Ann. Tabac, 1985, Sect. 2-19, p. 91-100., ISSN.0399-0354

A new procedure for the cotyledon test

The principle of the cotyledon test, an accelerated breeding technique, relies on two elements which are necessary for the expression of the seedling genes at the cotyledon stage : the magnesium supply and the factor of continuous light. When these conditions are not strictly adhered to, the efficiency of the test is reduced. This situation may occur when the sand used as a support for germination contains elements other than magnesium Mg2+. To avoid this drawback the authors propose a modification of the technique : the seedlings are subjected to a continuous magnesium supply, thanks to which the absorption of other cations is limited by antagonism, and which, at the same time, prevents the inevitable toxic phenomena occurring when Mg2+ concentration in the sand solution is increased. Under these conditions, a better expression of the genes linked to the resistance to Peronospora tabacina and to the production of chlorogenic acid and nicotine was obtained as compared to the conventional method.