EFFICIENCY OF PHOSPHORUS USE IN YOUNG PLANTS OF Eucalyptus urophylla S. T. Blake

The objective of this study is to select superior genotypes for efficiency of phosphorus use in seedlings of Eucalyptus urophylla, correlating them with initial height growth in the field, at age eight months. A completely randomized block design was used in the nursery, consisting of eight clones, three replicates and four plants per plot. The same design was used in the field, consisting of eight clones, four replicate blocks and nine plants per plot. Data being collected in the nursery at age 120 days included: phosphorus concentration in shoot (CPPA); phosphorus concentration in root (CPR); phosphorus content in shoot (CtPPA); phosphorus content in root (CtPR); total phosphorus content in seedling (CtPT); phosphorus use efficiency in shoot (EUP-PA); phosphorus use efficiency in root (EUP-R) and total phosphorus use efficiency (EUP-T). Analyses of variance showed significant genetic differences among clones for all traits and, given the high heritability values found, estimated genetic gains were generically very high. As regards predicted indirect genetic gain, it was noted that selection on nursery seedlings for all EUPs provided the highest values of indirect gain in height of field seedlings.