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TO T IPO T EN CY AND M O R PH O G EN E SIS O F PLANT C EL LS

IN V IT R O

THEROLEOFCYTOKININSINAPROCESSOFMEGAGAMETE

ACTIVATIONDURING IN

VITRO

CULTUREOF

PANICUM M ILIACEUML.

UNFERTILIZEDOVARIES

A .S.Kashin, E.A .Blyudneva, M.A.Sylkin

AgriculturalResearch Institute o fSouth-East, Tulaikova st., 7, 410020 Saratov, Russia,

Regularities of megagamete activation and of regulation of early

embryogenesis have been investigated using

in vitro

culture of unfertilized

ovaries of m ille t, cv. Saratovskoye 6. It was revealed that for megagamete

activation to parthenogenetic development it is necessary culturing in the

dark and a high sucrose content (70-90 g/l) in the medium with the a u x in :

cytokinin ratio from 1:2 to 1:5. A cold pretreatment acted unfavorably. For

subsequent development of the activated structures the light is necessary,

as well as lowering of sucrose level (10-50 g/l) and the auxin : cytokinin ratio

from 5:1 to 10:1. The formation of embryoids was marked on a medium,

supplemented with 0.1 mg/l NAA, 0,2 mg/l 2,4-D, and 0.03 mg/l BAR During

subsequent cultivation it was observed embryogenic callus formation and

(or) the direct development of plantlets. Use of Potato-2 medium decreased

the frequency of callus formation, but increased the direct plantlet development

percentage. Ovary culture gave the best yield of plantlets (0.35%), when the

Potato-2 medium was used, and the MS medium gave the highest induction

frequency of callus formation (1.39%). These results and also data of literature

confirm our hypothesis [1] that among phytohormones (PH) just cytokinins

are that very factor, which limits the megagamete activation. But for the

maintenance of induced structure proliferation and subsequent embryo

differentiation the PH ratio is necessary, which is favorable usually for

proliferation of somatic cells. Probably, it is a reflection of a natural dynamics

o f auxin - cytokinin balance in ovaries in the processes of megagamete

activation and early embryogenesis. A decrease of the requirements for

sucrose during the formation of embryoids is, probably, connected with

reaching the stage when an embryo becomes capable of autotrophy. That is

why the light acts negatively at the stage of activation, and at subsequent

stages the light is necessary for activated structure development.

1. Kashin A. S. Physiological aspects of apomixis in Angiosperms.

2. Possible role of cytokinins and auxins in mechanism of megagamete

activation//Apom ixis Newsletter. 1992. №4. P.20-22.

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