Variation in growth, flowering and cone production in a clonal seed orchard of Aleppo pine grown in Greece

Abstract

In a clonal seed orchard of Aleppo pine, established in 1987, with a total number of 2630 trees, height growth, flowering and cone production were studied and the following results were obtained: Female flowers appear from the first year after the establishment of the seed orchard but they are low in number and restricted to only few trees of certain clones. The mean numbers of female flowers per tree for all clones were found to be 21 and 56 for the years 1990 and 1991 respectively with ranges from 1 to 59 for the year 1990 and 7 to 136 for 1991. The differences between clones were statistically significant. Male flowers appeared at age 4 years on a small number of clones (27.6% of the total) and substantially increased the following year (44.7%). Considering the whole seed orchard only 11.2% and 18.3% of trees produced male strobili at ages 4 and 5 years respectively. Variation among clones in the number of cones produced at ages 9 and 10 years were found to be statistically significant. However, the clone x year interaction effect was insignificant, indicating that high cone producers of one year continue to do so and the following years. The overall mean number of cones/tree of the entire seed orchard was found to be 168 for the year 1995 and 155 for 1996, with ranges among clones from 40 to 348 for the first and 40 to 343 for the second year. Year to year correlation coefficients on clonal averages were very strong for female flower productions (r = 0.94) and strong for cone production (r = 0.74). Female flowering and cone production are highly inherited characteristics with broad sense heritability (h2) estimates of 0.86 and 0.83 for female flowering (1990, 1991) and 0.46 and 0.41 for cone production (1995, 1996).