Branch architecture QTL for Pinus elliottii var. elliottii x Pinus caribaea var. hondurensis hybrids

Abstract

Putative quantitative trait loci (QTL) of moderate, additive effect were identified for branch diameter, average number of branches per whorl per tree, average whorl spacing and regularity of whorl spacing in a single Pinus elliottii var. elliottii $\times$ P. caribaea var. hondurensis family. There was no evidence of additive $\times$ additive epistasis or pleiotropy. No marker-trait associations were detected for the average branch angle per whorl per tree. The detection of gene effects that were seemingly larger but less numerous than those expected for traits with low to moderate heritabilities was attributed to bias in the estimation of QTL magnitude and limited power to detect QTL due to a small sample size. Branch architecture traits exhibited considerable variation within the family with ranges of 4-6 standard deviations (SD) and tended to be less variable than height and diameter. Branching characters were largely independent of one another as well as growth, form and wood density properties. Branching characters other than branch angle were not influenced by macro-environmental factors.