AJCS 18(07):395-400 (2024) ISSN:1835-2707
https://doi.org/10.21475/ajcs.24.18.07.pne-43
Trade-offs between grain number, grain weight and fruiting efficiency
of different bread wheat genotypes in response to anthesis drought
stress
Hanane Ouhemi
1,*
and Ali Amamou
2
1
Laboratory of Agronomy, Regional Center of Agricultural Research of
Settat, National Institute of Agricultural Research, Avenue Ennasr, BP
415 Rabat Principale, 10090, Morocco
2
Laboratory of Wheat Breeding, Regional Center of Agricultural
Research of Settat, National Institute of Agricultural Research, Avenue
Ennasr, BP 415 Rabat Principale, 10090, Morocco
Abstract: Cereal crops in Morocco are mainly
cultivated under rainfed conditions of dryland
regions. Under these conditions, they are mostly
exposed to drought stress that affects different yield
components. We studied the effect of anthesis
drought stress on the relationships among the
components of grain number (GN), thousand grains
weight (TGW), fruiting efficiency (FE) and yield. And
we examined fruiting efficiency (FE= grains set per g
of spike dry weight at anthesis) as promising trait for
further increasing yield without compromising yield
components. Greenhouse experiments were
Submitted:
07/11/2023
Revised:
26/01/2024
Accepted:
24/04/2024
Full Text PDF
conducted on 2019/2020, 2020/2021 and
2021/2022 cropping seasons. Two contrasting water
regimes, irrigated and stressed treatments at anthesis
growth stage were assessed. Results showed that
anthesis drought stress affects negatively all
components studied. Substantial decrease of 10%,
16%, 9% and 34% were recorded for GN, TGW, FE, and
yield, respectively, under water stress compared to
irrigated treatments. Two genotypes, namely 15/42
and Achtar, were found to be the most adapted to
both stressed and irrigated conditions. Under
stressed conditions yield becomes less correlated
with GN (r = 0.36) and FE (r = 0.37) and more
correlated with TGW (r = 0.56*). GN becomes less
correlated with FE (r = 0.02) and TGW (r = -0.14).
While, FE becomes more correlated with TGW (r =
0.73*). To the extent of this study, FE was found as
promising selection criterion under stress conditions
without compromising TGW component.
Keywords: wheat; water stress; anthesis; fruiting efficiency; grain
number; thousand grain weight.
Abbreviations: GN_Grain number; TGW_thousand grains weight;
FE_fruiting efficiency; ns_no-significant; p_P
value
;
r, coefficient of
correlation.
Introduction
Water is the main factor limiting crop production of arid and semi-arid
regions. The amount of rain and its distribution, affect the crop
growth and productivity (Alqudah et al., 2011; Khakwani et al., 2012).
Previews studies reported several effects of anthesis drought stress on
metabolic, morpho-physiologic, and agronomic traits of wheat
(Qaseem et al., 2019; Fan et al., 2022; Ru et al., 2022). However, the
amount of these effects varied with genotypes and across
environments (Elía et al., 2016; Ferrante et al., 2017; Terrile et al.,
2017; Pretini et al., 2020).
Concerning agronomic traits; number of grains per unit area and
average grain weight are the main components of yield. The grains
number is determined during flowering time (Alqudah et al., 2011; Liu
et al., 2015). It recognizes a decrease under water stress due to pollen
abortion in the young microscope stage of pollen development, and
spikelets and florets abortion in the floral development stage (Ji et al.,
2010; Mahrookashani et al., 2017; Slafer et al., 2023). Other causes of
grain loss may be related to reduced spike dry weight at anthesis
(SDWa) (Terrile et al., 2017; Rivera-Amado et al., 2019; Pretini et al.,
2021), or reduced duration of the late reproductive phase (Gonzalez-
Navarro et al., 2016). Similarly, grain size started its construction just
before anthesis which make it vulnerable to anthesis drought stress
and to the lack of sufficient assimilate to fill the grain during grain
filling growth stage (Ji et al., 2010; Weldearegay et al., 2012).
However, longer phase from terminal spikelet to anthesis, results in
later grain filling conditions and consequently smaller grains
(Gonzalez-Navarro et al., 2016).
One of the alternatives for further increasing yield is increasing
fruiting efficiency (grains set per unit of spike dry weight at anthesis).
Increasing FE may be achieved by an accelerated rate of floret
development, an enhanced partitioning of spike assimilates, a long
stem elongation duration, or by reducing the abortion of grains
(Gonzalez-Navarro et al., 2016; Terrile et al., 2017; Slafer et al.,
2023). The fruiting efficiency has been used recently in breeding
program as a promising trait to enhance grain number and therefore
grain yield of wheat crop (Ferrante et al., 2015;
Table 1. Year of release and the pedigree of the genotypes studied.
Genotypes Year of release Pedigree
15/42
2020
BT1735/ACHTAR//HUBARA
-
8
44/10/17
-
MINO
132-88 - UP2338*2/KKTS*2//YANAC
132-93 - BAJ #1/KISKADEE #1
Achtar
1988
HORK/YMH//KAL/BB
Amal
1993
Bow’s’/Buc’s’
Table 2. Means of treatments, mean squares and significance of ANOVA.
GN/S
TGW (g)
FE (grains.g
spike
-
1
)
Yield (g/pot)
Mean irrigated treatments
25.14
±0.83
29.19
±0.88
35.22
±1.53
9.42
±0.34
Mean stressed treatments
22.59
±0.90
24.40
±1.35
31.91
±1.35
6.26
±0.36
Source of variation (
mean square
ns, *, **, *
**
)
Water regime (WR) 176.46
**
619.44
**
296.08
ns
269.611
***
Genotype (G) 121.44
***
65.42
ns
184.82
ns
3.885
ns
Year (Y)
4734.07
***
1353.48
***
3400.35
***
129.961
***
WR x G
12.64
ns
35.84
ns
29.82
ns
2.438
ns
WR x Y 84.79
*
390.31
**
1052.22
***
34.336
**
G x Y 78.33
**
72.141
ns
140.36
ns
7.978
ns
WR x G x Y
18.76
ns
9.32
ns
82.36
ns
4.356
ns
± standard error. ns: no-significant; *: significant at p<0.05; **: highly significant at p<0.01; ***: very highly significant at p<0.001.
Joudi et al., 2016; Gerard et al., 2019; Curin et al., 2021; Pretini et al.,
2021). The eco-physiological model defined above encompasses the
grain number as the result of the spike dry weight and fruiting
efficiency at anthesis (Pretini et al., 2021). However, the trade-off
recorded between FE and grain weight may limit its usefulness
(Gonzalez-Navarro et al., 2016; Terrile et al., 2017; Slafer et al.,
2023). In response to that, the objectives of this study were to identify
the best-performant genotypes among six bread wheat genotypes
exposed to anthesis drought stress, to underly the resulting
relationship among yield, grain number, grain weight and fruiting
efficiency, and to discuss the resulting trade-offs between these
traits.
Results
Effect of anthesis drought stress on grain number, grain weight,
fruiting efficiency and yield
Analysis of variance revealed significant difference (p<0.05) between
water regimes (WR) for GN/S, TGW and yield. Average decrease of
10%, 16%, 9%, 34% were observed for GN, TGW, FE and yield,
respectively, under water stress compared to control treatment (Table
2). Highly significant difference (p<0.001) between genotypes was
recorded for NG/S. In fact, all genotypes recorded substantial
decrease due to water stress in GN/S, TGW, FE and yield. However,
15/42 and Achtar genotypes recorded small amount of decrease
between water regimes for GN/S and FE components. Amal variety
recorded the same value of TGW (25 g) under both water regimes. And
the three genotypes, Amal, Achtar and 15/42 recorded small amount
of decrease in yield between both water regimes (Fig. 1).
The range of variation in GN/S among genotypes oscillated between
20 and 29 grains under irrigated regimes (9 grains of difference),
while this range lowered to 6 grains of difference when it is exposed
to stress (Fig. 1a). Likewise, TGW showed a range of 9 g of difference
between genotypes (from 26 to 35 g) when it was irrigated, while this
range was lowered to 3 g when it was exposed to water stress (Fig.
1b). Similarly, FE ranged between 28 and 41 (13 grains/g.
spike
of
difference) when it was irrigated, while this range was lowered to 7
grains/g.
spike
(from 29 to 36) when it was subjected to water stress
(Fig. 1c). Finally, grain yield recorded a range from 9 to 11 g/pot when
it was irrigated, while it ranges around 6 g/pot when it was stressed
(Fig. 1d).
Genotypes ranking under stressed and irrigated environments
The results of the centered scatter plot revealed that the six
genotypes studied varied noticeably in reaction to stressed or irrigated
environment for each trait. 15/42 and Achtar genotypes showed the
best performance under stressed environments for grain number
component (GN/S) (Fig. 2a). For thousand-grain weight (TGW), all
genotypes except 132-93 performed better in stressed environment
(Fig. 2b). Whereas, for the fruiting efficiency trait (FE), 132-93, 15/42,
and Achtar genotypes showed the best performance under stressed
conditions (Fig. 2c). Finally, for grain yield, 15/42, Amal, and Achtar
genotypes performed better in stressed environment (Fig. 2d).
Trade-offs: grain number, grain weight, fruiting efficiency and yield
As shown in Table 3, Grain number (GN) recorded significant and
positive correlation with FE (r = 0.48*) under irrigated conditions. This
trend was changed under stressed conditions by reducing the positive
correlation to r = 0.02. On the other side, significant negative
correlation between GN and TGW (r = - 0.66*) was recorded under
irrigated conditions. While under stressed conditions, this negative
correlation becomes much lower (r = - 0.14). Additionally, FE
recorded a negative correlation with TGW (r = - 0.11) under irrigated
conditions. This trend was changed under stressed conditions by
favoriting the positive correlation between FE and TGW (r = 0.73*).
Finally, yield recorded significant (<0.001) and positive correlation
with GN (r = 0.76*) and FE (r = 0.61*), and significant and negative
correlation with TGW (r = - 0.50*) under irrigated conditions. While
under stressed conditions it records less positive correlation with
Fig 1. Means of genotypes under stressed and irrigated treatments for a) grain number per spike (GN/S); b) thousand-grain weight
(TGW); c) fruiting efficiency (FE); and d) yield. Different small letters indicate significant difference according to Tukey’s test.
Table 3. Pearson’s correlation coefficients of different traits under irrigated (above) and stressed (below) conditions
Correlations Irrigated
Stressed
- NG/S TGW FE Yield
NG/S
-
-
0.66*
0.48*
0.76*
TGW
-
0.14
-
-
0.11
-
0.50*
FE 0.02 0.73* - 0.61*
Yield 0.36 0.56* 0.37 -
*: significant correlation at p<0.05.
GN (r = 0.36) and FE (r = 0.37) and high positive correlation with TGW
(r = 0.56*).
Discussion
The present study assessed the effect of water stress at anthesis
growth stage on grain number per spike (GN/S), thousand grain
weight (TGW), fruiting efficiency (FE) and yield traits. The resulting
trade-offs between these traits were discussed.
Water stress applied at anthesis, acts as an indirect method of
thinning the grains, it caused substantial decrease in GN/S (10%), TGW
(16%), FE (9%) and yield (34%) (Table 2). Reduced grain number under
water stress was estimated between 20 to 60% (Jatoi et al., 2011;
Mahrookashani et al., 2017; Qaseem et al., 2019). This decrease was
related to ovarian abortion or pollen sterility (Alqudah et al., 2011;
Mahrookashani et al., 2017). In our study the tolerant varieties in this
component, were 15/42 and Achtar genotypes, they maintained a
lower decrease and they are those adapted to stressed environments
(Figs. 1a and 2a). Likewise, anthesis water stress caused a decrease in
TGW. The estimated decrease ranges between 10% and 30% (Jatoi et
al., 2011; Mahrookashani et al., 2017). Amal variety was less affected
by this stress and was the most adapted to stressed environments for
this component (Figs. 1b and 2b).
In fact, anthesis drought stress in some cases may led to less
reduction in TGW, which could be due to less formed grain numbers
which conduct to heavier grains (Weldearegay et al., 2012). Similarly,
FE recorded substantial decrease under water stress. 15/42 and
Achtar genotypes maintained less reduction and are well positioned
on the stressed environment (Figs. 1c and 2c). The FE is the final
result of floret development rate and the proportion of kernel formed
per fertile floret per unit of spike dry weight (Slafer et al., 2015; Elía et
al., 2016; Garcia et al., 2019). In fact, higher persistence of floret
primordia, and/or a reduced level of grain abortion characterize the
efficient genotypes (Slafer et al., 2015; Elía et al., 2016; Garcia et al.,
2019). Also, Amal, Achtar and 15/42 genotypes recorded the lowest
decrease in grain yield, which reflect their ability to resist water stress
(Fig. 1d). This result is in line with the centered environment biplot
result, which ranked these three genotypes as the best performant
genotypes to stressed environment (Fig. 2d). The recorded decrease in
grain yield under anthesis drought stress was previously reported by
several studies on the wheat crop (Khakwani et al., 2012; Weldearegay
et al., 2012). And it was estimated at 40 to 50% of grain yield loss
(Mahrookashani et al., 2017; Qaseem et al., 2019).
The strong positive correlation between GN and FE (r = 0.48*) under
irrigated conditions, indicates a great
Fig 2. Genotypes ranking according to their performance in irrigated or stressed environment for a) grain number per spike (GN/S),
b) thousand-grain weight (TGW), c) fruiting efficiency (FE), and d) yield.
a) Environment-centred data for NG/S
132-93
Achtar
44/10/17
132-88
Amal
15/42
Stres
sed
Irrigated
Genotype scores
b) Environment-centred data for TGW
132-93
Achtar
44/10/17
132-88
Amal
15/42
S
tressed
Irrigated
Genotype scores
c) Environment-centred data for FE
132-93
Achtar
44/10/17
132-88
Amal
15/42
Stres
sed
Irrigated
Genotype scores
d) Environment-centred data for yield
132-93
Achtar
44/10/17
132-88
Amal
15/42
Stresse
d
Irrigated
Genotype scores
contribution of GN to FE (Table 3). In fact, the positive relationship
between FE and GN in normal conditions makes FE as a promising trait
for further increasing GN (Rivera-Amado et al., 2019; Zhang et al.,
2019; Pretini et al., 2021; Sierra-Gonzalez et al., 2021). However, this
relationship was reduced (r = 0.02) by water stress (Table 3), which
reduces the potential contribution of GN to FE. While, the strong
negative correlation between GN and TGW (r = -0.66*) under optimal
conditions reflects the great trade-off between these two components
(Table 3). In fact, the normal trend of the relationship between GN and
TGW is negative (Gonzalez-Navarro et al., 2016; Terrile et al., 2017;
Sierra-Gonzalez et al., 2021). Because of germplasm that can maintain
high GN is not able to maintain high TGW (Ji et al., 2010). Under
stressed conditions, this negative correlation becomes much lower (r
= -0.14) (Table 3), indicating that at this stress level, TGW was not
limited by the sink capacity but by the compensation effect between
GN and TGW. Similarly, FE recorded a negative correlation with TGW (r
= -0.11) under optimal conditions, which indicate the great trade-off
between FE and TGW (Table 3). Thus, genotypes with high fruiting
efficiency will have smaller fertile florets or smaller grains (García et
al., 2014; Ferrante et al., 2015;
Slafer et al., 2015; Gonzalez-Navarro et al., 2016; Rivera-Amado et
al., 2019). This trend was changed under stressed conditions by
favoring the positive correlation between FE and TGW (r = 0.73*)
(Table 3).
The positive correlation between GN and FE and the recorded trade-
offs between TGW and GN and between TGW and FE under optimal
conditions (Table 3), reflect that any increase in GN and subsequently
in FE could be at the expense of TGW. In fact, the negative correlation
between TGW and FE components could be caused by different
processes; the most reported one is that the increase in FE would
increase the proportion of grains of smaller potential size, which
represents the grains from the distal position, without necessarily
reducing the potential size of grains already existing under low FE
situations (Ferrante et al., 2015; Terrile et al., 2017; Garcia et al.,
2019). And this negative correlation was explained by the reduced
demand of individual florets to develop normally, the final size of the
fertile floret will be smaller by increasing FE (the same amount of
resources to satisfy normal growth, by smaller florets) (Slafer et al.,
2015). Consequently, the negative correlation between TGW and FE
would not present any trade-off with TGW (Ferrante et al., 2012;
González et al., 2014; Terrile et al., 2017; Garcia et al., 2019; Gerard
et al., 2019).
The positive correlations between yield and GN (r = 0.76*) and FE (r =
0.61*) indicate the important contributions of these traits to yield.
Analyzing all sources of variation, genotypic or environmental, yield
was found to be closely correlated to grain number (Ferrant et al.,
2012; Elía et al., 2016). And several studies suggest FE as a secondary
or physiological trait for yield improvement (Pretini et al., 2021).
Overall, the extent of the relationship between yield and GN and FE
components decreased with water stress (GN: r = 0.36, FE: r = 0.37),
and the recorded trade-off between yield and TGW (r = -0.50*)
becomes lower under stress conditions (r = 0.56).
Materials and methods
Site description
A greenhouse experiment was carried out at National Institute of
Agricultural Research, Settat - Morocco (N: 33.167 and W: 7.4). During
three cropping seasons: 2018/2019, 2019/2020 and 2021/2022. The
soil used is a vertisol with a clay texture, an alkaline pH (8.2), and a
medium organic matter (2.7%).
Crop managements and treatments
Six genotypes (15/42, 44/10/17, 132/88, and 132/93, Achtar and
Amal) were tested for their ability to tolerate anthesis water stress.
Table 1 gives the characteristics of the genotypes studied. Sowing was
carried out on the 20
th
, 24
th
and 16
th
December of the three cropping
seasons consecutively, 2018/2019, 2019/2020 and 2021/2022. A pot
of 10-liter containing 1/3 compost and 2/3 soil was used. Sufficient
nutrients were applied. Weed, disease and insect were controlled. The
treatments consisted of the control with sufficient irrigation twice a
week from sowing to the end of grain filling, and stressed treatment
consisted of restricting irrigation at anthesis for 15 days (from the
beginning of anthesis to the beginning of grain filling). The
experimental design was a split-plot with three replications.
Plant measurements
Five plants were harvested after the period of water stress to measure
the spike dry matter at anthesis. And a sample of 15 plants was taken
at harvest to measure the grain number per spike (GN/S), thousand
grain weight (TGW), fruiting efficiency (FE: grains set per g of spike dry
weight at anthesis) and yield in each treatment.
Statistical analysis
Analysis of variance (ANOVA) was used to extract the effect of
genotype, water regime and their interaction. Mean comparison test of
Tukey was used to classify the treatments. Genotype ranking using a
centered scatter plot was recorded by GGE-biplot. A pearson’s
correlation analysis was recorded. All statistical analyses were
performed using GenStat software, 15
th
edition (VSN International,
Hermel Hempstead, UK, 2011).
Conclusion
Anthesis drought stress reduced all components studied. However,
the persistence of genotypes was evaluated by their ability to maintain
a low reduction under water stress in comparison to irrigated
treatment. Two genotypes, namely 15/42 and Achtar, were found to
be the most adapted to both stressed and irrigated conditions. The
high correlation between GN and FE under irrigated conditions makes
FE as promising trait to take in consideration in breeding program.
However, its importance is reduced under stress conditions. While, the
recorded trade-off between FE and TGW under irrigated conditions
decreased under stressed conditions, the origin of that indicate that
increasing FE could be achieved without compromising TGW. To the
extent of this study, further investigation of the physiological process
of florets development and grain filling is needed.
Acknowledgements
This research has been done under Cereal research program (PRMT-
Cereal) of National Institute of Agricultural Research INRA-Morocco..
Conflict of Interest
The authors declare no conflict of interest.
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