Journal of Heredity 23:465-466
"IAROVIZATION"
A New Factor in Plant Breeding Technique

A. J. BRUMAN.
Division of Foreign Plant Introduction U. S. Department of Agriculture.

IT IS announced that the difficulties experienced by plant breeders in crossing plants of different blooming dates can now be overcome by the employment of a series of new methods worked out at the Odessa Institute of Genetics and Plant Breeding by Prof. T. D. Lissenko.

The details of Lissenko's methods have not been published outside of Russia but the strikingly novel ideas upon which these methods are based together with some rather convincing illustrations are presented in the June, 1932, number of Der Züchter by A. A. Sapegin, the Director of the Odessa Institute.

According to Lissenko, the development of an organism manifests itself chiefly in well recognizable consecutive stages each of which is characterized by its own specific morphology and physiology. The individual developmental stages require for their completion different complexes of environmental conditions just as different biotypes require such different environments for their normal development.

Lissenko has worked out, for instance, the temperature and temperature duration requirements for the first developmental stages of wheat. In speaking of the first development stage he apparently has in mind the pre-germination stage, i.e., the period when the swollen seed is just going through the most primary life processes of metabolic activity.

Light and darkness are other essential components of the environmental complex, particularly in the case of the so-called "short day" types of plants. Darkness for these "short day" types is just as indispensable as light and is, especially, essential for the completion of the vegetative and the transition into the reproductive stage. But what is particularly striking is Lissenko's alleged discovery that this darkness does not necessarily have to alternate with light and that it can be applied in the required quantity all at once. In other words, a plant can receive its full quota of darkness in its early pre-seedling stage and can then be grown to maturity in uninterrupted light. This is not only true of darkness but also of temperature and other factors making up the environmental complex of the plant. Lissenko's experiments with wheat, millet, corn, cotton, sorgo, sudan grass, vetch, and soybeans have shown that the influence of the direct external factors and their duration, necessary for the completion of the vegetative and for the transition to the reproductive state, is required in exactly the same manner whether the plant is in the state of an ungerminated seed which has been only slightly stimulated into its primary life processes by soaking or whether it is in the state of active vegetative advance. This occurrence has been designated by Lissenko with the term "Iarovizatzia" which, unfortunately, cannot be anglicized. "larovization" has already been adapted by Soviet plant breeders for the purpose of shortening the vegetative period thus accelerating their variety breeding work two or three times. The matching of the blooming periods in parent plants, the breaking up of the persistent vegetative stage in some hybrids and bringing into maturity any exotic plant in a totally strange environment are some of the other possible applications claimed for "iarovization" in plant breeding work.

The direct application of "iarovization" to agricultural practice is also manifold. It has already been employed in Soviet Russia it is claimed in 1930 and 1931 on an area of over a quarter of a million acres in cases where winter wheat has frozen out or where it has been killed by drouth. By "iarovizing" their remaining seed material and sowing it in the spring the Soviet farmers were enabled to obtain a normal yield of high quality grain. In regions where hot, dry winds prevail during the critical period of seed formation the possibilities offered by "iarovization" in shortening the vegetation period are especially important.

Lissenko asserts that "iarovization" does not by any means supplant plant breeding but rather supplements it, that all work on "iarovization" was developed on the basis of differences in the degree of reaction of different biotypes against changes of external conditions. Lissenko expects that in the future "iarovization" will become superfluous through breeding, i.e., that such varieties will be obtained which will require no more "iarovization."

Bruman (1937)