July 2010
Effects of 1-MCP and Quadris on cotton growth and yield
G. Wang and R. K. Asiimwe
Maricopa Ag Center / School of Plant Sciences, University of Arizona
Summary
A field experiment was conducted at University of Arizona Maricopa
Agricultural Center to assess the effects of 1-MCP and Quadris on cotton’s
reproductive structure, shedding and crop yield under well-watered (WW) and
water-stressed (WS) conditions. Applying 1-MCP and/or Quadris at 14 and 28
days after pinhead square (PHS) did not affect cotton growth or yield in the WW
treatment. Whereas under WS conditions, cotton with two 1-MCP applications
at 14 and 28 days after PHS produced more node and had higher uppermost
first position harvestable boll (UHAB). Cotton plants in the Quadris treatment
had higher UHAB compared to the control in the WS conditions. Plant mapping
analysis showed that applying 1-MCP and/or Quadris increased boll number on
some nodes, but the increase is not enough to affect cotton yield. This is because
the long growing season in Arizona makes it possible for cotton plants to
compensate minor changes in boll setting during the main fruiting cycle.
Introduction
Heat is one of the major factors limiting cotton crop production during the summer in Arizona. The summer
monsoon weather is characterized by high temperatures during the day and night with increased humidity and dew
point. The high temperature and rising humidity can force canopy temperatures above the optimal range (>82.4-86
F) for proper fruit development, resulting in significant shedding of reproductive structures and crop yield loss
(Brown, 2008).
Ethylene, produced naturally by plants, has been studied extensively for its role in the regulation of the fruit ripening
process. Ethylene is also produced by plants under stress and plays a significant role in shedding of plant structures.
It has been proven that ethylene level in cotton plants is related to the fruit abscission process (Guinn, 1982).
Reducing ethylene biosynthesis may help cotton plants resist drought stress and reduce fruit shedding.
1-methylcyclopropene (1-MCP) is a cyclopropene derivative that inhibits ethylene production in plants by
occupying ethylene receptors. The affinity of 1-MCP for the receptors is approximately 10 times greater than that of
ethylene (Watkins, 2006). This chemical has been widely used to improve shelf life and quality of agricultural
products and can reduce the effects of water stress level in cotton plants by inhibiting ethylene production and
reducing boll losses (Watkins, 2006; Kawakami et al., 2009). Quadris is a broad-spectrum fungicide that could
enhance physiological processes within plants and increases crop yield. In this study, we tested if 1-MCP or 1-MCP
applied with Quadris can alleviate the adverse effects of drought and heat stress on cotton square/boll setting and
consequently increase crop yield.
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Materials and Methods
The experiment was conducted at the University of Arizona’s Maricopa Agricultural Center (MAC). Cotton variety
‘Delta Pine 164 B2RF’ was planted on 40 inch beds with 3.8 inch in-row spacing on April 24, 2008 and irrigated on
April 26, 2008. Two irrigation treatments, a well-watered (WW) and a water-stressed (WS) treatment were applied
starting June 25, 2008, 10 days after pinhead square (PHS) stage. A weather station was installed in each of the
WW and WS treatments to monitor precipitation, soil moisture, and air temperature. The WW treatment followed
Arizona Irrigation Scheduling System recommendation (Martin and Slack, 2003). During June to August the soil
water tension at 4 inch depth reached 70-80 kPa right before irrigation for the WW treatment. Cotton in the WS was
irrigated when soil moisture reached 130 to 200 KPa.
The WW and WS treatments were placed into two blocks. Within each irrigation block, experimental design was a
randomized complete block design with each plant growth regulator (PGR) treatment plot paired with a control plot.
Four PGR treatments were established to study the effects of 1-MCP and Quadris on cotton square and boll setting:
(1) MCP14+28: 10 g/A of 1-MCP plus 0.035 v/v Silwet L77 (surfactant) applied at 14 and 28 days after PHS, (2)
MCP28: 10 g/A of 1-MCP plus 0.035 v/v Silwet L77 applied at 28 days after PHS, (3) Quadris: 45 g a.i./A of
Quadris plus 0.25 v/v NIS (surfactant) applied 14 days after PHS, and (4) QDSMCP: 10 g/A of 1-MCP and 45 g
a.i./A of Quadris plus 0.25 v/v NIS applied at 14 days after PHS. The treatment was replicated six times. Each plot
was 20 feet wide and 50 feet long.
Three and seven days after application, cotton phyto-toxicity was observed. The final irrigation was applied to the
WW plots on August 27, 2008 and to WS treatment plots on September 8, 2008. Ginstar defoliants were applied at
a rate of 12 ounces/ac on October 14, 2008.
Five plants were randomly chosen from the second and fifth row of each plot for cotton mapping before harvest on
November 20, 2008. In addition to mapping, boll positions on each cotton plant, the height, number of nodes, height:
node ratio, number of the node of the first fruiting branch (NFFB), number of the node with the uppermost first
position cracked boll (NUCRB), number of the node with the uppermost first position harvestable boll (NUHAB)
were also recorded. Cotton was harvested on November 24, 2008. Only the middle two rows were picked using a
two-row cotton picker. Seed cotton in each plot was collected in a bag and weighed for yield.
Results and Discussion
Cotton plants reached PHS on June 16, 2008. The irrigation treatments started on June 25, 2008. The total water
applied plus rainfall was 52 inches on WW plots and 42 inches on WS treatment plots (Fig 1). The drought stress
occurred during July and August, with three dry periods in the WS treatment plots (Fig 2). As a result, air
temperature on WW plots was lower than WS treatment plots, indicating cotton plants in the WW plots were cooled
down by transpiration more than WS treatment plots (Fig 3).
There was no crop phytotoxicity observed following PGR application in any of the treatment plots. For any
measurement, each particular treatment was compared to its paired control using paired t test. In the WW plots,
there were no significant differences between PGR treatments and their paired controls in cotton height, total node,
height node ratio, number of the node of the first fruiting branch (FFB), and number of the node with the uppermost
first position harvestable boll (UHAB). In the WS treatment plots, the MCP14+28 treatment had larger node and
UHAB numbers compared to its paired control, and the Quadris treatment had larger UHAB numbers compared to
its paired control.
The PGR treatments were compared using the differences in each treatment and its paired control. In the WW plots,
there were no differences detected among treatments in cotton height, node, height node ratio, FBB, and UHAB
measurements (Table 1). In the WS treatment plots, the MCP14+28 treatment increased plant height more than
other PGR treatments. The MCP14+28 and Quadris treatment increased cotton UHAB more than the MCP28 and
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QDSMCP treatments.
Neither of the PGR treatments affected cotton yield compared to its paired control. There were no differences in
cotton yield among PGR treatments under either WW treatment or WS treatment (Table 2). Detailed plant mapping
with node-by-node comparison shows that the MCP14+28 and QDSMCP treatments increased boll number at node
5 compared to their paired control. The MCP28 treatment had more bolls on node 10 but fewer bolls on node 16
compared to its paired control, and QDSMCP had fewer bolls on node 22.
1-MCP has been reported to increase boll size in Arkansas, boll retention and seed size in one out of two years in
Texas. 1-MCP did not increase cotton yield compared to the surfactant control in Texas (Scheiner, 2007). Research
in Arkansas showed that 1-MCP treatments did not significantly increase cotton yield compared to the untreated
control in either 2006, 2007, or 2008 (Kawakami et al., 2006; Kawakami et al., 2007; Storch et al., 2008). However,
when the data from three years were combined for analysis, 1-MCP was reported to have reduced ethylene synthesis
of cotton reproductive structures and increased cotton yield if applied twice during growing season (Oosterhuis,
2010).
Conclusions
1-MCP and Quadris applied at 14 and/or 28 days after PHS did not affect cotton yield in this study.
Applying 1-MCP twice (14 and 28 days after PHS) increased cotton plant height, uppermost first position
harvestable boll, and boll number on some nodes. However, the increase was not enough to affect cotton yield. The
long cotton growing season in Arizona makes it possible for cotton plants to compensate minor changes in boll
setting during growth, resulting in no significant changes in cotton yield.
Reference
Brown, P.W. 2008. Cotton heat stress. http://cals.arizona.edu/pubs/crops/az1448.pdf.
Guinn, G. 1982. Fruit age and changes in abscisic acid content, ethylene production, and abscission rate of cotton
fruits. Plant Physiology. 69:349.
Kawakami, E.M., D. M. Oosterhuis, and J.L. Snider. 2009. Physiological effects of 1-Methylcyclopropene on wellwatered and water-stressed cotton plants. Journal of Plant Growth Regulation. 2009. Online first publication.
Kawakami, E.M., D.M. Oosterhuis, E.D. Gonias, and A.C. Bibi. 2006. Effect of 1-MCP on the growth and yield of
cotton. http://arkansasagnews.uark.edu/552-11.pdf.
Kawakami, E.M., D. M. Oosterhuis, and J.L. Snider. 2007. Effect of 1-MCP on the physiology and yield of cotton.
http://arkansasagnews.uark.edu/562-17.pdf.
Martin E.C. and D.C. Slack. 2003. Arizona irrigation scheduling system recommendation.
http://ag.arizona.edu/crops/irrigation/azsched/azsched.html
Oosterhuis, D.M. 2010. The Effects of 1-Methylcyclopropene on the physiology and yield of cotton. 2010 Cotton
Beltwide Conferences.
Scheiner, J.J. 2007. Effect of 1-Methylcyclopropene on upland cotton. Master Thesis. Texas A&M University.
Storch, D.K., Oosterhuis, D.M., and E.M. Kawakami. 2008. Effect of 1-Methylcyclopropene on the biochemistry
and yield of field-grown cotton. http://arkansasagnews.uark.edu/573-10.pdf
Watkins, C.B. 2006. The use of 1-methylcyclopropene (1-MCP) on fruits and vegetables. Biotechnology Advances
24, 389-409.
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Table 1. The difference between treatment plots and their paired control plots in cotton growth parameters in WW
or WS treatment.
WW treatment
WS treatment
PGR
Height
Height
Treatment
Node
Ratio
FBB* UHAB
Node
Ratio
FBB
UHAB
(inch)
(inch)
MCP14+28 -0.60 a -0.33 a
0.01 a
0.50 a
0.37 a
1.40 a
1.63 a
-0.04 a -0.80 a
2.73 a
MCP28
1.43 a
1.00 a
-0.03 a
0.43 a
0.87 a
-0.87 b
0.07 a
-0.03 a -0.73 a -1.13 b
Quadris
-2.07 a
0.37 a
-0.10 a -0.07 a
0.10 a
-0.53 b
0.90 a
-0.07 a -0.67a
1.93 a
QDSMCP
2.10 a
0.37 a
0.05 a
-0.13 a
0.67 a
0.37 b
0.20 a
0.01 a
0.17 a
-1.77 b
* FFB: number of the node of the first fruiting branch; UHAB: number of the node with the uppermost first position
harvestable boll.
Table 2. The difference in cotton yield (lbs/333 ft2) between each treatment and its paired control in WW or WS
treatment.
Yield difference between PGR and
Yield difference between PGR and
Treatment
control treatment in WW treatment
control treatment in WS treatment
(lbs/333 ft2)
(lbs/333 ft2)
MCP14+28
-0.43 a
-0.08 a
MCP28
0.83 a
0.03 a
Quadris
0.53 a
0.31 a
QDSMCP
-0.13 a
0.16 a
Numbers in the same column followed by different letters are significantly different.
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60
Well-w atered
Irrigation plus rainfall (inch)
50
Water-stressed
40
30
20
10
PHS
0
0
5
10
15
20
25
Weeks after planting
Fig 1. Accumulated irrigation plus rainfall in WW and WS treatment plots during cotton growing season.
250
Soil water tension (KPa)
Well-watered
Water-stressed
200
150
100
50
0
0
5
10
15
20
25
Weeks after planting
Fig. 2. Soil moisture in WW plots and WS treatment plots during cotton growing season
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Well-watered
95
Water-stressed
Air temperature (F)
90
85
80
75
70
65
60
0
5
10
15
20
25
30
Week after planting
Fig 3. Weekly mean air temperature in the middle of WW and WS treatment plots during cotton growing season.
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