Genetic variability of canker resistance trait in Cupressus sempervirens L. progenies

The genetic basis of the resistance of the common cypress to Seridium cardinale was investigated in the environmental condition of Central Italy. The cortical canker caused by the fungus affects the common cypress since the 1970's in Europe and the genetic improvement for the resistance is considered an effective tool to cope with the bark canker epidemics. General and specific combining abilities of thirty mother plants were estimated by means of a North Carolina II mating design including four cypress clones as testers showing divergent degree of canker resistance. The strong differences among testers and general combining effects showed that the character under investigation has an additive genetic control. The best combinations were identified within the families from the crosses with the resistant tester. The results however showed that an early classification of the mother trees, based on a simple unreplicated resistance screening test, is not effective to predict the behaviour in crosses. Replicated screening tests based on morpho-physiological and chemical characteristics are suggested, because the bark canker resistant traits is not sufficiently stable in cypress trees.