Tolerance to Lime - Induced Chlorosis and Drought in Grapevine Rootstocks - Abiotic Stress: Plant Responses and Applications in Agriculture - page 286

iron reduction to ferrous iron, d) enhancement of release of reducing/chelating compounds
e.g. phenols.
• Strategy II is characterized by an enhancement of release of non-proteinogenic amino acids
and by a high affinity uptake system.
Bavaresco (1990) formulated the following hypothesis: the response mechanism of tolerant
grapevine rootstocks corresponds probably with Strategy I (Bavaresco et al., 1989) however,
the vines are normally grafted and the behaviour of the whole plant towards lime-induced
chlorosis is governed by the following two properties: (i) by the ability of roots to satisfy iron
requirement of leaves; (ii) by the iron requirement of leaves to secure a normal iron nutrition
of the plant (Pouget & Ottenwalter, 1973).
The reason that Fe deficiency results in a rapid inhibition of chlorophyll formation is not fully
understood, even though this problem has been studied for many years (Bertamini & Nedun‐
chezhian, 2005). The reduction of plant biomass of susceptible plants is related to a reduced
root growth due to soil bicarbonate and to a lower photosynthesis rate which also depends by
a decrease of leaf chlorophyll, under Fe stress conditions (Bavaresco, Giachino, Pezzutto,
2003). According to the growth rate of sink tissues and such organs as the roots, shoot apex,
fruits and storage organs can be limited by supply of photosynthates from the source leaves
or by a limited capacity of the sink to utilize the photosynthates (Marschner, 1995). In some
cases, lime-induced chlorosis is related to a low Fe uptake and its translocation to leaves
(Bavaresco et al., 1992), in others to a high content of Fe in leaves, which has to be somehow
inactivated (Mengel, Breininget, Bübl, 1984; Bavaresco et al., 1993).
Screening tests of tolerance to chlorosis are performed on plants grown under conditions of a
high content of bicarbonates in soil. This evaluation can be performed also in vitro on a medium
containing a high level of bicarbonates (Bavaresco et al., 1993). The identification of real causes
of the occurrence of the lime-induced chlorosis under conditions of a given vineyard is very
important for the improvement and/or elimination of these biotic stress situations. The
selection of a suitable rootstock is very important above all in situations when the uptake of
iron is blocked due to a high content of lime in soil and also due to unsuitably chosen rotstocks.
3.3. Tolerance to lime-induced chlorosis in wild species and rootstocks varieties
Rootstocks represent a very important part of the concept how to prevent the occurrence of
lime-induced chlorosis in vineyards. A perfect knowledge of soil conditions existing in a given
locality and also of the resistance of individual rootstocks to lime enables to optimise the
management of selection of rootstocks on the base of soil conditions.
Use of genotypes tolerant to chlorosis induced by iron blocking is a reliable tool how to solve
problems of chlorosis occurrence (Jimenez et al ., 2008).
Chlorosis resistance or susceptibility of grapevine varieties and rootstocks is related not only
to the root ability to supply adequate iron to the leaves, but also to their iron requirements,
which can differ between genotypes. On the basis of this concept, the grapevine varieties were
ranked according to their chlorosis resistance or tolerance (Branas, 1974). Breeding also greatly