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In 2004, abundant flowering of Norway spruce (Picea abies (L.) Karst.) was observed in two second- generation seed orchards: (1) ‘Outbreeding’, promoting crossing between clones of five geographically distant populations; and (2) ‘Kolonowskie’, restoring a population whose offspring exists only in an international experiment (IUFRO 1964/1968). In bothseed orchards, female strobili were produced by 91.3% and 91.7% of clones, represented by 64.1% and 55.5% of grafts, respectively, and statistically significant differences between clones were found in the number of mature cones. In the case of the seed orchard ‘Outbreeding’, the number of mature cones in individual clones was significantly correlated with latitude of the origin of maternal populations (r = 0.8826, p = 0.0470). The majority (95%) of cones in seed orchards ‘Outbreeding’ and ‘Kolonowskie’ were produced by only 28.2% and 38.5% of all clones, and 21.4% and 25.7% of all grafts, respectively. These data attest to a disparity between the level of genetic diversity in seed orchard progeny resulting from the observed numbers of cone-bearing clones and grafts and the genetic diversity expected from the actual participation of clones and grafts in seed orchard composition. The estimated seed production per 1 ha of seed orchard area in 2004 reached 21.05 kg for ‘Outbreeding’ and 21.72 kg for ‘Kolonowskie’.
The abundant flowering, observed in 2004 in a model outbreeding seed orchard established in Kórnik, Poland, promoted crossing between clones of five geographically distant populations of Norway spruce. The clones were selected from a group of ca. 1100 provenances participating in the international IUFRO 1964/68 experiment and performing best in terms of growth traits and adaptability. In the seed orchard, 91.3% of clones and 64.1% of grafts produced female and/or male strobili. Statistically significant differences between the clones were only found in the number of mature cones produced. The mean number of mature cones in individual clones was also significantly correlated with the latitude of the place of origin of maternal populations (r = 0.88, p = 0.047). The nearly equal percentages of clones representing each of the five populations in the outbreeding seed orchard (from 23.2 to 17.5%) resulted finally in the highly unequal production of full seeds by each population (from 62.9 to 0.7%). These data provide evidence to suggest that the level of genetic diversity in the progeny, expected from the number of growing clones, diverges from the level resulting from the contribution of clones to the full seed production which is an effective measure of the genetic composition of progeny. To avoid this divergence, an outbreeding seed orchard could be established with unequal proportions of clones from different provenances, considering the knowledge of their flowering phenology, and individual variation in flowering and cone production.
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