The photo below shows wheat plants showing symptoms on some leaves. The affected plants also show stunting of growth. You examined the leaves but no distinct structures were observed under dissecting microscope. Leaf sample was cultured on PDA (Potato Dextrose Agar) and Nutrient Agar (NA); however, no microorganism growth was observed. What is the most likely cause of the symptoms?

Question

BlackTom AI · Accepted Answer

Virus infections of plants typically produce chlorotic streaks, banding or mosaic patterns and systemic effects such as stunting, and they cannot be grown on artificial culture media because they are obligate intracellular parasites.

1) Relevant knowledge points and concepts
- Viruses cause patterns of chlorosis, mosaics, streaks or ring spots and often stunt growth because they interfere with host metabolism and movement of nutrients/hormones.  
- Fungi and bacteria usually produce visible structures (spores, pustules, fruiting bodies) or will grow on PDA (fungi) or NA (bacteria).  
- Nutrient deficiencies produce predictable, often symmetric symptoms (interveinal chlorosis, older vs younger leaf patterns) across many plants, not random streaking plus stunting in individual plants.  
- Genetic variation is typically stable, uniform across plants of the same cultivar, and not associated with patchy stunting.  
- Vascular wilts/soilborne fungi or bacteria often show vascular discoloration, wilting or can be cultured from diseased tissue.

2) Step‑by‑step reasoning
- Observation A: chlorotic streaks/stripes on leaves and stunted plants. These are classic viral symptom types.  
- Observation B: no distinct structures under a dissecting microscope (no fungal spores/pustules). This argues against a foliar fungal pathogen (e.g., rust) that would show pustules/spores.  
- Observation C: leaf samples plated on PDA and NA produced no growth. Fungi and bacteria would typically grow on those media; viruses will not grow on them because they need living host tissue.  
- Combine A–C: streaking + stunting + no microscopic pathogen structures + no culture growth = most consistent with a virus.

3) Intermediate/diagnostic steps (non‑numerical): elimination of organisms that produce visible structures or culture growth; recognition that viruses require molecular/serological tests (ELISA, PCR) for confirmation.

4) Why the correct answer is correct
The pattern of symptoms (striping/mosaic and stunting) together with the inability to isolate any microorganism on standard culture media and lack of visible fungal/bacterial structures point to a virus as the causal agent.

5) Why other options are incorrect (brief)
- Rust disease: would show characteristic pustules with spores visible microscopically.  
- Nutrient deficiency: tends to produce predictable, often symmetrical patterns across plants (e.g., interveinal chlorosis) rather than random streaks and stunting.  
- Natural genetic variation: would be uniform and not cause patchy stunting or progressive chlorosis in some plants.  
- Vascular/soilborne pathogen: such organisms (fungi/bacteria) are often culturable or produce vascular discoloration/other signs; absence of growth and signs makes this less likely.

Conclusion: The chlorotic streaks and stunting are most likely symptoms of a disease caused by a virus, which matches the provided correct answer.

类似问题

Citrus greening disease was first introduced to which state?

What structures can be found in the fungal disease shown in the photo?

Which of the following statements correctly describe post-harvest disease infection?

Which method listed below is correct about non-visual symptoms caused by plant pathogens?

What does it tell you when a non-wounded inoculated fruit did not produce any symptoms whereas, wounded inoculated fruit became infected?

You notice one of the plants in your glasshouse trial shows severe necrosis, dieback and chlorosis on the leaves as shown in the photo below. You suspect a bacterial infection of the leaves. What will be your next step to confirm your diagnosis?

Which of the following statement are CORRECT about root and wood rot fungi that infect plants?

What organism causes the deadly “sudden oak death disease”?

更多留学生实用工具

智能学习助手

风格化写作助手

论文查重助手

文献引用助手

课堂转译助手

课堂笔记助手

Quiz搜索助手

学校历年真题

智能刷题助手

智能匹配练习

希望你的学习变得更简单