The monoterpene composition of Picea abies and Abies alba resin was analysed in relation to growth by Heterobasidion spp. Fifteen-year-old P. abies and A. alba trees were inoculated on branches with three species of Heterobasidion annosum s.l. After 4 months of incubation, each host was colonized to a significantly greater degree by the pathogen specific to that host (H. parviporum on P. abies, H. abietinum on A. alba) than by the other fungi. Analysis of the enantiomeric monoterpene profiles in the spruce and fir showed that the response in terms of the relative proportions of the monoterpene compounds in the resin differed between tree species. Following challenge with Heterobasidion spp., A. alba trees did not show changes in monoterpene composition in addition to those in the wounding response (increase in ())-a-pinene and ())-camphene, and decrease in b-phellandrene). In P.abies, ())-a-pinene, (+)-a-pinene and d-3-carene increased following Heterobasidion attack but not after wounding alone.

Thirty-five Norway spruce, Picea abies, clones from Sweden were tested for resistance to Heterobasidion parviporum. Rooted cuttings of the clones were planted in Italy and Greece and cultivated for two growing seasons before inoculation with H. parviporum. Extent of infection was determined 6 weeks later. The results were compared to those of earlier inoculations in Sweden. Plant growth traits were under strong genetic control in all locations with broad sense heritability estimates between 0.14 and 0.54. Lesion and fungal extension heritabilities were moderate, H 2 ranged from 0.09 to 0.20, and exhibited rather large genetic variation. There was significant genotypic correlation between Italy and Greece with respect to both lesions and fungal extension. No such correlations were found between Sweden and the two other countries. The lack of repeatability in testing susceptibility is unsatisfactory. It could be explained by C-effects associated with propagation of the host plants. Height growth correlated significantly and positively among all countries.

A B S T R A C TTo study simultaneous biotic and abiotic stress effects on monoterpene mediated defence response, four-year-old seedlings of two clones of Picea abies (c386: "relatively resistant" c386; c171: "relatively susceptible" clone 171) were inoculated with an isolate of rot fungus Heterobasidion parviporum and simultaneously subjected to a drought stress recovery cycle. Fungal growth into the wood was generally higher in well-watered (W) than in drought-stressed (D) plants. As predawn water potential decreased, gas exchange and maximal photochemical efficiency of PSII also declined. Water potential and chlorophyll fluorescence showed differences between clones in D plants, c386 being more tolerant than c171, while stomatal conductance and net photosynthesis differed between clones in W plants; c171 showing higher values than c386. A recovery of physiological functions was observed after re-watering. The clones showed different constitutive monoterpene profiles. The infection generally caused some extensive compositional changes in the relative contents of several monoterpenes and their enantiomers; also, sterile infection (wounded only samples) affected the relative proportions of monoterpenes, although to a lesser extent than reactions elicited by the fungus. The trend in monoterpene response to disease treatments was the same in D and W plants of both clones. In particular, higher proportion of δ-3-carene was found constitutively in c386 in comparison with c171; besides, infection with H. parviporum increased the relative contents of δ-3-carene in all the samples, even if proportions of this monoterpene in wounded plus inoculated tissues of c386 were significantly higher than cortical tissues from non-inoculated branches only in W seedlings 44 days after treatment.Although drought stress decreased the total absolute contents of monoterpenes, total monoterpene concentrations significantly increased in response to infection by H. parviporum.

SummaryAmplification profiles of the M13 minisatellite core sequence from 47 isolates of Heterobasidion annosum s.l., collected mostly from Abies alba in different European countries, were analysed in comparison with profiles of four isolates of H. annosum s.s. and three isolates of H. parviporum. Genetic variation within and among groups of populations was studied by analysis of molecular variance. A dendrogram constructed with the Neighbor-Joining method differentiated the three species from each other. Isolates of H. abietinum from Balkan peninsula, Italian peninsula and French Pyrenees each separated into clusters according to geographical origin. Such clear geographic clustering was not detected among isolates from central Europe. The variations between H. abietinum isolates in relation to the migration history of Abies are discussed.

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