conference schedule and program with abstracts - Horticulture ...

O-31
Mapping genetic loci for tolerance to iron induced chlorosis in grapevine (Vitis vinifera L.)
S. Decroocq, L. Bordenave, M. Donnart, C. Hévin, J.-P. Dodane, N. Ollat, P-F. Bert*
Institut des Sciences de la Vigne et du Vin, UMR 1287 Ecophysiologie et Génomique
Fonctionnelle de la Vigne INRA, Université de Bordeaux 1, Université Victor Ségalen Bordeaux
2, Centre INRA de Bordeaux, Villenave d’Ornon, France
*Corresponding author: pfbert@bordeaux.inra.fr
Iron is essential to plants for chlorophyll formation as well as for the functioning of various ironcontaining
enzymes. Iron deficiency chlorosis is a wide-spread disorder of plants, in particular of
those on calcareous soils. In the soil matrix, Fe exists in one of two forms, Fe2+or Fe3+.
However, many environmental conditions, including the high pH of calcareous soils, can result
in little Fe2+ availability ("lime-induced chlorosis"). To survive in iron limiting environments,
plants have evolved two iron uptake strategies, Strategy I and II. Dicot species, including
grapevine, utilize the Strategy I mechanism to take up the Fe2+ ion. Strategy I plants utilize an
ATPase to secrete protons from the roots to acidify the rhizosphere which aids the release of Fe
from chelating agents in the soil. A root membrane reductase reduces the prevalent Fe3+ion to
the biologically usable Fe2+ ion, which can then be transported into the roots of the plant where
it is available for use in various cellular processes. For Strategy I plants, the iron reduction by
plant roots has been identified as the rate-limiting step in iron deficiency. Strategy II plants, such
as monocot species, release phytosiderophores from the roots that chelate Fe3+ ions. The entire
phytosiderophore iron complex is then transported into the root system of the plant. Complex
genetic and environmental interactions have made iron induced chlorosis an extremely difficult
trait to study in field trials and today, the mechanisms of tolerance remain poorly understood.
The aim of the experiment was to characterize the genetic basis of grapevine chlorosis tolerance
under lime stress conditions. A segregating population of 138 F1 genotypes issued from an interspecific
cross between V. vinifera Cabernet Sauvignon (tolerant) × V. riparia Gloire de
Montpellier (sensitive) was developed and grown both as cuttings and as rootstock grafted plants
with Cabernet Sauvignon scions in pots of non-chlorosing and chlorosing soils. Tolerance was
evaluated by chlorosis score, chlorophyll contents and growth parameters of shoots and roots.
Experiments were done in 2001, 2003 and 2006 and the material from the 2006 assay was reused
in 2007. The most significant findings of the trial were: (a) the soil properties strongly affected
both shoot and root development; (b) there are differences in tolerance among segregating
genotypes when grown as cuttings or as rootstocks on calcareous soil; (c) calcareous conditions
induced chlorosis and revealed QTLs implicated in polygenic control of tolerance; (d) rootstock
strongly contributes to lime-induced chlorosis tolerance and; (e) a QTL with strong effect (from
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