Effect of the type of closure for culture bottles on micropropagation efficiency of apricot

Papers on micropropagation of apricot generally report difficulties in all culture phases, and also suggest genotype-dependent requirements. So far, the effect of the gaseous microenvironment has not been studied in apricot tissue culture. The effect of using different types of closures [i.e., hermetic (H), polyvinylchloride (PVC) sealing and cotton plugs (C)] for culture bottles on ethylene (C2H4) and carbon dioxide (CO2) accumulation by shoots of apricot (Prunus armeniaca L.), cv San Castrese, Boreale and Vitillo were investigated. The direct and long-term effects of the gaseous microenvironment on culture behavior were shown, following treatment with different aminoethoxyvinylglycine (AVG)/closure type combinations were also examined. High C2H4 and CO2 concentrations (up to about 1 mol mol−1 and 20 mmol mol−1, respectively) were found in the H-closed bottles at the end of subculture. In particular, C2H4 accumulation was mainly due to production within the first 10 days culture. Increased shoot weight and proliferation, and also higher shoot length in ‘San Castrese’, were found in the H-closed bottles; moreover, subsequent rooting of these shoots was not negatively affected in comparison to other closures. These effects were more related to C2H4 than CO2 accumulation. However, culture responses were also greatly genotype dependent. In particular, ‘Boreale’ produced the highest number of axillary shoots from one initial explants, while ‘Vitillo’ showed the best root development. ‘San Castrese’ was characterized by the lowest C2H4 production in the proliferation phase and appeared to be the most sensitive to its accumulation with regard to shoot elongation. The addition of 1 M aminoethoxyvinylglycine (AVG) to the proliferation medium reduced shoot elongation both in H- and PVC-closed bottles. However, better root development was subsequently noted in shoots from the PVC/AVG combination