Distinguishing Characteristics of the Jonathan Spot and Lenticel Spot Disorders in the ‘Jonathan’ Apple Fruit1

Abstract

The disorder known as Jonathan spot commonly observed on ‘Jonathan’ apples actually consists of 2 spot types which must be distinguished in order to define the affecting factors and to resolve the confusing and contradictory evidence in the literature. The spots which occur in the epidermal tissues without definite relation to lenticels are considered as Jonathan spot. Those which occur directly around the lenticels are defined as lenticel spots. Histologically, the epidermal tissues afflicted with Jonathan spot showed a significant radial compression of the collenchyma cells in the 4 to 7 subepidermal tiers; whereas, such modification was not always apparent in tissues affected with lenticel spot. For the latter, some degree of rupture of the epidermis and the 3 to 5 subepidermal collenchyma tiers was usually noted. Jonathan spot development was inhibited by high temperature (70°F). It was favored by delayed harvest, yet none was observed until the fruit was stored at low temperature for several months. Conversely, lenticel spot often was present at harvest time and its development was accelerated at high temperature and inhibited at low temperature. High relative humidity (90%) enhanced lenticel spot development, whereas, humidity level had no effect on Jonathan spot.

Investigations of Multiple Approaches to Reduce Green Spot Incidence in ‘WA 38’ Apple

“…Symptoms of GS emerge approximately three months after full bloom and worsen until harvest. Unlike other cork-like physiological disorders such as bitter pit and Jonathan spot [4,6], GS symptoms on 'WA 38' apples seem to develop exclusively preharvest; worsening of severity during storage has not been observed [46].…”

“…Physiological disorders continue to pose challenges to the fruit production and marketability of apple (Malus × domestica Borkh.). Over the last century, many reports have characterized symptoms, etiology, and mitigation steps for several apple disorders [1][2][3][4][5][6]. Some physiological disorders, such as lenticel breakdown, bitter pit, sunscald, and stain, typically emerge following harvest but are believed to be induced by preharvest factors [4,[6][7][8][9].…”

“…Over the last century, many reports have characterized symptoms, etiology, and mitigation steps for several apple disorders [1][2][3][4][5][6]. Some physiological disorders, such as lenticel breakdown, bitter pit, sunscald, and stain, typically emerge following harvest but are believed to be induced by preharvest factors [4,[6][7][8][9]. Both pre-and postharvest disorder incidence and severity are influenced by interactions of environment, cultural practices, and genetics.…”