Title: Fruit size affects physiological attributes and storage disorders in cold stored "Gala" apples Authors
Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 25, 2013
Publication Date: N/A
Interpretive Summary: Availability of apples months after fruit is harvested is possible because of storage technology that slows fruit ripening. Recently, ‘Gala’ apples, a popular variety that typically has a long storage life, has been found to develop an internal browning after several months in storage. The browning is somewhat atypical as it begins at the fruit stem end. Disorder progression can continue so symptoms appear in tissues near the fruit equator. ARS scientists examining factors that may contribute to disorder development have shown fruit of large size are more likely to develop browning compared with smaller fruit. Also, storage technologies that slow ripening delay or prevent the progression of ripening.
Technical Abstract: ‘Gala’ apple [Malus sylvestris (L.) Mill var. domestica (Borkh.) Mansf.] fruit can be susceptible to the development of postharvest disorders such as flesh breakdown, and cracking (splitting) during and after cold storage. Previous work indicated fruit flesh breakdown and stem-end browning incidence was likely associated with fruit size. The objective of this research was to investigate fruit size and 1-MCP treatment effects on fruit physiological attributes and incidence and severity of storage disorders in ‘Gala’ apples held in cold storage. In 2011, fruit segregated at harvest into two groups based on size (120-175, 250-350 g•fruit-1) were stored in air at 0.5 oC for 6 months and then at 20 oC for 7 days. In 2012, fruit were sorted into four groups (<200, 200-240, 241-280, and >280 g•fruit-1), treated with 0 or 1 µL•L-1 1-MCP for 12 hr and then stored in air at 0.5 oC for 3 or 6 months. Storage disorders were only detected at 6 months, regardless of 1-MCP treatment. In both control and 1-MCP treated fruit, flesh breakdown incidence increased with fruit size while severity was less associated with size. The progression of flesh breakdown developed in overall cortex tissue of control fruit but only detected in the stem-end tissue of 1-MCP treated fruit. Internal ethylene concentration (IEC) decreased and CO2 production increased with increased fruit weight, however, 1-MCP treated fruit had low IEC regardless of weight. Cortex tissue lightness (L*) increased with fruit size, irrespective of tissue localization (stem-end, equatorial, calyx-end) at harvest. During 6 months storage, L* decreased with increased fruit size in controls but not 1-MCP treated fruit. Fruit fresh weight loss increased with fruit size and storage duration, more so in controls when compared with 1-MCP treated fruit. Furthermore, fruit circumference increased during storage with fruit size only for control fruit. These physical changes are associated with susceptibility of large fruit to flesh breakdown more so than small fruit. Reduced flesh breakdown incidence, progression of symptoms from stem-end into the cortex, and symptom severity in 1-MCP treated fruit may indicate flesh breakdown is related to fruit ripening and senescence.