Relative contributions of crown and phenological traits to growth of a pseudo-backcross pine family ((slash×loblolly)×slash) and its pure species progenitors

One pseudo-backcross [(slash × loblolly) × slash] (BC1) and open-pollinated families of the pure species progenitors were established in a single test in North Central Florida. Multivariate analysis was used to estimate the intra-trait correlation among the taxa, and path analyses were used to determine the relative contributions of crown architectural and phenological traits to first-year height growth. The multivariate analysis indicated that BC1, slash, and loblolly pine have different relationships among the traits studied, suggesting that a separate path analysis was required for each taxon. Path analysis coefficients of determination of the final models were 0.69, 0.73, and 0.65 for the pseudo-backcross, loblolly, and slash pine families, respectively. The ranking of traits by relative magnitude of effect on total growth was, for the pseudo-backcross crown projected area (CPA), fascicle length (FL), number of nodes (NN), number of branches (NB), number of needles per fascicle (NF), and fascicle diameter. For loblolly, this was CPA, NB, FL, NN, NF, initiation, and specific leaf area. For slash, this was CPA, NN, FL, NF, and NB. The study indicated that all crown traits considered in the path analysis had moderate effects on first-year height growth, with the exceptions of the consistently large effect of CPA and the minimal effect of the phenological traits.