Genetic Diversity of Tropical Fruit - Fruit Ripening: Physiology, Signalling and Genomics - page 232

another important model species used to
study climacteric ripening (Ayub et al. ,
1996). Additionally, within this species,
both climacteric and non-climacteric
varieties are reported. For example,
Cantalupensis melon types are climacteric,
whereas Inodorus melon types are non-
climacteric. The coexistence of both types
of ripening variety make melon also a
suitable model system to study the genetic
control of fruit ripening (Ayub et al. , 1996;
Nishiyama et al. , 2007). Both climacteric
and non-climacteric regulation coexist
during climacteric fruit ripening, as
presented in Fig. 13.1.

The QTL approach will be of immense
use for localization of loci on genetic maps
responsible for at least part of the
phenotypic variation, which enables the
quantifi cation of their individual effects.
The molecular mechanism of fruit ripening
is a complex phenomenon and is con-
trolled by multiple genes and epigenetic
factors leading to limited studies in fruits
of economic importance. Tropical fruit
species with a fl eshy mesocarp and of a
highly perishable nature need urgent
attention for such studies to improve
breeding strategies for enhanced shelf-life
of their fruits.

Non-climacteric fruit Climacteric fruit

SAM
ACC synthase

?

ACC

ACC oxidase

Ethylene

Ethylene-independent
gene expression

Ethylene-dependent
gene expression

Autocata-
lytic
regulation

Cell-wall-
degrading
enzymes

Degradation of
chlorophyll;
development of
aroma, volatile
oil, flavour

Sugar
acidity

Cell-wall-
degrading
enzymes

Flesh
colour

Fruit
softening

Fruit
softening

Abscission

Climacteric ethylene
biosynthesis

Onset of ethylene
biosynthesis

Fig. 13.1. General scheme showing the presence of ethylene-dependent and -independent processes in
ripening melon fruit. Modifi ed from Pech et al. (2008).