Population variation in drought resistance and its relationship with adaptive and physiological seedling traits in Turkish red pine (Pinus brutia Ten.)

Variation in drought resistance and its relationship with adaptive and physiological traits in forest trees are important in choosing suitable seed sources for reforestation and afforestation programs. A common garden experiment using 240 half-sib families originating from coastal and inland populations of Turkish red pine (Pinus brutia) in Turkey was set up with three replicates. The aims were to determine variation of drought damage, height growth, and phenology among populations and to investigate the relationship between drought damage and physiological traits (i.e. plant moisture stress and proline content). Three-year-old seedlings were subjected to drought treatment during the summer of 2000 and adaptive and physiological traits were measured. Except for bud burst, the majority of the variation resided between populations, leading to low heritability estimates for all traits. On average, inland populations were more resistant to drought and taller, with earlier bud burst and bud set times, than coastal populations. Proline content increased with higher drought damage, especially in cold-resistant and inland families. Inland populations are more drought-resistant than coastal populations. The results of the study demonstrate the possibility of selection for drought resistance for Turkish red pine at the population level.