Investigation on the Effect of Increasing Water Insufficiency on the Productivity and the Physical Grain Properties of Common Winter Wheat Cultivars

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Turkish Journal of Agricultural and Natural Sciences
Special Issue: 1, 2014
1177
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Investigation on the Effect of Increasing Water Insufficiency on the Productivity and the
Physical Grain Properties of Common Winter Wheat Cultivars
a
Margarita NANKOVA,
a
Genoveva BANKOVA-ATANASOVA,
b
Nikolay TSENOV,
a
Tatyana PETROVA,
a
Albena IVANOVA
a
Dobrudzha Agricultural Institute – General Toshevo, BULGARIA
b
Agronom I Holding, Dobrich, BULGARIA
Corresponding author: nankova_margo@abv.bg
Abstract
The trial was carried out in a specially constructed greenhouse. During the period of investigation (2011 –
2013), the experiment involved 11 common wheat cultivars in 4 replications. The cultivars were grown on
Haplic Chernozems under two regimes of water supply – optimal (OWS) and increasing water insufficiency, or
water deficit (WD) till the end of the growing season. The water regimes were imitated by watering and
maintenance of 80-85 % of MSMA (marginal soil moisture absorption) and by causing of drought at 45-50 %
MSMA. Under the optimal water regime, cultivars Bojana, Bolyarka, Rada and Bezostaya 1 formed maximal
total shoot biomass. The water insufficiency sharply decreased the productivity of the cultivars with a mean of
35.52 % in comparison to the optimal water regime. Highest total shoot biomass was measured in cultivars
Yantur, Bojana and Rada. Under both regimes of water supply, cultivars Bojana, Bolyarka, Lazarka, Rada and
Yantur had highest productivity. The increasing water insufficiency during the growing season of the crop
caused lower amplitudes in the variation of the investigated indices in cultivar Lazarka as compared to all other
cultivars. This cultivar had the highest harvest index under severe drought. The working efficiency of a
vegetation mass unit regardless of the water supply was highest in cultivar Bolyarka. Under severe water
insufficiency the same was valid for cultivars Lazarka, Neda, Slaveya and Yantur. The water insufficiency
contributed to the decrease of the absolute weight of the grain with 28.3 % and caused significant variation of
the values depending on the cultivar. Cultivars Bojana, Bezostaya 1, Bolyarka, Dragana and Lazarka were
significantly less affected by the severe insufficiency of soil moisture and possessed larger grain than the rest of
the cultivars. Under optimal water supply in the course of the growing season, cultivar Bolyarka had the largest
grain. This tendency was valid in all three years of the experiment, the differences with the other cultivars
being within the range 5 – 19.9 g.
Key words: Wheat, Cultivars, Drought stress, Yield components, Physical grain properties, Correlation
Introduction
Drought is a polygenic stress and is
considered as one of the most important factors
limiting crop yields around the world. As climate
change leads to increasingly hotter and drier
summers, the importance of drought constraints
on yield and yield components has increased in the
world. The ability of a cultivar to produce high and
satisfactory yield over a wide range of stress and
non-stress environments is very important (Kilic
and Yagbasanlar, 2010; Johari-Pireivatlou and
Maralian, 2011; Montazar and Azadegan, 2012).
The response of plants to water stress depends on
several factors such as developmental stage,
severity and duration of stress and cultivar
genetics (Duan et al, 2008; Li et al, 2011; Khakwani
et al, 2012).
All stages of crop growth are not uniformly
susceptible to water scarcity. On the other hand,
some stages can cope-up with water shortage very
well, while others are more susceptible and water
shortages at such stages may result in distinct yield
losses. Moisture stress is known to reduce
biomass, tillering ability, grains per spike and grain
size at any stage when it occurs. So, the overall
effect of moisture stress depends on intensity and
length of stress (Akram, 2011; Kharel et al, 2011;
Jäger et al, 2014).
Wheat (Triticum aestivum L.) is an important
crop in Bulgaria, where high temperatures and
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Turkish Journal of Agricultural and Natural Sciences
Special Issue: 1, 2014
1178
water stress often reduce plant growth and crop
yields. Therefore, wheat yield is lowered. Wheat
production in Bulgaria has always been related to
the necessity of tolerance to abiotic stress. The
annual meteorological anomalies present constant
challenge to winter wheat breeding (Tsenov and
Penchev, 1995; Tsenov et al, 2006; Tsenov et al,
2008
а, b
). The higher cold and drought tolerance,
the lower production losses will be in the future.
One of the practical possibilities to do this is to
carry out breeding for increasing grain yield by
increasing tolerance to abiotic stress (Vassileva et
al, 2011; Ivanova and Tsenov, 2011; Tsenov et al,
2012; Tsenov et al, 2013).
The role of the cultivar depending on the
level of different agronomy practices can vary from
8 to 15 %, or even 20 %. Under abiotic stress, the
effect of the factor cultivar can be significantly
higher (Tsenov, 2006).
The aim of this investigation was to study the
effect of long-term and increasing water stress
during the growth season of various Triticum
aestivum L. cultivars on their productivity and
physical properties of grain.
Material and Methods
The investigation was carried out during
2011 – 2013 in a rain-out shelter constructed for
simulation of drought at the Laboratory complex of
Dobrudzha Agricultural Institute – General
Toshevo. The soil in the trial area was slightly
leached chernozem (Hapliс Chernozems –WRBSR,
2006).
The tolerance of wheat to long drought was
tested in two variants: 1) optimal regime of water
supply (OWS) during the entire growing season by
maintaining 80-85 % of marginal soil moisture
absorption (MSMA); 2) Increasing water deficiency
(WD) till the end of the growing season by
maintaining 45 – 50 % of MSMA. Before sowing,
the experimental area was equalized by soil
moisture reserves in the 0-60 cm layer. The
determined initial soil moisture for both variants
prior to sowing was averagely 21.93 %.
Table1. Soil moisture after harvesting, %
Depth, cm OWS WD
0-20 11.05 7.44
20-40 13.02 8.68
40-60 15.42 8.47
During the growing season of wheat, in the
variant with OWS, watering was applied two or
three times, the last of which after heading-
flowering. In the variant with increasing water
deficiency, no water supply was available till the
end of the growing season. Soil moisture,
expressed as percent of its absolute dry weight
after harvesting of wheat, varied significantly down
the soil profile under both water regimes (Table 1).
In the variant with optimal water supply, the
soil moisture determined after harvesting was
averagely 60.0 % from the initial one, and in the
variant with increasing water deficiency it was 37.4
%.
Eleven common winter wheat (Triticum
aestivum L.) cultivars were tested, including 10
Bulgarian varieties and the Russian cultivar
Bezostaya 1 (Table 2).
The agro chemical analyses carried out to
characterize the experimental area and to
determine soil moisture were done in 4
replications at both plots where soil moisture
regimes were imitated (Table 3). The analysis on
the mobile forms of the main macro elements
showed that optimal nutrition regime was
ensured.
Table2. Characteristics of the tested wheat varieties
No
Varieties
Origin
Year
Pedigree
1
Bojana Bulgaria
2010 Obrij / Milena
2
Bolyarka Bulgaria
2004 Pryaspa / F 2076 W2-11
3
Dragana Bulgaria
2009 Miryana / Nadia
4
Lazarka Bulgaria
2007 Una /Flamura 85
5
Neda Bulgaria
2004 GP 2558-128 //Sadovo 1/Roason
6
Rada Bulgaria
2012 Enola / Preslav
7
Slaveya Bulgaria
2001 GP 2558-128/2 x Pliska
8
Stoyana Bulgaria
2010 2477-2 / Slaveya
9
Yantur Bulgaria
1983 Aurora / Era
10
Bezostaya 1 Russia
1955 Skorospelka 2 / Lut. 17
11
Dobrudzhanka Bulgaria
1996 Pliska / 2* Albidum 114

Turkish Journal of Agricultural and Natural Sciences
Special Issue: 1, 2014
1179
Table3. Agro chemical analysis of the trial area prior to sowing of wheat
Water
regime
Depth,
cm
pH
H
2
O
pH
KCl
NH
4
NO
3
Summ P
2
O
5
K
2
O
mg/1000 g soil mg/100 g soil
OWS 0-20 6,74 8,12 2,98 31,26 34,24 17,56 22,64
WD 0-20 7,21 8,08 4,35 36,11 40,46 24,31 24,81
OWS 20-40 6,73 8,16 3,01 17,99 21,00 8,48 22,19
WD
20
-
40
7,17
8,11
2,58
13,47
16,04
7,21
22,19
OWS 40-60 6,89 8,11 2,15 16,13 18,28 3,86 20,65
WD 40-60 7,06 7,92 2,48 30,91 33,39 3,97 20,68
The analysis of the variances of the
investigated productivity characteristics of the
tested wheat cultivars in the variant with optimal
water supply showed maximal level of statistical
significance of the factors year and cultivar (Table
4). Similar tendency was observed in the variant
with increasing soil moisture deficiency till the end
of the growth season, which was not valid only for
the non-grain part of the spike with regard to the
effect of the investigated years. The genotype as a
factor, however, maintained a high effect on this
plant organ marked with a high level of
significance.
The interaction of the two factors under both
regimes of water supply undoubtedly had
significant effect of the formed biomass of leaves
and stems, as well as on the grain size. Under
optimal water supply, the effect of the combined
interaction of the factors on the formed vegetative
and total shoot biomass and on the non-grain part
of the spike was significant. Under conditions of
long and increasing water deficit, the interaction of
the factors in the other indices was not significant.
Table4. Analysis of the variances of the shoot biomass formed by plant organs
Source Dependent Variable df
OWS
WD
F
p
-
value
F
p
-
value
Years
Leaves
2
180,756
,000
23,601
,000
Stems
2
51
,776
,000
11,456
,000
Spikes 2 13,343 ,000 4,394 ,000
Grain 2 11,555 ,000 5,410 ,000
Non
-
grain part of spikes
2
15,848
,000
1,971
,044
NS
V
.
mass
2
68,042
,000
6,766
,000
T
.
mass
2
19,824
,000
6,960
,000
OneVmGrain 2 37,453 ,000 3,706 ,000
GHI 2 35,670 ,000 3,616 ,000
1000
grain weight
2
353,913
,000
366,429
,000
Genotypes
Leaves
10
32,859
,000
479,027
,000
Stems
10
28,417
,000
234,660
,000
Spikes
10
6,647
,000
120,488
,000
Grain 10 6,027 ,000 134,200 ,000
Non-grain part of spikes 10 9,868 ,000 12,982 ,000
V
.
mass
10
27,826
,000
175,368
,000
T
.
mass
10
11,536
,000
210,021
,000
OneVmGrain
10
5,374
,000
18,035
,000
GHI
10
4,388
,000
16,177
,000
1000 grain weight 10 296,571 ,000 1602,096 ,000
Years * Genotypes Leaves 20 2,862 ,000 2,635 ,001
Stems
20
4,223
,000
2,617
,001
Spikes
20
1,624
,062
NS
1,247
,234
NS
Grain
20
1,499
,099
NS
1,861
,024
NS
Non
-
grain part of spikes
20
2,018
,012
,943
,535
NS
V. mass 20 4,234 ,000 1,357 ,163
NS
T
.
mass
20
2,348
,003
1,760
,036
NS
One
VmGrain
20
,950
,528
NS
,999
,470
NS
GHI
20 ,831 ,671
NS
1,012 ,456
NS
1000
grain weight
20
19,291
,000
61,441
,000

Turkish Journal of Agricultural and Natural Sciences
Special Issue: 1, 2014
1180
Figure1. Total shoot biomass per plant at OWS in soil, g (Waller-Duncan N=12)
The obtained results showed significant
variation of the cultivars’ productive potential over
years (Figure 1). Regardless of some variations in
the total productivity per spike-bearing plant, it
was found that under conditions of OWS during
vegetation, cultivar Bojana had highest mean total
shoot biomass (4.013 g), exceeding the mean
productivity of the group with 23.2 %.
To some extent cultivars Bolyarka and
Rada were characterized with similar powerful
development of the total formed shoot biomass at
technical maturity stage. Cultivars Dobrudzhanka,
Lazarka, Stoyana, Slaveya and Dragana formed
shoot mass below the mean value of the group. A
marked peculiarity of cultivar Lazarka was the
formation of total shoot biomass yield with lowest
amplitude of variation over years. The Waller-
Duncan test redistributed the obtained mean
yields into 7 groups, cultivars Bojana and
Dobrudzhanka markedly standing out. In all other
genotypes close or more distant similarity in the
response to the tested conditions of the trial field
was found.
In the variant with increasing water
deficiency till the end of the growing season, the
mean formed total shoot biomass was 2.100 g,
which was 64.48 % from the biomass formed
under optimal available soil moisture reserves
(Figure 2). This means that the mean decrease of
the total formed shoot biomass as a result from
increasing water stress was with 35.52 %. Cultivars
Bojana and Yantur had higher mean values of total
shoot biomass, averaged for the period, and fell
into groups “d” and “cd”, respectively. Their
exceeding above the mean values of the groups
was with 17.74 % and 12.63 %, respectively. In
cultivars Bezostaya 1, Stoyana, Slaveya and
Dobrudzhanka the formed mean yield of total
biomass was below the mean yield of the group of
cultivars and was 96.38 %, 94.61 %, 93.95 % and
74.47 % from it, respectively.
The Waller-Duncan test distinguished the
obtained results for the total shoot biomass
formed during the years of investigation (Table 5).
Under regime of optimal water supply (OWS), the
differentiation in the values of the index was less
expressed in comparison to variants with
increasing water stress during the growing season.
Table5. Effect of the year conditions of
investigation on the total formed shoot biomass of
wheat
Years (Waller-Duncan
N=44)
T. mass
OWS WD
2011 2,927 a
2,306 b
2012 3,417 b
1,352 a
2013 3,427 b
2,643 c
In the organs forming the vegetative mass
there was a significant differentiation in the values
of the formed dry matter depending on the
genotype and the water regime applied during the
growing season (Table 6). The highest percent of
the vegetative mass belonged to the stems; in all
cultivars decrease of the stem biomass was
observed under severe drought. Averaged for the
group of tested cultivars, this decrease was with
28.84 % in comparison to the regime with optimal
a
def
cde
bc
bcd
ef
bcd
b
bcd
f
g
1,500
2,000
2,500
3,000
3,500
4,000
4,500
5,000
Bojana
Bolyarka
Dragana
Lazarka
Neda
Rada
Slaveya
Stoyana
Yantur
Bezostaya 1
Dobrudzhanka
g/plant
2011 2012 2013 2011-2013

Turkish Journal of Agricultural and Natural Sciences
Special Issue: 1, 2014
1181
water supply. Under drought, most significant
decrease of the stem biomass was found in
cultivars Bojana and Bolyarka; their stem mass was
63.86 % from the mass formed under OWS regime.
Two of the tested cultivars had lowest dry matter
loss from the stems – Yantur and Lazarka; their
stem mass under WD regime was 82.20 % and
80.67 %, respectively, from the mass formed under
OWS regime.
Figure2. Total shoot biomass per plant under increasing water deficit (WD), g (Waller- Duncan N=12 )
Table6. Effect of the water supply regime on dry matter by organs of vegetative mass per plant, g
Genotypes
(Waller-Duncan N=12)
Leaves Stems Non-grain part of spikes
OWS WD OWS WD OWS WD
Bojana ,519 f ,443 g 1,200 g ,767 g ,400 fg ,248 a
Bolyarka ,389 e ,341 bc ,974 e ,622 cde ,372 def ,249 a
Dragana ,368 cde ,367 de ,742 a ,553 ab ,412 g ,382 b
Lazarka ,313 b ,354 cd ,755 ab ,609 bcd ,338 cd ,237 a
Neda ,357 cd ,393 f ,818 bc ,623 cde ,334 bc ,245 a
Rada ,377 de ,390 ef ,983 ef ,677 ef ,397 fg ,310 ab
Slaveya ,347 c ,354 cd ,826 c ,576 bc ,378 efg ,242 a
Stoyana ,304 ab ,325 b ,896 d ,665 def ,298 ab ,213 a
Yantur ,391 e ,438 g ,841 cd ,691 f ,345 cde ,253 ab
Bezostaya 1 ,380 de ,366 cde 1,051 f ,692 f ,382 fg ,268 ab
Dobrudzhanka ,284 a ,268 a ,717 a ,498 a ,272 a ,185 a
Similar tendency was observed for the non-
grain part of the spike as well. The mean dry
matter loss according to the OWS variant was with
28 %. Cultivars Dobrudzhanka, Bolyarka, Slaveya
and Bozhana had mean loss from 32 % to 38 %.
The dry matter loss from the non-grain part of the
spike was lowest in cultivar Dragana – only 7.2 %.
An interesting tendency was noted in the response
of the cultivars with regard to the changes in the
dry matter of the leaf mass at the end of the
growing season. Averaged for the period of
investigation and the tested cultivars, significant
variations in the leaf mass formed per plant under
both tested water supply regimes (OWS – 0.366 g
and WD – 0.367 g) were not observed. In all three
years of the investigation, cultivars Bojana and
Bolyarka had highest dry matter loss from their
leaf mass under drought, which amounted to
about 14 %. Similar tendency was observed in
cultivars Bezostaya 1 and Dobrudzhanka but their
loss was between 2.7 % and 3.8 %. In the other
cultivars, the leaf mass maintained the same dry
matter weight, and in the case of cultivars Lazarka
and Yantur it was even higher.
Finally, the vegetative biomass formed in the
variants with increasing water deficiency at
technical maturity of plants was 73.40 % from the
biomass formed in the OWS variants. The
differentiation between the cultivars was well
expressed; under both water regimes the obtained
a
b
cd
b
b
bc
bc
b
bc
b
d
1,000
1,500
2,000
2,500
3,000
3,500
Bojana
Bolyarka
Draga na
Lazarka
Neda
Rada
Slaveya
Stoyana
Yantur
Bezostaya 1
Dobrud zhanka
g/pl ant
2011 2012 2013 2011-2013

Turkish Journal of Agricultural and Natural Sciences
Special Issue: 1, 2014
1182
vegetative mass yields were distributed into 5
groups according to the Waller-Duncan test (Figure
3). Cultivar Bojanka (“е”) had highest values of the
vegetative biomass formed per plant under both
water regimes, while cultivar Dobrudzhanka (“а”)
had the lowest.
Under OWS regime, the differences were
clearly defined, as well as the sameness of the
cultivars’ response at significantly less expressed
similarity. In the variant with increasing water
deficit only the response of cultivars Bojana and
Dobrudzhanka was clearly differentiated. All other
cultivars were characterized with significantly
higher similarity in their response to the moisture
deficiency in soil.
Under regime of optimal available moisture
reserves in soil (OWS) all tested cultivars formed
grain yield per spike above 1 g. The variation of
productivity was from 1.135 g (Dobrudzhanka) to
1.912 g (Bolyarka) (Figure 4). Cultivars Bozhana and
Rada also had high grain yield. The mean
productivity of the tested cultivars was 1.643 g
grain per spike.
In the variants with increasing water deficit
the mean productivity of the cultivars was 0.842 g.
This mean yield was 51.25 % from the yield
obtained under optimal water supply of the plants.
Averaged for the investigated period, grain yield
per spike varied within a rather wide range: from
0.613 g in cultivar Dobrudzhanka to 1.016 g in
cultivar Bojana. Cultivars Yantur, Lazarka and
Bolyarka were close to a maximum degree to
cultivar Bojana by their grain yield per spike.
Cultivar Lazarka had much lower amplitude
of variation of the values of the total formed shoot
biomass and grain between the two water supply
variants in comparison to the other cultivars
(Figure 5).
The working efficiency of a vegetative mass
unit varied significantly in the individual cultivars
depending on the water supply variant (Table 7). In
the variant with optimal water supply, a vegetative
mass unit produced grain above 1 g, with the
exception of cultivars Dobzudzhanka, Bojana and
Bezostaya 1, which fell within the group of lowest
order. Highest values, averaged for the period,
were determined in cultivar Neda, followed by
most of the tested cultivars, which were referred
to group “cd”.
Figure 3. Vegetative biomass per plant depending on the water regime of soil, g (Waller-
a
d
c
bc
c
d
bc
b
c
d
e
a
cde
de
bc
b
de
bcd
bc
bcd
bc
e
0,500
0,700
0,900
1,100
1,300
1,500
1,700
1,900
2,100
2,300
Bojana
Bolyarka
Dragana
Lazarka
Neda
Rada
Slaveya
Stoyana
Yantur
Bezostaya 1
Dobrudzhanka
g/plant
OWS WD

Turkish Journal of Agricultural and Natural Sciences
Special Issue: 1, 2014
1183
Figure4. Effect of the water supply regime on grain yield per spike, g (Waller-Duncan N=12)
Figure5. Amplitude of variation of the formed total mass and grain yields between the two water supply
variants, g/plant
The increasing water deficit during the growing
season of the crop sharply decreased the
productivity of a vegetative mass unit and
averaged for the cultivars it was 64.34 % from the
productivity determined under optimal water
supply, i.e. there was a decrease with 35.7 %.
Comparing in absolute values the results obtained
in the variant with increasing water deficit,
regardless of the decreased productivity, best
results were obtained from cultivars Bolyarka and
Lazarka, in which a vegetative mass unit produced
from 0.710 to 0.743 g of grain.
a
bc
bcd
bc
bc
cde
bcd
b
bcd
ede
a
ab
d
bc
bc
bc
cd
cd
bc
cd
d
0,500
0,700
0,900
1,100
1,300
1,500
1,700
1,900
2,100
Bojana
Bolyarka
Dragana
Lazarka
Neda
Rada
Slaveya
Stoyana
Yantur
Bezostaya 1
Dobrudzhanka
g/plant
OWS WD
0,500
0,700
0,900
1,100
1,300
1,500
1,700
Bojana
Bolyarka
Dragana
Lazarka
Neda
Rada
Slaveya
Stoyana
Yantur
Bezostaya 1
Dobrudzhanka
g/plant
T.mass Grain

Turkish Journal of Agricultural and Natural Sciences
Special Issue: 1, 2014
1184
Table7. Grain production per vegetative mass unit
depending on the water supply regime.
Cultivars OWS WD In % to OWS
Bojana ,904 a ,673 bcd 74,45
Bolyarka 1,101 cd ,710 cd 64,49
Dragana 1,102 cd ,649 bcd 58,89
Lazarka 1,061 cd ,743 d 70,03
Neda 1,112 d ,693 cd 62,32
Rada 1,013 bc ,598 ab 59,03
Slaveya 1,019 cd ,680 bcd 66,73
Stoyana 1,076 cd ,641 bc 59,57
Yantur 1,060 cd ,694 cd 65,47
Bezostaya 1 ,916 ab ,514 a 56,11
Dobrudzhanka ,892 a ,630 bc 70,63
Mean 1,023 0,657 64,34
These results were clearly reflected in the
data on the percent of vegetative biomass and its
components according to the total shoot biomass
formed (Table 8). The established differences at
level cultivar became greater in the variant with
increasing moisture deficit. On the whole, while
productivity decreased under water deficiency, the
percent of vegetative biomass increased.
This increase was with 21.6 %, averaged for
the tested cultivars. In the respective components
forming the vegetative mass, the increase for
leaves was with 65.0 %, for stems – with 12.2 %,
and for the non-grain part of spikes – with 11.8 %.
These results showed that significant restructuring
occurred in the percent of the respective organs
ultimately responsible for the flow of assimilates to
the grain. Among all cultivars, Bezostaya 1 had
highest percent of the vegetative mass, especially
in the variant with water deficit, which reflected on
the values of the harvest index as well (Table 9).
Under optimal water regime of soil, the
percent of grain in all cultivars was above 50 %
from the total biomass formed, with the exception
of cultivars Dobrudzhanka, Bezostaya 1 and
Bojana. Highest harvest index, averaged for the
period, was registered in cultivars Bolyarka,
Dragana and Neda (0.52).
The artificial imitation of severe water stress
reduced the percent of grain in the total biomass
with 21.9 %. The genotypic differentiation was
strongly expressed, the variation being from 33.38
% (Bezostaya 1) to 42.27 % (Lazarka). In all three
years of the investigation, cultivar Lazarka ranked
first by this index. This cultivar had lower values in
the variation between the two variants of water
supply by a number of other indices, as well, which
was also reflected in the high grain yield per spike
under increasing water deficit.
Absolute grain weight was also influenced by
the water regime of soil besides by the type of
cultivar (Table 10). Under optimal water regime
cultivar Bolyarka had largest grain. Averaged for
the three years of investigation, the values of this
index were 62.00 g, followed by cultivars Dragana
and Neda.
Under conditions of water deficit, the
variation of the values was from 30.37 g to 41.84
and 41.89 g in the cultivars Dobrudzhanka, Bojana
and Bezostaya, respectively. Cultivars Bolyarka,
Dragana and Lazarka conceded to them with about
1 g in absolute values. Under both regimes of
water supply, cultivar Dobrudzhanka had the
smallest grain.
The established correlations between the separate
organs of the shoot biomass demonstrated high
statistical significance (Table 11).
Table8. Percent of vegetative mass organs from the total formed biomass, %
No Cultivars Vegetative biomass Leaves Stems Non-grain part of
spike
OWS WD OWS WD OWS WD OWS WD
1
Bojana 53,02 60,41 12,92 18,43 29,78 31,23 10,05 10,33
2
Bolyarka 47,99 59,56 10,73 16,59 26,79 30,33 10,24 12,12
3
Dragana
47,97
61,23
11,79
17,72
23,30
26,78
12,89
16,61
4
Lazarka 49,17 57,73 10,98 17,02 26,30 29,24 11,74 11,47
5
Neda 47,83 59,29 11,43 18,28 25,86 29,33 10,56 11,65
6
Rada 49,91 61,37 10,74 17,63 27,90 31,37 11,29 14,02
7
Slaveya 49,22 59,47 11,26 17,87 26,54 29,34 12,03 12,42
8
Stoyana 48,28 61,50 9,76 16,41 28,89 33,93 9,75 10,90
9
Yantur 49,03 60,02 12,18 18,71 25,93 29,46 10,66 11,12
10
Bezostaya 1 52,71 65,16 10,99 18,56 30,21 34,73 11,10 13,44
11
Dobrudzhanka 53,73 61,92 11,96 17,43 29,82 32,14 11,41 12,09
Mean 49,90 60,70 11,34 17,69 27,39 30,72 11,07 12,38

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1185
Table10. Absolute grain weight depending on the
water regime, g (Waller-Duncan N=12)
Genotypes 1000 grain weight
OWS WD
Bojana 50,43 c 41,84 f
Bolyarka 62,00 h 40,38 e
Dragana 56,90 g 40,69 e
Lazarka 51,24 d 40,77 e
Neda 56,93 g 35,39 b
Rada 54,62 f 36,28 c
Slaveya 51,76 d 36,29 c
Stoyana 47,41 b 35,12 b
Yantur 52,86 e 38,26 d
Bezostaya 1
56,2
9 g
41,8
9 f
Dobrudzhanka 41,81 a 30,37 a
This high significance considerably increased
for leaves and stem under conditions of water
stress. The correlation of grain yield with the
organs producing the vegetative mass in both
water supply variants was higher for stems than for
leaves. A tendency was observed toward sharp
increase of the correlation coefficient values
expressing the relation in the grain-and-leaves
apparatus under drought (r = .846
**
). The increase
in comparison to the OWS variant was 2.3 times.
Grain yield was in well expressed
significant correlation with the mass of the non-
grain part of spike. It had high values under OWS,
where r = .724**. In the variant with increasing
water stress, regardless of the high statistical
significance, the values of the correlation
coefficient decreased almost 2 times (r = .350**).
Under both regimes of water supply, grain
size was in high correlation with the biomass
formed by organs and with the GHI. The values of
the correlation coefficients significantly increased
under water stress in comparison to OWS in all
investigated correlations, with the exception of the
correlation with the non-grain part of spike.
Regardless of the decrease of the correlation
coefficient values of absolute grain weight and the
mass of the non-grain part of the spike, this
coefficient had high statistical significance.
Table11. Correlations between some main characteristics of productivity according to the regime of water
supply (Pearson Correlation)
Indices
Leaves Stems Glumes V. mass
OWS WD OWS WD OWS WD OWS WD
Leaves ,734** ,887** ,386** ,414** ,838** ,902**
Stems ,734** ,887** ,571** ,399** ,965** ,917**
Spikes ,383** ,839** ,703** ,863** ,796** ,641** ,725** ,929**
Grain ,365** ,846** ,696** ,881** ,724** ,350** ,700** ,828**
Non-grain part of
spikes ,386** ,414** ,571** ,399** ,688** ,708**
V. mass ,838** ,902** ,965** ,917** ,688** ,708**
T. mass ,632** ,916** ,889** ,942** ,767** ,564** ,909** ,961**
GHI -,427** ,393** -,099 ,420** ,227** -,111 -,139 ,285**
1000 grain weight ,352** ,725** ,338** ,706** ,515** ,363** ,427** ,709**
Indices
Grain T. mass GHI Mass of 1000
OWS WD OWS WD OWS WD OWS WD
Leaves ,365** ,846** ,632** ,916** -,427** ,393** ,352** ,725**
Stems ,696** ,881** ,889** ,942** -,099 ,420** ,338** ,706**
Spikes ,994** ,944** ,943** ,979** ,558** ,569** ,540** ,696**
Grain ,934** ,951** ,595** ,742** ,520** ,693**
Non-grain part of
spikes ,724** ,350** ,767** ,564** ,227** -,111 ,515** ,363**
V.mass ,700** ,828** ,909** ,961** -,139 ,285** ,427** ,709**
T. mass ,934** ,951** ,278** ,523** ,517** ,734**
GHI ,595** ,742** ,278** ,523** ,216* ,317**
1000 grain weight ,520** ,693** ,517** ,734** ,216* ,317**
* Correlation is significant at 0.05 level (2-tailed); ** Correlation is significant at 0.01 level (2-tailed).
Conclusions
Under optimal water regime, cultivars
Bojana, Bolyarka, Rada and Bezostaya 1 formed
maximum total shoot biomass. The water deficit
sharply reduced the shoot biomass of the cultivars
– with an average of 35.52 % according to the

Turkish Journal of Agricultural and Natural Sciences
Special Issue: 1, 2014
1186
optimal water regime. Cultivars Yantur, Bojana and
Rada were characterized with the highest total
shoot biomass.
Under conditions of drought, the mass of
stems decreased with 28.84 %, and of the non-
grain part of spike – with 28.15 %, as compared to
the optimal water supply regime. Significant
differences in the mean leaf mass formed in the
two water supply variants were not found, but the
genotypic specificity remained the same. Cultivars
Bojana and Bolyarka had lower values of dry
matter in the leaf and stem mass. Regardless of
this fact, however, under both water regimes
cultivar Bojana maintained maximum amount of
vegetative mass.
Cultivars Bolyarka and Bojana had high grain
weight of spike under optimal water supply, and
under conditions of increasing water stress till the
end of the growing season these were cultivars
Bojana and Yantur. The mean yield from the tested
cultivars under increasing drought till the end of
the growing season was 51.25 % from the yield
obtained under optimal water supply, or the mean
decrease of productivity was with 48.75 %.
The increasing water deficit caused the
lowest amplitude in the variation of grain yield in
cultivar Lazarka in comparison to the other
cultivars. This cultivar had the highest harvest
index under severe drought.
The working efficiency per vegetative mass
unit regardless of the water supply was highest in
cultivars Bolyarka and Dragana. Under severe
water deficit this was valid for cultivar Lazarka as
well, followed by cultivars Dragana and Yantur.
The water deficit contributed to 28.34 %
lower grain weight and to considerable variation of
the values depending on the cultivar. Under
optimal water supply in the course of the
vegetation, cultivar Bolyarka had largest grain
followed by cultivars Neda, Dragana and Bezostaya
1. Under conditions of water stress, cultivars
Bojana and Bezostaya 1 maintained the largest
grain size, followed by cultivars Bolyarka, Lazarka
and Dragana.
Cultivar Dobrudzhanka had the lowest values
of all investigated indices under both regimes of
water supply.
Significant correlations were found between
the investigated elements of productivity; the
values of the correlation coefficients significantly
increased under water stress as compared to
optimal water supply.
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