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

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 behaviour 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.