MN55 is an apple (Malus 3domestica Borkh.) cultivar recently released by the University of Minnesota apple breeding program, with fruit marketed in the U.S. as Rave®. When stored for 4 months at 0 to 4 °C, MN55 fruit can develop several storage disorders, including skin dimpling. Skin dimpling incidence was greater for fruit harvested 1 week later than those harvested earlier. Dimpling was not alleviated by prestorage treatments of 1-methylcyclopropene or diphenylamine or by holding fruit at room temperature for 1 day before long-term cold storage. However, dimpling incidence was very low when fruit were stored at 6 to 7 °C. Because viruses have been implicated in other fruit dimpling disorders, the presence of viruses in MN55 leaves and fruit was studied. Apple stem pitting virus (ASPV) was detected by microscopy, reverse transcriptase polymerase chain reaction (RT-PCR) methodology, and high throughput sequencing (HTS) in peel of fruit from MN55 trees that exhibited skin dimpling after 4 months of storage at 0 to 1 °C. ASPV was also detected in supermarket-purchased fruit of other cultivars with noticeable skin dimpling. Although ASPV was not conclusively demonstrated to cause skin dimpling in our work, its prevalence indicates that further investigations are warranted to determine the relationship between viruses and skin deformities in stored apples.
Bibliographical noteFunding Information:
Received for publication 6 Apr. 2021. Accepted for publication 6 Apr. 2021. Published online 8 June 2021. We thank Nicholas P. Howard and Gary Kinard for reviewing the manuscript; Ben Y. Ma for laboratory assistance; John Tillman, Baylee Miller, and Adam Sauve for field assistance; John Oja at the University of Minnesota Imaging Centers for technical assistance and the Imaging Centers for use of its microscopes; and Agro-Fresh for SmartFresh/SmartTabs. Funding was provided by the MN Experiment Station to project MN21-043 and the U.S. Department of Agriculture Agricultural Research Service for Research Project 8042-22000-302-00-D. The use of trade, firm, or corporation names in this publication does not constitute an official endorsement or approval by the U.S. Department of Agriculture or the Agricultural Research Service of any product or service to the exclusion of others that may be suitable. J.J.L. and D.B. are entitled to royalties from the MN55 cultivar described in this paper. The University of Minnesota also has a royalty interest in MN55 and related intellectual property. These relationships have been reviewed and managed by the University of Minnesota in accordance with its Conflict of Interest policies. R.G.K. is currently at the Kenya Agricultural and Livestock Research Organization, P.O. Box 14733-00100, Nairobi, Kenya. C.B.S.T. is the corresponding author. E-mail: firstname.lastname@example.org. This is an open access article distributed under the CC BY-NC-ND license (https://creativecommons. org/licenses/by-nc-nd/4.0/).
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- Cold storage
- RNA virus