Dormancy development during cold hardening of in vitro cultured Malus domestica Borkh. plants in relation to their frost resistance and cryotolerance

Abstract

The development of dormancy, frost resistance and cryotolerance of in vitro apple plants (Malus domestica Borkh.), cv. Greensleeves during their exposure to cold hardening was studied. In vitro cultures were cold hardened at 4°C under a short photoperiod up to 25 weeks. The dormancy status, non-structural saccharides, proline, water content and frost resistance were evaluated for optimization of cryopreservation. According to regrowth tests, in vitro cultures exhibited endogenous dormancy after the maximal frost resistance was reached. The highest regeneration ability of shoot tips after cryopreservation by encapsulation-dehydration method coincided with the period of the plant's dormant state and maximum of frost resistance. All studied saccharides and proline exhibited the maximal values at the beginning of cold hardening and/ or the dormancy phase. Contrary to the accumulation of saccharides and proline, water content showed the inverse time behaviour. According to these results, the cold hardening-induced endodormancy, high frost resistance and accumulation of saccharides and proline are the important prerequisites for the successful cryopreservation of shoot tips of in vitro grown apple plants.

Cold acclimation efficiency of different Prunus and Fragaria species and cultivars in vitro

“…After 8 weeks, the cold tolerance decreased, and after 20 weeks of cold acclimation it was on the level of nontreated control plants. At the end of the cultivation, the cold tolerance was even lower than in the control plants (Bilavčík et al, 2012). The cold tolerance in these experiments was higher than that obtained by Kushnarenko et al (2009), who showed that plantlets had the lowest lethal temperature (LT50) values after 1-3 weeks of cold acclimation under short day (8 h light) at 2°C, followed by a 48 h period at −3°C.…”

“…Such correspondence between in vitro and in vivo results for investigated Rosacea species (except Prunus) was obtained only after 56 days of cold acclimation. According to Bilavčík et al (2012), in vitro apple plantlets were the most cold tolerant after 7 weeks of cold-treatment, 1 week before entering endodormancy. After 8 weeks, the cold tolerance decreased, and after 20 weeks of cold acclimation it was on the level of nontreated control plants.…”

“…Two weeks before assessing of endodormancy in the 8 th week, leaves of apple plantlets ceased growing, became yellowish, brownish, and went down. This was apparently connected with entering the endodormant period, for which the increased production of abscisic acid (ABA), the main hormone controlling endodormancy and the associated autumn leaf fall in plants, is typical (Arora et al, 2003;Bilavčík et al, 2012). Changes in the expression of hundreds of genes, total reconfiguration of metabolite profiles and accumulation of specific compounds during cold acclimation have been demonstrated in different plants (Kaplan et al, 2007;Rohloff et al, 2012).…”

“…Electrolyte leakage can reflect the change of ion exosmosis, and can be used as a measure of the level of cellular damage. There are several examples of selection for winter hardiness and cold tolerance investigations in vitro (Kushnarenko et al, 2009;Bilavčík et al, 2012). A technology of screening cold hardy strawberry seedlings in early development stage has been developed .…”

Adaptation to seasonality and the winter freeze

“…Since most species have not been tested for cold adaptations, absence of data does not necessarily indicate absence of traits. However, since cold climates arose after major radiations in seed plants, presence data (based on Krug, 1991; De la Rosa et al, 2000; Kawamata et al, 2002; Wilson et al, 2002; Karlson et al, 2004; Streck and Schuh, 2005; Lopez and Runkle, 2006; Fausey and Cameron, 2007; Kalberer et al, 2007; Mewes and Pank, 2007; Rohwer and Heins, 2007; Svendsen et al, 2007; Padhye and Cameron, 2008, 2009; Pietsch et al, 2009; Zlesak and Anderson, 2009; Biasi et al, 2010; Byard et al, 2010; Ghelardini et al, 2010; Kaymak and Guvenc, 2010; Kubota et al, 2010; Lenahan et al, 2010; Rantasen and Palonen, 2010; Caffarra et al, 2011; Cave et al, 2011; Charrier et al, 2011; Dogramaci et al, 2011; Lin et al, 2011; Adhikari et al, 2012; Andreini et al, 2012; Bilavcik et al, 2012; Diaz-Riquelme et al, 2012; Nishitani et al, 2012; Sanchez-Perez et al, 2012; Whitman and Runkle, 2012; Alessandro et al, 2013; Guzy-Wrobelska et al, 2013; Jones et al, 2013; Mojtahedi et al, 2013) indicates multiple origins of cold adaptive traits across the phylogeny.…”