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Title: HIGH FREQUENCY REGENERATION OF PLANTLETS FROM LEAF EXPLANTS OF COMMERICAL PEAR (PYRUS COMMUNIS L.) CULTIVARS 'ONWARD' AND 'OLD HOME'

Author
item SUN, QINGRONG - TAIAN CHINA
item Davis, Robert
item Zhao, Yan

Submitted to: Congress on In Vitro Biology
Publication Type: Abstract Only
Publication Acceptance Date: 1/29/2005
Publication Date: 6/1/2005
Citation: Sun, Q., Davis, R.E., Zhao, Y. 2005. High frequency regeneration of plantlets from leaf explants of commerical pear (Pyrus communis l.) cultivars 'Onward' and 'Old Home'. Congress on In Vitro Biology. 41:49A.

Interpretive Summary:

Technical Abstract: Pear (Pyrus communis L.) is an important deciduous fruit with high commercial value. However, pear production is often hampered by bacterial, fungal, and viral diseases. As part of our program aimed at improving resistance of pear crops to diseases via genetic engineering, we studied the influence of medium composition and growth regulators on adventitious shoot formation from in vitro propagated leaf explants of two popular commercial pear cultivars, 'Onward' and 'Old Home'. Among three basal media (NN69, WPM, and C) tested, NN69 appeared to be the most suitable for promoting shoot regeneration. The cytokinin thidiazuron (TDZ) was much more effective than 6-benzylaminopurine (6-BA) in promoting shoot regeneration in both cultivars. The effect of two auxins, indole-3-butyric acid (IBA) and alpha-naphthalene acetic acid (NAA), was genotype-dependent. Regeneration frequency of 'Onward' reached 90% in NN69 basal medium plus 4 mg/l TDZ and 0.7 mg/l IBA. Regeneration frequency of 'Old Home' reached 100% when leaf explants were subjected to a two-phase culture regimen. In the initial shoot primordium induction phase, leaf segments were cultured on NN69 basal medium supplemented with 4 mg/l TDZ and 0.3 mg/l NAA; in the subsequent shoot elongation phase, emerging shoots were cultivated on Murashige-Skoog (MS) medium supplemented with 0.3 mg/l BA and 0.1 mg/l IBA. A comparative structural analysis revealed that shoot regeneration from 'Onward' leaf explants essentially occurred via direct organogenesis and that shoot regeneration from 'Old Home' leaf explants followed an indirect organogenesis pathway. Shoots regenerated from both cultivars were successfully rooted on ¼ MS salts supplemented with 0.3 mg/l NAA and 2% sucrose. The high efficiency regeneration protocols established in this study make it possible to use commercially important pear cultivars for eventual genetic engineering of disease resistance and for other pear improvement programs.