Option-wise explanation

1. Triticum monococcum

   • This is domesticated einkorn wheat, derived from a wild ancestor.

   • It is itself a cultivated species, not the wild relative being asked for.

2. Triticum compactum

   • Known as club wheat, this is a hexaploid cultivated wheat (a form of bread wheat).

   • It is not a wild species; it is one of the soft/bread wheat types.

3. Triticum vulgare

   • An older name often used synonymously for Triticum aestivum, common bread wheat.

   • Again, this is a fully domesticated crop species, not a wild relative.

4. Triticum boeoticum – correct

   • This is wild einkorn wheat, a diploid wild species considered a wild progenitor/relative of cultivated einkorn (T. monococcum) and part of the A‑genome gene pool of wheat.

   • It is widely recognized in crop‑wild‑relative literature as an important wild relative of wheat, serving as a source of useful alleles for breeding.

Therefore, the wild relative of wheat among the options is Triticum boeoticum (option 4).