Vol.3, No.5, 658-662 (2012) Agricultural Sciences
http://dx.doi.org/10.4236/as.2012.35079
Effects of Trinexapac-Ethyl on different wheat
varieties under desert conditions of Mexico
Raúl Leonel Grijalva-Contreras1*, Rubén Macías-Duarte1, Gerardo Martínez-Díaz1,
Fabián Robles-Contreras1, Fidel Nuñez-Ramírez2
1National Research Institute for Forestry, Agricultural and Livestock (INIFAP), Caborca, México;
*Corresponding Author:
2Agricultural Science Institute, University Autonoma of Baja California (ICA-UABC), Baja, México
Received 4 May 2012; revised 16 June 2012; accepted 15 July 2012
ABSTRACT
A field study was conducted to determine the
effect of Trinexapac-Ethyl (TE) on four wheat
varieties (Rafi C97, Altar C84, Nacori C97 and
Rayon F86) at three growth stages (first node,
second node and flag leaf). TE application (150 g
a.i. ha−1) reduced plant height and decreased
grain yield at any growth stage. Yield decrease
was associated to a significant reduction in the
number of grains per spike and in grain weight.
TE delayed flowering time and grain maturity,
while stem diameter and spikes·m−2 were not
affected. Further studies are needed to clarify
the effect of TE on wheat under desert condi-
tions of Mexico.
Keywords: Growth Regulators; Moddus; Yield;
Plant Height; Lodging
1. INTRODUCTION
Wheat is annually grown in 825.1 thousand hectares in
Mexico, with a production of 4.14 million tones [1].
Profitability of this crop depends of yield, production
cost and grain price. To obtain high yields it is necessary
the use of new varieties resistant to pests and diseases,
proper sowing date, good water management practices
and proper nitrogen fertilization. However, yield may be
affected by other factors such as frost damage and lodg-
ing [2].
Lodging in wheat is a serious problem under soils with
high fertility (>300 kg·N·ha−1), irrigated condition and
high planting density [3,4]. Lodging can result in yield
reduction up to 50%, reduced kernel weight, increase the
N (protein) content of the grain, and reduce the milling
quality [5-7].
Proper variety selection and use of growth regulators
may reduce lodging in wheat [4]. Major types of growth
regulators used to reduce this problem have been Cyco-
cel (Chloromequat chloride), Ethrel (Ethephon), Apogee
(Prohexadione-Ca) and Moddus (Trinexapac-ethyl) [8].
Trinexapac-ethyl (TE) belongs to cyclohexandione group
and inhibits gibberellins biosynthesis [9,10]. TE prevents
lodging not only by reducing the crop height, but also by
strengthening the stem and crown root structures. In
comparison to other growth retardants it is effective to
increase yield grain and reduce plant height [7,11-18].
TE has other effects on wheat as increasing number of
grains per spike, weight of 1000 grains, ear length and
stem diameter [15,17]. TE applications can delay grain
maturity [7] but have little effect on photo-synthesis ac-
tivity, root growth and development [19] and protein
content in grain [17].
The objective of this experiment was to determine the
effects of TE on the grain yield, growth traits, yield
components and grain quality applied in different growth
stages of four winter wheat varieties grown under desert
conditions of Mexico.
2. MATERIALS AND METHODS
2.1. Site and Wheat Management
The experiment was carried out in an Experimental
Station of the National Research Institute for Forestry,
Agricultural and Livestock (INIFAP) in Mexico (Lati-
tude 30˚42'55''N, Longitude 112˚21'28''W and altitude
200 m) during 2005-2006. The soil was sandy loam with
pH 7.96 and electrical conductivity of 1.22 dSm−1.Wheat
varieties were sown on December 15, 2005 at 150 kg·ha−1.
Size of experimental plot was of 5.0 m × 6.0 m (30.0 m2).
Sowing was done using furrow (1.0 m) distance with two
rows for each furrow spacing of 0.35 m. Water was ap-
plied with drip irrigation and the rate of fertilization was
220-60-00 kg·NPK·ha−1, applying 60 kg·ha−1 of N and P
at sowing time. The remaining N was applied through the
irrigation system during crop development. Other agri-
cultural practices (weeds, pests and diseases control) were

R. L. Grijalva-Contreras et al. / Agricultural Sciences 3 (2012) 658-662 659
applied according to recommendations for this crop in
this agricultural area [2].
2.2. TE Applications and Varieties
TE was applied at the dose of 150 g a.i. ha−1 on four
wheat varieties: Rafi C97, Altar C84, Nacori C97 and
Rayon F89. The characteristics of wheat varieties are
described in Table 1 [2]. TE was applied at three growth
stages: First node, second node and flag leaf just visible
31, 32 and 37 according a Zadocks scale [20] and there
was a check. Applications were made with a gasoline
powered mist blower.
2.3. Measured Variables
Ten plants prior to harvest were randomly taken from
the middle row of each plot to measure plant height, stem
diameter, number of grains per spike and weight of 1000
grains. The number of spikes·m−2 was determined taking
two samples in each plot. Plant lodging was measured in
plot center using a lodging scale from 0 to 5, where 0
was wheat standing upright and 5 was wheat totally flat.
Grain yield was obtained for the plot area and then con-
verted to kg·ha−1.
2.4. Statistical Analysis
Analysis of variance was done considering a split plot
design with three replications. The varieties were placed
in the main plots and TE applications in sub plots. Means
were separated with the least significant difference test
(LSD) at 0.05 probability level.
3. RESULTS AND DISCUSSION
3.1. Grain Yield
TE at 150 g a.i. ha−1 decreased grain yield in the four
wheat varieties at any growth stage. Grain yield reduc-
tion was 9.1%, 13.3% and 10.1% when TE was applied
at first node, second node and flag leaf, respectively, with
respect to the control. Altar C84 was less affected by TE
application than Rafi C97 which had a yield reduction of
18.2% (Table 2).
Results from this work disagree to other researchers
who report a grain yield increase when TE was applied at
different rates and different growth stages in wheat [7,
11-18]. An increase of 40% to 50% in grain yield was
reported when TE was applied in wheat [11]. Few studies
have reported a decrease of grain yield in wheat due to
TE. Other studies obtained significant yield loss on
Dollinco wheat variety when TE was applied a low rates
(75 g a.i. ha−1), showing that TE was phytotoxic to wheat
due to high temperatures (23˚C) [16]. Similar injuries
were reported by other researchers [7,21] when TE was
applied in early stages of wheat development and at
higher rates (>125 g a.i. ha−1). In this work 150 g a.i. ha−1
was applied which might explain the reduction in grain
yield. In addition, temperatures in the dessert are higher
than in temperate zones. Both factors might have caused
phytotoxicity of Trinexapac-ethyl to wheat. In a previ-
ous experiment conducted in Caborca, Sonora, Mexico
TE was applied at 0.6 g a.i. ha−1 in two stages of wheat
development and no damage to wheat was found [2].
This finding supports the idea that in the actual experi-
ment the rate of the 150 g a.i. ha−1 becomes dangerous to
wheat.
3.2. Growth Traits
TE had a significant effect on plant height reduction
according to the stage at which it was applied. At second
node the treatment had the highest plant height reduction
(26.1%), while at first node and flag leaf plant height
reduction was 21.1% and 6.1%, respectively; this re-
sponse was similar among wheat varieties (Table 2).
Stem diameter was not affected by TE application but by
the variety. Rafi C97 had the highest stem diameter (3.85
mm) although it was statistically similar to Nacori C97
(3.72 mm). Rafi C97 also had the lowest plant height
(78.0 cm) (Table 2). Stem diameter and plant height are
traits genetically controlled. Lodging was observed only
in Rayon F89 in the untreated plots. Plants in that plots
had the highest plant height and lower stem diameter,
morphological traits associated with lodging problems
[22,23].
A decrease of plant height from 5% to 27% due to TE
has been reported [7,11-18], values that are similar to this
study. According to other researchers [7,11] the greatest
response was obtained when TE was applied at the sec-
ond node. Other studies indicated that early TE applica-
Table 1. Genetic and phenological characteristics of the four wheat varieties.
Variety Type Grain color Flowering (days) Maturity (days) Plant height (cm)
Rafi C97 Durum Amber 99 - 105 135 - 147 83 - 91
Altar C84 Durum Amber 99 - 111 135 - 144 84 - 97
Nacori C97 Durum Amber 96 - 112 135 - 147 88 - 98
Rayon F89 Bread Red 98 - 105 131 - 144 88 - 102

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660
Table 2. Effect of TE applied in different growth stages on grain yield, plant height and stem diameter in four wheat varieties.
Factor Treatments Grain yield (kg·ha−1) Plant height (cm) Stem diameter (mm)
Variety (V) V0 = Rafi C97 6749 a 78.0 b 3.85 a
V
1 = Altar C84 5046 b 86.2 a 3.54 b
V
2 = Nacori C97 5768 b 84.6 a 3.72 ab
V
3 = Rayon F86 5123 c 84.5 a 3.54 b
Significance
** ** **
Growth stage (S) S0 = Control 6445 a 97.1 a 3.63
S
1 = First node 5859 b 76.6 c 3.61
S
2 = Second node 5586 b 71.8 d 3.77
S
3 = Flag leaf 5795 b 91.4 b 3.65
Significance
** **
N.S.
Interaction (V × S) V0 S0 7818 91.3 c 3.75
V
0 S1 6568 69.7 g 4.07
V
0 S2 6103 67.7 g 3.95
V
0 S3 6508 83.3 d 3.66
V
1 S0 6202 97.3 b 3.81
V
1 S1 5805 78.3 e 3.16
V
1 S2 5945 74.3 ef 3.65
V
1 S3 6232 94.6 bc 3.53
V
2 S0 5508 97.6 ab 3.53
V
2 S1 5130 75.3 e 3.58
V
2 S2 4798 74.3 ef 4.03
V
2 S3 5057 91.0 c 3.76
V
3 S0 6252 102.0 a 3.43
V
3 S1 5937 83.0 d 3.63
V
3 S2 5500 71.0 fg 3.45
V
3 S3 5387 96.7 b 3.65
Significance N.S. ** N.S.
Means followed by the same letter in a column do not differ significantly (LSD 0.05); **Significant at 0.01 probability level; N.S. = Non-significant.
tions decreased internodes length, while late applications
shortened the peduncle of the plant [12]. TE has in-
creased stem diameter of wheat [14,16] results that con-
trast to this experiment. The absence lodging was also
reported by other studies [12,17]. In this experiment no
lodging might be due to the absence of rain and strong
winds during the crop development and due to an ade-
quate water management through drip irrigation.
TE delayed the time flowering (2 - 5 days) and grain
maturity (4 - 7 days) with respect to untreated plots (data
not shown). Similar results were reported in other ex-
periment [7].
3.3. Yield Components
TE did not affect the number of spikes·m−2. In contrast,
there were differences among varieties for spikes·m−2
(Table 3). Rayon F86 had the highest number of spikes·
m−2 (496.2), followed by Rafi C97 (423.2), Nacori C97
and Altar C84, with 358.2 and 359.7 spikes·m−2, respec-
tively. TE decreased the number of grains per spike at

R. L. Grijalva-Contreras et al. / Agricultural Sciences 3 (2012) 658-662 661
Table 3. Effect of TE applied in different growth stages on spikes per m2, grains per spike and weight of 1000 grains in four wheat
varieties.
Factor Treatments Number spikes (m−2) Grains per spike Weight of 1000 grains (g)
Variety (V) V0 = Rafi C97 423.2 b 66.1 a 48.7 c
V
1 = Altar C84 359.7 c 69.6 b 51.1 b
V
2 = Nacori C97 358.2 c 59.1 c 54.4 a
V
3 = Rayon F86 496.2 a 61.6 c 40.8 d
Significance
** ** **
Growth stage (S) S0 = Control 412.2 74.6 a 51.3 a
S
1 = First node 399.0 61.0 c 48.7 b
S
2 = Second node 424.6 54.0 d 47.5 c
S
3 = Flag leaf 401.3 66.8 b 47.4 c
Significance N.S. ** **
Interaction (V × S) V0 S0 394.6 83.2 a 51.4 de
V
0 S1 428.6 65.4 bcd 48.2 g
V
0 S2 458.0 45.9 h 48.8 fg
V
0 S3 411.3 70.0 b 46.5 h
V
1 S0 394.6 79.4 a 53.0 bcd
V
1 S1 337.3 70.2 b 49.3 fg
V
1 S2 353.3 59.6 def 50.4 ef
V
1 S3 353.3 69.5 b 51.9 cde
V
2 S0 350.0 70.4 a 56.9 a
V
2 S1 362.0 53.6 fg 52.7 bcd
V
2 S2 371.3 51.4 gh 54.4 b
V
2 S3 349.3 61.0 cde 53.7 bc
V
3 S0 509.3 65.4 bcd 43.8 i
V
3 S1 468.0 55.0 efg 40.0 j
V
3 S2 516.0 59.2 defg 40.9 j
V
3 S3 491.3 67.1 bc 37.6 k
Significance N.S. ** **
Means followed by the same letter in a column do not differ significantly (LSD 0.05); **Significant at 0.01 probability level; N.S. = Non-significant.
any growth stage. At second node had the highest per-
centage of reduction (27.6%), whereas at first node and
flag leaf, percentage of reduction was 18.2% and 10.4%,
respectively. Rafi C97 was more sensitive to TE since its
reduction was 44.8% and Rayon F86 was the least sensi-
tive (Table 3). The 1000 grain weight decreased with TE
application at any growth stage. The highest reduction on
1000 grains weight was observed when TE was applied
at flag leaf and second node growth stage (7.6% and
7.4%). Rafi C97 and Rayon F86 were more affected by
TE applied at leaf flag stage, while Altar C84 and Nacori
C97 when TE was applied at first node stage (Table 3).
TE did not affect the number of spikes·m−2, which
agrees to result obtained by [16] and are different to
results from [14,15] when they applied TE at a similar
dose. In contrast, there were differences for spikes·m−2
among varieties (Table 3). Grain yield reduction due to
TE in this experiment was due to reduction number of
grains in the spikes and reduction in the weight of 1000
grains, results that are opposite to [14,17]. The differ-

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662
ences in yield components among wheat varieties are due
to their genetic traits as reported by other researchers [24,
25].
4. CONCLUSION
Trinexapac-ethyl at 150 g a.i. ha−1 applied at different
growth stages reduced significantly plant height and de-
creased average grain yield in different wheat varieties.
The decrease of grain yield was associated to a signifi-
cant reduction in the number of grains per spike and
weight of 1000 grains. Further studies are needed to clar-
ify the effect of TE on wheat under desert conditions of
Mexico.
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