You know that if you cross a cocker spaniel with a poodle, you get a cockapoo unless you’re down under. In Australia, the resulting offspring is a called a spoodle. I’m sure they are the same hybrid dog. And being a hybrid means that these dogs have half the chromosomes from each breed. The hybrids do not themselves breed true. In a cross of two cockapoo, the next generation may express a variety of characteristics. If looked at individually, these characteristics might be explained through Mendel’s Laws which he developed cross breeding pea plants. When it comes to wheat, our understanding of the rules completely changes. Our concept of species is challenged by the complexity of a genome that contains more than 16 billion basepairs. The human genome in comparison contains only about 3 billion basepairs – 1/5 the number found in wheat.

I like Mark Nesbitt’s definition of domestication as “the process by which humans take reproductive control of plants or animals modifying them for their own purposes”. In his contribution to “Wheat Taxonomy”, he further explains how with wheat, the domestication process involved selecting plants which did not break up at maturity to distribute the seeds. (illustration). The obvious advantage is that the seeds were then available for harvest and not strewn about the ground. Nesbitt provides a great deal of information about archaeobotany and he admits there is still a lot of study to be done.

At this point I will cut straight to the chaff. Wheat is classified according to the number of chromosomes. The major categories of wheat are:

• diploid - eikorn (14 chromosomes),
• tetraploid - emmer (28 chromosomes)
• hexaploid - (42 chromosomes).

Wheat crossbreeds in nature easily and selection of varieties for domestication took many centuries and occurred in many geographic regions. In an earlier blog I noted that in Canada, early scientists led by Dr. Cyril Goulden produced rust-resistant Selkirk wheat through selection, hybridization and careful plant breeding. They started from a few stems found and carefully cultivated by Malcolm McMurachy in 1930 and this led to the 1954 release to farmers of the rust-resistant Selkirk wheat.

As with any type of domesticated plant or animal, the traditional method of developing a new wheat type was to cross-breed plants with characteristics that are needed, followed by self-pollinating generation after generation of the resulting hybrid until the desired characteristics breed true. Many generations, much time. In the biotech of today, scientists produce haploid embryos: half the normal number of chromosomes. The chromosome number is then doubled to the diploid number with the application of colchicine, a chemical. The resulting chromosomes are therefore identical and the plant is true-breeding.

As early as the 1950’s, genes responsible for gluten were being mapped onto chromosomes. Two current genomic studies of wheat should be of particular interest to those persons with gluten intolerance. A major project to sequence and study the wheat genome is under the umbrella of the International Wheat Genome Sequencing Consortium (IWGSC). The IWGSC promises some exciting results in the near future. The other major study I noticed is the one coming from the Royal Netherlands Academy of Arts and Sciences. They note that since up to 0.5% of the European and American population suffers in various degrees from gluten-intolerance to gluten hypersensitivity (celiac), a close examination of up to 150 different gluten-related genes is crucial. They hypothesize that their project could lead to the total elimination of allergenic sequences from the wheat genome while retaining the industrial quality of the gluten proteins. While this may seem like an ambitious long term project, the immediate results will be the identification of genetic markers enabling the improvement of non-toxic cultivars. Additionally, there will be a development of knowledge about gluten gene expression under various conditions and a means of detection of potentially toxic gluten sequences in food. I believe both of these projects will improve dietary health without the use of drugs.

In the next blog in this sequence, I will be examining the human genome and what we have learned about the genomics associated with gluten intolerance.