Plant 250

Secale cereale L. (Poaceae)



The small genus Secale is distributed through Eurasia into Central Asia and Africa. It is best known as the commercial crop rye. Rye is unusual among most European-grown cereals; it is outcrossing. That is, pollen must be transferred among open flowers for grain to be produced. Yield depends on the efficiency of wind pollination.

For Pliny, rye was a 'very poor food' that 'only serves to avert starvation', although he accepted it would grow anywhere, and enrich soil. It has been grown for hundreds of years in northern and eastern Europe, and its cultivation exported to North America in the wake of European immigration. Rye is used as animal feed, to make black bread and crispbread and even distilled into whiskey and vodka.

Rye has its centre of diversity in western and central Asia, where numerous different types can be found. These are grouped into domesticated varieties, weedy races and wild forms. The weedy races infest wheat fields, whilst it appears domesticated varieties may have been selected from these tolerated weeds. Within its centre of diversity, complex patterns of gene exchange between wild, semi-domesticated and domesticated types has led to the evolution of numerous landraces.

Landraces have been important for rye breeding, but rye is also one of the parents of the intergeneric hybrid crop triticale (xTriticosecale); the other parent is wheat (Triticum). Triticale is primarily a fodder and forage crop, combining the agricultural and nutritional advantages of both parents.

Many grasses can become infected with the parasitic, ascomycete fungus ergot (Claviceps purpurea). Rye is one of the best-known cereal hosts for ergot. Spores land on the exposed stigmas of the flower, grow into the ovary and develop into a spur-like structure (sclerotium) that replaces the rye grain. When ergot-infested rye is harvested, the crop may therefore be contaminated with ergot sclerotia.

The sclerotium contains high concentrations of the alkaloid ergotamine, which contains lysergic acid; Albert Hofmann synthesised the hallucinogen lysergic acid diethylamide (LSD) from ergotamine in 1938. Sustained, inadvertent ergot consumption leads to ergotism (St. Anthony's fire) that can produce hallucinogenic effects, gangrene and eventually limb loss. However, ergot has also been used, in controlled amounts, during childbirth and to induce abortions.

Periodic outbreaks of ergotism in Europe and North America have occurred for hundreds of years, and attempts have been made to link these outbreaks with concerns over witchcraft. Ergotism outbreaks have declined as grain-cleaning techniques have improved.

Further reading

Bennett JW and Bentley R 1999. Pride and prejudice: the story of ergot. Perspectives in Biology and Medicine 42: 333-355.

Ren T et al. 2011. Evolutionary trends of microsatellites during the speciation process and phylogenetic relationships within the genus Secale. Genome 54: 316-326.

Zohary D et al. 2012. Domestication of plants in the Old World. Oxford University Press.

Stephen Harris