Question

The ploidy of bread wheat is
A. $$4n$$
B. $$6n$$
C. $$2n$$
D. $$8n$$

Answer 1

Hint: ploidy level means was developed by the hybridization of two different genus due to which it has a hexaploid level.

Step by step answer:Bread wheat is known by the scientific name Triticum aestivum.
Bread wheat was developed by intergeneric hybridization. Intergeneric hybridization means the hybridization between two different genera.
The two genera that were used to develop the Bread wheat or Triticum aestivum were Triticum dicoccoides, and Aegilops squarrosa. Triticum dicoccoides have $$2n=4x=28$$chromosomes. This means that its genome is of the type $$AABB$$.
Aegilops squarrosa is a diploid species. It has $$2n=2x=14$$chromosomes. This means that its genome is of the type$$DD$$.
When Triticum dicoccoides and Aegilops squarrosa are crossed together for hybridization, then, the results obtained are a trihybrid. It is then treated with colchicine to induce the polyploidy. Colchicine causes the chemical mutation which results in the inability of the chromosomes to segregate during the anaphase. Thus, the species then obtained is Triticum aestivum which is hexaploid or more precisely allohexaploid $$\left(6n\right)$$.
Thus, the ploidy level of bread wheat is $$6n$$.
Hence, the correct answer is option (B).

Note: Triticum dicoccoides is also known as the Emmer wheat. It is a wild form of wheat. It is a tetraploid species. On the other hand, Aegilops squarrosa is a plant from the Poaceae family. It is commonly used for animal feed. It is added to wheat because it is believed to be a natural source of disease resistance in wheat. It is susceptible to the disease-causing Barley mild mosaic bymovirus. It is a diploid species.