There are three clearly defined species of rye:
- Secale cereal L., the cultivated species, which also exists as a highly diverse annual weed in farms in Iran, Afghanistan an Transcaspia;
- Secale montanum Gussh., an out-breeding, widely distributed assemblage of perennial races located from Morocco east through the Mediterranean countries to Iraq and Iran;
- Secale sylvestre Host., an annual in-breeder, which is widely distributed from Hungary to the steppes of southern Russia.
One additional taxon, Secale vavilovii Grossh., may be sufficiently unique to warrant species status.
Most authorities believe that S. cereale evolved from S. montanum Gush.
These two species are similar cytologically, but vary by two reciprocal translocations involving three pairs of chromosomes.
As with oats, rye developed as a secondary crop. It was probably picked up as a weed when the wheat-barley assemblage arrived in western Asia, where the native species are widely distributed.
Like the other grain species, agronomic traits, such as rachis fragility, ear branching and growth habit, are determined by only a few genes.
The precise origin of rye domestication is unknown, but it was being cultivated at several locations in the general area of Turkey, north western Iran and Armenia by 6000 BP.
Rye arrived in Europe as a cultivated crop by 4000 BP. Because of its tough constitution, it may have performed better than wheat and barley in the cooler, nutrient poor northern climates and therefore attracted human attraction.
In modern times, tetraploid and hexaploid wheat have been artificially hybridized with rye to form the new crop called Triticale.
Rye
