AQA · GCSE · Biology

    Course version: 8461 · Version from Sept 2018

    Tobacco mosaic virus (TMV) is a widespread plant pathogen affecting many…

    Full specification wording

    Viral diseases: Tobacco mosaic virus (TMV) is a widespread plant pathogen affecting many species of plants including tomatoes.

    TMV is transmitted mechanically, not by vectors.

    Checked against the AQA 8461 specification (opens in a new tab) on .

    • Point 8 of 9
    • 2 key terms

    Study notes

    From the checked teaching notes for this specification point.

    The idea

    TMV is transmitted mechanically, not by vectors. Tobacco mosaic virus is a plant pathogen affecting many species, including tomatoes. It is described as widespread because it occurs in many regions and survives in plant debris, soil, and sap. It damages commercial glasshouse crops and garden plants. The virus spreads when sap containing virus particles enters a plant through tiny wounds, for example during handling or pruning. Once inside, it hijacks the plant's cells to make more virus particles. Because it is a virus, antibiotics are useless; control relies on removing infected plants, disinfecting tools, and using resistant varieties.

    What earns the marks

    • TMV is transmitted mechanically, not by vectors.
    • TMV is a virus, so it is a pathogen that infects plants.
    • Control measures include removing infected plants, sterilising tools and growing resistant varieties.

    Common mistakes and how to put them right

    • Assuming TMV is spread by vectors.

      Put it right: TMV is transmitted mechanically through wounds.

    • Treating TMV as a bacterium and suggesting antibiotics.

      Put it right: TMV is a virus, so antibiotics are ineffective.

    • Thinking the mosaic pattern is caused by a mineral deficiency.

      Put it right: The pattern is a symptom of viral infection.

    Exam tips

    • Quote the full name tobacco mosaic virus at least once, then use TMV.
    • Link the word widespread to persistence in soil or plant debris, not just to visible symptoms.

    Try the lesson

    The start of the Viral diseases: Tobacco mosaic virus (TMV) is a widespread plant pathogen affecting many species of plants including tomatoes. lesson, made from checked teaching notes for this specification point.

    Have a go first

    Which of the following is a correct description of tobacco mosaic virus (TMV)?

    Listen

    TMV is transmitted mechanically, not by vectors. Tobacco mosaic virus is a plant pathogen affecting many species, including tomatoes. It is described as widespread because it occurs in many regions and survives in plant debris, soil, and sap. It damages commercial glasshouse crops and garden plants. The virus spreads when sap containing virus particles enters a plant through tiny wounds, for example during handling or pruning. Once inside, it hijacks the plant's cells to make more virus particles. Because it is a virus, antibiotics are useless; control relies on removing infected plants, disinfecting tools, and using resistant varieties. A strong answer earns marks for these points. TMV is transmitted mechanically, not by vectors. TMV is a virus, so it is a pathogen that infects plants. Control measures include removing infected plants, sterilising tools and growing resistant varieties. A common slip: Assuming TMV is spread by vectors. Instead, TMV is transmitted mechanically through wounds. Exam tip: Quote the full name tobacco mosaic virus at least once, then use TMV.

    See it

    A top-down flowchart. The top node reads 'Tobacco mosaic virus (TMV)' and points down to 'Viral plant pathogen'. From that node, four branches lead down. The first branch goes to 'Affects many plant species', which leads to 'Tomatoes (named example)'. The second goes to 'Widespread', which leads to 'Persists in plant material'. The third goes to 'Transmitted mechanically, not by vectors', which leads to 'Sap enters plant through tiny wounds', which leads to 'Hijacks plant cells to make more virus particles'. The fourth goes to 'Antibiotics are useless', which leads to 'Control: remove infected plants, disinfect tools, use resistant varieties'.
    Shows TMV as a widespread viral plant pathogen affecting tomatoes, spreading mechanically through wounds, with antibiotics useless and control by removal, disinfection and resistant varieties.

    Key words

    Say what each word means before you turn the card.

    Viral infection

    Try answering aloud or in your head before turning the card.

    Disease control

    Try answering aloud or in your head before turning the card.

    See every definition
    Viral infection
    A virus hijacks the plant's cells to make more virus particles, and the mosaic pattern is a symptom of it.
    Disease control
    Control relies on removing infected plants, disinfecting tools, and using resistant varieties, because antibiotics are useless against a virus.

    Label the diagram

    Some boxes have lost their names. Pick the right name for each number.

    The diagram again, with 3 boxes numbered instead of named. A top-down flowchart. The top node reads 'Tobacco mosaic virus (TMV)' and points down to 'Viral plant pathogen'. From that node, four branches lead down. The first branch goes to 'Affects many plant species', which leads to 'Tomatoes (named example)'. The second goes to 'Widespread', which leads to 'Persists in plant material'. The third goes to 'Transmitted mechanically, not by vectors', which leads to 'Sap enters plant through tiny wounds', which leads to 'Hijacks plant cells to make more virus particles'. The fourth goes to 'Antibiotics are useless', which leads to 'Control: remove infected plants, disinfect tools, use resistant varieties'.

    • 1Box 1

    • 2Box 2

    • 3Box 3

    0 of 3 labelled

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