The Pattern of Genetic Variation in Shoot Growth of Pinus brutia TEN. Populations Sampled from the Toros Mountains in Turkey

The pattern of genetic variation in shoot growth of Turkish red pine (Pinus brutia TEN.) was studied in 180 open-pollinated families from a south to north transect in southern Turkey. Seedlings from 1 coastal, 1 inland and 2 centrally located populations (45 open-pollinated families each) were grown for 2 growing seasons in a forest nursery located near Antalya. The study revealed that both populations and families within populations varied significantly in all seedling traits except for free growth in the second year (SCHT92). In most seedling traits, the pattern genetic variation among populations suggests that there may be a as a clinal variation with respect to the distance from the Mediterranean Coast, but this needs to be tested further. The component of variation due to populations varied from 0% in SCHT92 to 57% in total height growth in the first growing season (FINHT91) while variance component due to families was from 0% in SCHT92 to 75.7% in seed weight (SW). Estimated family heritabilities were generally high for most traits, ranged from 0.20 in number of flushing in the first year (FLU91) to 0.96 in SW (estimated heritability for this trait is really a repeatability value). Genetic correlations between seed related traits and growth traits were moderately strong and positive, suggesting presence of maternal effect on early performances of seedlings. Generally, there were also moderate (0.22) to strong (0.93) genetic correlations between number of flushing and increment traits. Genetic correlations between phenological traits and increment as well as biomass related traits were not very strong and in most cases they were negative, indicating that those seedlings with more height growth and biomass are not necessarily the ones with longer growing seasons. In general, centrally located and coastal populations had similar shoot growth pattern-that is, families in these populations had more shoot flushes, heavier, more lateral branches and greater contribution to annual height increment by second more flushes than those families from the inland population. But, in all populations, the great portion of annual height increment in Turkish red pine was due to first flush (i.e. predetermined growth) indicating a conservative shoot growth pattern in early ages. The implications of this kind of shoot growth pattern as related to early evaluations of families in Turkish red pine breeding programs were also discussed in the paper.