Marioara Urda _Grebenisan_ rezumat_teza_engleza - USAMV Cluj ...

Marioara 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
- 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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