apomixis

From a position of S.S. Khokhlov’s conception (1946) in the light of the modern data on embryology and genetics of apomixis the perspectives of plant evolution is discussed. On the example of Poaceae it is demonstrated, that apomixis is the mechanism, which helps the modern plants to achieve the reproductive success. 

In a course of investigation of seed productivity under the pollenless regime of flowering in 154 natural populations of 98 species of 46 the Asteraceae genera from Saratov province gametophytic apomixis has been discovered in populations of 24 species from 14 genera. For the first time this mode of reproduction has bean revealed in 7 genera and 16 species of the family (Hieracium largum, Pilosella echioides, Tragopogon dubius, Lactuca serriola, Scorzonera ensifolia, Chondrilla latifolia. Ch.

We have studied the characteristics of seed reproduction Artemisia 14 species from various parts of the Saratov region. It is shown that a population of five of them (A. vulgaris, A. salsaloides, A. dracunculus, A. glauca, A. austriaca) are characterized by high (at least 20-30%) frequency of gametophytic apomixis in plants, and three species (A. abrotanum, A. absinthium, A. armenica) have lower (10-15%) frequency of gametophytic apomixis.

In 1949 S. S. Khokhlov (one of the founders of the Russian scientifi c school on the problem of apomixes) proved the original conception of the progressive evolutionary role of apomixis. He contended that the basic direction of the reproductive system evolution in angiosperms is a gradual failure of sex reproduction and transition to apomixis. This hypothesis was heavily criticized and called a “scientist’s fantasy”.

Saratov Scientific School by Biology and Genetics of Plant Reproduction Systems was formed under the leadership of Doctors of Biology S. S. Khokhlov and V. S. Tyrnov. Most of the unique research was performed in the Laboratory of Radiation and Experimental Genetics, established in 1958. Later it was transformed into the Department of genetics and reproductive biology of the Saratov State University Botanical Garden. Over the past 60 years, Saratov scientists have made a significant contribution to the development of fundamental and applied science.

The article is focused on studying of cytoembryological preconditions of polyembryony in the not pollinated ovary of the apomictic maize line АТ-1 under in vitro and in vivo conditions. For an assessment of a nutrient medium role in polyembryony induction a relative analysis of the embryo sacs in cultivated in vitro and native plants ovaries has been lead. Dynamics of formation in them an apomictic twin proem- bryo is traced.

Poa bulbosa L. is a native cereal of the European and Mediterranean flora and an invasive species in North America. The study of its reproductive strategy in different environmental and climatic conditions is important for the development of effective methods of containment and prevention of invasions. Plants of two coenopopulations were investigated embryologically. In addition, the morphology of reproductive organs was analyzed in 175 herbarium specimens collected in the flora of the Lower Volga region from 1919 to 2017.

In 1949 S. S. Khokhlov (one of the founders of the Russian scientifi c school on the problem of apomixes) proved the original conception of the progressive evolutionary role of apomixis. He contended that the basic direction of the reproductive system evolution in angiosperms is a gradual failure of sex reproduction and transition to apomixis. This hypothesis was heavily criticized and called a “scientist’s fantasy”. In the second half of the 20th century the discovery of recombination repair led to a reassessment of the role of meiosis in the evolution.