Effect of culture jar seal on in vitro rooting and subsequent acclimatization of three Italian apricot varieties

•Hermetically (H)-closed jars had high C2H4 and CO2 concentrations.•Polyvinylchloride (PVC) seal enhanced in vitro root numbers compared to H.•Ex vitro survival was lower for plantlets from H- than cotton-closed jars.•Ex vitro growth was lowest for plantlets from H-closed jars.•In vitro rooting aptitude and ex vitro plantlet survival were also genotype-dependent.

Low rooting and survival in the acclimatization phase are among the main factors that can negatively affect in vitro propagation of apricot. We investigated: (a) the effect of different jar closure types [hermetic (H), cotton plugs (C) and polyvinyl chloride (PVC) sealing] on C2H4 and CO2 accumulation, and in vitro rooting of apricot shoots, cv. San Castrese, Boreale and Vitillo; (b) plantlet behavior after transfer ex vitro. ‘San Castrese’ showed the highest rooting aptitude, regardless of the jar closure type. The H closure strongly increased C2H4 (up to 567 ηmol mol−1 in ‘San Castrese’) and CO2 (to a mean of 85 mmol mol−1) accumulation inside jars, without affecting in vitro rooting percentages; however, it significantly reduced root number in comparison to PVC. The H closure also lowered survival rates in the acclimatization phase, especially compared to C, and caused reduced root growth in ‘Boreale’ and ‘Vitillo’ if compared to PVC and C, respectively. Moreover, plantlets from H were generally shorter.

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