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The panmictic (xenogamous) population of cross fertilizers has higher

genetic diversity and higher adaptive potential than the autogamous one. In

contrast self-fertilization restricts the genetic diversity but can stabilise particular

features or produce seeds in lack of pollinators. Many genera exist in which

the self-incompatibe cross fertilizing (outbreeding, xenogamous) species are

predominantly perennials and self-fertilizers (inbreeding, autogamous) are

annuals. In most cases the self-fertilization is facultative and is induced by

harsh conditions including lack of pollinators. Asexuality produces little if any

genetic variability, but maintains levels of heterozygosis (S t e b b i n s, 1974;

R i c h a r d s , 1990, 1996).

There are different levels and mechanisms for prevention of self-fertilization -

from the opening of the flower to the first division of the zygote. These are

dioecy, dichogamy, monoecy, or hermaphrodity with hercogamy, dichogamy

and self-incompatibility (S t e b b i n s, 1974; D a f n i, 1992; R i c h a r d s , 1990,

1996).

The term „breeding systems" includes, in its broad sense, all the aspects

of sex expression in plants which affect the relative genetic contributions to

the next generation of individuals within the species (W у a 11,1983; R i c h a r d s ,

1990,1996; D a f n i, 1992). There are two main approaches to the investigation

of the breeding systems: 1/ direct methods: exclusion techniques, and hand-

pollination with comparative test of the fruit and seed set; analyses of genetic

markers e. g. allozyms (D a f n i, 1992). 2/ Indirect methods to estimate the rate

of outcrossing are based on morphological analysis or pollen ovule ratio - P :0

ratio ( C r u d e n , 1976; Da f n i , 1992). The direct methods are more precise

but there are some obstacles. Genetic markers methods are expensive and

highly technological. Exclusion techniques in the field depend on many factors

including pests and herbivores. Selfers may differ from their outcrossing

relatives by a series of traits such as: fewer and smaller flowers, less scent and

nectar, close proximity between the anther and the (smaller) stigma, fewer

pollen grains etc. Many authors observed that the flowers of the self-incompatible

and xenogamous species produce more pollen grains compared to their self

compatible autogamous relatives and at the same time the number of the

ovules is more or less permanent. In these species the evolutionary shift from

xenogamy to autogamy reflects in decrease of pollen - ovule (P:0) ratio. Thus

the P :0 ratio indicates the breeding system (Ar r oyo , 1973; C r u d e n , 1973,

1976; S c h о e n, 1977; Lo r d , 1980; C a m p b e 11 et al., 1986; Sm a s 11, 1986;

L l oyd , 1987; P h i l b r i c k , A n d e r s o n , 1987; R i t l a n d , R i t l a n d , 1989;

P l i t m a n n , Le v i n , 1989; Mi o n e , A n d e r s o n , 1992; G a l l a r d o et all,

1994). Cruden (1973, 1976) considers P :0 ratio as a more reliable indicator

of the breeding systems than the morphological characters.

The aim of this study is to investigate the breeding systems of 6 species

Gentiana

namely -

G. lutea

ssp.

symphiandra

(Murb. ) Ha y e k ,

G. punctata

L.,

G. asclepiadea

L.,

G. pyrenaica

L.,

G. vema

L.,

G. utriculosa

L.;

Gentianella

bulgarica

(Ve l e n ) Ho l ub ,

Swertia perrenis

L.,

Centaurium erythraea

Rafn.

applying P :0 ratio method.

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