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GCSE Biology · key term
A knobbly swelling formed by abnormal, disorganised growth of plant tissue.
Used by OCR
Paper 1 (Foundation), Paper 2 (Foundation), Paper 3 (Higher), Paper 4 (Higher)
Revise: Plant DiseasesCrown gall is caused by the bacterium Rhizobium radiobacter, also known as Agrobacterium tumefaciens. It affects the roots and stems of many woody and herbaceous plants, including some fruit crops, vegetables and ornamental plants.
For each named disease, link it to the correct pathogen type: tobacco mosaic virus—virus; ash dieback—fungus; crown gall—bacterium.
Do not mistake harmless nitrogen-fixing nodules on the roots of pea-family plants for crown gall.
For crown gall, connect the stages clearly: bacteria enter through a wound, alter plant cells and cause disorganised tissue growth, producing a gall.
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