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T O T IPO T EN C Y AND M O R PH O G EN E SIS OF PLANT C E L L S

IN V IT R O

THEPOTENTIALFO R MEGAGAMETEDEVELOPMENT INSOME

APOMICTIC AND SEXUAL FORMS OF

H IERACIUM

AND

TARAXACUM

OVARYCULTURES

IN VITRO

A.S.Kashin, E.ABlyudneva*, O.V.Sedletskaya

University ofSaratov, Astrakhanskaya st., 83, 410071 Saratov

Agricultural Research Institute ofSouth-East, Tulayikova st., 7, 410020 Saratov, Russia

vapr@scnit.saratov.su

Two variants of modified MS medium (supplemented with phytohormones

and growth-regulator-free medium) have been used for the

in vitro

culture of

unfertilized ovaries of sexual species [Taraxacum serotinum (Waldst. et Kit.)

Poir. (2x=16), Hieracium umbellatum L. (2x=18), Pilosella echioides (Lumn.)

F. Schultz et Sch. Bip. (2x=18)], diplosporous [T. officinale Wigg. (3x=24)],

and aposporous [P. officinarum F. Schultz et Sch. Bip. (6x=54), P. officinarum

x cymosa (5x=45)].

Parthenogenetic development of gametes was observed in apomictic

forms. In diplosporous form a direct plantlet development took place more

frequently than callus formation (21.5 and 9.5%, respectively), whereas in

aposporous forms callus formation was mainly observed; in hybrid form the

frequency of its induction being higher in comparison with nonhybrid form

(27.2% and 5.8%, respectively). Besides that, the hybrid form was the only

one among aposporous forms in which there was induced a direct plant

development (4.6±1.5%). Parthenogenesis has not been revealed in the sexual

relative of diplosporous forms. But the sexual relative of aposporous forms

gave induction o f callus formation in 7.5±2.1% cases on average.

Cytoembryological investigation confirmed that in T.officinale ovaries

megagametes develop in the normally differentiated embryos, whereas in

P.officinarum the embryos remain undifferentiated and can only grow

irregularly.

The results obtained suggest that (1) megagametes of apomictic forms

have the considerably greater potential for development in

in vitro

culture; (2)

in diplosporous embryo sacs (ESs) megagametes easier proceed to

parthenogenetic development of differentiated embryo; (3) aposporous ESs

of nonhybrid forms have no the sufficient potential for differentiation and their

megagametes undergo only an irregular growth; (4) aposporous ESs of hybrid

forms have the greater potential for parthenogenetic embryo development

(including differentiated ones) in comparison with aposporous ESs

nonhybrid forms.

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