ROOTSTOCK EFFECTS ON THE REACTION OF CYPR ESS TO SEIRIDIUM-CARDINALE BARK CANKER DISEASE

Reciprocal grafting was carried out on Cupressus sempervirens resistan t or susceptible clones previously grown from self-rooting. When the s cions were 10 mm in diameter, they were inoculated and then infection by Seiridium cardinale was observed over 2 years. The rootstock had no noticeable effect on the basic behaviour of scions. The susceptible c lones died while resistant clones survived However, the reactions of r esistant clones to disease and scarring varied according to the rootst ock clone. Resistance was correlated with tree growth, namely to the v igour conferred to scions by the rootstock. Resistance and growth, bot h induced by meristematic activity show a good linear regression. It w ould be interesting to select vigorous rootstock clones, in order to i ncrease resistance or tolerance as a consequence of an earlier compart mentalization and decrease the heterogeneity resulting from grafting o n seedlings at random. Such a progress would require a good knowledge of self-rooting techniques.