Genetic variation of Nothofagus obliqua in seedling growth traits

BARBERO, FERNANDO; VARELA, SANTIAGO; GALLO, LEONARDO ARIEL; PASTORINO, MARIO JUAN

Bordeaux

Conferencia; IUFRO Conference “Genetics of Fagaceae and Nothofagaceae”; 2012

INRA

We analyzed intra and inter-population genetic variation of Nothofagus obliqua, a South American beech with a high breeding potential, in traits related to seedling growth. A common garden trial was established in 2009 with 960 one-year-old seedlings from 4 natural populations represented by 10 open pollinated families each. We measured height (H) and diameter (D) in 2010 and 2011 winters, leaf area (LA) and weight in 2011 summer, and dates of bud burst (BB) in 2010 spring and bud set (BS) in 2011 autumn by surveying all seedlings every 48 hours during both processes. We derived height and diameter growth (HG and DG), specific leaf area (SLA) and duration of vegetative period (VP). In a sample of 120 seedlings we additionally measured net photosynthetic activity at saturating PAR (Pn) and instantaneous water use efficiency (WUEi) in 2011 summer. Significant differences among populations were shown for all variables but for WUEi, H2010 and the diameter traits through an ANOVA test with a linear mixed model with random families nested within fixed populations (a reduced model without “family” was used for Pn and WUEi). The family factor was significant for all variables but for BS and DG. The intra-population variation was characterized by estimating heritabilities of each trait in each population. Highest h2 were estimated for H2011 (between 0.40 and 0.80). LA, BB and VP showed a moderate h2, while those estimated for SLA and BS were low, the same as for HG, DG and D2011. Pair-wise comparisons unravel that the northernmost population (Epulaufquen) was the only one that differed. It had the lowest height growth, the largest and heaviest leaves, the highest Pn, and the shortest vegetative period. However, diameter differences were not significant and the differences in height growth were not as large as that observed in the other traits. This can be explained by the existence of a sort of balance between the larger and more efficient photosynthetic apparatus of this population and its shorter vegetative period, which seems to be an adaptive strategy to escape from frost damage.