Objective  Optimal medium formulation and effect of plant growth regulators for germination of Prunus salicina var. cordata cv. Younai embryos were investigated.

  Method  Culture media with or without addition of plant growth regulators were varied to determine the effects on the embryonic germination of Younai seeds.

  Result  The highest germination rate of the semi-abortive breeding embryos inoculated in the WPM medium without any added growth regulator was 40.00%. With the regulator addition, the WPM medium including 2.0 mg·L⁻¹ 6-BA and 0.1 mg·L⁻¹ IBA (Treatment No. 6) achieved a maximum germination rate of 46.67%. For the intact embryos, the rate reached 100.00% on either MS, WPM, or WPM with the addition of either 1.0 mg·L⁻¹ 6-BA and 0.1 mg·L⁻¹ NAA (Treatment No. 2) or 2.0 mg·L⁻¹ 6-BA and 0.2 mg·L⁻¹ NAA (Treatment No. 3) or Treatment No. 6.

  Conclusion  The WPM medium with 2.0 mg·L⁻¹ 6-BA and 0.1 mg·L⁻¹ IBA delivered the highest germination rate of the semi-abortive seed embryos among all treatments. The germination of the intact embryos was found always higher than that of semi-abortive embryos. And, without added plant growth regulators, the WPM or MS medium could, nonetheless, provide acceptable embryo germination for Younai seeds.