Influence of Gene x Environment
Whilst the general biosynthesis and regulation of colour pathways has
been elucidated, the final colour of the fruit is determined by both
genetic and environmental factors. The genetic background determines the
ability of fruit to produce certain pigments, whilst environmental
factors affect the final composition and amounts of pigments in a ripe
fruit. The fruit skin, which acts as a barrier protecting the internal
tissues of developing fruit, including the photosynthetic machinery, is
where the greatest effects of environmental factors on fruit pigment
production are normally detected. Both controlled and field studies with
cultivated and wild ecotypes have provided a better understanding of
gene x environment (GxE) interaction in fruit pigment production
(Jaakola & Hohtola 2010). Such studies have identified variation in
anthocyanin content between fruit ecotypes or cultivars growing in
different geographical locations (Fredes et al. 2014;
González-de-Peredo et al. 2019; Sikuten et al. 2021). With
wild Vaccinium berries, field studies have often shown high
variation in the anthocyanin composition between growth location and
seasons (Connor et al. 2002; Rohloff et al. 2015).
However, specific geographical trends also have been observed, such as
higher total anthocyanin contents and a higher proportion of delphinidin
branch anthocyanins towards northern latitudes (Åkerström et al.2010; Latti et al. 2010; Lätti, Riihinen & Kainulainen 2008) and
at higher altitudes (Zoratti et al. 2015). A controlled study
with southern and northern bilberry ecotypes indicated that ecotypes
from higher altitudes produced a higher concentration of anthocyanins
irrespective of day length and temperature conditions (Uleberg et
al. 2012). Geographical variation has also been detected in the
carotenoid contents of different fruit species and cultivars (Diaset al. 2021). In some cases, climatic factors have been found to
have greater impacts on carotenoid biosynthesis than cultivar
differences, for instance in papaya (Kimura, Rodriguez-Amaya & Yokoyama
1991), mango (Mangifera indica ) (Mercadante & Rodriguez-Amaya
1998), and West Indian cherry (Malpighia glabra ) (Rodriguez-Amaya
2001). A comprehensive analysis of the carotenoid content in Portuguese
fruit showed variation between the same apple and orange (Citrus
sinensis ) cultivars grown in different geographical regions (Dias,
Camões & Oliveira 2009). High variation in carotenoid content was
detected between wild Seabuckthorn (Hippophae rhamnoides )
populations growing at different altitudes trans-Himalaya in India
(Korekar et al. 2014). The major stressors are considered in the
following sections, with the proviso that GxE can have additional and
compounding effects.