Agriculture Reference
In-Depth Information
Fig. 4.8
Parthenocarpic fruit
(
a
) and normal fruit derived
from fertilization (
b
) (Costa
and Ramina
2012
)
greater susceptibility to storage diseases. All these traits are genetically controlled
and their elucidation will contribute to choose proper harvesting time and to de-
velop new post-harvest strategies.
Temperate fruits are divided in climacteric or non-climacteric depending
upon the increase in respiration and the biosynthesis of ethylene at the ripening
stage (Fig.
4.9
). In general, during fruit development, the respiration gradually
decreases until it reaches the lowest values during senescence. However, this is
true for the non-climacteric fruit in which the respiration rate can be higher than
that of climacteric ones. Climacteric fruit show a different behaviour and show
a respiration peak, which decreases in the post-climacteric phase representing
the transition towards senescence. The rise of climacteric respiration is concur-
rent with the achievement of the maximum fruit size and with the main changes
occurring during ripening. Ethylene biosynthesis follows the same trend of the
climacteric respiration and controls most of the processes defining the ripening
syndrome (Giovannoni
2004
; Barry and Giovannoni
2007
). The stimulation of
ethylene evolution is the result of activation of two key biosynthetic enzymes,
i.e. ACC synthase (ACS) and ACC oxidase (ACO), responsible for the hormone
autocatalysis characteristic of the ripening phase. While the role of ethylene in
climacteric fruit ripening has been sufficiently investigated, the auxin-ethylene
interaction need further elucidation. In fact, exogenous applications of auxin may
delay or stimulate ripening according to the stage of fruit development. In peach,
it has been shown that an up-regulation of genes associated to IAA perception/
action occurs at late S3, preceding the ethylene climacteric rise (Ramina et al.
2008
). In addition, in tomato and peach, it has been shown that the expression of
some members of the AUX/IAA family is stimulated by ethylene. The involve-
ment of ethylene in grape, a non-climacteric fruit, has been assessed by means of
