Robertson, J. Food Qual. Smith, P. Wakabayashi, K. Williamson, J. State Hort. Zhou, H. User Account Login to save searches and organize your favorite content.
Not registered? Recently viewed 0 Save Search. Advanced Search Help. Authors: Ming-Wei S. Kao 1 , Jeffrey K. Brecht 1 , Jeffrey G.
Williamson 1 , and Donald J. Huber 1. Free access. Get Citation Alerts Get Permissions. Download PDF. Keywords: Prunus persica ; respiration ; ethylene ; polygalacturonase ; pectin methylesterase ; freestone ; clingstone. Ethylene production and respiration rate determination In , respiration rate CO 2 production and ethylene production were monitored in a static system consisting of mL glass containers with airtight lids containing individual fruit that were sealed for 0.
Quality analysis Skin ground color and flesh color determination. Flesh firmness determination. Soluble solids content, titratable acidity, and pH. Polygalacturonase and pectin methylesterase assays Preparation of cell-free protein extract. Polygalacturonase activity. Pectin methylesterase activity.
Table 1. Table 2. Serrano, M. Riguelme, F. Romojaro, F. Masoodi, F. Brecht, J. Sherman, W. Sims, C. Harrison, J. Dal Cin, V. Labavitch, J. Scorza, R. Bassett, C. Nickerson, M. Abeles, F. Costell, E. Crisosto, G. Echeverria, G. Puy, J. Garner, D. Bowerman, E. Baumgardner, R. Brady, C. Remon, S. Negueruela, A. Oria, R. Bennett, A. Cook, F. Huber, D. Sargent, S. Heintz, C. Chordas, A. Jun, J. A few varieties of peaches are flat or doughnut White Peach shaped. This type is known as Pan Tao or Peen To.
Peento peaches come in various colors and flavors. True doughnut peaches have the pit exposed to the outside—the pit can be pushed out without cutting the peach, leaving a doughnut-like fruit.
Types of Peaches. Melting Flesh Peaches Melting flesh peaches have flesh that become soft over time when canned. Photo credits: UC Davis. This gene endoPG encodes the cell wall pectin-cleaving enzyme, known as endopolygalacturonase, and also plays a major fruit softening role in many other fruit crops; like pear, avocado, and melon.
Figure 2: Left A juicy freestone melting flesh peach. Carries two functional endoPG genes at the Freestone-Melting flesh locus. Right Clingstone melting flesh without the Freestone endoPG gene.
Still delicious! Commercially exploitable differences in peach fruit softening profiles have been associated with different endoPG alleles. For example, one breeding line contains a unique allele associated with gradual softening over a week into a pleasing melting texture.
In contrast, there are alleles from wild sources associated with immediate mushiness and others where fruit splits too easily along the suture Fig. Co-localization of cellulose and endo-PG fluorescence is shown in G. For a long time fruit softening was mainly attributed to the disassembly of polysaccharide networks in the cell wall Rose et al. PG-catalysed depolymerization of pectin in the primary wall and middle lamella was long believed to be the principal process underlying fruit softening, although this has been refuted through reverse genetics studies in tomato Brummell and Harpster, They proposed a model in which the cuticle affects the softening of intact tomatoes both directly, by providing a physical support, and indirectly, by regulating the water status.
They also highlighted the mechanistic distinction between a reduction in firmness, or resistance to compression, of intact fruit and ripening-related textural changes in the pericarp tissue. In this study, the role of endo-PG in peach softening was investigated, taking into consideration the hypothesis that the reduction in firmness and the textural changes are two distinct processes based on different mechanisms as has been demonstrated in tomato.
The availability of MF and NMF peach cultivars showing different softening behaviours is a useful tool for this purpose. In the present experiments the morphological analysis of MF and NMF pericarp tissues showed that during softening the mesocarp cells of both fruit types decreased their turgidity, losing their shape.
These data agree with the reduction of cell turgor during softening previously demonstrated for tomato Shackel et al. Nevertheless, the comparison of the two types of ripe peach revealed that NMF mesocarp cells, unlike MF mesocarp cells, not only appeared less turgid but also put pressure on each other. The pressure seemed to originate from the exocarp layer in which cells increased their volume during softening and appeared larger and swollen. It can be supposed that during softening the water gradually moved from the mesocarp cells into exocarp cells driven by osmotically active solute concentrations and water transpiration.
The authors demonstrated that the fruit cuticle plays a fundamental role in regulating the loss of firmness by modulating transpirational water loss. In the present study the increase in cell size was observed only in the exocarp of NMF ripe fruit. Thus, during softening in both MF and NMF cultivar types, mesocarp cells lose their turgidity, but only in ripe NMF fruit do exocarp cells increase their size. It thus emerges that the change in cell turgidity is a process common to MF and NMF fruit but it can be speculated that, like in tomatoes, a less permeable cuticle should decrease transpirational water loss, reducing the softening in NMF.
Indirect evidence supporting this hypothesis is that the decline of peach weight 2 weeks from harvest was greater in MF cultivars, suggesting greater water loss in this fruit data not shown.
Nevertheless, the involvement of cuticle structure and composition in peach fruit softening remains only a hypothesis to test in the future. However, the morphology of the pericarp tissues was clearly different in ripe MF and NMF fruit also in terms of the presence of larger apoplastic spaces originating from the partial loss of cell wall adhesion in the whole MF pericarp.
The partial cell separation is achieved by polyuronide degradation which is principally mediated in peaches by the endo-PG enzyme Trainotti et al. Therefore, to define the contribution of endo-PG degradation of pectins to softening, enzyme expression and localization were investigated.
Nevertheless, the detected amounts of endo-PG and the number of protein isoforms were significantly higher in ripe MF fruit pericarp, the only tissue in which the protein was localized in a position corresponding to the middle lamella and the enzyme activity was detected. These data showed that endo-PG activity is highly regulated in ripening peaches at both the transcriptional and post-translational level.
Moreover, the occurrence of large apoplastic spaces in ripe MF fruit only when the endo-PG was localized in the middle lamella reconfirmed the critical role of the enzyme in cell separation through pectin solubilization and depolymerization.
The occurrence of cell separation takes place in parallel to the loss of firmness and, for this reason, it has been long believed that it was at least one of the molecular mechanisms causing softening.
Nevertheless, the loss of firmness can also occur in NMF fruit in which endo-PG isoforms are few and expressed at a low level, and where the enzyme never localizes in the separation septum. In contrast, the loss of mesocarp cell turgidity is a physiological process common to both MF and NMF fruit softening. In their review, Vincent et al. From this perspective, in agreement with literature data Shackel et al. In conclusion, the data suggest that endo-PG may contribute to the loss of fruit firmness, releasing solutes in the apoplast and thus influencing cell turgor, but its activity is not essential for this process.
Taken together, the present results suggest that in peach, as in tomato, the loss of firmness and the textural changes seem to be related to different, though interconnected, cellular mechanisms: the cell turgor variation and the cell wall disassembly, respectively. The authors wish to thank Professor Ilaria Mignani for technical help with ethylene measurements. Google Scholar. Google Preview. Oxford University Press is a department of the University of Oxford.
It furthers the University's objective of excellence in research, scholarship, and education by publishing worldwide. Sign In or Create an Account. Sign In. Advanced Search. Search Menu. Article Navigation. Close mobile search navigation Article Navigation. Volume Article Contents Abstract. Materials and methods. A comparative study of melting and non-melting flesh peach cultivars reveals that during fruit ripening endo-polygalacturonase endo-PG is mainly involved in pericarp textural changes, not in firmness reduction.
Ghiani , A. Oxford Academic. E-mail: sandra. Revision received:. Cite Cite A. Select Format Select format. Permissions Icon Permissions. Abstract Peach softening is usually attributed to the dismantling of the cell wall in which endo-polygalacturonase endo-PG -catalysed depolymerization of pectins plays a central role.
Endo-polygalacturonase endo-PG , flesh texture , fruit firmness , fruit ripening , Prunus persica. Table 1. Ripening classes of peach cultivars. Open in new tab. Open in new tab Download slide.
0コメント