CELLULAR SELECTION OF WHEAT RESISTANT TO UV-B IRRADIATION
Peter Lapshin, Natalia Zagoskina, Raisa G. Butenko
Russian Academy of Science, Timiriazev Plant Physiology Institute, 35 Botanical str., 127276, Moscow, Russia, ifr@ippras.ru - abstracts for conferense January, 2002 Nikita, Yalta, Crimea, Ukraine

The screen of ozone in atmosphere defends the surface of the Earth from a harmful effect of UV-light. As a result of human activity in high layers of atmosphere enter the great many of chlorofluorocarbons (freons, CFCs). As a result the quantity of UV-B irradiation (280-315 nm) on the surface of the Earth are increasing. The effects of UV-B light in higher plants cells can be destructive and mutative. The plant resistance to UV-irradiation consist of integrated defence mechanisms. The resistance mechanisms are include photorepair, absorbtion radiation by epidermal pigments. One of them is the increased synthesis of phenolic compounds. Accumulation of some phenolic compounds often correlated with plant resistance to UV radiation. The breeding of UV-toleranced sorts of agricultural crops is very actual. This, in particular, concerns such culture, as a wheat, which is broadly used in the production of products of feeding.In our work we are use "in vitro" culture for obtaining strain of spring common wheat which stable to increase UV-irradiation. Also we are analysis of morpho-physiological and biochemistry parameters of this tissues.

On an example of one genotype of spring common wheat Triticum aestivum: the Fotos line (Fotos-L 40959, Bashkir Bread-stuffs Institut) studied possibility of obtaining (with the help of an in vitro culture methods) a cell culture, having boosted stability to a medium ultra-violet radiation (in a range of lengths of waves from 280 up to 320 нм - UV-B). As a result of individual selection to characteristic of intensity of increase of a grown, from individual callus aggregates were selected a some cell lines, capable to save a high level of increase callus mass in presence UV-B irradiation.

Initial material for in vitro selection is immature (14-16 dayes old) embryoses. To obtain the primary callus, isolated embryos were cultivated in modified Murashige & Scoog agar medium with FeNa-EDTA, vitamins, sucrose 2%, and as hormonelike effector 2,4D (2,4-dichlorophenoxyacetic acid) 2 mg/l. Average frequency of callus formation on this media is 98-99%.

For a selective agent we are used the light of the analog of bactericidal lamp named PRK-2. This lamp apart from UV-B contains also bactericidal radiation. For exception of bactericidal radiation we have used glass filters. For the secection we are used intensities of irradiating 0,55 Vt/м² on UV-B (with 6,15 Vt/м² of UV-A) and 0,39 Vt/м² on UV-B (with 4,42 Vt/м² of UV-A). The radiation time was 2 hours each day approximately in the middle of a 16-hour light duration of exposure by white light (5Klx). The control - culture under UV-B non-transparent glass. Selection for resistance was conducted both at the stage of callus formation and the the stage of callus growth. At the start of selection the embryoses formed callus with medium density, bright yellow in colour, but under the further subcultivation moustly calluses became pale yellow colour without any sign of morphogenesis.

Installed dependency of growing of cell cultures of wheat from the intensity and duration of influence UV-B irradiation. UV-B negatively influences both percent of derivated calluses and their weight. Callus weight was determined by personal weighing in sterile conditions on torsion weights at the moment of next passage. It has allowed to dedicate cell lines which are carrying on the genesis from one primary explant. As a result of selection we was obtain 13 UV-resistant clones (Fotos strain), keeping growth at a level of the control at UV irradiation.

Obtained cell lines had essential differences in biochemical characteristics. These change were registerred on length of long time after stopping an stress influence that can be indicative of the genetic nature of changes to selected on stability in UV-B radiating cell lines. In selected lines we determined the common contents of dissoluble amino acids, phenols and lignin. Some amino acids are the predecessors of phenols. Phenyl alanine and some other amino acids are the predecessors at a biosynthesis of phenols. The changes in ballance of free amino acids in the selected lines was displayed. The heightened contents of phenolic compounds (up to 5 onses with control) in selected lines was showed. The content of sum of phenols may be used as a biochemical index of tolerance of callus for increase of UV-irradiation.

Also the UV-B irradiation causes changes in morpho-physiological characteristics in the wheat cell cultures was shown. This is sizes of cells (it was reduces), parameters of a cell wall (it was thicken)

The scheme of selection on stability to UV-B with using an artificial UV-light sourse was work out. The possibility of getting a cell line of wheat, which save ability to growing in presence of UV-B was shown. It can be used for selection of the new sorts of wheat, having stability to the this factor.