Durum Wheat (Triticum durum Desf.)

The species of the genus Triticum can be grouped in three catego ries, accord ingto the number of chromosomes, i.e ., 14 (diploid), 28 (tetraploid) and 42 (hexaploid). The basic set of chromosomes is 7, and the above designations signify 2 × 7 (2n), 4 × 7 (4n), and 6 × 7 (6n) respectively. Triticum durum Desf. (durum wheat) belongs to the tetraploid group and is characterized by “naked” grains incomparison with the “hulled” wheats where the glumes are hard, difficult to remove and remain attached to the grain. Before the chromosome numbers in wheat were known, they were classified on morphological characters into three main groups called Einkorn, Emmer and Dinkel (Schulz 1913). These groups whose chromosome number is 2n, 4nand 6 n, are diploid, allotetraploid and allohexaploid. In the allot etrapl oid there are two genomes derived from one species and two form a different species. During mitosis, as in the diploids homologous chromosomes are in pair s. For each pair of homologous chromosomes in one set of chromosomes there is a pair of related homologous chromosomes in the other set. The chromosomes in the one pair that are partially but not fully homologous with the chromosomes in the corresponding pair in the different genome are termed “homeologous” . Similarly in the allohexaploid species there are three different set of chromosome pairs. In the genus “Triticum” there are three different genomes, each composed of seven chromosomes. Kihara (1924) designed these genomes A, B, and D. The genome combination of “Triticum durum” cells is AABB, while diploid (Einkorn) and hexaploid (Dinkel) wheats have cells with genomes AA and AABBDD, respectively.