Miscanthus is a genus of high‐yielding perennial rhizomatous grasses with C4 photosynthesis. Extensive field trials of Miscanthus spp. biomass production in Europe during the past decade have shown several limitations of the most widely planted clone, M. × giganteus Greef et Deu. A 3‐yr study was conducted at five sites in Europe (Sweden, Denmark, England, Germany, and Portugal) to evaluate adaptation and biomass production potential of four acquisitions of M. × giganteus (No. 1–4) and 11 other genotypes, including M. sacchariflorus (Maxim.) Benth. (No. 5), M. sinensis Andersson (No. 11–15), and hybrids (No. 6–10). At each site, three randomized blocks containing a 5‐ by 5‐m plot of each genotype were established (except in Portugal where there were two blocks) with micropropagated plants at 2 plants m−2. In Sweden and Denmark, only M. sinensis and its hybrids satisfactorily survived the first winter following planting. Mean annual yields across all sites for all surviving genotypes increased each year from 2 t ha−1 dry matter following the first year of growth to 9 and 18 t ha−1 following the second and third year, respectively. Highest autumn yields at sites in Sweden, Denmark, England, and Germany were 24.7 (M. sinensis hybrid no. 8), 18.2 (M. sinensis hybrid no. 10), 18.7 (M. × giganteus no. 3), and 29.1 t ha−1 (M. × giganteus no. 4), respectively. In Portugal, where irrigation was used, the top‐yielding genotype produced 40.9 t ha−1 dry matter (M. sinensis hybrid no. 7). Highest‐yielding genotypes in Sweden and Denmark were among the lowest yielding in Portugal and Germany, demonstrating strong genotype × environment interactions.

The reasons for these requirements can be summarized as follows. Biomass with moisture contents below Miscanthus spp. are high-yielding perennial C 4 grasses, native to 200 to 250 g kg Ϫ1 fresh matter can be stored safely Asia, that are being investigated in Europe as potential biofuels. Production of economically viable solid biofuel must combine high without the danger of self ignition (Clausen, 1994) and biomass yields with good combustion qualities. Good biomass com-burns more efficiently while ash lowers the heating value bustion quality depends on minimizing moisture, ash, K, chloride, N, of the biomass and causes slagging of the boiler heat and S. To this end, field trials at five sites in Europe from Sweden exchangers (Hartmann et al., 1999). High levels of K to Portugal were planted with 15 different genotypes including M. ϫ are undesirable because it decreases the ash melting giganteus, M. sacchariflorus, M. sinensis, and newly bred M. sinensis point, but critical levels will depend on combustion techhybrids. Yield and combustion quality at an autumn and a late winter/ nique. Chloride can lead to corrosion through reaction early spring harvest were determined in the third year after planting with water to form HCl or with K to form gaseous when the stands had reached maturity. As expected, delaying the KCl, both of which are corrosive and reduce boiler life harvest by three to four months improved the combustion quality of (Baumbach et al., 1997). Furthermore, high chloride all genotypes by reducing ash (from 40 to 25 g kg Ϫ1 dry matter), K (from 9 to 4 g kg Ϫ1 dry matter), chloride (from 4 to 1 g kg Ϫ1 dry concentrations can lead to emissions of dioxine and matter), N (from 5 to 4 g kg Ϫ1 dry matter), and moisture (from furane (Siegle and Spliethoff, 1999). Nitrogen concen-564 to 291 g kg Ϫ1 fresh matter). However, the delayed harvest also trations in biofuels need to be as low as possible to decreased mean biomass yields from 17 to 14 t ha Ϫ1 . There is a strong minimize fertilizer off-takes and to reduce emissions interaction among yield, quality, and site growing conditions. Results of NO x during combustion. To avoid SO 2 emissions, show that in northern regions of Europe, M. sinensis hybrids can be biomass S concentrations also need to be as low as recommended for high yields (yielding up to 25 t ha Ϫ1 ), but M. sinensis possible. (nonhybrid) genotypes have higher combustion qualities. In mid-and To date, most research on Miscanthus sp. as an energy south Europe, M. ϫ giganteus (yielding up to 38 t ha Ϫ1 ) or specific crop has concentrated on maximizing the yield of a high-yielding M. sinensis hybrids (yielding up to 41 t ha Ϫ1 ) are more genotypes selected, there were four acquisitions of M. ϫ gigan-

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The pollination pattern in a Scots pine (Pinus sylvestris L.) seed orchard consisting of 28 clones was studied using nine microsatellite (SSR) loci. The nine SSR loci produced unique multilocus genotypes for each of the orchard's 28 clones and allowed paternal assignment of the studied 305 seed using paternity exclusion probability of 99.9 %. Fifty two percent of the studied seeds were sired by outside the orchard pollen sources (i.e., pollen contamination) and as expected, low selfing (2.3 %) was detected. These results are valuable for the evaluation of the seed orchard function and the impact of contamination on the expected genetic gain.

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We have constructed nearly complete linkage maps of Pinus sylvestris (L.) using AFLP markers based on a two-way pseudo-testcross strategy in a full-sib family founded in an advanced breeding program. With 39 primer combinations, a total of 737 markers (320 from the mother and 417 from the father) segregated in a 1:1 ratio, corresponding to DNA polymorphism: heterozygous in one parent and null in the other. In the maternal parent, 188 framework markers were mapped in 12 linkage groups, equivalent to the Pinus haploid chromosome number, with a total coverage of 1,695.5 cM. In the paternal parent, 245 framework markers established a map with 15 linkage groups, spanning a genome length of 1,718.5 cM. The estimated total map length was L(F) = 1,681 cM for the female and L(M) = 1,645 cM for the male using a modified method-of-moment estimator. Combining these values with those estimated from the observed map lengths in both parents, we estimated the genome length in Scots pine to be between 1,600 and 2,100 cM. Our genome coverage was estimated to be more than 98% with a framework marker interval of 20 cM for both parents. Most of the female and male linkage groups were associated through the analysis of the intercross markers.

Genetic parameters were estimated for the diameter-height (d-h) relationship and three other tree stem-form characteristics (total height, breast height diameter, and total tree volume) for data from 10 diallel progeny trials of Scots pine (Pinus sylvestris L.), at about 30 years of age in Sweden. Linear mixed models were fit to the data, where adjustments for intertree competition and microsite heterogeneity were made by means of covariates in a nearest-neighbour analysis. The d-h relationship was analyzed with a covariate (tree height) adjusted model of diameter. Average estimates of the additive coefficient of variation and narrow-sense heritability for the d-h relationship were 7.4% and 0.22, respectively. Estimates of dominance were comparatively small (average dominance: phenotypic variance ratio of 0.04). The results indicate that there is scope to modify the d-h relationship by selection and breeding. Additive genetic correlations between the d-h relationship and height were negative, with a mean of -0.62. Selection for height would thus result in stems that are more slender than average, suggesting that tall trees allocate relatively more resources to height growth than to diameter growth. Selection based on height alone will negatively affect volume gain. Résumé :Les auteurs ont estimé les paramètres génétiques de la relation entre le diamètre et la hauteur (d-h) des arbres et de trois autres caractères de forme de la tige (hauteur totale, diamètre à hauteur de poitrine et le volume total de l'arbre) à partir des données de 10 tests de descendances diallèles de pin sylvestre (Pinus sylvestris L.) âgé d'environ 30 ans en Suède. Des modèles linéaires mixtes ont été ajustés aux données, incluant des ajustements pour la compétition entre les arbres et l'hétérogénéité des microsites effectués au moyen de covariables dans une analyse du plus proche voisin. La relation d-h a été analysée à l'aide d'un modèle de diamètre ajusté pour une covariable (la hauteur de l'arbre). Les estimations moyennes du coefficient de variation additive et de l'héritabilité au sens strict pour la relation d-h affichaient des valeurs respectives de 7,4 % et 0,22. Les estimations de dominance étaient comparativement faibles (le rapport moyen de la variance de dominance sur la variance phénotypique était de 0,04). Les résultats indiquent qu'il est possible de modifier la relation d-h par la sélection et les croisements. Les corrélations génétiques additives entre la relation d-h et la hauteur étaient négatives, avec une moyenne de -0,62. La sélection pour la hauteur produirait donc des tiges plus effilées que la moyenne, ce qui porte à croire que les grands arbres allouent relativement plus de ressources à la croissance en hauteur qu'à la croissance en diamètre. La sélection pour la hauteur uniquement aura un effet négatif sur le gain en volume.[Traduit par la Rédaction]

Genetic differences are described between improved and unimproved Scots pine (Pinus sylvestris L.) in 36 northern Swedish field tests, covering wide geographical and climatic gradients (latitude 62.3°–67.8°N). Improved trees were represented by progenies from controlled crosses of first-generation, phenotypically selected plus trees, whereas unimproved trees originated from unselected natural stands. Improved trees were superior in terms of height (9.2%), stem diameter (5.4%), and stem volume (18.9%) at the age of 27.4 years. The height growth of improved trees from ages of 10.5 years to 27.4 years was similar to that of unimproved trees at a site with a higher site index. Improved trees had a 5.5% greater height/diameter ratio (i.e., were more slender) than unimproved trees, whereas differences between the tree categories in terms of survival and frequencies of ramicorns and stem breaks were minor and mostly insignificant. Little or no interaction between tree categories and site conditions for growth characters was found, implying that the results are generally applicable. No difference in response to competition between the improved and unimproved trees was detected. However, differences in their reactions to transfer were found: survival rates increased more and height growth decreased less in improved trees than in unimproved trees when grown at a site south of their geographical origin. The use of competition and height indices based on neighbouring trees to adjust for bias and site variability in single-tree plots significantly improved the estimates.