Structure of genetic variation in vegetative phenology of Cedrela odorata L.: implications for tree breeding

Abstract

The study of vegetative phenology is important to understand adaptation to different environments and potential trade-offs with growth traits. Crown leaf-out and leaf-fall phenology was evaluated on 168 open-pollinated families from 19 Cedrela odorata provenances in an eleven-year-old provenance/progeny trial established in the state of Veracruz, Eastern coast of Mexico. The objectives were: (a) to evaluate the extent of inter- and intra-population genetic variation of leaf phenology traits; (b) to examine the relationship between leaf phenology traits and climate variables at the population level; (c) to estimate the genetic relationships between leaf phenology and growth traits; and (d) to evaluate the accuracy, in terms of genetic control, of using alternative methods to measure leaf phenology in broadleaf trees. The study revealed significant genetic variation in leaf phenology traits both among and within populations. Leaf-out traits showed higher genetic variation than leaf-fall traits. A moderate to large genetic differentiation among Cedrela odorata populations was found; Q_st values for leaf-out were 2–6 times higher than those for leaf-fall. Leaf-fall was primarily associated with mean annual temperature, while leaf-out and length of the leafless period were related to annual precipitation and the aridity index of the site of origin. Leaf phenology traits showed moderate to high genetic control (h²_i = 0.12–0.67; h²_f = 0.27–0.72). However, it was higher for leaf-out traits, so they might play a more important adaptive role. Genetic correlations between leaf phenology and growth traits allow selecting early flushing genotypes within populations to increase adaptation and growth, but caution should be taken when selecting among populations.