Long-duration, high-frequency plant regeneration from cereal tissue cultures

Area of Science:

• Plant Biotechnology
• Agricultural Science
• Cell Biology

Background:

• Plant regeneration from callus cultures is crucial for crop improvement.
• Distinguishing between embryogenic (E) and non-embryogenic (NE) callus is vital for efficient regeneration.
• Previous methods lacked consistent visual criteria for E callus selection.

Purpose of the Study:

• To establish visual criteria for identifying embryogenic callus in cereal species.
• To optimize media for both E callus production and subsequent plant regeneration.
• To quantify the regeneration efficiency difference between E and NE callus.

Main Methods:

• Visual examination of calli derived from wheat, oats, rice, proso millet, and pearl millet seeds.
• Culturing calli on media supplemented with specific plant growth regulators (auxins and cytokinins).
• Transferring selected E callus to regeneration media and assessing plantlet formation.

Main Results:

• Embryogenic callus cells are small and isodiametric (avg. 31 μm), while NE callus cells are elongated and tubular (avg. 52x355 μm).
• Specific auxin combinations (2,4-D or 2,4,5-T with IAA or Trp+Kin) promoted E callus production.
• Media with auxin alone promoted NE callus production.
• Regenerated plants were formed 33 times more frequently from E callus than NE callus.
• Optimized protocols yielded ~1,000 regenerated plants from 26 seeds within six passages.

Conclusions:

• Visual selection of E callus is a highly effective method for improving plant regeneration efficiency in cereals.
• Defined media compositions differentially influence E and NE callus development.
• This approach significantly increases the number of regenerated plants from cereal tissue cultures.