Neck shrivel is a nonpathogenic, physiological disorder of european plum that occurs preharvest during late fruit development and that continues to develop postharvest. Symptomatic fruit is perceived to be poor quality so has reduced commercial value (Widmer and Stadler, 2003). Visual symptoms are a loss of turgescence in the pedicel (proximal) end of the fruit, whereas the stylar (distal) end remains turgescent. Cultivars differ in susceptibility to neck shrivel, but several commercial cultivars are susceptible. In Germany, these include several clones of ‘Hauszwetsche’.
There has been no systematic research on neck shrivel in european plum. Causes of the disorder are unknown. The lack of a mechanistic understanding makes it difficult to derive effective counterstrategies for breeders or to develop cultural practices for its mitigation. European plum is not the only fruit susceptible to preharvest shrivel. Shrivel symptoms are also reported in grapes [Vitis vinifera L. (Bondada and Keller, 2012)], kiwifruit [Actinidia chinensis Planch. (Burdon et al., 2014)], and sweet cherries [Prunus avium L. (Schlegel et al., 2018)].
The only article in a peer-reviewed journal in more than 30 years on neck shrivel in european plum is that of Stösser and Neubeller (1985). The authors hypothesized that neck shrivel was associated with 1) cracks in the cuticle; 2) a thinner cuticle in the pedicel end, compared with the stylar end; 3) a decrease in cuticle constituents believed to inhibit transpiration (wax, alkanes, fatty acids); and 4) large day/night temperature fluctuations. The latter were thought to cause tension in the cuticle, which was thought to cause microcracking. Unfortunately, no theoretical or experimental evidences were presented in support of these supposed causal relationships. Consequently, the aforementioned conclusions remain largely speculative.
Widmer and Stadler (2003) conducted a questionnaire in a fruit-growing region in Switzerland to try to identify common factors involved in the disorder. The results are that: 1) european plum cultivars differ in susceptibility to neck shrivel; 2) the rootstock has no effect on the incidence of neck shrivel; 3) hot and dry weather conditions increase neck shrivel; and 4) cuticular microcracks do not necessarily result in neck shrivel.
The evidence suggests that increased transpiration through microcracks in the cuticle may be an important factor contributing to neck shrivel. We do know that microcracks impair the barrier properties of the cuticle and this increases transpiration (Knoche and Peschel, 2006). Hence, fruit exhibiting neck shrivel is expected to have a greater rate of transpiration than fruit without neck shrivel. Furthermore, for a given fruit with neck shrivel, transpiration near the pedicel end should exceed that near the stylar end.
The objective of our study was to test this hypothesis. We quantified transpiration through the surfaces of european plums with and without symptoms of neck shrivel.
Athoo, T.O., Winkler, A. & Knoche, M. 2015 Pedicel transpiration in sweet cherry fruit: Mechanisms, pathways, and factors J. Amer. Soc. Hort. Sci. 140 136 143
Bondada, B.R. & Keller, M. 2012 Not all shrivels are created equal—Morpho-anatomical and compositional characteristics differ among different shrivel types that develop during ripening of grape (Vitis vinifera L.) berries Amer. J. Plant Sci. 3 879 898
Considine, J. & Brown, K. 1981 Physical aspects of fruit growth—Theoretical analysis of distribution of surface growth forces in fruit in relation to cracking and splitting Plant Physiol. 68 371 376
Geyer, U. & Schönherr, J. 1988 In vitro test for effects of surfactants and formulations on permeability of plant cuticles, p. 22–33. In: B. Cross and H.B. Scher (eds.). Pesticide formulations: Innovations and developments. Amer. Chem. Soc., Washington, DC
Grimm, E., Pflugfelder, D., van Dusschoten, D., Winkler, A. & Knoche, M. 2017 Physical rupture of the xylem in developing sweet cherry fruit causes progressive decline in xylem sap inflow rate Planta 246 659 672
Knoche, M. & Peschel, S. 2006 Water on the surface aggravates microscopic cracking of the sweet cherry fruit cuticle J. Amer. Soc. Hort. Sci. 131 192 200
Knoche, M. & Peschel, S. 2007 Deposition and strain of the cuticle of developing european plum fruit J. Amer. Soc. Hort. Sci. 132 597 602
Knoche, M., Peschel, S., Hinz, M. & Bukovac, M.J. 2000 Studies on water transport through the sweet cherry fruit surface: Characterizing conductance of the cuticular membrane using pericarp segments Planta 212 127 135
Lai, X., Khanal, B.P. & Knoche, M. 2016 Mismatch between cuticle deposition and area expansion in fruit skins allows potentially catastrophic buildup of elastic strain Planta 244 1145 1156
Lang, A. & Volz, R.K. 1998 Spur leaves increase apple fruit calcium by promoting xylem inflow and outflow J. Amer. Soc. Hort. Sci. 123 956 960
Maguire, K.M., Lang, A., Banks, N.H., Hall, A., Hopcroft, D. & Bennett, R. 1999 Relationship between water vapour permeance of apples and micro-cracking of the cuticle Postharvest Biol. Technol. 17 89 96
Nobel, P.S. 1999 Physicochemical & environmental plant physiology. Academic Press, San Diego, CA
Peschel, S. & Knoche, M. 2005 Characterization of microcracks in the cuticle of developing sweet cherry fruit J. Amer. Soc. Hort. Sci. 130 487 495
Schlegel, H.J., Grimm, E., Winkler, A. & Knoche, M. 2018 Orange peel disorder in sweet cherry: Mechanism and triggers Postharvest Biol. Technol. 137 119 128
Stösser, R. & Neubeller, J. 1985 Histologische und chemische Untersuchung der “Halswelke” bei der Hauszwetsche (Prunus domestica L.) Gartenbauwissenschaft 50 97 104
Winkler, A., Brüggenwirth, M., Ngo, N.S. & Knoche, M. 2016 Fruit apoplast tension draws xylem water into mature sweet cherries Scientia Hort. 209 270 278