Genetic variation in drought tolerance in Picea abies seedlings and its relationship to growth in controlled and field environments

Drought tolerance, phenology, height-growth and biomass were studied in 36 open-pollinated Picea abies families in a growth chamber over two growth periods. Three different irrigation treatments were applied: well-watered, periodic drought and lethal drought (involving watering during the first growth period and withholding water during the second). The periodic drought treatment yielded significantly smaller seedlings than the well-watered treatment. In the lethal drought treatment 5.6% of the seedlings were still alive after 3 months without irrigation. Heritabilities for drought damage score, days to wilting and days to necrosis in the lethal drought treatment were 0.41, 0.23 and 0.20, respectively. Additive genetic correlation estimates between drought tolerance traits and growth traits in the growth chamber treatments and in four field progeny trials were weak and mainly non-significant. High drought tolerance was correlated with early budset and, to a lower extent, late budburst. In conclusion, selection for height growth and late budburst as practised in Swedish breeding and propagation populations is not likely to reduce seedling drought tolerance.