Elimination of viruses through thermotherapy and meristem culture in apple cultivar ‘Oregon Spur-II’

Abstract

In the present study, an attempt was made to eliminate apple chlorotic leaf spot virus, apple mosaic virus, apple stem grooving virus and apple stem pitting virus from apple cultivar 'Oregon Spur-II'. Thermotherapy was carried out at 37-40 °C for 4 weeks followed by culturing of meristems of different sizes. During establishment of explants, highest survival percentage (62.35%) and proliferation (30.68%) was recorded during summer season. However, size of meristems and position of buds from where meristems were excised also influenced their survival. The meristems of size 0.6-0.7 mm were found to be the most appropriate for maximum establishment. Meristems excised from buds positioned on distil portions of actively growing shoots showed better results. MS medium supplemented with BA (1.0 mg/l), IBA (0.05 mg/l) and GA (0.1 mg/l) resulted in 56.62% establishment of explants, while maximum number of meristems proliferated with low BA (0.5 mg/l), IBA (0.08 mg/l) and same GA concentration. Two to fourfold multiplication was observed. Virus indexing of shoots raised from different sizes of meristems was carried out and found that 0.3-0.6 mm size was able to eliminate ACLSV, ApMV, ASGV and ASPV. However, some of 0.5-0.6 mm sized shoots were found infected with ACLSV. Larger meristems could not completely eliminate the viruses under study.

In vitro tissue culture of apple and other Malus species: recent advances and applications

“…In vitro culture is a successful method to eradicate apple viruses and detailed information on this subject before the twenty-first century can be found in several comprehensive reviews (Laimer and Barba 2011;Panattoni et al 2013;Barba et al 2015). Advances on this subject since 2000 reported improvements of in vitro-based methods for apple virus eradication, including thermotherapy (Paprštein et al 2008;Hu et al 2015bHu et al , 2017Vivek and Modgil 2018;Wang et al 2018b), chemotherapy (James et al 1997;Paprštein et al 2013;Hu et al 2015b), combining chemotherapy with thermotherapy (Hu et al 2015b), shoot tip culture from adventitious buds (Wang et al 2016), cryotherapy (Li et al 2016;Romadanova et al 2016a;Bettoni et al 2018) and combining thermotherapy with cryotherapy (Zhao et al 2018) (Fig. 5).…”

Exogenous application of melatonin improves eradication of apple stem grooving virus from the infected in vitro shoots by shoot tip culture

“…So far, ASGV has been successfully eradicated from infected apple and pear plants by thermotherapy‐based methods such as thermotherapy followed by shoot tip culture (Hu et al ., ; Vivek & Modgil, ; Wang et al ., ), chemotherapy followed by thermotherapy (Hu et al ., , ; Wang et al ., ), thermotherapy followed by shoot tip grafting (Hu et al ., , ; Wang et al ., ) and thermotherapy followed by shoot tip cryotherapy (Wang et al ., ; Zhao et al ., ). Contrary to these findings, Paprstein et al .…”

“…Secondly, virus eradication by exogenous application of melatonin does not require extra facilities and can be conducted in any tissue culture laboratory, whereas ASGV eradication by thermotherapy and cryotherapy requires expensive growth chambers in the former, and cryogenic procedures which may not be available in some laboratories in the latter. Thirdly, ASGV eradication frequencies obtained in the present study (95%) were comparable with those reported in previous studies (Hu et al ., , ; Vivek & Modgil, ; Zhao et al ., ). Furthermore, 100% survival and 85% shoot regrowth levels of the shoot tips were obtained in the present study, which were higher than 62.5% (Paprstein et al ., ) and 62.4% (Vivek & Modgil, ) of shoot tip survival levels in thermotherapy followed by shoot tip culture, 65% of shoot tip survival when combining thermotherapy with chemotherapy (Hu et al ., ), 63.0% of shoot tip grafting success in thermotherapy followed by shoot tip grafting (Hu et al ., ) and 33–76% of shoot regrowth levels in thermotherapy followed by cryotherapy (Zhao et al ., ).…”

“…So far, ASGV has been successfully eradicated from infected apple and pear plants by thermotherapy-based methods such as thermotherapy followed by shoot tip culture (Hu et al, 2015a;Vivek & Modgil, 2018;Wang et al, 2018a), chemotherapy followed by thermotherapy (Hu et al, 2012(Hu et al, , 2015bWang et al, 2018a), Table 2 Effects of exogenous application of melatonin at different concentrations to shoot proliferation medium on apple stem grooving virus (ASGV) eradication by shoot tip culture from the virus-infected in vitro shoots of apple cultivar Gala.…”

“…Production and maintenance of virus‐free planting materials is pivotal for the control of viral disease. With continuous efforts exerted to produce virus‐free apple plants, various techniques have been established for apple virus eradication, including shoot tip culture (also called meristem culture; Laimer & Barba, ; Wang et al ., ), shoot tip cryotherapy (Li et al ., ) and thermotherapy‐based methods including thermotherapy followed by shoot tip culture (Paprstein et al ., ; Laimer & Barba, ; Vivek & Modgil, ; Wang et al ., ), combining thermotherapy with chemotherapy (Laimer & Barba, ; Hu et al ., ; Wang et al ., ), thermotherapy followed by shoot tip grafting (Hu et al ., , ; Wang et al ., ), and thermotherapy followed by shoot tip cryotherapy (Wang et al ., ; Zhao et al ., ). ASGV has been shown to be a difficult‐to‐eradicate virus (Paprstein et al ., ; Massart et al ., ; Li et al ., ; Wang et al ., , ,b; Zhao et al ., ).…”