Phenotypic plasticity of the bud set process in a Populus nigra L. mapping pedigree and characterization of phenology in a P. nigra European association population
Author(s)
Fabbrini, Francesco
Date Issued
March 10, 2011
Type
Doctoral Thesis
Abstract
Among forest trees, poplars are important components of riparian ecosystems and are now accepted by the scientific
community as ideal model to study perennial plants. They offer several advantages as a model system, including rapid
growth, ease of cloning, prolific sexual reproduction, small genomic size and facile transgenesis. This study has the
objective to contribute to the knowledge of the genetic control of bud set (apical bud formation in the fall) in black
poplar (Populus nigra). For this purpose the genetic variability and the broad-sense hereditability at individual and
genotypic level, have been examined in a full-sib family (POP5) and in different european natural metapopulations of
black poplar grown in a common garden experiment. In addition QTLs (Quantitative Trait Loci) analysis for the most
discriminative traits of phenotypic variation in POP5 has been done using a genetic linkage map produced using 154
genotypes. The full-sib family was obtained crossing two parents selected in the germplasm collection (DISAFRI –
University of Tuscia) from Italian natural populations and divergent for phenology and other adaptive traits. The full-sib
family was planted in two sites in central (Viterbo 42°25’N, 12°05’E) and northern Italy (Cavallermaggiore 44°42’N,
07°40’E). The european natural populations were sampled in 4 different countries and 814 genotypes, from 14
metapopulations were planted in a common garden study in Northern Italy (Savigliano 44°36’N, 07°37’E). A
randomized block design was defined for the establishment of the experimental plantations in each site. Six complete
blocks were used with one replicated genotype randomly assigned to each block. The phenological study has been
realized on the basis of a protocol designed to monitor six crucial phenological phases of bud set in black poplar. Data
analysis have allowed to decompose the contribution of the different phases to the dynamics of bud set. Results showed
that the onset of growth cessation is a quantitative trait under strong genetic control. Night length is the most important
signal triggering the physiological process, but the role of other environmental factors such as temperature increase
during the process. Taking advantage of two contrasting experimental sites a considerable role of GxS interactions has
been found in all the different phenological phases and the low temperature seems to influence the sensitivity of some
more plastic genotypes. The large number of QTLs mapped in the POP5 genetic map, each one characterized by small
or modest effect, highlighted the complex nature of traits involved in the apical bud formation-maturation process.
Additional information
Dottorato di ricerca in Ecologia forestale
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