Juvenile – Mature Genetic Correlations in Pinus pinaster Ait. Under Different Nutrient x Water Regimes

Juvenile - mature (JM) correlations and selection efficiencies among one-year old Pinus pinaster seedlings and 8-yr field performance were analyzed in order to study the possibilities of early selection in the maritime pine breeding program in Galicia (NW Spain). Twenty four open-pollinated families from a first generation clonal seed orchard were grown in the greenhouse under two nutrient crossed with two water regimes. Several growth and dry mass traits were assessed 30 weeks after sowing and compared with field performance (height, diameter and volume) of four 8-yr-old progeny tests established in the coastal area of Galicia. Family mean correlations and genetic correlations were computed for each greenhouse trait, greenhouse treatment, field test site and field trait combination. Except for a few cases, most of the JM correlations were weak and in many cases negative. There was no detectable pattern of JM correlations regarding to combinations of greenhouse treatments and test site water availability and/or fertility. The large variation in the JM correlations for the same traits in different environments and sites (even changing sign in several cases) suggest a large influence of the genotype x environment interaction in the JM estimations. Other possible causes of the weak JM correlations are discussed. Based on the results of this study it may be concluded that none of the combinations of trait and treatment included in this experiment can be recommended for incorporation into early testing in the Galician Pinus pinaster breeding program. Indications for further research to optimize an early selection procedure are included.