TY - JOUR

T1 - Russet susceptibility in apple is associated with skin cells that are larger, more variable in size, and of reduced fracture strain

AU - Khanal, Bishnu P.

AU - Le, Thi Lieu

AU - Si, Yiru

AU - Knoche, Moritz

N1 - Funding information: This research was funded in part by a grant from the Deutsche Forschungsgemeinschaft (DFG). The publication of this article was funded by the Open Access fund of Leibniz University of Hannover.

PY - 2020/9

Y1 - 2020/9

N2 - Russeting is an economically important surface disorder in apple (Malus × domestica Borkh.). Indirect evidence suggests an irregular skin structure may be the cause of the phenomenon. The objective of this study was to characterize epidermal and hypodermal cell morphology and the mechanical properties of the skins of apple cultivars of differing russet susceptibility. Dimensions of epidermal and hypodermal cells were determined using microscopy. Stiffness (S), maximum force (Fmax), and maximum strain (ɛmax) at failure were quantified using uniaxial tensile tests of skin strips. Particularly during early fruit development, epidermal cells (EC) and hypodermal cells (HC) in russet non-susceptible cultivars occurred in greater numbers per unit area than in russet-susceptible ones. The EC and HC were lower in height, shorter in length, and of reduced tangential surface area. There were little differences in S or Fmax between non-susceptible and susceptible cultivars. However, the ɛmax were higher for the skins of non-susceptible cultivars, than for those of susceptible ones. This difference was larger for the young than for the later growth stages. It is concluded that russet-susceptible cultivars generally have larger cells and a wider distribution of cell sizes for both EC and HC. These result in decreased ɛmax for the skin during early fruit development when russet susceptibility is high. This increases the chances of skin failures which is known to trigger russeting.

AB - Russeting is an economically important surface disorder in apple (Malus × domestica Borkh.). Indirect evidence suggests an irregular skin structure may be the cause of the phenomenon. The objective of this study was to characterize epidermal and hypodermal cell morphology and the mechanical properties of the skins of apple cultivars of differing russet susceptibility. Dimensions of epidermal and hypodermal cells were determined using microscopy. Stiffness (S), maximum force (Fmax), and maximum strain (ɛmax) at failure were quantified using uniaxial tensile tests of skin strips. Particularly during early fruit development, epidermal cells (EC) and hypodermal cells (HC) in russet non-susceptible cultivars occurred in greater numbers per unit area than in russet-susceptible ones. The EC and HC were lower in height, shorter in length, and of reduced tangential surface area. There were little differences in S or Fmax between non-susceptible and susceptible cultivars. However, the ɛmax were higher for the skins of non-susceptible cultivars, than for those of susceptible ones. This difference was larger for the young than for the later growth stages. It is concluded that russet-susceptible cultivars generally have larger cells and a wider distribution of cell sizes for both EC and HC. These result in decreased ɛmax for the skin during early fruit development when russet susceptibility is high. This increases the chances of skin failures which is known to trigger russeting.

KW - Epidermis

KW - Hypodermis

KW - Malus × domestica

KW - Mechanical properties

KW - Russet

UR - http://www.scopus.com/inward/record.url?scp=85093897294&partnerID=8YFLogxK

U2 - 10.3390/plants9091118

DO - 10.3390/plants9091118

M3 - Article

AN - SCOPUS:85093897294

VL - 9

SP - 1

EP - 19

JO - Plants

JF - Plants

IS - 9

M1 - 1118

ER -