Embryo rescue — Hybrid embryos that would otherwise abort can be salvaged by growing them under what condition?

Introduction / Context:
Wide crosses often fail because developing hybrid embryos abort before seeds mature. Embryo rescue techniques excise the immature embryo and culture it in vitro on nutrient media, allowing development into viable plantlets that carry the desired hybrid genome.

Given Data / Assumptions:

• Embryos are delicate and require balanced sugars, minerals, vitamins, amino acids, and plant growth regulators.
• The developmental stage at excision dictates the medium composition (e.g., higher sucrose for very immature embryos).
• Sterile technique and supportive temperature/light regimes are essential.

Concept / Approach:
Embryo rescue replaces the failing maternal endosperm/seed environment with an artificial medium that supplies nutrition and hormones, preventing collapse. Therefore, the correct condition is growth in an artificial medium tailored to the embryo’s stage and species.

Step-by-Step Solution:

Verification / Alternative check:
Classic successes include interspecific Brassica, lily, and grape hybrids obtained through embryo culture followed by acclimatization.

Why Other Options Are Wrong:

Common Pitfalls:
Using adult tissue media for embryos; instead, tailor osmoticum and regulators to the embryo stage to avoid vitrification or necrosis.

Final Answer:
In an artificial (in vitro) culture medium optimized for embryo growth.