DIALLEL ANALYSIS AND INTEGRATION IN THE B REEDING PROGRAM OF MARITIMEPINE OF SENSITIVITY TO TWISTING RUST

Maritime pines of the Landes provenance from two diallel mating design s have been studied between the third and fifth growing seasons for se nsitivity to twisting rust (Malampsora pinitorqua), growth and phenolo gy. The best criterion for sensitivity to twisting rust is the percent age of shoots with at least one canker occurring in the same growing s eason. Expression of rust sensitivity by this trait is partly dependen t on vigour (positive correlation) and lateness (negative correlation) . However, the major part of between-families variability for percenta ge of attacked shoots may be related to the original behaviour for thi s trait, uncorrelated to vigour and phenology. Genetic analysis of sen sitivity has shown that the part of variability attributable to matern al effects is unsignificant. The same is true for genetic variability of dominance effects. On the other hand, additive genetic variability is great and highly significant. This variability would enable to real ize important genetic gains for Melampsora resistance in Landes origin of maritime pine. Genetic correlation between rust sensitivity and po lycyclism seems to be non-existent. Genetic correlation between rust s ensitivity and juvenile growth expressed by 5 years height is not stab le. It has a minor potential influence on integration of rust resistan ce criterion in the breeding program of maritime pine where volume gro wth is an important goal.