Genetical determination OF ANDROCLYNIA IN WHEAT:
THE EMBRYOLOGICAL ASPECT
Institute of Biology, Ufa Sci. Centre of Russian Academy of Sciences
Androclynia is the phenomenon which consists in the formation of plant-regenerant (sporophyte) in vitro conditions from the sporogenous cell which usually gives the origin to pollen grain (gametophyte) in vivo conditions. This phenomenon is the foundation of the isolated anther culture method which is one of the perspective approaches in modern genetical investigations.
The key problem of androclynia is the determination of sporophytic pathway of sporogenous cells in vitro conditions. This problem remains investigated insufficiently.
On the mind of absolute majority of researchers and according to our results, the general factor determining the switch of “gametophyte” to “sporophyte” is the genotype of donor plant. The purpose of the research was the investigation of such important aspect of genotype influence on sporophytic pathway of sporogenous cells as the embryological status of anthers in the moment of its inoculation to cultural medium. The object of investigation was the collection of spring soft wheat genotypes. The periodicity of cereal anther development prepared by us (Круглова, 1999) was used.
The anthers of cereals and of wheat in particular are characterised by asynchronous development of sporogenous cells. According to the data obtained anthers that contain prepondirating number (more than 50 %) of microspore in strongly-vacuolated phase had the greatest responsiveness on the cultural conditions in all genotypes. In other words this phase of sporogenous cell development is optimal for the induction of androclynia in genotypes under studied. Such microspore we call the morphogenic microspore. The data of light and electronic microscopy testified to the similarity of structural organisation (mainly of polarity) of morphogenic microspore and egg cell in wheat. Besides this phase is apparently one of the critical phases in the development of sporogenous cells and this phase is characterised by the greatest sensitivity to the action of outward factors. “Critical characteristic” of this phase in that case is clearly defined by premitotic state of the cell; the role of outward factor play exogenous hormones of appointed concentration including in the composition of nutrient medium.
From the approach to anther as the complex integrated system it is important to take into consideration the status not only of sporogenous tissue but also tissues of anther loculus wall on all developmental stages. So, the anther loculus wall of wheat including the morphogenic microspores is represented by well-developed exothecium and endothecium cells and by degenerating middle layer and tapetum cells.
Thus response reaction of anther of concrete wheat genotype on the in vitro conditions to a great extent was determined by its embryological status in the moment of inoculation on nutrient medium. Embryological status undoubtedly interconnects with others important characteristics of inoculated anther and generally with the level of endogenous hormones.
The work is executed at support by the Russian Foundation for Basic Research