Impact of explant type, duration and initiation time on the co-culture effect in isolated microspore culture of wheat (Triticum aestivum L.)

The effect of co-culture explant type, duration and initiation time on the culture of blender-isolated microspores of the spring wheat (Triticum aestivum L.) genotypes 'Mahri' and Hja 24201 was investigated. Microspore-derived embryo-like structures (ELS) were obtained only with co-culture. Wheat ovary, glume, floret and anther co-cultures produced ELS in both genotypes. Among the explant types, ELS formation and plant regeneration were highest with ovary co-culture. Five days of nb initio ovary co-culture were sufficient to induce embryogenesis, although prolonged co-culture durations resulted in improved ELS and plant production. Addition of ovaries to the culture medium 5 days after microspore isolation still produced ELS but addition after 10 days gave ELS only in 'Mahti'. We conclude that the positive coculture effect on wheat microspore embryogenesis was obtained with non-embryogenic glume explants, indicating that the effect was not ovary-specific and that for optimal efficiency the co-culture should be applied for at least 5 days, the first application taking place no later than 5 days after microspore culture initiation.