A simple two-step model for evaluation of in vitro regeneration protocols is proposed based on callus induction and regeneration from immature scutella of two Canadian barley (Hordeum vulgare L.) genotypes, AC Metcalfe and SB92559 using the Enhanced Regeneration System (ERS). The number of explants producing embryogenic callus, the number of plants per embryogenic callus and the number of plants per explant were considered. Tissue culture parameters included three combinations of growth regulators, two carbon sources in culture media, and three cold treatment regimes of spikes prior to scutella isolation. Culture medium containing 5 µM 2,4-dichlorophenoxy acetic acid (2,4-D) and 0.5 µM benzyl adenine (BA) induced the highest percent of embryogenic calli and the highest number of shoots per embryogenic callus from AC Metcalfe. Medium containing 3.75 µM 2,4-D and 0.75 µM BA gave the best response for SB92559. Both genotypes produced more shoots on maltose than on sucrose medium. A 2-d treatment of spikes at 4°C resulted in best response for SB92559. Regeneration response from AC Metcalfe scutella from spikes was unaffected by being subjected to 2, 4 or 6 d of cold. Conditions resulting in best responses from both genotypes were tested on four commercial barley varieties. However, these lines showed inferior regeneration compared to SB92559 and AC Metcalfe. Key words: Hordeum vulgare, scutella, embryogenic callus, shoot production
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