Superficial scald, additionally known as storage scald, is a physiological dysfunction of apple [Malus sylvestris (L.) Mill var. domestica (Borkh.) Mansf.] and pear [European (Pyrus communis L.) and Asian (Pyrus serotina Redh.)] fruit (Fig. 1). Scald is a time period loosely utilized to a gaggle of pores and skin issues of apples and pears. It’s manifested as brown or black patches on the fruit pores and skin, however can take a number of associated types, together with rugose and lenticel scald (Meigh, 1970; Wilkinson and Fidler, 1973). With rugose scald, the pores and skin initially develops a faint bronze shade, however later these areas flip gentle brown to very darkish brown. Many lenticels stay inexperienced, nonetheless, standing out prominently from the sunken areas. In lenticel scald the harm is predominantly across the lenticels, in order that it seems as a recognizing moderately than a blotchy dysfunction. Most of these scald and superficial scald are expressions of the identical drawback; particular cultivars are extra susceptible to at least one kind or one other. Scald is an expression of harm and demise throughout the floor layers of cells in localized areas. It by no means happens on the tree, solely after comparatively lengthy durations of low temperature storage. The dysfunction often develops after fruit have been faraway from chilly storage, though after prolonged storage it might be seen on fruit previous to elimination to hotter temperatures. The primary report of scald within the literature seems to be that of Powell and Fulton (1903), its identification as an issue being related to the arrival of refrigerated storage about 1890. The time period ‘superficial scald’ was coined by Tiller (1929). The dysfunction is in line with a two-stage occasion the place the induction occasions are separated from symptom growth (Bramlage and Meir, 1990), and is considered a type of chilling harm to the fruit (Watkins et al., 1995).
In ‘Granny Smith’ fruit, scald outcomes from necrosis of the hypodermal cortical tissue, the dermis being concerned solely in extreme harm (Bain, 1956; Bain and Mercer, 1963). Browning happens solely in cells which comprise chloroplasts, however these usually are not disorganized (Bain, 1956). Scalded tissues are related to higher water loss as indicated by nuclear magnetic resonance imaging (Golding et al., 1997; Paliyath et al., 1997). In a examine of scald growth in ‘Cortland’ and ‘Scrumptious’ fruit utilizing chlorophyll fluorescence, Mir et al. (1998a,b) didn’t detect any relationship between the physiological standing of the chloroplasts and scald growth.
Different variants of scald, in all probability senescence associated, embrace lenticel spot scald, stem-end browning, senescent scald and light-induced scald (Wilkinson and Fidler, 1973). Sunscald, through which pores and skin darkening happens throughout storage, is a non-enzymatic and non-oxidative course of (Lurie et al., 1991b). Scald-like signs may be induced by N2 therapy of fruit after storage, however the relationship of this harm to regular scald stays unclear (Dilley et al., 1963; Bauchot et al., 1999). Scald signs, assumed to be superficial scald, have been elevated by ethylene dibromide utility to ‘McIntosh’ apples, however inhibited in ‘Scrumptious’ fruit (Poapst et al., 1974). One other dysfunction that has been described as scald-like (Burmeister and Dilley, 1995) is prone to be exterior CO2 harm (Watkins et al., 1997; Fawbush et al., 2008). Exterior CO2 harm has some similarities to superficial scald together with injury to the hypodermal cells and management by diphenylamine (DPA), however differs in its response to delayed CA storage (Watkins et al., 1997). Diffuse pores and skin browning, a dysfunction related to 1-MCP therapy of ‘Golden Scrumptious’ apples shouldn’t be affected by DPA therapy and seems distinct from superficial scald (Larrigaudiere et al., 2010). Different widespread scalds, resembling mushy scald, are prone to be types of low temperature breakdown (Watkins et al., 2004).
Analysis on scald has adopted an fascinating path, largely decided by discovery of particular management strategies, which has affected the depth of analysis over time. Air flow and use of oil wraps (Brooks et al., 1919) have been the one strategies obtainable till the invention that the antioxidants diphenylamine (DPA) and ethoxyquin (6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline) inhibited scald in apples and pears (Smock, 1955, 1961). The efficacy of those antioxidants resulted in diminished analysis curiosity on scald within the US, however analysis continued elsewhere, particularly in Australia and England, due to slower or absent registration of the chemical substances. Persevering with considerations about postharvest therapies, together with the necessity for co-application of postharvest fungicides, nonetheless, have resulted in renewed analysis exercise on scald, together with re-evaluation of strategies which can be at present not price efficient compared with DPA and ethoxyquin. DPA utilization shouldn’t be permitted in a number of European international locations and registration could also be phased out in others. Though, DPA is being changed by the broadly registered inhibitor of ethylene notion, 1-methylcyclopropene (1-MCP), and/or newer managed environment (CA) storage applied sciences, the influence of the lack of constantly dependable and simply utilized know-how on the worldwide market could possibly be substantial.
Varied facets of the etiology and management of scald have been reviewed (Smock, 1961; Meigh, 1970; Wilkinson and Fidler, 1973; Ingle and D’Souza, 1989; Wang and Dilley, 1999). A lot is now identified in regards to the bodily, physiological and biochemical mechanisms chargeable for fruit susceptibility to scald, however a full understanding stays elusive. The biochemistry of scald etiology has targeted nearly solely on the involvement of α-farnesene and its oxidation, and little consideration has been given to various concepts such because the involvement of elevated pentose phosphate pathway exercise in its growth (Faust et al., 1967).
A number of postharvest elements that scale back scald growth have been recognized. Nevertheless, no single methodology for scald management seems relevant throughout the vary of pome fruit industries in several rising areas around the globe; every trade has completely different scales, various levels of technological sophistication, in addition to differing emphases on native and export markets. Right here we evaluation present data about scald on the physiological and biochemical stage, and try to clarify the consequences of postharvest therapies in relation to the current understanding of scald etiology. Whereas our focus on this evaluation is aimed in direction of current analysis, older work is cited the place acceptable.
Preharvest elements that have an effect on susceptibility of fruit to scald have been reviewed by Emongor et al. (1994) and usually are not thought of intimately right here. Salient factors that needs to be thought of in understanding scald etiology and management are as follows: cultivars range drastically in susceptibility to scald, e.g. ‘Granny Smith’, ‘Legislation Rome’, ‘Fuji’ and ‘Scrumptious’ are inclined, whereas ‘Empire’, ‘Gala’, ‘Braeburn‘, ‘Pink Girl’ and ‘Golden Scrumptious’ are resistant (Little and Holmes, 2000; Tsantili et al., 2007); rising area and seasons affect susceptibility, with fruit grown in hotter, dry climates/seasons being extra inclined than these grown in cooler climates (Little and Taylor, 1981; Bramlage and Watkins, 1994; Whitaker et al., 2009); scald is often extra prevalent on sooner than later harvested fruit (Wilkinson and Fidler, 1973; Wang and Dilley, 1999); low night time temperatures within the interval earlier than harvest lower the incidence of scald, and an inverse relationship between the variety of days beneath the brink temperature of 10 °C and the incidence of scald has been famous (Merritt et al., 1961; Blanpied et al., 1991; Bramlage and Watkins, 1994; Thomai et al., 1998; Ma et al., 2001).