Softening at the onset of grape ripening alters fruit rheological properties and decreases splitting resistance

Chang, Ben-Min; Zhang, Yun; Keller, Markus

doi:10.1007/s00425-019-03226-y

Cited by 9 publications

(20 citation statements)

References 43 publications

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“…Sugar content similar to that measured here in berries from the tip and middle portion of BS bunches is commonly found in healthy grape berries just after the brief initial softening period that precedes the start of anthocyanin biosynthesis. Also, the sugar content of berries near the base and shoulder of BS bunches resembled that of healthy berries that have started accumulating sugar and just begun to change colour from green to red/blue (Keller and Shrestha 2014, Zhang and Keller 2017, Chang et al 2019). Moreover, the berries with the most severe visual symptoms also had the lowest cell viability, TSS, and pH, indicating that phloem import ceased first in those berries.…”

Section: Discussionmentioning

confidence: 99%

Onset and progression of the berry shrivel ripening disorder in grapes

Hoff

Bondada

Keller

2020

Australian Journal of Grape and Wine Research

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Background and Aims The grape ripening disorder called berry shrivel is characterised by cessation of sugar accumulation, low pH, impaired anthocyanin biosynthesis in dark‐skinned cultivars and water loss. We tested whether damage to the bunch peduncle vasculature can induce berry shrivel and whether cell death in the rachis precedes cell death in the berries. Methods and Results Peduncle phloem removal, but not xylem removal, resulted in symptoms resembling berry shrivel. Fluorescein diacetate staining, however, and microscopic observations of non‐manipulated bunches showed that cell death in the berries often preceded that in the rachis. Mesocarp cell death started around the central vasculature proximal to the seeds and spread outward as symptoms worsened. Berries near the bunch tip were the earliest to be affected and developed the most severe symptoms, but ripening of all berries on symptomatic bunches was impaired. Conclusions Loss of functionality of the rachis phloem may not be the primary cause of berry shrivel. The disorder may originate in the distal berries of a bunch and spread towards the proximal berries as they soften at the onset of ripening. Significance of the Study This study contributes towards an eventual understanding of the causes and consequences of an important grape ripening disorder.

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Section: Discussionmentioning

confidence: 99%

Onset and progression of the berry shrivel ripening disorder in grapes

Hoff

Bondada

Keller

2020

Australian Journal of Grape and Wine Research

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“…berries, like other fleshy fruits, are susceptible to splitting. The driving forces for berry splitting include excessive internal pressure 8 – 10 , excessive surface-water absorption 11 , or physical damage, e.g. by insects or birds 12 .…”

Section: Introductionmentioning

confidence: 99%

“…In a sphere with a thin (<10% of sphere radius) outer shell composed of a homogenous material, σ h may be quantified by applying thin shell theory: where P i is the internal pressure against the shell, r is the radius of the pressurized sphere, and t s is the shell thickness 15 . Although a fruit skin is not a homogeneous material, shell theory has been successfully applied to fruits as a convenient simplification 10 , 16 . For instance, recent work found that immature, green-hard grape berries behaved like thick-shell spheres but changed to pressurized thin-shell spheres during berry softening at the onset of ripening and suddenly became susceptible to splitting 11 .…”

Section: Introductionmentioning

confidence: 99%

“…While berry skin cell turgor is similar to or higher than flesh cell turgor 18 , 19 , skin cells are smaller and have thicker cell walls than flesh cells 1 . Therefore, skin cell walls have higher E than flesh cell walls to resist the cell turgor and restrict cell expansion during ripening 5 , 8 , 10 . In other words, unlike in immature (i.e., hard) berries, the comparatively low E of flesh cells in ripening (i.e., soft) berries prevents the flesh from dissipating P i which is therefore transmitted to the skin 10 .…”

Section: Introductionmentioning

confidence: 99%

“…Therefore, skin cell walls have higher E than flesh cell walls to resist the cell turgor and restrict cell expansion during ripening 5 , 8 , 10 . In other words, unlike in immature (i.e., hard) berries, the comparatively low E of flesh cells in ripening (i.e., soft) berries prevents the flesh from dissipating P i which is therefore transmitted to the skin 10 . However, defining stress-bearing and nonstress-bearing structures in a real fruit is challenging, and the stress-bearing structure might not be homogeneous material.…”

Section: Introductionmentioning

confidence: 99%

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Cuticle and skin cell walls have common and unique roles in grape berry splitting

Chang

Keller

2021

Hortic Res

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The skin protects a fruit from environmental stresses and supports the fruit’s structure. Failure of the skin leads to fruit splitting and may compromise commercial production for fruit growers. The mechanical properties of the cuticle and skin cell walls might influence the splitting susceptibility of fleshy fruits. Thin shell theory and fracture mechanics were utilized in this study to target the potential factors contributing to splitting susceptibility. The study analyzed the structure of the cuticle and epidermis in ripening grape berries and examined the temporal dynamics of berry splitting. Cuticular waxes were partially removed, and skin cell walls were manipulated using wall stiffening and loosening solutions that altered reactions involving hydrogen peroxide. A more than twofold difference in cuticle thickness among grape cultivars did not account for their differences in splitting resistance. However, while removing predominantly epicuticular wax did not alter the berries’ splitting resistance, their surface appearance and increasing yield strength following partial wax removal support the notion that cuticular waxes contribute to berry mechanical properties. Immersing berries in H2O2-based cell wall loosening solutions increased the splitting probability and accelerated berry splitting, whereas cell wall stiffening solutions decreased the splitting probability and delayed berry splitting. These results showed that both cuticle and skin cell walls contribute to the mechanical properties of grape berries and to their splitting resistance. The results also suggest that the two current explanations for fruit splitting, the critical turgor model and the zipper model, should be viewed as complementary rather than incompatible.

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