Journal of Heredity 24: 165-166
RUSSIAN METHODS FOR ACCELERATING SEXUAL REPRODUCTION IN WHEAT
Further Information Regarding "Iarovization"
H. H. McKinney and W. J. Sando*
*Senior pathologist and associate agronomist, respectively.
Division of Cereal Crops and Diseases, United States Department of Agriculture
institut selectii. Builleten iarovisatsii No. 1. Jan., 1932. Nos.
2 and 3 [bound together] Sept. 1932. Odessa, 1932.
THE general instructions, decrees, and resolutions on "Iarovization," together with 17 research papers on the subject, are contained in three bulletins.* These bulletins are written entirely in Russian, but English abstracts and complete translations of all the papers are in preparation.+ These will be deposited in the Library of the United States Department of Agriculture, Washington, D. C.
"Iarovizatsii" or "Iarovization" in the Russian means "springization." Lysenko3 appears to have coined the term to designate early sexual reproduction in spring-sown winter wheat which had been chilled near freezing before sowing. However, the term is now applied to other methods of treatment and to many spring-planted crops such as spring wheat, corn, millet, and cotton.
The general instructions for chilling ("Iarovizing") large quantities of wheat seed are outlined in Iarovization Bulletin No. 1. These methods are briefly summarized as follows:
Winter wheats: The grain is spread in a layer from 6 to 7 inches deep on a floor. Water at the rate of about one-third of the weight of the seed is sprinkled over the seed, the water being applied in thirds with intervals of 8 hours between the applications. The final moisture content of the seed should be 50 to 55 percent. The seed is allowed to germinate at 50 to 60º F. for 24 hours and is shoveled over three or four times during the process. The germinated seed is held at 32 to 34.2º F. for 40 to 55 days and is stirred many times during the process of chilling.
Spring wheats (durums): The moisture content is raised only to 45 to 50 percent. The germinated seed is held at 33.8° to 41º F. for 10 to 15 days.
Facilities for chilling: The low temperatures of winter are employed for the treatment of the germinated seeds. The temperature is regulated by opening and closing the windows and doors of rooms or graineries manually.
Retarding the rate of germination during the chilling treatment: The rate of germination is retarded by avoiding an excess of moisture in the seeds. Seeds are sometimes treated with salt solutions to reduce the germination rate during the chilling treatments. Sea water and synthetic salt solutions resembling the combinations of salts found in sea water have given the best results. Apparently this method has not been used on a large scale.
Drilling: After the end of the chilling treatment the germinated seed may be dried and sown by means of a grain drill properly set for germinated seed. Such seed may be stored and transported. However, it is claimed that germinated seed that has been treated with a salt solution does not withstand drying so well as does seed not so treated.
In 1929. a popular article in a Russian newspaper1 stated that chilled winter wheat was being sown in several areas in the Ukraine, and it was claimed that advantages were to be gained from the sowing of chilled Spring varieties.
Sapehin2,4 has stated that 250,000 acres in Russia were sown with chilled seed in the spring of 1932. He claims that the method is of great value in resowing areas in which the fall sowing has winterkilled, in areas which have too little or too much moisture during the autumn, and in many of the dry-land areas.
"Iarovizing" Other Crops
Sexual reproduction is accelerated in so-called short-day plants such as corn, millet, Sudan grass, sorghum, and soybean by germinating the seeds slowly in uninterrupted darkness at moderately high temperatures for suitable periods. The rate of germination is retarded by controlling the moisture content of the seed. Table I shows the moisture content of the seed, the temperature, and the duration of exposure for the crop plants mentioned. The time of exposure at the suitable temperature is calculated from the time of the first signs of germination. Different varieties of the same species sometimes require different treatments for the best results.
Lysenko3 emphasizes the importance of darkness. He considers that short-day plants do not require an alternation of definite periods of light and darkness but rather a certain total amount of light and a certain total amount of darkness and he takes the view that the cause of the late maturity of short-day plants in northern regions is not the long day but the short night.
Water content of seed, temperature, and time of exposure in darkness
to stimulate early sexual reproduction in certain plants having the spring growth habit.
|Crop||Percentage of water
by weight in seed
|Temperature of seed (ºF)
during exposure in darkness
of exposure at
|Corn||30||68 to 86||10 to 15|
|Millet||26||77 to 86||5|
|Sudan crass||26||77 to 86||8 to 10|
|Sorghum||26||77 to 86||8 to 10|
|Soybeans||75||68 to 77||10 to 15|