Taxonomic scope — Which of the following are recognized classes of hybridization used in plant breeding?

Introduction / Context:
Plant breeders exploit hybridization at multiple taxonomic levels to introgress traits, widen genetic bases, and create novel combinations. The category depends on the taxonomic distance between the parents: within a species, between species, or between genera.

Given Data / Assumptions:

• Intervarietal crosses involve varieties/lines of the same species.
• Interspecific crosses bridge species barriers, sometimes requiring embryo rescue.
• Intergeneric crosses can produce wide hybrids or allotetraploids with chromosome doubling.

Concept / Approach:
All listed categories are valid and routinely referenced in breeding literature. The feasibility and fertility of hybrids generally decrease with increasing taxonomic distance, but biotechnological aids can overcome barriers.

Step-by-Step Solution:

Verification / Alternative check:
Examples include: wheat intervarietal breeding; triticale (interspecific/intergeneric with rye and wheat ancestry); Brassica triangle interspecific crosses.

Why Other Options Are Wrong:

Common Pitfalls:
Assuming only within-species crosses are feasible; modern breeding routinely attempts wider crosses with appropriate techniques.

Final Answer:
All of these.