Virus infection reduces shoot proliferation of in vitro stock cultures and ability of cryopreserved shoot tips to regenerate into normal shoots in 'gala' apple (malus × domestica)

Authors: WANG, M-R - Northwest Agricultural & Forestry University; HAO, X-Y - Northwest Agricultural & Forestry University; ZHAO, L - Northwest Agricultural & Forestry University; CUI, Z-H - Qingdao Agricultural University; Volk, Gayle; WANG, QIAO-CHUN - Northwest Agricultural & Forestry University

Submitted to: Cryobiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/2/2018
Publication Date: 8/6/2018
Citation: Wang, M., Hao, X., Zhao, L., Cui, Z., Volk, G.M., Wang, Q. 2018. Virus infection reduces shoot proliferation of in vitro stock cultures and ability of cryopreserved shoot tips to regenerate into normal shoots in 'gala' apple (malus × domestica). Cryobiology. 84:52-58. https://doi.org/10.1016/j.cryobiol.2018.08.002.
DOI: https://doi.org/10.1016/j.cryobiol.2018.08.002

Interpretive Summary: This manuscript compared the regrowth levels of cryopreserved apple shoot tips that were and were not infected with Apple Stem Grooving virus. The results reveal that shoot tips cryopreserved from stock cultures that were infected with Apple Stem Grooving virus had lower levels of regrowth, higher levels of cell mambrane damage, increased total soluble protein, soluble sugar, and free proline, and altered levels of indoleacetic acid and zeatin riboside compared to cryopreserved shoot tips that were not infected with the virus. We demonstrate that virus infection affects the physiology and biochemistry of shoot tip regrowth and healthy stock cultures yield preferable results when used for shoot tip cryopreservation. It is suggested that the variation in laboratory-to-laboratory results when cryopreservation procedures are applied may be partially due to the presence of viruses in the stock cultures.

Technical Abstract: Plant cryopreservation has provided secure back-ups of germplasm collections of vegetatively propagated crops. Often, recovery levels vary among laboratories, even when the same cryogenic procedures are used for the same genotypes. The present study investigated the effects of Apple stem grooving virus (ASGV) on shoot proliferation and recovery of cryopreserved shoot tips of ‘Gala’ apple. Results showed that virus infection reduced shoot proliferation and decreased the survival and regeneration of normal shoots after cryoexposure. Virus infection increased the total soluble protein, total soluble sugar and free proline levels, and altered the endogenous levels of indoleacetic acid (IAA) and zeatin riboside (ZR). Virus infection also induced severe cell membrane damage in the in vitro stock shoots. The altered levels of IAA and ZR were most likely responsible for the reduced shoot proliferation. In addition, cell damage and changes in the cellular ultrastructure were observed in ASGV-infected shoot tips. To the best of our knowledge, this is the first study that compared the effects of virus infection on recovery after cryopreservation. These results emphasize that healthy stock cultures should be used for cryopreservation.