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© 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/). Notwithstanding the ProQuest Terms and Conditions, you may use this content in accordance with the terms of the License.

Abstract

Virus and viroid-free apple rootstocks are necessary for large-scale nursery propagation of apple (Malus domestica) trees. Apple stem grooving virus (ASGV) and Apple chlorotic leaf spot virus (ACLSV) are among the most serious apple viruses that are prevalent in most apple growing regions. In addition to these viruses, a new infectious agent named Apple hammerhead viroid (AHVd) has been identified. We investigated whether thermotherapy or cryotherapy alone or a combination of both could effectively eradicate ACLSV, ASGV, and AHVd from in vitro cultures of four apple rootstocks developed in the Cornell-Geneva apple rootstock breeding program (CG 2034, CG 4213, CG 5257, and CG 6006). For thermotherapy treatments, in vitro plants were treated for four weeks at 36 °C (day) and 32 °C (night). Plant vitrification solution 2 (PVS2) and cryotherapy treatments included a shoot tip preculture in 2 M glycerol + 0.8 M sucrose for one day followed by exposure to PVS2 for 60 or 75 min at 22 °C, either without or with liquid nitrogen (LN, cryotherapy) exposure. Combinations of thermotherapy and PVS2/cryotherapy treatments were also performed. Following treatments, shoot tips were warmed, recovered on growth medium, transferred to the greenhouse, grown, placed in dormancy inducing conditions, and then grown again prior to sampling leaves for the presence of viruses and viroids. Overall, thermotherapy combined with cryotherapy treatment resulted in the highest percentage of virus- and viroid-free plants, suggesting great potential for producing virus- and viroid-free planting materials for the apple industry. Furthermore, it could also be a valuable tool to support the global exchange of apple germplasm.

Details

Title
Thermotherapy Followed by Shoot Tip Cryotherapy Eradicates Latent Viruses and Apple Hammerhead Viroid from In Vitro Apple Rootstocks
Author
Bettoni, Jean Carlos 1   VIAFID ORCID Logo  ; Fazio, Gennaro 2 ; Larissa Carvalho Costa 3 ; Hurtado-Gonzales, Oscar P 3   VIAFID ORCID Logo  ; Maher Al Rwahnih 4   VIAFID ORCID Logo  ; Nedrow, Abby 2 ; Volk, Gayle M 5   VIAFID ORCID Logo 

 The New Zealand Institute for Plant and Food Research Limited, Batchelar Road, Palmerston North 4410, New Zealand 
 USDA-ARS Plant Genetic Resources Unit, 630 W. North Street, Geneva, NY 14456, USA; [email protected] (G.F.); [email protected] (A.N.) 
 USDA-APHIS Plant Germplasm Quarantine Program, 9901 Powder Mill Road, Bldg 580, BARC-East, Beltsville, MD 20705, USA; [email protected] (L.C.C.); [email protected] (O.P.H.-G.) 
 Department of Plant Pathology, University of California-Davis, Davis, CA 95616, USA; [email protected] 
 USDA-ARS National Laboratory for Genetic Resources Preservation, 1111 S. Mason Street, Fort Collins, CO 80521, USA; [email protected] 
First page
582
Publication year
2022
Publication date
2022
Publisher
MDPI AG
e-ISSN
22237747
Source type
Scholarly Journal
Language of publication
English
ProQuest document ID
2637768373
Copyright
© 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/). Notwithstanding the ProQuest Terms and Conditions, you may use this content in accordance with the terms of the License.