Marioara Urda _Grebenisan_ rezumat_teza_engleza - USAMV Cluj ...

UNIVERSITY OF AGRICULTURAL SCIENCES AND 

VETERINARY MEDICINE CLUJ-NAPOCA 

THE DOCTORAL SCOOL 

FACULTY OF AGRICULTURE 

Biol. Marioara URDA (căs. GREBENIŞAN) 

Summary of the PhD thesis 

Research on the structure of di- and tetraploid red 

clover seed plants and the influence of meiotic 

anomalies on the fertility of autotetraploid forms 

Scientific coordinator: 

Prof. univ. dr. MIRCEA SAVATTI 

CLUJ-NAPOCA 

2011

Marioara GREBENIŞAN Summary of the PhD thesis 

Research on the structure of di- and tetraploid red clover seed plants and the influence of meiotic 


THESIS CONTENT 

Foreword ………………………………………………………………………. 

CHAPTER I 

1. Autopolyploidy-genetic phenomenon and comparative aspects with 

diploid red clover ………………………………………………………. 

1.1. General view ………………………………………………………... 

1.2. Selection for the seed number per flower head ……………………... 

1.3. The importance of red clover culture and main objectives studied …. 

1.3.1 Production capacity ……………………………………………. 

1.3.2. Chemical composition ………………………………………… 

1.3.3. Nutritional value ………………………………………………. 

1.3.4. Agrotechnical importance ……………………………………... 

1.3.5. Honey plants …………………………………………………... 

1.3.6. Ecological plasticity …………………………………………… 

1.4. Induction of polyploidy in red clover ……………………………….. 

1.4.1. Methods used in inducing polyploidy 

1.5. Comparative aspects between diploid and tetraploid forms of 

red clover ……………………………………………………………. 

1.5.1. Plant morphology ……………………………………………… 

1.5.2. Anatomical characters of stem ………………………………… 

1.5.3. Characteristics of sexual elements …………………………….. 

1.5.4. Physiological characters ………………………………………. 

1.5.5. Quantitative and qualitative aspects of production ……………. 

1.6. Causes of low fertility in red clover with different levelsof ploidy … 

1.6.1. Morphological causes …………………………………………. 

1.6.1.1. Changing productivity elements for seed yield ………... 

1.6.2. Modification of morphological characters that affect pollinating 

insects flight ……………………………………………………... 

1.6.3. Red clover pollinating species and ways to improve their work ……. 

1.6.4. Cytological causes …………………………………………….. 

1.6.4.1. Meiosis abnormalities …………………………………. 

1.6.4.2. Meiosis in autotetraploid red clover …………………... 

1.6.4.3. Aneuploidy ……………………………………………... 

1.6.5. Embryological causes …………………………………………. 

1.6.6. Genetic causes …………………………………………………. 

1.6.7. Parasterility ……………………………………………………. 

1.6.8.Independent causes of the genetic basis ……………………….. 

C H A P T E R I I 

2. Pedoclimatic conditions in which experiments were conducted ……… 

2.1. Experiment location ……………………………………………... 

2.2. Agro-physical, hydro-physical, agrochemical and agro-biological 

traits of soil ……………………………………………………... 

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2.3. Climatic conditions in which experiments were conducted …….. 

2.3.1. Thermal regime …………………………………………. 

2.3.2. Rainfall …………………………………………………... 

2.3.3. Other weather conditions ………………………………… 

C H A P T E R I I I 

3. Research on the structure of red clover seed plants and the effect on 

seed yield …………………………………………………………….. 

3.1. Introduction ……………………………………………………… 

3.2. Materials and methods …………………………………………... 

3.3. Results and discussion …………………………………………... 

3.3.1. Components of red clover seed yield ……………………. 

3.3.1.1. Number of flower heads/plant and per s. m ……… 

3.3.2. The number of flowers/flower head ……………………... 

3.3.3. The number of seeds per flower head ……………………. 

3.3.4. The average percentage of seeds formation ……………… 

3.3.5. Thousand kernel weight (TKW) …………………………. 

3.3.6. The calculated and real seed yield ……………………….. 

3.3.6.1. Flowering stages and seed yield …………………. 

C A P I T O L U L I V 

4. Pollination and seed formation process in diploid and tetraploid red clover 

(Trifolium pratense L.) for Transylvania conditions ……………………… 

4.1. Red clover pollination particularities in relation with the number and type 

of pollinators …………………………………………………………. 

4.1.1. Introduction ……………………………………………… 

4.1.1.1. Research method ………………………………… 

4.2. Result and disscutions ………………………………………… 

4.2.1. Abiotic and biotic factors involved in red clover 

pollination ………………………………………………... 

4.2.2. Flowering period ………………………………………… 

4.2.3. Pollinators distribution in seed crops ……………………. 

4.2.4. Total number of bees and bumble bees ………………….. 

4.2.5. Daily frequency of bees and bumble bees ……………….. 

4.2.6. Bees and bumble bees waiting time on red clover flower 

heads ……………………………………………………….... 

4.2.7. Comparative aspects regarding the total number of 

“insect-units” and the relative fertility of red clover ……. 

4.3. Aspects of correlation between weather conditions and pollinators 

flight ……………………………………………………………. 

CHAPTER V 

5. The comparative effects of the micro- and macrosporogenesis of the red 

clover with different levels of ploidy, in relation with its fertility ……… 

5.1. The evolution of embryogenesis and its influence on fertility …. 

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5.1.1. General view ……………………………………………... 

5.2. Material and method …………………………………………... 

5.3. Results and discussions ………………………………………... 

5.3.1. Testing pollen quality ……………………………………. 

5.3.2. Testing germination, elongation and the indicator of 

in vitro pollen viability …………………………………... 

5.3.3. The growth of in vitro pollen tubes ……………………… 

5.3.4. The growth of in vitro pollen tubes in detached pistils ….. 

5.4. Embryogenesis in di- and tetraploid red clover ……………….. 

5.4.1. General view ……………………………………………... 



5.6.1. Phases of embryogenesis ………………………………… 

5.6.2. Comparative aspects regarding the fertility of di- and 

tetraploids ……………………………………………….. 

CHAPTER VI 

6. The influence of meiotic anomalies on the fertility of autotetraploid 

forms of red clover ……………………………………………………. 

6.1. Introduction ……………………………………………………. 


6.3. Meiosis and its consequences upon fertility …………………... 

6.3.1. Meiosis in the case of eutetraploids …………………………. 

6.3.2. The relationship between meiosis and fertility …………... 

6.4. Meiosis in the case of tetraploids ……………………………... 

6.5. Meiosis in the case of aneuploids ……………………………... 

6.5.1. The relationship between meiosis and fertility ………….. 

CHAPTER VII 

7. The influence of haploid and diploid pollen in the fertilization process 

in red clover (Trifolium pratense L.) ………………………………… 

7.1. General view …………………………………………………... 



7.3.1. The number of flowers per flower head …………………. 

7.3.2. The average number of seeds per flower head …………... 

7.3.3. The influence of the number of diploid pollen grains in 

diploid red clover flower heads (unisolated plots) ……... 

7.3.4. The influence of the haploid pollen on the average 

number of seeds per flower head in tetraploid red clover 

(unisolated plots) ……………………………………….. 

7.3.5. The influence of the diploid pollen on the average number 

of seeds per flower head in diploid red clover (plots 

isolated with sainfoin) …………………………………... 


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number of seeds per flower head in tetraploid red clover 

( plots isolated with sainfoin) …………………………… 

7.3.7. The average percentage of seed formation ……………… 

7.3.8. The influence of the diploid pollen on the average 

percentage of formed seeds in diploid red clover 

(unisolated plots and plots isolated with sainfoin) ……... 


percentage of formed seeds in tetraploid red clover 

(unisolated plots and plots isolated with sainfoin) ……... 

CONCLUSIONS................................................................................................. 

BIBLIOGRAPHY............................................................................................... 

SUMMARY IN ROMANIAN 

SUMMARY IN ENGLISH 

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The economic importance of red clover favoured the development of 

research in the direction of deeper knowledge of its biological characteristics, with 

special focus on those related to genotype fertility, in order to counteract the 

oscillating tendency of the seed yields and to elaborate methodologies able to 

ensure high seed yields. 

The research development in this area increased mainly after 1940, when the 

Swedish scientist LEVAN created the first tetraploid clover. The autotetraploid red 

clover is important for breeding and production, as it is capable to provide 30-40% 

more forage mass than the diploid forms, as well as better resistance to biotic and 

abiotic stress. 

In spite of all its advantages, the extensive spreading of red clover in cultures 

is quite limited, due to its relatively low fertility, as compared to the diploid 

genotype. 

This fact generated a lot of biological, genetic and agricultural investigations, 

leading to the conclusion that the negative biological feature is determined by 

morpho-physiological factors but mainly by the genetic ones. 

The subject was dealt with from the point of view of the aspects which have 

a negative influence on the fertility of the red clover with different ploidy levels. 

Here are some of the aspects that were taken into consideration: 

- the direct decrease in fertility of the autotetraploid red clover as a result of 

the morphological modifications that plants go through because of 

polyploidization; 

- the influence of the pollination process and the effectiveness of the 

entomophile pollination correlated with abiotic factors upon fertility; 

- the cytologic causes that could have a negative impact upon red clover 

genotypes, such as factors in the category of meiotic anomalies at tetraploid 

and aneuploid levels; 

- causes of embryological nature conditioned by the quality of pollen, 

fertilization and endosperm formation, development and abortion etc. 

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- the influence of environmental conditions on the seed production process 

- independent causes of genetic nature, facilitated by the disturbing effect of 

haploid pollen on the process of tetraploid genotypes fertilization 

The present thesis has tried to elucidate the phenomenon by correlating our own 

data with the various suggestions offered by scientific literature. 

Most research has pointed out the fact that partial sterility of tetraploid red 

clover is not a simple phenomenon, but the result of cytologic, genetic and 

physiological imbalance in which a large number of genes are involved. As a 

consequence, genetic variability may be used by selection, with a view to increasing 

the fructification percentage, which will then generate better fertility by reducing 

the frequency of irregularities in the fructification process, irrespective of any 

causal phenomena and the stage they occur at. 

In order to cover a larger area when analysing red clover fertility and ploidy 

factors, we used two base fields, situated in Cluj-Napoca and Jucu (24 km from 

Cluj-Napoca), as well as other locations, the Cojocna Farm belonging to UASVM- 

Cluj-Napoca and cultures belonging to private farmers within the area between 

Cluj-Viseul de Jos and from Viseul de Jos. 

In spite of the well-known inconstant seed yield in red clover, we usually 

consider it enough to determine it empirically, without analysing the causal 

relations, the importance of the individual components of the seed yield or the 

possibilities to influence them. 

The red clover seed yield is the result of cumulated action of four main 

components: the number of flower heads/plant, the number of flowers to turn to 

fruit/ flower head, the seed weight/plant and the weight-of-thousand-kernels. There 

are differences between these components in what regards their contribution to the 

total seed quantity, the genetic variation and the potential selection response. 

It was noticed there is a relationship between the structure of the red clover 

seed plants and their capacity to produce a certain seed quantity per surface unit. 

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The determination of blooming flower heads has revealed a wide range of 

oscillation according to genotype, as the diploid forms are superior to the tetraploid 

ones, and also in relation with the ecological culture area (table 3.1). 

As regards the intrinsic aspects of seed production, it has been proved that 

there are significant differences between the number of flower heads/individual 

plant and the number of flower heads/surface unit (table 3.2). The diploid forms 

appear to be superior to the tetraploid ones, if we consider the number of flower 

heads/sq m, which has a negative impact upon the yield of the tetraploid seed 

plants. 

The number of flowers/flower head is a determinant element for plant 

sexuality in clover, being considered a quite precise indicator of potential fertility. 

The highest values occur at maximum flowering time; generally speaking, diploid 

forms provide a higher number of flowers per flower head, as compared to 

tetraploid genotypes (table 3.3). 

Another observation is that, by delaying the first cut, there occurs a 

decreasing tendency in what regards the number of seeds/flower head, in direct 

correlation with the ecological culture area (table 3.5). 

The weight-of-thousand-kernels indicator displays the most reduced 

oscillation. Apparently there is a certain influence of the first cut timing upon this 

trait. The differences that occur are in favour of the tetraploid genotypes (1.6-1.7 g 

for 2n and 2.2-2.4g for 4n) and are not an advantage in the process of initiating 

tetraploid red clover cultures. 

As far as the determination of the production capacity of the seed plants is 

concerned, the calculations of the biological yield based on average values of the 

individual production factors outline significant differences between the calculated 

yield and the real yield, the one obtained in the field. These differences are 

conditioned by the ecological culture area, climatic conditions and genetic 

differences of the biological material. Major influence comes from the lack of 

uniformity in what regards the flowering and seed ripening, precarious pollination, 

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field work, harvesting periods, as well as the inherent loss occurring in the field, all 

these leading to the already mentioned differences (table 3.11). 

One of the key-ways that can lead to the reducing of the seed yield loss lies 

in directing the seed plant flowering process, which has to last for a short time, with 

a flowering climax, thus ensuring the uniform ripening of the seed plants. 

It was noticed that the poliploidization process of the red clover produces 

certain morphological modifications in the plant, which cause a diminishing of the 

productive capacity of the seed plants of the 4n type rather that of those of the 2n 

type. 

These modifications are enhanced by soil conditions and climatic factors, 

which can influence, in a positive or negative way, upon the productivity 

differences of the two forms of red clover with different ploidy levels. 

The existence of genetic variability that can be used, for certain categories of 

seed production, with tetraploid genotypes of red clover draws us to the conclusion 

that the fructification potential of tetraploid red clover can be improved by 

selection. However, the full exploitation of this potential requires substantial 

improvement of the pollination conditions. 

The determinations referring to the pollinating entomofauna and the 

pollination frequency show the fact that the main pollinators of the red clover are 

honey bees and bumble bees species (table 4.3). 

There is also an interrelation between the biotic and abiotic factors and the 

efficiency of the pollination done by apoides in the case of red clover seed plants. 

An analysis of the total number of bees and bumble bees that visit the red 

clover fields highlights the fact that, as compared to the total number of apoides, 

only 49.2-88.6% visits the tetraploid red clover, which has a negative influence 

upon the percentage of formed seeds in this genotype (table 4.4). 

As for the daily frequency during maximum flowering time, the number of 

apoides that visit the tetraploid red clover represents 57.1-81.5% of the total number 

of the ones that visit the diploid red clover. 

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The abiotic factors, which also include the weather conditions, can have a 

direct or indirect influence on red clover pollination, by consistently affecting both 

the flowering dynamics and the flight of the pollinators. 

The comparative data collected in Cluj-Napoca show the fact that the 

morphological modifications determined by the increase of the ploidy level affect 

the pollination and seed formation processes, in favour of the diploid red clover 

genotypes, which explains, to a certain extent, the difference in productivity 

potential between the seed plants belonging to different ploidy groups (table 4.9). 

There has been noticed an influence, either positive or negative, of the 

weather factors upon the interrelationships red clover-pollinators. The good 

understanding of the correlations between these two factors can allow for the 

determination of the most favourable exploitation period for red clover seed plants. 

By studying the evolution of embryogenesis it was possible to highlight the 

action of multiple factors that contribute to the diminishing of the red clover 

fertility. 

The phases that the pollen grain goes through as part of the pollination and 

fertilization process must give an answer to the question if its participation in this 

process can produce any beneficial effects upon the seed yield in the case of red 

clover. 

The tests regarding germination, elongation, pollen viability indicators, as 

well as the growth of pollen tubes in compatible and non-compatible pistils have 

pointed out major differentiations between red clover genotypes with different 

ploidy level. 

The ploidy level correlates with pollen viability; as the percentage of 

abnormal and unviable pollen is higher in tetraploids, the fertility of these genotypes 

is lower (table 5.1). 

The in vitro germination of pollen takes place in the first two hours after the 

pollination, and the elongation of the pollen tubes is faster in the first 12 hours, 

whereas in the next 12 hours the growth rate is very low. 

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The duration of the pollen tubes growth is similar for the 2n and 4n forms, 

the differences occurring in the growth speed and the length to the ovary. 

germination. 

A population effect was noticed, with positive influence upon pollen 

The repetition of compatible and incompatible pollination weakens the 

mechanisms of self-incompatibility of the red clover, mainly of the tetraploid forms. 

An interesting aspect of the comparison regarding the fertility of red clover 

with different ploidy levels is represented by the evolution of embryogenesis. The 

research undertaken for the interval pollination-seed formation has shown the 

development of ovaries and embryos under the conditions of free pollination (PIL), 

spontaneous pollination (APS) and artificial self-pollination (APA). 

The study of embryogenesis from the point of view of the development of 

the pre-embryo, suspensor, cotyledons and apex highlighted the fact that, in the case 

of free pollination (PIL), the difference between di- and tetraploids consists mainly 

in the more obvious earliness of the tetraploids in the first 10 days after pollination, 

whereas both ploidy forms reach the maximum development of embryos in 14-15 

days after pollination (table 5.7). 

Self-pollination does not bring any morphological changes during 

embryogenesis. However, a higher percentage of normal ovaries and ovules was 

noticed in diploid forms. 

Another observation was that the tetraploids provided a higher percentage of 

aborted embryonic sacs than the diploids, whereas after pollination, the fertility 

decrease percentage is similar in di- and tetraploids. 

It appears that poliploidization affects fertility more in macrosporogenesis, as 

compared to the same phenomenon in diploids. 

The fertility decrease seems to happen owing to the abortion of one of the 

ovules present in a normal ovary, the abortion of the second one or of the embryo 

being also possible (table 5.9). 

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The high number of aborted ovules in the tetraploid genotypes can be 

explained by several causes, among which ovary sterility, determined by anomalies 

of the embryonic sac, represents a limitative factor for the seed production capacity 

in plants. Another cause of low fertility is represented by the high number of 

unfertilized ovules, respectively the low number of ovules with formed embryos 

(table 5.13 and 5.14). 

Although the study of embryogenesis does not intend to fully explain the 

causes of the lower fertility of the tetraploid red clover genotypes, it still points out 

some genetic aspects with causal effects upon unsatisfactory seed yields. 

Analyzing the various factors that can reduce fertility in autotetraploid red 

clover , we were interested in cytological and genetic causes triggering multivalent 

chromosomes, gametes and aneuploidy plants, ovaries and embryo abortion, 

overcoming a number of alleles/locus caused by abnormal meiosis in tetraploid 

forms, low pollen fertility etc. 

It should be noted that the families of tetraploid red clover used in our 

studies are differentiated in terms of average fertility. From here we can draw the 

conclusion that there occurs a “family effect”, which should be taken into account 

in establishing relationships between meiosis and fertility abnormalities. The studies 

have revealed three types of abnormalities, with a relatively high frequency, 

namely: the presence of monovalent, divalent and tetravalent, the irregular presence 

of anaphase I, the presence of supernumerary microspores. 

It was shown that the irregular distribution of anaphase leads to the finding 

that approximately 50% of infertility is due to this cause. 

It was noted that unviable pollen grains are the result of meiotic 

abnormalities, without being able to explain that this phenomenon singularly 

influences the low fertility of polyploids. 

If abnormalities occur in the case of macrosporogenesis, they are 

undoubtedly the cause of a decrease in fertility due to the abortion of non-equivalent 

embryos (table 6.4, table 6.5). 

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The presence of triploid plants can also contribute to the diminishing of the 

general fertility of a tetraploid population. 

It may be suggested that the chromosomal abnormalities which lead to the 

formation of embryos of viable or aborting aneuploids are responsible for part of the 

impairment of fertility and viability of autotetraploid populations and that the 

viability of triploid embryos has adverse consequences upon yield (table 6.8). 

One of the causes that may interfere with the formation of tetraploid red 

clover seed may be due to causes independent of the genetic base, being caused by 

the disturbing influence of the haploid pollen and the influence of environmental 

conditions. 

The presence of haploid and diploid pollen can cause anomalies in the seed 

production process. Countering this situation is facilitated by implementing 

appropriate isolation distances between di-and tetraploid seed lots or by providing a 

“washing strip” between them. 

A particularly disturbing effect was found when tetraploid seed plants were 

pollinated with haploid pollen from the diploid genotypes. 

The obvious disturbing influence on the average number of seeds in 

tetraploid genotypes flower heads occurred in the immediately adjacent rows of 

diploid red clover, the effect being visible on a 7 m distance from the haploid pollen 

source (table 7.4). 

The negative influence of the diploid pollen on the number of seeds in seed 

heads, in diploid forms, is insignificant and not statistically assured. 

In the case of intercalation of an insulation strip (sainfoin) between red 

clover seed lots with different degree of ploidy, there is an increase in the number of 

of seeds / flower head in tetraploid forms, as a result of “washing out” the insects on 

the isolation strip (table 7.6 ). 

The decrease in productive capacity of the tetraploid red clover when placed 

near the diploid onecan be explained by the fact that haploid pollen tubes, as 

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compared with the diploid ones, grow faster on tetraploid plant stigmas and, as a 

result of fertilization, a large number of triploid embryos are formed. 

Triploids can abort at a very early stage in their development, thus negatively 

influencing upon plant fertility. 

It is recommended that, in the case of the clover seed plants with different 

levels of ploidy, proper isolation distances (200 m) should be ensured, with the 

intercalation of a “washing strip” with pollen plants, or the removal, before 

harvesting, of a 7.0 m wide strip of the different ploidy clover crops sown near each 

other. 

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Tipo Agronomia, Cluj-Napoca 

BANYAI, L., 1962, Poliploidizarea unor specii de trifoliene prin tratamente cu 

colchicină, Agrobotanika, vol. VII 

BARBUR, Z., 1974, Studiul fertilităţii trifoiului roşu autotetraploid de Transilvania. 

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autotétraploides chez le tréfle violet (Trifolium pratense L.). Ann. 

Amélior. Plantes. Vol.18. No.4 

BOND, D.A., and J.L. FYFE, 1968, Corolla tube length and nectar height of F1 red 

clover plants (Trifolium pratense) and their Seed yield following 

honey – bee pollination J. Agric. Sci. comb. Vol. 70 

BRAGDØ-ASS, MARIE, 1969, Fertility of tetraploid red clover. Norges 

Landbrukshgskole-Meldinger. Vol.49 

CEAPOIU, N.; 1968; Metode statistice aplicate în experienţele agricole şi biologice, 

Ed. Agro-Silvică, Bucureşti 

CIURDĂRESCU G., M. SAVATTI, 1974, Contribuţii la cunoaşterea insectelor 

polenizatoare ale trifoiului în Transilvania. Ann. ICCPP, vol. X 

DENNIS, B.A., 1980, Breeding for improved seed production in autotetraploid red 

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DEZMIREAN, GRAŢIA, L.AL. MǍRGHITAŞ, M. SAVATTI, D.S. DEZMIREAN, 

2001, The effect of pollination with Apoidae on diploid and tetraploid 

cultivars of red clover Trifolium pratense L., Bull. USAMV-CN, 55-56 

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ELLERSTROM, S., J. SJODNI, 1966, Frequency and vitality of aneuploids in a 

population of red clover, Hereditas, vol. 55 

ESKILSON, L., S. BINGEFORS, 1972, Studies on the use of induced autopolyploidy 

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and tetraploids. Z. Pflanzenzüchtung. Band 67. Heft. 2 

GORAL, S., 1970, The effect of nectar yield and numbers of pollinating insects on 

the seed setting in diploid and tetraploid red clover. 1. Production of 

the nectar. Herbage Abstracts, vol. 40, no.1 

HOLM, S.N., 1972, Seed yields in red clover in relation to the number of 

pollinating bees influenced by a growth regulator. Royal Vet. and 

Agric. Univ. 

JULÉN, G., 1950, Fertility condition of tetraploid red clover. I. Seed setting of 

tetraploid red clover in the presence of haploid pollen. Hereditas. Vol. 36 

JULÉN, G., 1954, Aspect of the breeding of tetraploid red clover with special 

reference to the seed setting problem. Em. Grasel. Conf. Paris. CERC 

KAZIMIERSKI T; KAZIMIERSKA-EM, 1995, Cytogenetics, embryology and 

fertility of red clover (Trifolium pratense L.) with short flowers and 

anthocyanin spots on the leaves, Journal-of-Applied-Genetics, 36: 4 

LACZINSKA-HULEWICZOWA, T., 1963, Self fertility and breeding in tetraploid 

red clover. Genetica Polonica, Vol. 4. No. 2 

LEVAN, A., 1942, Plant breeding by induction of polyploidy and some results in 

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MACKIEWICZ, T., 1965, Seed setting in tetraploid red clover (Trifolium pratense 

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6. No. 1 

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MAIZONNIER, D., 1970, Etude de l’influence des anomalies de la meiose sur la 

fertilité des formes autotètraploides de Trifolium pratense L., Rezumat 

al tezei de doctorat 

MAIZONNIER D., J. PICARD, J. BERTHAUT, 1970, Le manque de fertilité chez 

la trèfle violet autotètraploide (Trifolium pratense L.). III. Etude 

comparè de la fertilité des euploides et des aneuploides. Ann. Amélior. 

Plantes. Vol. 20. No.4 

MANSAT, P., J. PICARD, 1965, Creation de tetraploides et sélection préalable au 

niveau diploide. Acta Agriculturae. Scand. Vol. 16 

MOUSSET-DECLAS, C. 1992, Le tréfle violet. In Amèlioration des espéces 

vegetales cultivées. Cord. A. Gallais et H. Bannerot, I.N.R.A 

MUNTEAN, L., 2002, Studiul resurselor genetice de trifoi roşu (Trifolium pratense 

L.) în vederea ameliorării, Teză de doctorat, USAMV Cluj-Napoca 

NÜESCH, B., 1970a, Investigations on tetraploid Mattenklee (Trifolium pratense 

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