Breeders try to develop strains of rye more suitable to Finland
By Arja Kivipelto
The popular image is that rye bread is a quintessentially Finnish food. However, the grain itself is rarely grown on farms in Finland today. No more than one third of the rye flour used in Finnish bakeries cis of Finnish origin. Most of it is imported from the Baltic Countries, Germany, and Russia.
Farmers in Finland shun rye, because it is a very challenging crop. The difficulty of cultivation stems from two characteristics - its long stalk, and the germination of the grain before harvest.
Both characteristics can be altered, says researcher Teija Tenhola-Roininen at Agrifood Research Finland (MTT). For her doctoral thesis, she studied the genes of rye, and found DNA markers which could make it possible to develop strains which would be more suitable for the conditions that prevail in Finland.
Rye can grow to heights of about two metres. When the grain ripens, whole fields can be seen waving beautifully in the summer wind, but it also easily bends down so far that it ends up flat against the ground, making it difficult to harvest. This reduces the harvest yield and weakens the quality of the grain.
If the field is damp at the time that the grain ripens, the individual grains can start sprouting, greatly lowering the quality. “At worst, there are roots and stalks there”, Tenhola-Roininen says.
“The long stalks and the premature sprouting show that rye is a somewhat primitive grain, which has been refined fairly little compared with what has been done with wheat and barley”, says Esa Teperi, a plant breeder at Boreal Plant Breeding Ltd.
Rye originates in an area comprising modern Turkey, Iran, and Armenia. it is classified as a grass plang, and has spread widely as a weed, mixed in with other grains.
Although rye can withstand infertile soil and difficult weather conditions, the Finnish winter is still challenging for it. Autumn rye is mainly grown in Finland. It is planted in the late summer, when it sprouts. It is left in the field through the winter, and is harvested the following year in July or August.
Two characteristics of rye, the long stalk and the deep roots, appear to be linked with one another.
“Previous attempts to shorten rye have failed because the root system has grown smaller, and the ability to get through the winter has declined”, Teperi says.
In her work Tenhola-Roininen uses diploid plants, with two complete sets of chromosomes - one from each parent plant.
In nature, rye cross-pollinates, getting seven chromosomes from each parent plant.
This means that the plant also contains recessive genes, which can emerge when an individual plant happens to inherit the same recessive characteristic from each of the parent plants.
Diploids make it easy to select individual plants, as they are exactly what they look like.
The diploids are prepared by hand through anther culture. The researcher or an assistant opens the flower of the rye, pinches off the stamen and moves its anther, which is six millimetres long, into a growth medium.
Anthers that are taken at the right time contain precursors of pollen grains, which develop into embryonic structures as well as undifferentiated tissue.
These grow into green, or albino plants. Only one or two out of every 100 anthers are green. The rest are albinos, and as such, unusable.
Out of 30,000 anthers, only 800 started to grow, and of them, 130 survived, and just 89 were of sufficient quality.
“I can pluck 1,000 anthers a day myself. My assistants are clearly more nimble, Dr. Tenhola-Roininen says.
The anthers and the tissue that is grown from them have a simple set of chromosomes. In tissue culture, it duplicates itself in some of the cells.
Diploids are individual plants, which have been differentiated from such sells with the help of plant hormones.
With the help of her diploids, Tenhola-Roininen compiled a gene map for rye. With its help she deduced which DNA markers and genes could be linked to having a short stalk, and a propensity to premature germination.
A DNA marker is a piece of the genotype, which is located near the gene, which affects the desired characteristic.
With her anther culture Tenhola-Roininen produced two rye populations, in which short stalkedness and early germination varied.
One of them is a line of mutants called EM 1, with the characteristic of having a short stalk. It has a “dwarf gene”, which is known to be located in chromosome five.
In the same chromosome, the researcher also isolated the genetic region linked with early germination, and near it, three promising looking microsatellites.
In addition she found a DNA marker allowing breeders to choose short-stalked rye with an error margin of 13 per cent.
“It may be that the sign works. It may be that it is the best possible”, said Sven Andersen, who first checked through the thesis.
The rye chosen with this marker is already growing at the experimental farm of Boreal Plant Breeding.
“At least last summer’s population appeared uniform”, Esa Teperi says. He hopes that no high stalks will emerge this summer.
If there are many deviant individuals, there is no point in developing the strain any further.
Helsingin Sanomat / First published in print 14.4.2009
Boreal Plant Breeding Ltd.
ARJA KIVIPELTO / Helsingin Sanomat