The variation in flowering abundance was studied in a Norway spruce seed orchard, located in southern Finland (62°13'N, 25°24'E), consisting of 67 clones from northern Finland (64°-67°N). The flowering variation in 1984-1996 was studied at the annual, clonal and graft level. In addition, the genetic diversity of an imaginary seed crop was estimated using a concept of status number.The between-year variation was large in both female and male flowering. Differences in flowering abundance among the clones were large and statistically significant in all the years studied. The average broad-sense heritability values for female and male flowering were 0.37 and 0.38, respectively, but varied considerably from year to year. The correlations between the flowering abundance of the clones in different years were usually positive and significant. However, the correlations for two pairs of successive good flowering years showed that the same clones usually flowered well in the first year in both pairs of years, and the other clones in the second year. The clonal differences in flowering could not be explained by geographic origin, but were more dependent on the graft size. Our results demonstrate that the variation in the ramet number, flowering abundance and pollen contamination must be included when estimating the genetic diversity of the seed crop in a seed orchard. The relative status number of the seed orchard was 84% of the number of clones when the variation in the ramet number was included. The relative status numbers after adjusting for the variation in female and male flowering were on the average 46 and 55%, respectively, and 59% when adjusting for both genders together. Pollen contamination increased the status number considerably.

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The aim of the present work was to study pollen-tube competition in Picea abies. Controlled crossings were performed with pollen mixtures including pairs of pollen lots with fast and slowly elongating pollen-tubes. Paternity analysis using isozyme markers was performed on the progenies in order to study whether the in vitro pollen-germination vigour corresponds to the proportion of seeds sired by the pollen donor. Paternal success was found to be unequal, 15 out of 23 crossings producing progeny that differed significantly from the hypothetical ratio of 1:1. The paternal contribution in the majority of the crossings was as expected: the pollen parent with more-vigorous in vitro germination sired more seeds than the less-vigorous pollen. In the case of two pollen mixtures, however, the seed-siring success summed over the maternal trees was the opposite to the expected value. Despite these aberrations, the results support the hypothesis that pollen-tube competition is one of the factors contributing to male fitness in P. abies.However, when all the other factors affecting pollination and seed set under natural conditions are taken into account, it is clear that the seed-siring success of a particular paternal genotype cannot be predicted reliably by measuring only the in vitro pollen vigour.

The reproductive success of orchard and nonorchard pollens was studied in seeds from megastrobili exposed during different stages of pollen shedding in a Pinussylvestris L. seed orchard. Wind pollination was controlled experimentally by isolating and then temporarily exposing the megastrobili to four different stages of pollen shedding by orchard trees. The amount of pollen contamination in the seed crop was determined using isozyme markers and an undetected gamete model. The estimated level of pollen contamination was 48% when megastrobili were exposed during the entire pollination season. Contamination was highest (60%) when megastrobili were exposed before actual pollen shedding by orchard trees, and lowest (27%) in seeds from megastrobili exposed during maximum pollen shedding by orchard trees. Reproductive success was measured several ways: as the total number of seeds produced in each treatment, as the ratio or proportion of mature cones per megastrobilus, and as the number of seeds produced per cone or megastrobilus. In 1991, reproductive success was highest before maximum pollen shedding by seed orchard trees. Pollen shedding by orchard trees occurred a few days after most megastrobili became receptive.