91Ó°ÊÓ

Hexaploid bread wheat, scientifically known as *Triticum aestivum*, is one of the most widely grown wheat species in the world. Understanding its genomic complexity is key to grasping its agricultural significance. A hexaploid organism means it has six sets of chromosomes. In the case of bread wheat, these six sets are divided among three distinct genomes: A, B, and D. Each genome contributes equally to the chromosome total, so each genome has 7 chromosomes. This makes for a total of 42 chromosomes in bread wheat:

• 7 chromosomes from the A genome
• 7 chromosomes from the B genome
• 7 chromosomes from the D genome

These genomes arose from natural crossings and hybridizations between different grass species over thousands of years. Hexaploid wheat's vast genetic diversity provides resilience against diseases and environmental stress.
It also influences various traits important for agriculture, like yield, grain quality, and adaptability.

Tetraploid durum wheat, known scientifically as *Triticum turgidum*, is another important species commonly used in pasta and other semolina products. Being tetraploid means that durum wheat has four sets of chromosomes. These sets are organized into two genomes, A and B, with each genome contributing 7 chromosomes. Thus, durum wheat has a total of 28 chromosomes:

• 14 chromosomes from the A genome (2 sets)
• 14 chromosomes from the B genome (2 sets)

Durum wheat has been a staple in human diets for centuries, particularly in regions around the Mediterranean. The distinction between durum and bread wheat in terms of ploidy level and genome composition impacts their physical and nutritional characteristics. Durum wheat’s sturdy nature helps produce pasta with that well-loved al-dente texture, contributing to its global popularity.

The concept of chromosome count in wheat is essential to understand genetic makeup and plant breeding. In wheat, chromosome count is directly linked to its classification as either hexaploid or tetraploid:

• Hexaploid bread wheat: 42 chromosomes in total (3 genomes)
• Tetraploid durum wheat: 28 chromosomes in total (2 genomes)

Knowing how many chromosomes are present in the organisms is critical for plant scientists and breeders. The distribution of these chromosomes among the genomes (A, B, and, if present, D) dictates not only the physical characteristics of the plant but also its adaptability and resistance to diseases.
Unique attributes like disease resistance and environmental resilience underscore the importance of understanding chromosome count in different wheat species. Each genome represents a pool of genetic traits that can be selectively emphasized or suppressed depending on breeding goals. By manipulating chromosome count, breeders can develop new varieties that better meet agricultural needs and consumer preferences.