Climacteric and Non-climacteric Ripening - Fruit Ripening: Physiology, Signalling and Genomics - page 5

1.3.3 Characterization of non-climacteric
fruit ripening

Grape has been classifi ed as a non-
climacteric fruit due to the lack of an
obvious increase in ethylene production
and concomitant increase in respiration at
the veraison stage during which the berry
size and concentrations of anthocyanin
and sugars start to increase dramatically
as the fruit grows (Coombe and Hale,
1973). However, the levels of endogenous
ethylene display a relatively small peak
prior to the veraison stage, and the
application of ethylene leads to an
increase in this low-level peak (Coombe
and Hale, 1973; El-Kereamy et al. , 2003;
Chervin et al. , 2004). Exogenous ethylene
treatment at the veraison stage also
hastens the fruit coloration and cell
growth, increases the internal ethylene
content (Coombe and Hale, 1973; El-
Kereamy et al. , 2003) and stimulates the
expression of genes related to anthocyanin
biosynthesis as well as the alcohol
dehydrogenase gene (El-Kereamy et al. ,
2003; Tesniere et al. , 2004). Moreover, the
application of 1-MCP prior to the veraison
stage suppresses the acidity decrease, cell
enlargement and anthocyanin accumu-
lation (Chervin et al. , 2004).
The exposure of citrus fruits to exo-
genous ethylene accelerates the respiration
rate and stimulates chlorophyll degradation
(Purvis and Barmore, 1981) and carotenoid
biosynthesis (Stewart and Wheaton, 1972).
Furthermore, treatments with the ethylene
antagonists 2,5-norbornadiene and silver
nitrate prevented the degreening process
(Goldschmidt et al. 1993). Katz et al.
(2004) reported that young citrus fruitlets
were able to synthesize ethylene in an
autocatalytic manner similar to system II
in climacteric fruits, although the mature
fruit did not respond to exogenous
ethylene with the exception of the
degreening of the skin. In the Nijisseiki
Japanese pear cultivar, a non-climacteric
fruit, the continuous exposure to
propylene, which is an analogue of
ethylene, hastened skin degreening but did
not induce ethylene production or
climacteric respiration (Downs et al. ,
1991). In conclusion, these aspects of non-
climacteric fruit ripening may underscore

In non-climacteric fruits, such as straw-
berry, grape, citrus, pineapple and cherry,
the maturation and ripening process
progresses without a burst of ethylene
production or an increase in respiration,
which is in contrast to that of climacteric
fruits (Fig. 1.1). Generally, ethylene is not
required for the ripening process (Given et
al. , 1988; Pretel et al. , 1995). None the less,
non-climacteric fruits have the capacity to
produce a certain level of endogenous
ethylene and to respond to exogenous
ethylene. Recently, the possibility that
ethylene is involved in the ripening pro-
cess of non-climacteric fruit ripening has
been proposed.
In mature strawberry, exogenous ethyl-
ene applied after harvesting does not
accelerate fruit ripening (Perkins-Veazie et
al. , 1996), and ethylene and 1-MCP treat-
ments do not affect its storage life (Bower et
al. , 2003). Recently, however, experiments
have suggested the involvement of ethylene
in strawberry fruit ripening. The respiration
rate in strawberry fruit was stimulated by
ethylene in a dose-dependent manner and
resulted in a slight acceleration of the
coloration and fl esh softening (Tian et al. ,
2000). Iannetta et al. (2006) investigated
ethylene production and CO 2 levels from
the fl owering stage to fruit maturity in
strawberry. An increase in ethylene levels
was observed at the expanded pale-green
and red-ripe stages, and an upsurge in the
CO 2 level was also detected in association
with the ethylene burst at the red-ripe
stage. Moreover, ethylene production was
regulated by negative feedback until the
fruit was expanded and by positive
feedback when it was red-ripened. Trainotti
et al. (2005) showed that the expression
level of the ethylene receptor increased in
response to the increase in ethylene levels
in strawberry fruit, thereby suggesting the
possibility that a low level of ethylene is
suffi cient to trigger the ripening process.
These fi ndings support the possible role
of ethylene in fruit ripening and/or
senescence in strawberry fruit.