Cytonuclear origin in a wheat introgression line: The variety “Rendezvous,” with eye-spot (Pseudocercosporella herpotrichoides) resistance derived from Aegilops ventricosa, has its chloroplast genome derived from which genus?

Introduction / Context:
When resistance is introduced from wild relatives into wheat, nuclear genes may originate from the donor, but cytoplasmic genomes (chloroplasts/mitochondria) are usually maternal and remain from the recurrent wheat parent unless cytoplasm substitution is performed. Understanding cytonuclear origins helps interpret phenotypes and breeding behavior.

Given Data / Assumptions:

• Rendezvous carries eye-spot resistance introgressed from Aegilops ventricosa.
• Standard backcrossing uses wheat as the recurrent maternal parent.
• Chloroplasts are generally maternally inherited in Triticeae.

Concept / Approach:
In typical introgression lines, nuclear segments from Aegilops are transferred into the wheat background. Unless specific cytoplasm substitution is performed, the chloroplast genome remains that of Triticum, the cultivated wheat parent. Thus, resistance can be donor-derived while the chloroplast genome is wheat-derived.

Step-by-Step Solution:

Verification / Alternative check:
Pedigree records for introgression lines typically indicate wheat cytoplasm unless explicitly stated otherwise; cytoplasmic substitution lines are specially designated due to their distinct properties.

Why Other Options Are Wrong:

• Aegilops: would require donor cytoplasm or maternal donor crosses, not standard for such varieties.
• Both equally: chloroplast genomes are not a mix; they are inherited uniparentally.
• S-alleles: unrelated to chloroplast inheritance.
• Secale: rye cytoplasm is irrelevant here.

Common Pitfalls:
Assuming that nuclear introgression automatically changes organelle genomes; organelles follow cytoplasmic inheritance rules independent of nuclear introgressions.

Final Answer:
Triticum