Introduction aux sciences du vivant

• How to classify viruses ? What nomenclature to use ?

  05/10/2011 Administrateur

  Virology is a recent subject. One could expect a structured nomenclature and a well codified use. This is not the case, but the subject benefits from mitigating circumstances.

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  Why study plant viruses ?

  05/10/2011 Administrateur

  Virus diseases of plants have an important economical effect. They cause a reduction of the plant’s strength and very often modify the aspect of certain plant organs. In all cases, a decrease of more or less importance in yield is observed.

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• What is a viroid and how does-it differ from a virus?

  05/10/2011 Administrateur

  Viroids have been discovered in 1971 by the specialist of plant diseases T. O. Diener. These particles, smaller than viruses, are made of a single stranded RNA and do not have protein coat (capsid).

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• What is a virus ?

  05/10/2011 Administrateur

  Viruses are pathogenic organisms of very small dimension, invisible to optical microscopes. They can’t multiply themselves out of a living cell, they are obligatory parasites.

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• What are the consequences of weediness ?

  05/10/2011 Administrateur

  Losses in production due to weeds affect the world food production, but more particularly that of developing countries. It’s actually in tropical zone that the loss estimate is the highest: 25 % of production as opposed to 5 % in developed countries. Already in 1967, the first world analysis showed that in Africa, these losses were between 10 and 56%.

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