Quantitative analyses of formation and reduction of yield elements in
winter wheat cultivars Senta and Vlada (in 1988/1989 and 1989/1990), S
T 146 line (1988/1989) and Vega cultivar (1989/1990) were performed at
decisive growth stages under the following model conditions: stand de
nsity (seeding rates 2.5, 4.0, 5.5 million germinable seeds.ha-1); sow
ing date (first - September 20, second - October 5, third - October 20
). As a basic method of statistical evaluation the analysis of varianc
e of two-fold classification with replications was used. Differences b
etween individual mean variant values were verified using the Tukey te
st. The study was aimed at assessing the characteristics of yield elem
ent formation, reduction and compensation in different winter wheat ge
notypes and increased utilization of yield potential by controlling yi
eld elements. The data on characteristics of the genotypes studied are
presented in Tabs I and II. The Senta genotype manifested intensive t
illering; the tillers formed were considerably reduced. It was charact
erized by a high floret formation, a kernel number per spike and their
weight. The Vlada genotype had a low tiller number; however, their hi
gh realization secured a high productivity of the stand density. It fo
rmed lower potential as well as actual spike productivity. The Vega ge
notype showed a lower intensity of tiller production, however, with a
high percentage of their realization. It produced a high floret number
per spike which was considerably reduced. It reached a high kernel we
ight. The ST 146 line established high numbers of tillers and producti
ve stems. It considerably reduced the florets formed and showed a low
spike productivity. Yield element formation was significantly controll
ed by stand density (Tabs III, IV). At the raising seeding rate a numb
er of tillers and productive stems per plant reduced; however, the pro
ductive density of the stand did not significantly differ at the seedi
ng rates investigated (it was compensated by a plant number). The seed
ing rate was in negative correlation with both the number of formed fl
orets and actual kernels per spike. A higher kernel number per spike a
t the seeding rate of 2.5 million germinable seeds.ha-1 significantly
increased the spike productivity and stand sink, which positively affe
cted the grain yield. Spike weight was not significantly influenced. T
illering dynamics, floret formation and reduction was influenced by so
wing dates (Tabs V, VI). A later sowing date significantly reduced a t
iller number established both per spike and 1 m2. Their unevenness inc
reased (Tab. VII). The first sowing date secured a higher number of pr
oductive stems per unit area as compared to both later ones. Plant dev
elopment at various sowing dates was delayed and therefore, floret for
mation and reduction always took place in different periods and were i
nfluenced by weather conditions. At a later sowing date, a kernel numb
er per spike as well as stand sink fell down. This reduction was not c
ompensated by an increased kernel weight and grain yield decrease was
noticed. Based on the results obtained the following conclusions can b
e drawn. Considering the grain yield formation early growth stages wer
e very important during ontogenesis; they affected a tiller (spike) nu
mber and significantly expressed in subsequent formation of a final ke
rnal number which expresses accumulation capacity. Early and balanced
tillering is desirable. This requirement is dependent on the influence
of weather conditions during the year. In winter wheat, it can be lim
ited by an early sowing date. The seeding rate of 2.5 million seeds.ha
-1 optimized the ratio between yield elements and positively affected
grain yield. The results showed that from the point of view of breedin
g for production ability the genotypes not only with high production p
otential but as well as with its high realization are suitable.