Epicuticular wax content and morphology as related to ethylene and storage performance of ‘Navelate’ orange fruit

Abstract

Elsevier Cajuste, JF.; Gonzalez-Candelas, L.; Veyrat, A.; García-Breijo, F.; Reig Armiñana, J.; Lafuente, MT. (2010) The effect of ethylene (2 L L −1 ) on total and soft epicuticular wax content and wax morphology has been investigated in mature 'Navelate' (Citrus sinensis, L. Osbeck) oranges held under non-stressful environmental conditions (22• C and constant high relative humidity (90-95% RH)). In addition, the objective of the study was to understand whether the ethylene-induced changes in epicuticular wax might participate in the beneficial effect of ethylene reducing non-chilling peel pitting, by modifying peel water, osmotic or turgor potential, or disease incidence caused by Penicillium digitatum (Pers.:Fr.) Sacc. Ethylene increased total and soft epicuticular wax content in 'Navelate' fruit and induced structural changes in surface wax that might be related to the formation of new waxes. Changes in epicuticular wax morphology, but not in its content, might be involved in the protective role of ethylene reducing non-chilling peel pitting, although the beneficial effect of the hormone is not related to water stress. Cell water and turgor potentials in freshly harvested fruit and fruit stored in air under non-stressful conditions suggest that water stress is not a limiting factor leading to the development of this physiological disorder. In addition, the results indicated that formation of new waxes in fruit treated with ethylene may partially cover stomata, cracks or areas lacking wax occurring in stored fruit and is likely to improve physical barriers to P. digitatum penetration.

Analysis of cuticular wax constituents and genes that contribute to the formation of ‘glossy Newhall’, a spontaneous bud mutant from the wild-type ‘Newhall’ navel orange

“…Moreover, the absolute and relative contents of each wax constituent in WT mature fruit waxes were also inconsistent with those of Wang's report. Previous reports revealed that the fruit surface waxes of citrus varied widely among different species, organs, developmental states and growth conditions (Baker et al 1975;Freeman et al 1979;El-Otmani and Coggins1985;Sala et al 1992;Sala 2000;Cajuste et al 2010). Even in the same orchard, the fruit wax load and composition from the same citrus cultivar were different between different growth years (Wang et al 2014).…”

“…In summary, alkanes, aldehydes, primary alcohols, fatty acids and triterpenoids are the major wax fractions in citrus fruits (Albrigo 1972;Baker et al 1975;Freeman et al 1979;El-Otmani and Coggins 1985;El-Otmani et al 1986;Sala et al 1992;McDonald et al 1993;Nordby and McDonald 1994;Sala 2000;Cajuste et al 2010;Liu et al 2012;Wang et al 2014). However, in most previous studies, fruit waxes were extracted by dipping the intact surface of an organ into organic solvents.…”

“…This hydrophobic wax layer confers essential ecophysiological functions, including the regulation of water loss (Albrigo 1972), protection against pathogen penetration (Schirra and D'hallewin 1997;Schirra et al 2000;Dore et al 2009), and exchanges of gases through the cuticle (Ben-Yehoshua et al 1985;El-Otmani et al 1986). Several studies have reported that the amount, composition and structure of citrus cuticular waxes vary widely among cultivars, organs and developmental states (Baker et al 1975;Freeman et al 1979;El-Otmani and Coggins 1985;Sala et al 1992;Cajuste et al 2010). Recently, epicuticular waxes have been selectively separated from the mature fruit surfaces of Satsuma mandarin (Citrus unshiu) and 'Newhall' navel orange (Citrus sinensis) by gum arabic and investigated by gas chromatography and mass spectrometry (GC-MS).…”

ABA-deficiency and molecular mechanisms involved in the dehydration response and ripening of citrus fruit

“…Within this context, it is interesting to note the link existing between water stress and the occurrence of NCPP in citrus fruit Lafuente and Zacarías, 2006). Although dehydration is not a limiting step (Lafuente and Sala, 2002;Cajuste and Lafuente, 2007;Cajuste et al, 2010), it enhances the development of this peel disorder (Alférez and Burns, 2004). 'Pinalate' fruit is prone to dehydration and much more susceptible to develop NCPP than its parental 'Navelate' .…”

“…Furthermore, it cannot be excluded that physico-chemical properties of the fruit surface may be altered in the mutant since ABA may affect epicuticular wax biosynthesis in plants (Islam et al, 2009) and also cuticle permeability, development and composition in fruits (Curvers et al, 2010). Although the effect of different hormones on the synthesis or morphology of epicuticular waxes have been shown in citrus fruits (El-Otmani et al, 1986;Cajuste et al, 2010), that of ABA has not been described yet. Therefore, the availability of the spontaneous 'Pinalate' ABA-deficient mutant and its high susceptibility to dehydration encourages new investigations aimed to determine how ABA deficiency impacts the cuticle wax composition.…”