VARIATION AND INHERITANCE OF RESISTANCE TO CYPRESS APHID, CINARA-CUPRESSI BUCKTON IN CUPRESSUS-LUSITANICA MILLER

Cupressus lusitanica seedlings from open-pollinated seeds of 18 famili es were inoculated with day-old first instar Cinara cupressi. Aphid su rvival was used to determine the genetic basis and inheritance of resi stance to the insect. There was marked variation in aphid survival bot h between and within families. An individual-tree narrow-sense heritab ility of 0.76 +/- 0.30 shows strong additive genetic control which cou ld allow effective selection and breeding for resistance. Resistant pa rents produced resistant progeny while susceptible parents produced su sceptible progeny. There were notable exceptions as some susceptible p arents produced highly resistant progeny, indicating that they had acq uired pollen from resistant neighbours. Recovery of aphid damaged tree s is evident implying that care should be taken in selecting for resis tance. The strong additive variance and potentially high heritability indicate that one cycle of selection may yield a resistant population, while intraspecific crossing may give better results. Implications of the results in a C. lusitanica breeding programme are discussed.