Second PaReTree (SSF) Workshop
“Genetic Basis of Defences in Trees”
Kronlund, Vindeln, Umeå, 22-24 February 2012
Genetic variation in resistance to multiple enemies in pine trees (II): defensive traits
providing resistance and strategies of intraindividual variation in defensive allocation.
Luis Sampedro1, Rafa Zas2, Xoaquin Moreira2,3, Alex Solla4
1
Centro de Investigación Forestal de Lourizán, Associate Unit to MBG-CSIC. Pontevedra, Spain
(lsampe@uvigo.es) www.genecolpines.weebly.com
2
Misión Biológica de Galicia (MBG-CSIC). Pontevedra, Spain.
3
Department of Ecology and Evolutionary Biology, UC-Irvine, CA, USA
3
Ingeniería Técnica Forestal. Universidad de Extremadura, Plasencia, Spain
In this second part of our talk I first focused on intrapopulation genetic variation in
defensive traits and at what extent those traits are found to be associated to effective
resistance. Then we moved to the sources of phenotypic variation in within plant allocation
of chemical defences.
The general pattern in our studies of within population genetic variation is finding
significant additive genetic variation in most traits related to growth and defense. We have
found that families differ in the constitutive expression of anatomical traits, such as resin
canals, and in the total concentration of defensive chemical (total terpenes, tannins,
phenolics). Particularly when analyzing terpenoids, we usually find high narrow sense
heritability for the concentration of many individual terpenoids species. We also found that
inducibility of those compounds (the ability to increase the concentration after induction by
real herbivory or methyl jasmonate application) is also usually genetically variable.
On the other hand, although we have found that families differ in effective field resistance
against several pests and pathogens (it was the topic of the part 1 of the talk by Rafa Zas),
and we have some cues that susceptible and resistant families differ in some chemical
properties, it is not so common in our research to find significant genetic correlations among
individual chemical traits and effective field resistance. We should perform multivariate
associational studies for exploring the nature of field resistance, including not only traits of
resistance for getting information about possible trade-offs with other life history functions.
As an “extra” source of phenotypic variation, we have been interested in genetic
variation in within plant in the allocation of defensive traits in young pine trees. In several
independent experiments, we have found that constitutive and inducible allocation of
chemical defences differ across plant parts, across plant tissues, among the chemical
compounds considered and as well depends on the nature of the damage. Moreover, all
these strategies were found to vary across pine species, and also across families within
populations in the two species that were investigated. Altogether, these results suggest that,
in spite the pressure exerted by herbivores, existence of genetic variation in defensive traits
is the common pattern in pine trees, and it is quantitatively relevant. Thus, we have to be
more specific formulating our questions about genetic variation in defensive investment, as
variation across genotypes and within plant can be confounding factors when looking for
traits providing resistance.