rattle virus?

20 How does a virus-vector nematode usually introduce a plant virus into a healthy root?

21 A vegetable field contains irregular patches of stunted and chlorotic plants. The symptoms become more severe during dry periods, but no distinctive lesions occur on the leaves. Which action would best help determine whether plant-parasitic nematodes are involved?

22 Roots collected from a declining crop have numerous short, swollen branches but no large galls. Which nematode-related symptom is most consistent with this observation?

23 A farmer observes poor crop growth in circular to irregular field patches. Plants outside the patches grow normally under the same fertilizer program. Why does this distribution support a possible nematode diagnosis?

24 Two root samples show swellings. Sample 1 has smooth galls that are continuous with the root tissue, while Sample 2 has small bodies attached to the root surface that can be removed. What is the best interpretation?

25 Plants inoculated with a weakly pathogenic fungus remain nearly healthy, but plants inoculated with both the fungus and a root-lesion nematode develop severe root rot. Which interpretation best fits the result?

26 A root-knot-resistant cultivar becomes severely wilted when exposed to both a wilt pathogen and a high nematode population. Which nematode effect most directly explains this change?

27 A crop has a moderate nematode population that causes little visible damage under adequate irrigation. After drought begins, severe wilting and yield loss occur. What is the most likely explanation?

28 In a controlled experiment, disease severity is recorded as 15% with a nematode alone, 20% with a bacterium alone, and 70% with both organisms. What does the combined treatment suggest?

29 A Fusarium-resistant tomato cultivar develops wilt when roots are heavily infected by root-knot nematodes. Which mechanism best explains the apparent breakdown of resistance?

30 A researcher applies a nematicide to soil containing both Pratylenchus and a root-rotting fungus. Root rot declines even though the fungal population remains similar. Which conclusion is most reasonable?

31 Disease is most severe when a root-lesion nematode is introduced seven days before a fungal pathogen. Why can the order of inoculation matter?

32 Which management program is most appropriate for a crop affected by a nematode–fungus root disease complex?

33 Tomato plants exposed to both root-knot nematodes and a bacterial wilt pathogen wilt earlier than plants exposed to the bacterium alone. Which nematode activity most likely promotes this outcome?

34 A bacterial pathogen enters plants mainly through wounds. Which nematode group would most directly increase infection opportunities by repeatedly migrating through root tissue?

35 A bactericide lowers bacterial wilt severity only slightly in a field with a large root-knot nematode population. Which additional measure is most likely to improve control?

36 In sterile soil, a nematode causes mild root damage. In naturally infested soil, the same nematode density causes extensive soft decay associated with bacteria. What is the best explanation?

37 A grapevine virus continues to spread slowly through a field even after virus-infected vines are removed. Soil samples contain dagger nematodes. Which process most likely maintains local spread?

38 A field has tobacco rattle virus and stubby-root nematodes. Which management decision addresses the biological link between them most directly?

39 A nematode acquires a plant virus from an infected root but fails to transmit it to healthy plants. Which explanation best reflects the specificity of nematode transmission?

40 A soil fumigation treatment sharply reduces a virus-vectoring nematode, but healthy plants are later infected after nematodes recolonize from an untreated field edge. Which conclusion is best supported?

41 A field contains irregular patches of stunted, chlorotic plants that wilt during midday but partially recover at night. The roots lack conspicuous galls but have shortened laterals and numerous small brown lesions. Which diagnosis is best supported by this symptom pattern?

42 Two root samples show swellings. Sample I has knots that are continuous with the root tissue, while Sample II bears small lemon-shaped bodies attached to otherwise distinct roots. Which interpretation is most accurate?

43 Plants in a uniformly fertilized field exhibit severe stunting in elongated bands parallel to the direction of cultivation. Nematode counts are high within the bands but low between them. What is the strongest interpretation of the spatial pattern?

44 A susceptible crop has extensive root galling but only moderate shoot suppression, whereas another field has little galling but severe stunting. Which conclusion is scientifically most defensible?

45 In a factorial experiment, mean disease severities are 5% in untreated plants, 20% with a nematode alone, 25% with a fungus alone, and 75% with both organisms. If independent additive effects predict approximately 40% severity after adjustment for the common baseline, what does the combined treatment indicate?

46 Which experimental result most strongly demonstrates predisposition rather than simple mechanical inoculation of a secondary pathogen?

47 A nematode increases root exudation, alters host defense signaling, and creates nutrient-rich feeding sites. Which consequence best integrates these effects in a disease complex?

48 A resistant cultivar limits nematode reproduction but still allows brief juvenile penetration. In pathogen-infested soil, disease remains higher than in nonpenetrated controls. Which mechanism can best explain this result?

49 In a tomato wilt complex, Meloidogyne infection increases Fusarium oxysporum disease even when roots are inoculated with the fungus several days after nematode penetration. Which mechanism is most consistent with this sequence?

50 Potato early dying becomes severe at inoculum densities of Verticillium dahliae that cause little disease in the absence of Pratylenchus penetrans. What does this observation most directly imply?

51 A fungicide suppresses fungal colonization in nematode-infected roots but does not restore yield to the nematode-free level. Which conclusion best fits the evidence?

52 A split-root plant has nematodes inoculated on one root half and a wilt fungus inoculated on the physically separate half. Fungal disease is enhanced despite no detectable nematode migration. Which inference is best supported?

53 Root-knot infection precedes inoculation with Ralstonia solanacearum, and bacterial wilt subsequently increases. Which explanation best accounts for enhancement beyond simple surface wounding?

54 Which relationship is most accurately described as a specialized association in which a seed-gall nematode introduces or facilitates a bacterium responsible for yellow ear rot or tundu disease of wheat?

55 After stem nematode invasion, bacterial soft rot expands rapidly through macerated tissues. Which causal model best explains the complex?

56 A bacterium is recovered from the external surface of field nematodes, but surface-sterilized nematodes do not transmit disease under controlled conditions. What conclusion is most justified?

57 A vineyard has fanleaf degeneration, and dagger nematodes are recovered from the rhizosphere. Which vector-virus pairing most specifically supports nematode-mediated spread?

58 A virus is retained in the feeding apparatus of an ectoparasitic nematode, does not replicate in the vector, and is inoculated during later feeding. Which transmission description is most accurate?

59 A potato field exhibits corky ringspot symptoms and abundant stubby-root nematodes. Which combination is the most coherent etiological hypothesis?

60 Two closely related virus isolates infect the same plant species, but only one is transmitted by a particular Xiphinema population. Both reach similar concentrations in roots. Which explanation best fits this specificity?