Influence of Two Commercial Agars on In Vitro Shoot Proliferation of ‘Almey’ Crabapple and ‘Seckel’ Pear

Shoot tips of ‘Almey’ crabapple [ Malus baccata (L.) Borkh. × M. pumila var. niedzwetzkyana (Dieck) Schneid.] and ‘Seckel’ pear ( Pyrus communis L.) were cultured on Murashige and Skoog (MS) medium containing 2 mg/liter 6-benzylamino purine (BA). The culture medium contained either TC agar or Bacto-agar at concentrations ranging from 0% to 1.2%. Optimum shoot proliferation in ‘Almey’ was obtained on media containing 0.3% of either agar. Increasing agar levels reduced shoot proliferation and shoot growth, but the reduction was especially severe with Bacto-agar. The differences in shoot proliferation between the 0.3% and 0.6% agar concentrations continued to be exhibited with Bacto-agar but not with TC agar when Mason jars, rather than 25 × 150-mm tubes, were the culture vessels. Shoot proliferation in ‘Seckel’ was best on medium containing 0.6% Bacto-agar; higher concentrations decreased shoot proliferation and shoot growth. TC agar did not influence fresh weight of ‘Seckel’ cultures, but increasing concentrations resulted in increased shoot proliferation.