The characteristics of cork and hypodermis tissues and cracking in Asian pear (Pyrus pyrifolia cv. Mansoo)

• The initial stage of cracking in Mansoo was oval-shaped and followed by extension.
• Cracking occurred on a crevice of cork tissue surrounding the filling tissue.
• Many intercellular spaces were in the parenchyma and between stone cell clusters.
• Mansoo fruit has thinner, more irregular, and less numerous hypodermis layers.
• Mansoo stone cell clusters in the peripheral pericarp were larger and closer together.

Mansoo is a russet pear cultivar cultivated in Korea and susceptible to cracking at maturity. Cracked regions were studied using light (LM), stereo (SM), and scanning electron microscopy (SEM) to compare the prevalence of this phenomenon in Mansoo and Niitaka cultivars. The initial cracking stage was observed as a short-length-shaped crack (SLSC) on the lenticel, followed by an enlargement and extension of the cracked region as a long-length-shaped crack (LLSC). Although the cracked region on the lenticel was discovered with the naked eye, cracking also occurred in the surrounding filling tissue region, which has a thin hypodermis because of a crevice of cork tissue. The cracking occurred in the intercellular space of parenchymal tissue and between stone cell clusters. Mansoo fruit has thinner, more irregular, and less numerous hypodermis layers than that of Niitaka. Stone cell clusters in the peripheral parenchyma were concentrated because they were larger and had a smaller distance between them in Mansoo cultivars than in Niitaka. These results demonstrate that the morphological and anatomical features observed in Mansoo fruit are cracking susceptibility factors.