Effectiveness of Mepiquat Chloride Application Timing on Physiological, Agronomic, and Fiber Quality Traits of Cotton (Gossypium spp.) Varieties

Mashenene Malima; Orhan Kurt; Sikitu Jonathan Kazungu; Muhammet Safa Hacikamiloglu; Thereza Fabiani Deus

doi:doi:10.11648/j.ijaas.20261202.15

Research Article |

| Peer-Reviewed

Effectiveness of Mepiquat Chloride Application Timing on Physiological, Agronomic, and Fiber Quality Traits of Cotton (Gossypium spp.) Varieties

Mashenene Malima^*

, Orhan Kurt

, Sikitu Jonathan Kazungu

, Muhammet Safa Hacikamiloglu

, Thereza Fabiani Deus

Published in International Journal of Applied Agricultural Sciences (Volume 12, Issue 2)

Received: 2 April 2026 Accepted: 13 April 2026 Published: 24 April 2026

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Abstract

A two-year field study underscores the importance of integrating genotype selection with optimized Mepiquat Chloride (MC) management to enhance cotton performance under a split–split–plot design. Significant genotype × environment × management interactions were observed in cotton growth, yield, and fiber quality responses MC application. Plant height was significantly affected by year × variety interaction (p < 0.01), with the tallest plants in Selin (2023) and Sezener (2022). Leaf area was higher in 2022, while 800 cc. ha^-1 enhanced leaf expansion. Monopodial branches were significantly greater in 2023 (9.59 plant^-1), with early MC application favoring branch initiation. Seed cotton yield was peak in Selin (3623 kg ha^-1), 25% greater than Sezener, with split application (400 + 400 cc. ha^-1) yielding best results. Boll number and individual fiber weight were higher in Selin and Sezener, respectively, with the latter showing a 48% increase under 400 cc. ha^-1. Seed index was significantly higher in Sezener, and fiber moisture increased in 2023 (8.94%). Fiber quality traits revealed pronounced year, genotype, and application timing effects: fiber length peaked in Sezener (30.33 mm), elongation reached 5.80%, and micronaire increased to 4.89 µg inch^-1 under split MC application. Fiber strength increased by 13.07% in 2023, and while uniformity (85.62%) maximized with later application. Short fiber content decreased by 14.81% in 2023. These findings highlight that MC concentration, timing, and genotype interactions significantly modulate morphophysiological traits, yield components, and fiber quality, with split or moderate-dose applications enhancing productivity and fiber properties under Mediterranean conditions.

Published in	International Journal of Applied Agricultural Sciences (Volume 12, Issue 2)
DOI	10.11648/j.ijaas.20261202.15
Page(s)	54-73
Creative Commons	This is an Open Access article, distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution and reproduction in any medium or format, provided the original work is properly cited.
Copyright	Copyright © The Author(s), 2026. Published by Science Publishing Group

Keywords

Cotton, Morphophysiological, MC, Timing, Quality Traits, Yield Components

1. Introduction

Cotton (Gossypium hirsutum L.), a major cash crop of the Malvaceae Family, is cultivated in more than 70 countries, particularly across tropical and subtropical regions

[1, 2]

. It holds substantial industrial and commercial importance and serves as a vital and sustainable source of income and employment for millions of smallholder farmers worldwide

[3-5]

. Its fibers contribute approximately 81% of the raw materials used in the global textile industry

[6]

, while its seeds serve as a major source of edible oils and livestock feed

[7, 8]

Despite substantial advancements in cotton production technologies, global productivity remains suboptimal due to the complex interplay of agronomic, climatic, environmental, socio-economic, and political factors

[9]

. Although cotton thrives in high-temperature environments—ideally between 40°C and 45°C—and is inherently suited for heat-prone regions

[10, 11]

, its productivity is increasingly constrained by the intensifying impacts of climate change

[12, 13]

. Major stressors such as erratic rainfall, prolonged drought, rising temperatures, and evolving pest and disease pressures have collectively disrupted the crop’s growth cycles, physiological stability, and reproductive development

[14-16]

. These challenges are especially detrimental during sensitive phenological stages, ultimately leading to significant yield reductions and threatening the long-term sustainability of cotton-based farming systems

[8, 17, 18]

In climate-stressed countries such as China, India, the United States, Brazil, Pakistan, and Turkey, early-maturing cotton varieties have been increasingly adopted as an adaptive strategy, owing to their shorter growth cycles and lower water requirements

[19]

. However, while early-maturing genotypes offer advantages under water-limited and heat-stressed conditions, tend to exhibit excessive vegetative growth when environmental conditions are favorable, often at the expense of reproductive development

[20]

. This vegetative-reproductive imbalance leads to poor boll retention, delayed maturity, and ultimately reduced fiber yield and quality

[21]

. Yield losses of 6–10% per 1°C rise above optimal temperatures (~30–32°C) have been reported, underscoring the urgency of developing adaptive strategies for sustaining productivity under warming conditions

[22, 23]

One promising approach to mitigate heat-induced vegetative–reproductive imbalance is the use of plant growth regulators, particularly mepiquat chloride (MC), a quaternary ammonium (N, N-dimethylpiperidinium chloride) compound that inhibits gibberellin biosynthesis

[24, 25]

. By restricting stem elongation, reducing node production, and promoting a more compact canopy architecture, MC can reallocate assimilates from vegetative to reproductive sinks

[26-28]

. Numerous studies have demonstrated its ability to enhance boll retention, increase boll number and weight, and improve fiber quality under conventional production conditions

[29-31]

. However, its efficacy appears strongly influenced by genotype, dose, timing, and environmental conditions

[32, 33]

Evidence from controlled-environment experiments shows that MC’s growth-suppressing effects are temperature sensitive

[34]

. At moderate day/night regimes (~32–35°C), MC markedly reduces plant height, node number, and leaf expansion, while increasing fruit retention

[34, 35]

. Under more severe heat (≥39°C), these effects diminish, and higher doses are required to maintain even partial growth control

[22, 36]

. Field studies in water-limited or high-radiation environments similarly report yield gains of 15–34% and improvements in boll retention and fiber traits (micronaire, strength, length, and uniformity) when MC is combined with nitrogen fertilization or applied at optimal growth stages

[25, 37, 38]

. Nevertheless, the magnitude of these benefits is inconsistent and tends to decline under intense heat stress

[39-42]

While MC shows potential as a tool for moderating heat-related yield losses, its ability to stabilize fiber quality under such conditions remains unclear. Most available data come from studies on mid- to late-maturing cultivars grown under non-stress conditions, with limited evidence from early-maturing genotypes commonly cultivated in the Mediterranean region of Turkey. Moreover, the dose × application timing × environmental conditions interaction governing MC effectiveness has not been systematically quantified, and the genetic variation in cotton responsiveness to MC under climate-stressed conditions is poorly understood.

Addressing these knowledge gaps is critical for developing climate-resilient cotton production systems. Specifically, there is a need to (i) define agro-meteorological thresholds beyond which MC loses efficacy, (ii) optimize its timing and dosage relative to concurrent heat + drought episodes, and (iii) evaluate genotypic differences in yield and fiber quality responses to MC under stress-prone field conditions. Such insights will enable the strategic integration of MC into adaptive management packages potentially in combination with adjusted sowing dates, irrigation scheduling, and canopy management practices to sustain cotton yield and fiber quality in the warming Mediterranean basin.

2. Materials and Methods

2.1. Description of the Study Site

The experiment took place during the 2022 and 2023 cropping years at the Eastern Mediterranean Agricultural Research Institute, situated at Adana/Turkey (at coordinates 36°51′ N latitude and 35°20′ E longitude). During summer, the Mediterranean region is characterized by warm and mild conditions, with mean monthly temperatures ranging from 20.30 to 30.49°C. Average monthly rainfall during this period varies between 2.20 mm and 41.20 mm, while relative humidity ranges from 40.95% to 54.95%

[43]

2.2. Soil Characteristics of the Study Site

Soil samples were collected from the 0–30 cm profile at the experimental site, and their characteristics were analyzed using air-dried fine earth fractions. Particle size distribution was determined following the method described by

[44]

. Soil pH (H₂O) was measured according to

[45]

, while organic carbon content was determined using the Walkley–Black wet combustion method

[46]

. Phosphorus was analyzed following the procedure of

[47]

, while calcium (Ca) and potassium (K) contents were determined using an atomic absorption spectrophotometer as described by

[48]

. The soil characteristics of the experimental site are presented in Table 1.

Table 1. Physicochemical characteristics of the experimental soil profile (0–30 cm depth).

Clay (%)	Silt (%)	Sand (%)	Texture	pH	CaCO₃ (%)	EC (ds/m)	P₂O₅ (kg/ha)	K₂O (kg/ha)	Organic Matter (%)
33.7	43.7	22.6	CL	7.89	21.5	1.0	43.3	474.5	0.98

CL Clay Loam, EC Electrical Conductivity, ds/m deciSiemens per metre

2.3. Weather Characteristics

The monthly rainfall during the 2022–2023 cotton growing seasons in the Mediterranean region of Turkey is illustrated in Figure 1. Across the two years, rainfall was well distributed in November but declined markedly in July and September of 2023. The total precipitation during the seven-month growing period was comparable between years, with 172.80 mm in 2023 and 170.20 mm in 2022, aligning with long-term regional climatic data reported by

[43]

over the past 91 years. Climatic conditions in 2023 were slightly warmer and more humid than in 2022, with mean maximum and minimum temperatures of 32.32°C and 17.40°C, respectively, compared with 31.84°C and 17.12°C in 2022, and mean relative humidity values of 65.70% and 64.39% (Figure 1)

[49, 50]

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Figure 1. Selected meteorological variables characterizing the experimental site during the 2022 - 2023 growing seasons.

2.4. Experimental Design and Treatments

A sample layout of a 2 x 2 x 4 factorial experiment arranged in a split-split-plot design with two cultivars (C₁ and C₂) as main-plot treatments, two spraying intervals (T₁ and T₂) as subplot treatments, and four Mepiquat Chloride (MC) levels (MC₀, MC₁, MC₂ and MC₃) as sub-subplot treatments, in three replications. MC treatments used in this study were MC₀ (0 cc. ha^-1), MC₁ (400 cc. ha^-1), MC₂ (400 + 400 cc. ha^-1) and MC₃ (800 cc. ha^-1). The cotton cultivars entailed of Selin and Sezener, both of which are early-maturing. The growth regulator and cotton seeds were supplied by the Eastern Mediterranean Agricultural Research Institute. MC rates were applied manually using a calibrated twenty-liter sprayer on entire plots at two growth stages: at squaring (8 weeks after planting [WAP] in both years) and at the boll setting (11WAP in both years).

2.5. Field Management Practices

To enhance soil tilth, disrupt capillary continuity, and suppress weed emergence, tractor hoeing was conducted four times before planting. Plant seeds were sown mechanically in the experimental plots, with each sub-subplot containing four rows, each 3 meters long, with a 70 cm spacing between rows and 20 cm spacing between plants within each row. Planting took place on May 26 in the first year and June 12 in the second year, at a depth of 5 cm below the soil surface. Irrigation was scheduled monthly for the first four months after sowing, resulting in a total of four irrigation events, and was terminated at the boll development stage. Fertilization consisted of the application of nitrogen (N) and phosphorus (P) fertilizers to ensure adequate nutrient supply for crop growth. Nitrogen was supplied at a total rate of 16 kg N ha^-1, with half applied as 20-20-0 compound fertilizer prior to sowing and the remaining half as ammonium nitrate (26% N) during the first irrigation. Phosphorus was applied entirely before sowing at a rate of 8 kg P ha^-1. Pest management included targeted chemical applications: Movento (150 mL ha^-1) for controlling aphids and leafhoppers, Mosplan 20 SP (60 g ha^-1) against whiteflies, and Neemarin (60 g ha^-1) to suppress green bollworm infestations. All other necessary agronomic practices during the crop growth period were conducted as recommended.

2.6. Data Collection

In the current finding, various parameters, including leaf area per plant, yield, seed index, individual fiber weight, moisture, fiber length, length uniformity, micronaire, spinning coefficient index, and short fiber index, were measured. Leaf area was measured using the Microscopy Image Analysis method (ImageJ software). Three plants were randomly selected from the two central rows, excluding 60 cm from both ends of each row. Leaf area per plant was obtained according to the method of

[51]

, as indicated in equation (1). When the cotton bolls were fully mature and had opened, they were hand-harvested from ten plants in each plot to assess the seed cotton yield and 100-seed weight. The seed cotton was weighed using a scale with an accuracy of 0.01 g and then converted to kilograms per hectare (kg·ha^-1) as indicated in equation (2). The harvested seed cotton was ginned to separate the fibers from the seeds, and then the 100-seed weight was measured using the aforementioned scale. For analyzing fiber characteristics, all fibers were sent to the fiber quality laboratory of the Eastern Mediterranean Agricultural Research Institute for assessment based on quality grade standards, using a fully automated High-Volume Instrument (HVI) device. Individual fiber weight was determined according to the method of

[38]

, with some modifications, as indicated in equation (3).

Total leaf area per plant = averaged leaf area (cm²) * number of leaves per plant(1)

Seed cotton yield (kg. ha^-1) = amount weighed (kg) ×10,000 / number of harvested plants × harvested area in square meters (2)

Individual fiber weight (µg) =[fiber length (cm) x length uniformity (%) x (micronaire * 10,000,000)](3)

2.7. Data Analysis

The analysis of variance was performed using GenStat Discovery software (version 15.1), and mean comparisons were conducted using Duncan`s Multiple Range Test (P<0.05). All graphs were created using Excel software on Windows 21.

3. Results

3.1. Morphological Traits

3.1.1. Plant Height

Analysis of variance revealed a statistically significant interaction between year and variety on plant height (P<0.01; Table 2). Post hoc comparisons indicated that the tallest plants were observed in the Selin variety in 2023 (102.14 cm) and the Sezener variety in 2022 (100.40 cm). In contrast, the shortest plants were recorded for the Sezener variety in 2023 (96.61 cm) and the Selin variety in 2022 (95.85 cm) (Figure 2), underscoring the genotype-by-environment interaction effect on vegetative growth.

No significant main effects of year, concentration, variety, or application time were observed on plant height when considered independently (Table 2). However, a year-wise comparison exhibited that plant height was generally greater in 2023 compared to 2022 under MC treatments (Table 3). The maximum average plant height was recorded in 2023 (99.37 cm), corresponding to a 1.26% increase over the previous year.

Although not statistically significant, plant height was lowest under the 400 cc. ha^-1 MC application rate (96.80 cm), suggesting a potential inhibitory effect at this concentration. Similarly, plants treated with MCs at 8 WAP had the shortest mean height (96.71 cm), implying that later applications may suppress vertical growth (Table 3).

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Figure 2. Interaction of year and variety on PH. Different letters indicate significant difference at P<0.05.

3.1.2. Leaf Area

The year significantly affected leaf area (P≤ 0.05; Table 2). Mean comparisons revealed that plants grown in 2022 exhibited larger leaf areas than those in 2023. The maximum average leaf area was 1775.90 cm² per plant in 2022, representing a 12.75% increase over 2023 (Table 3).

No statistically significant effects of MC level, variety, application time, or their interactions were detected on leaf area (Table 2). Nevertheless, mean comparisons revealed some biologically meaningful patterns. Application of MC at 800 cc. ha^-1 produced the largest average leaf area (1721.33 cm² per plant), suggesting a potentially optimal concentration for leaf expansion. The Sezener variety responded with the highest increase in leaf area (4.84%) compared to Selin, though the difference was not significant (Table 3).

In terms of application timing, spraying at 8 WAP resulted in the lowest mean leaf area (1618.96 cm² per plant), whereas applications at 11 WAP yielded the highest (1719.97 cm² per plant), highlighting the possible importance of timing in maximizing foliar development.

Table 2. Variance analysis of some morphological traits, yield, and yield components of different cotton varieties influenced by application timing and MC concentrations in Mediterranean region (2022–2023).

S.O.V	df	Means Square
S.O.V	df	PH	LA	NMB	BN	SCY	SI	IFW
Years (Y)	1	37.15^ns	1087610^*	78.24^**	13.02^ns	2001863^ns	0.24^ns	313.82^**
Rep (R)	2	44.98	48367	0.55	7.94	708263	0.30	3.55
Varieties (V)	1	5.77^ns	156763^ns	3.38^ns	30.56^*	11160378^**	85.15^**	5.14^*
Y × V	1	609.51^**	150^ns	0.09^ns	3.44^ns	16263421^**	0.00^ns	1.92^*
App. T (T)	1	398.01^ns	244861^ns	1.72^ns	16.95^ns	2254964^ns	0.49^ns	0.00^ns
Y × T	1	28.10^ns	61026^ns	4.24^ns	1.42^ns	843536^ns	0.06^ns	1.14^ns
V × T	1	94.05^ns	13852^ns	0.21^ns	0.39^ns	2575772^*	8.45^**	0.12^ns
CONCs (C)	3	98.13^ns	44603^ns	0.36^ns	10.84^ns	490371^ns	0.40^ns	0.39^ns
Y × C	3	104.02^ns	98731^ns	8.88^ns	10.22^ns	239307^ns	0.12^ns	0.32^ns
V × C	3	61.61^ns	49668^ns	2.75^ns	6.28^ns	464700^ns	0.13^ns	0.61^ns
T × C	3	270.07^ns	226266^ns	0.67^ns	7.07^ns	1382954^ns	0.07^ns	0.51^ns
Y × V × T	1	202.44^ns	625431^ns	0.21^ns	50.84^*	1860115^ns	0.03^ns	0.30^ns
Y × V × C	3	79.40^ns	94443^ns	1.43^ns	10.55^ns	682080^ns	0.19^ns	1.30^*
Y × T × C	3	204.31^ns	63592^ns	2.34^ns	4.58^ns	414517^ns	0.04^ns	1.11^ns
V × T × C	3	55.07^ns	37690^ns	3.25^ns	2.71^ns	1180945^ns	0.49^ns	0.20^ns
Y × V × T × C	3	27.68^ns	16288^ns	4.18^ns	18.06^ns	1220443^ns	0.08^ns	0.08^ns
Error		8.753	431.507	2.03	2.77	970.98	0.31	0.65
CV (%)		8.90	11.94	12.15	16.93	16.10	3.10	6.70

3.1.3. Number of Monopodial Branches

A highly significant year effect was observed for the number of monopodial branches (P≤0.01; Table 2). Plants grown in 2023 developed more monopodial branches (9.59 per plant) compared to those grown in 2022 (7.78 per plant), indicating that seasonal variation may influence branch initiation and development (Table 3).

Although no significant differences were detected for MC level, variety, or application time (Table 2), mean comparisons recorded notable trends. The 800 cc. ha^-1MC treatment resulted in the highest average number of monopodial branches (8.86 per plant). Among the varieties, Selin produced a slightly greater number of monopodial branches (8.87 per plant) compared to Sezener (8.50 per plant), although this difference was not statistically significant (Table 3).

Application timing also influenced branching: MC application at 8 WAP led to a higher number of monopodial branches (8.82 per plant), whereas the lowest was recorded with application at 11 WAP (8.55 per plant), suggesting early application may be more favorable for branch proliferation.

Table 3. Effects of Mepiquat chloride concentrations and application timings on morphological traits, yield, and yield components of cotton varieties in the Mediterranean Region (2022–2023).

Treatments	Levels	PH	LA	NMB	BN	SCY	SI	IFW
Years	2022	98.13	1775.90^b	7.78^a	8.29	2581.75	10.02	7.98^a
	2023	99.37	1563.03^a	9.59^b	9.03	2870.56	9.92	11.59^b
	LSD0.05	3.64	179.42	0.85	1.15	403.72	0.13	0.27
Varieties	Selin	98.99	1629.05	8.87	9.22^b	3067.11^b	9.03^a	9.55^a
	Sezener	98.50	1709.87	8.5	8.10^a	2385.19^a	10.91^b	10.02^b
	LSD0.05	2.24	810.45	0.47	1.17	318.75	0.31	0.47
App. T	8 WAP	96.71	1618.96	8.82	8.24	2879.41	10.04	9.78
	11 WAP	100.78	1719.97	8.55	9.08	2572.89	9.90	9.79
	LSD0.05	4.88	380.49	1.14	1.12	342.82	0.16	0.26
CONCs	Control	97.26	1616.29	8.66	8.42	2740.46	9.79	9.65
	400	96.80	1664.83	8.65	7.83	2519.68	10.06	9.94
	400 + 400	100.04	1675.41	8.57	9.06	2822.33	10.06	9.82
	800	100.89	1721.33	8.86	9.33	2822.13	9.99	9.73
	LSD0.05	6.08	178.20	1.13	1.74	558.90	0.33	0.38

3.2. Yield and Yield Components

The analysis of variance revealed that the effects of cultivars and year × application timing x cultivar were significant on boll number. The effects of cultivars, year × cultivar and cultivar × application timing were also significant on seed cotton yield. Seed index was affected by cultivars and year x application timing. Moreover, individual fiber weight was influenced by years, cultivars, year × cultivar and year x cultivar x MCs, and seed index was affected by cultivars, and cultivar x application timing (Table 2).

3.2.1. Seed Cotton Yield

According to the results (Table 3), the mean comparison of the year × variety interaction revealed that the Selin variety in 2023 produced the highest seed cotton yield (3623 kg/ha), which was 2118 kg/ha greater than the yield of the Sezener variety in 2022 (Figure 3a). In contrast, the application timing × variety interaction indicated that the lowest yield (2375 kg/ha) was recorded for the Sezener variety when MC was applied at 8 WAP (Figure 3b).

When analyzed independently, the Selin variety exhibited the highest mean seed cotton yield (3067.11 kg/ha), which was 25.01% higher than that of the Sezener variety (2385.19 kg/ha) (Table 3). Among the Mepiquat chloride (MC) levels, the split application of 400 + 400 cc. ha^-1 produced the highest yield (2822.33 kg/ha), marginally surpassing the 800 cc. ha^-1 application (2822.13 kg/ha) (Table 3). In contrast, the 400 cc. ha^-1 treatment reduced seed cotton yield by 8.10% compared to the control (Table 3).

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Figure 3. Illustrates the interaction of year and variety (a) and variety and application time (b) on SCY. Different letters indicate significant difference at p < 0.05.

3.2.2. Boll Number per Plant

Mean comparisons for boll number revealed that the varieties were grouped into two statistically distinct categories (Table 2). The Selin variety produced the highest number of bolls per plant, while the Sezener variety had the lowest (Table 3). In the 2023 growing year, the Selin variety reached a maximum of 10.15 bolls/plant when MC was applied at 8 WAP (Table 4).

Among the MC levels, the 800 cc. ha^-1 foliar application resulted in the highest boll number (9.33 bolls/plant), although it was not significantly different from the 400 + 400 cc. ha^-1 split application, which produced 9.06 bolls/plant. Remarkably, the 400 cc. ha^-1 treatment reduced boll number by 6.81% relative to the control (Table 3).

Table 4. Interaction of year, variety and application timing on boll number, spinning consistency index, fiber length and uniformity index.

Treatments			BN	SCI	UHML	UI
2022	Selin	8 WAP	7.33^a	138.10^ab	29.70^c	83.33^a
	Selin	11 WAP	10.00^c	141.50^ab	29.75^c	83.55^ab
	Sezener	8 WAP	8.17^b	145.00^ab	30.33^d	83.85^ab
	Sezener	11 WAP	7.6^ab	134.20^a	29.47^c	83.21^a
2023	Selin	8 WAP	10.15^c	141.20^ab	28.35^b	84.83^c
	Selin	11 WAP	9.42^c	136.70^ab	27.75^a	84.17^bc
	Sezener	8 WAP	7.3^a	144.10^ab	29.52^c	84.81^c
	Sezener	11 WAP	9.24^c	147.00^b	29.92^cd	85.62^d

Different superscript letters (a, b, c, d) in each column indicate significant difference at p < 0.05. WAP Weeks After Planting, BN Boll Number, SCI Spinning Consistency Index, UHML Upper Half Mean Length, UI Uniformity Index

3.2.3. Individual Fiber Weight

As revealed in Table 3, the Sezener variety recorded the highest individual fiber weight (10.02 µg) compared to the other variety. Notably, in 2023, this variety produced 41.68% higher than that of the Selin variety in 2022, which had the lowest value (7.89 µg) (Figure 6c). Year-wise comparisons indicated a significant increase in individual fiber weight in 2023 (11.59 µg) compared to 2022 (7.98 µg) (Table 3). Furthermore, the Sezener variety in 2023 recorded the highest individual fiber weight (12.42 µg) when treated with 400 cc. ha^-1 of MC (Table 5). This value represented a 48.11% and 50.56% increase relative to the control × Selin (7.71 g) and 800 cc. ha^-1 × Selin (7.47 µg) treatments in 2023, respectively (Table 5).

Table 5. Interaction of year, variety and concentration on individual fiber weight, fiber length and micronaire.

Treatments			IFW	UHML	Mic
2022	Selin	Control	7.71^a	29.88^e	3.08^a
		400	8.05^a	30.19^e	3.19^a
		400+400	8.32^a	29.82^de	3.32^a
		800	7.47^a	29.02^bcd	3.12^a
	Sezener	Control	8.16^a	29.62^cde	3.31^a
		400	8.22^a	29.86^e	3.29^a
		400+400	7.85^a	30.41^e	3.09^a
		800	8.04^a	29.71^cde	3.24^a
2023	Selin	Control	11.45^bc	28.31^ab	4.77^c
		400	11.09^b	28.07^a	4.68^bc
		400+400	11.08^b	28.05^a	4.68^bc
		800	11.26^bc	27.78^a	4.80^c
	Sezener	Control	11.27^bc	29.96^e
		400	12.42^c	30.08^e	4.83^c
		400+400	12.04^bc	28.92^bc	4.89^c
		800	12.13^bc	29.92^e	4.74b^c

Different superscript letters (a, b, c, d, e) in each column indicate significant difference at p < 0.05. IFW Individual Fiber Weight, UHML Upper Half Mean Length, Mic Micronaire

3.2.4. Seed Index

The variety × application timing interaction significantly influenced seed index, with the lowest value (8.66) observed for the Selin variety when MC was applied at 11 WAP (Figure 4). Across both cropping seasons, the Sezener variety exhibited a significantly higher mean seed index (10.91) compared to Selin variety (9.03) under MC application (P<0.05; Table 3, Figure 4).

No significant main effects were found for year, concentration, or application timing individually on seed index (Table 2). However, when analyzed by year, higher seed index values were observed under MC treatments in 2022 compared to 2023, with the maximum value (10.02) representing a modest 1% increase over 2023 (Table 3).

Regarding MC levels, the control (0 cc. ha^-1) resulted in the lowest seed index (9.79), while the highest values (10.06) were observed under both 400 cc. ha^-1 and 400 + 400 cc. ha^-1 application rates. In terms of application timing, 8 WAP yielded a slightly higher seed index (10.04) compared to 11 WAP (9.90) (Table 3).

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Figure 4. Illustrates the interaction effects of variety and application time on seed index (SI), with different letters indicating significant differences at P<0.05.

3.3. Fiber Qualitative Properties

3.3.1. Moisture Content

Analysis of variance showed that year had a significant effect on fiber moisture content (P≤0.01; Table 6). Mean comparisons indicated that the fiber moisture content in the second year was higher than in the first year. Specifically, the moisture content was 8.94% in 2023, representing a 6.23% increase compared with 2022 (Table 7).

Varieties also significantly influenced fiber moisture content (P<0.05; Table 6). Across varieties, Selin exhibited higher moisture content (8.83%) than Sezener (8.51%) under MC treatment (Table 7). Furthermore, the year × variety interaction was significant (P<0.05; Table 6); the highest moisture content (8.97%) was recorded for Selin in 2023, which was 10.03% greater than that of Sezener in 2022 (Figure 5a).

Application timing significantly affected fiber moisture content (P<0.01; Table 6). The lowest moisture content (8.61%) was observed when MC was applied at 11 WAP (Table 7). The year × application timing interaction was also significant (P<0.05; Table 6). The 8 WAP treatment recorded the highest moisture content values (8.95% in 2023), whereas other timings showed relatively lower values (Figure 5b).

In contrast, moisture content did not differ significantly (P>0.05; Table 6) among MC application rates across both varieties. Nevertheless, the control (0 cc. ha^-1) treatment recorded the highest mean moisture content (8.73%) (Table 6).

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Figure 5. Illustrates the interaction effects on moisture, where (a) shows the interaction between year and variety, and (b) depicts the interaction between year and application time, with different letters indicating significant differences at P<0.05.

3.3.2. Spinning Consistency Index (SCI)

The analysis of variance revealed a significant (P<0.01; Table 6) three-way interaction among year × application timing × variety for the Spinning Consistency Index (SCI). Under varying MC application rates, the Sezener variety exhibited a significantly higher SCI (147.00) in 2023 when MC was applied at 11 WAP, whereas the lowest SCI (134.20) for this variety was recorded in 2022 (Table 4). Conversely, in the Selin variety, the SCI was slightly higher in 2022 (141.50) when MC was applied at 11 WAP than in 2023 (141.20) when MC was applied at 8 WAP (Table 4).

No significant main effects of year, variety, MC concentration, or application timing were detected when considered individually (Table 6). However, when the data were analyzed separately by year, higher SCI values were observed under Mepiquat chloride (MC) treatments in 2023 compared to 2022, with the maximum mean SCI (142.24) representing a modest 1.79% increase relative to 2022 (Table 7). Across MC levels, the control treatment (0 cc. ha^-1) produced the highest SCI (142.27), whereas the lowest value (137.97) was recorded under the 800 cc. ha^-1 rate. Regarding application timing, 8 WAP resulted in a slightly higher SCI (142.09) than 11 WAP (139.86) (Table 7).

Table 6. Variance analysis of some fiber qualitative properties of different cotton varieties influenced by application timing and MC concentrations in Mediterranean region (2022–2023).

S.O.V	df	Means Square
S.O.V	df	Mst	SCI	SF	Elg	UHML	MIC	Str	UI
Years (Y)	1	6.96^**	154.38^ns	35.79^**	0.30^*	20.60^**	55.86^**	384.99^**	45.22^**
Rep (R)	2	1.12	91.03	0.72	0.04	0.35	0.60	4.23	0.39
Varieties (V)	1	2.50^*	247.77^ns	0.77^ns	0.35^*	20.39^**	0.01^ns	0.78^ns	3.92^*
Y × V	1	1.79^**	274.15^ns	0^ns	0.28^ns	13.41^**	0.02^ns	3.73^ns	2.35^*
App. T (T)	1	0.36^**	119.02^ns	0.09^ns	0.00^ns	1.54^ns	0.02^ns	3.02^ns	0.11^ns
Y × T	1	0.31^*	49.75^ns	0.04^ns	0.04^ns	0.56^ns	0.27^*	1.00^ns	0.48^ns
V × T	1	0.02^ns	66.85^ns	1.10^ns	0.20^ns	0.01^ns	0.07^ns	12.43^*	0.54^ns
CONCs (C)	3	0.05^ns	97.61^ns	0.36^ns	0.13^ns	0.88^ns	0.05^ns	1.48^ns	0.59^ns
Y × C	3	0.06^ns	200.92^ns	0.71^ns	0.05^ns	1.53^*	0.04^ns	3.70^ns	1.40^ns
V × C	3	0.04^ns	136.66^ns	0.22^ns	0.08^ns	0.68^ns	0.03^ns	4.12^ns	2.10^*
T × C	3	0.07^ns	103.04^ns	0.32^ns	0.03^ns	0.19^ns	0.03^ns	4.86^ns	1.90^ns
Y × V × T	1	0.02^ns	703.56^**	1.59^ns	0.07^ns	5.53^**	0.06^ns	2.24^ns	8.15^**
Y × V × C	3	0.08^ns	64.03^ns	0.26^ns	0.01^ns	1.189^*	0.26^**	1.45^ns	0.64^ns
Y × T × C	3	0.02^ns	54.97^ns	0.29^ns	0.23^*	0.49^ns	0.11^ns	2.93^ns	0.06^ns
V × T × C	3	0.01^ns	168.18^ns	0.96^ns	0.02^ns	0.81^ns	0.07^ns	1.04^ns	3.17^**
Y × V × T × C	3	0.03^ns	9.63^ns	0.73^ns	0.06^ns	0.13^ns	0.01^ns	1.54^ns	0.83^ns
Error		0.23	9.31	0.67	0.28	0.65	0.25	1.75	0.86
CV (%)		2.6	6.6	8.1	5.0	2.20	6.30	5.70	1.00

ns, * and ** no significant, significant in 5 and 1% level. CONCs Concentrations, T Application timing, MST Moisture, SCI Spinning Consistency Index, SF Short Fibers, Elg Elongation, UHML Upper Half Mean Length, MIC Micronaire, Str Strength, UI Uniformity Index, CV Coefficient of variation, S.O.V. Sources of variations

3.3.3. Short Fiber Content

Analysis of variance revealed that the year had a significant effect on short fiber content (P≤0.01; Table 6). Mean comparisons showed that short fiber content was higher in 2022 (8.85%) than in 2023, reflecting a 14.81% decrease in the second year (Table 7).

No significant main effects of variety, MC concentration, or application timing, nor their interactions, were perceived when analyzed collectively (Table 6). However, within varieties, MC application resulted in higher short fiber content in Selin (8.33%) than in Sezener (8.15%) (Table 7). Across MC application doses, the 800 cc ha^-1 treatment produced the highest short fiber content (8.40%), while the lowest value (8.10%) was recorded under the split 400 + 400 cc ha^-1 rate (Table 7). MC applied at 11 WAP resulted in slightly higher short fiber content (8.27%) than at 8 WAP (8.21%) (Table 7).

Table 7. Effects of Mepiquat chloride concentrations and application timings on fiber qualitative properties of cotton varieties in the Mediterranean Region (2022–2023).

Treatments	Levels	Mst	SCI	SF	Elg	UHML	Mic	Str	UI
Years	2022	8.4^a	139.71	8.85^b	5.44^a	29.81^b	3.21^a	28.68^a	83.48^a
	2023	8.94^b	142.24	7.63^a	5.55^b	28.89^a	4.73^b	32.69^b	84.86^b
	LSD0.05	0.1	3.87	0.28	0.11	0.27	0.10	0.71	0.35
Varieties	Selin	8.83^b	139.37	8.33	5.56^b	28.89^a	3.96	30.78	83.97^a
	Sezener	8.51^a	142.58	8.15	5.44^a	29.81^b	3.98	30.60	84.37^b
	LSD0.05	0.17	6.44	0.4	0.11	0.27	0.10	0.71	0.35
App. T	8 WAP	8.73^b	142.09	8.21	5.50	29.48	3.95	30.86	84.20
	11 WAP	8.61^a	139.86	8.27	5.49	29.22	3.98	30.51	84.14
	LSD0.05	0.07	3.83	0.4	0.11	0.27	0.10	0.71	0.35
CONCs	Control	8.73	142.27	8.22	5.56	29.44	3.90	30.98	84.10
	400	8.69	141.94	8.24	5.52	29.55	4.00	30.57	84.32
	400 + 400	8.64	141.73	8.1	5.51	29.30	4.00	30.79	84.28
	800	8.63	137.97	8.4	5.39	29.11	3.97	30.41	83.98
	LSD0.05	0.11	5.41	0.37	0.16	0.38	0.14	1.01	0.50

Different superscript letters (a, b) in each column indicate significant difference at p < 0.05. CONCs Concentrations, APP.T Application timing, MST Moisture, SCI Spinning Consistency Index, SF Short Fibers, Elg Elongation, UHML Upper Half Mean Length, MIC Micronaire, Str Strength, UI Uniformity Index

3.3.4. Fiber Elongation

Analysis of variance indicated that the year had a significant effect on fiber elongation (P<0.05; Table 6). Mean comparison revealed that fiber elongation was higher in 2023 (5.55%) than in 2022, corresponding to a 2% reduction in the first year (Table 7). Varietal differences were also significant (P<0.05; Table 6), with Selin exhibiting greater fiber elongation (5.56%) than Sezener (5.44%) under MC treatment (Table 7). Moreover, a significant three-way interaction among year, application timing, and concentration was detected (P<0.05; Table 6). The highest fiber elongation (5.80%) occurred in the control treatment in 2023 when MC was applied at 8 WAP, whereas the lowest value (5.27%) was recorded in 2022 under the 800 cc. ha^-1 treatment at the same timing (Table 8).

Table 8. Interaction of year, application timing and concentration on fiber elongation.

Fiber Elongation
	Treatments	Control	400	400+400	800
2022	8 WAP	5.37^a	5.50^ab	5.55^ab	5.27^a
2022	11 WAP	5.62^ab	5.55^ab	5.35^a	5.32^a
2023	8 WAP	5.80^b	5.58^ab	5.51^ab	5.42^ab
2023	11 WAP	5.46^ab	5.44^ab	5.64^ab	5.56^ab

Different superscript letters (a, b,) in each column indicate significant difference at P<0.05. WAP Weeks After Planting

3.3.5. Fiber Length

Analysis of variance exhibited a significant effect of year on fiber length (P<0.01; Table 6). Mean comparison indicated that the longest fibers (29.81 mm) were recorded in 2022, representing a 3.13% reduction in 2023 (Table 7). Varietal differences were significant (P<0.01; Table 6), with Sezener producing longer fibers (29.81 mm) than Selin (28.89 mm) under MC treatment (Table 7). A significant year × variety interaction was detected (P<0.01; Table 6); Sezener in 2022 unveiled the longest fibers (29.90 mm), which were 6.30% longer than those of Selin in 2023 (Figure 6a).

A significant year × concentration interaction was also observed (P<0.05; Table 6). The longest fibers (30.12 mm) occurred under the 400+400 cc. ha-1 treatment in 2022, while the shortest fibers (28.49 mm) were recorded under the same treatment in 2023 (Figure 6b). Furthermore, a significant three-way interaction (year × application timing × variety) was identified (P<0.01; Table 6). Sezener produced the longest fibers (30.33 mm) in 2022 when MC was applied at 8 WAP, whereas the shortest fibers (27.75 mm) were recorded for Selin in 2022 at 11 WAP (Table 4). Additionally, the year × variety × concentration interaction was significant (P<0.05; Table 6), with Sezener treated with 400 + 400 cc. ha^-1 MC in 2022 exhibiting the longest fibers (30.41 mm), representing an 8.69% increase compared with the 800 cc. ha^-1 × Selin treatment (27.78 mm) in 2023 (Table 5).

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Figure 6. Illustrates the interaction effects on fiber quality traits, where (a) shows the interaction between variety and year and the interaction between year and concentration on fiber length (UHML) with different letters indicating significant differences at P<0.05.

3.3.6. Fiber Uniformity

Analysis of variance revealed that the year had a significant effect on fiber uniformity (P<0.01; Table 6). Mean comparison exhibited that fiber uniformity was higher in 2023 (84.86%) than in 2022 (83.48%), representing a 1.64% increase in the second year (Table 7). Varietal differences were also significant (p < 0.05; Table 6), with Sezener recording higher fiber uniformity (84.37%) than Selin (83.97%) under MC treatment (Table 7).

A significant year × variety interaction was observed (P<0.05; Table 6); Sezener in 2023 recorded the highest fiber uniformity (85.21%), 2.10% higher than Selin in 2022 (Figure 7a). The variety × concentration interaction was also significant (P<0.05; Table 7), with Sezener treated with 400 cc. ha^-1 showing the highest fiber uniformity (84.64%), while Selin treated with 800 cc. ha^-1 exhibiting the lowest (83.44%) (Figure 7b).

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Figure 7. Illustrates the interaction effects on fiber quality traits, where (a) shows the interaction between year x variety and the interaction between variety x concentration on fiber uniformity with different letters indicating significant differences at p < 0.05.

Furthermore, a significant three-way interaction among year, application timing, and variety was detected (P<0.01; Table 6). Under varying MC application rates, Sezener attained the highest fiber uniformity (85.62%) in 2023 when MC was applied at 11 WAP, while the lowest uniformity (83.21%) was recorded for the same variety in 2022 at the same timing (Table 4). Additionally, the variety × application timing × concentration interaction was significant (P<0.01; Table 6). The Sezener treated with 400 cc. ha^-1 at 11 WAP unveiled the highest fiber uniformity (85.09%), representing a 2.58% increase compared with the Selin × 800 cc. ha^-1 treatment (82.92%) at the 8 WAP (Table 9).

Table 9. Interaction of variety, application timing and concentration on uniformity index.

Uniformity index
Treatments		Control	400	400+400	800
Selin	8 WAP	84.93^de	83.86^abcd	84.59^bcde	82.92^a
Selin	11 WAP	83.58^ab	84.14^bcde	83.76^abcd	83.96^abcde
Sezener	8 WAP	83.72^abc	84.18^bcde	84.58^bcde	84.84^cde
Sezener	11 WAP	84.18^bcde	85.09^e	84.18^bcde	84.20^bcde

3.3.7. Fiber Strength

Analysis of variance indicated that the year had a significant effect on fiber strength (P<0.01; Table 6). Mean comparison exhibited that fiber strength was higher in 2023 (32.69 g tex^-1) than in 2022 (28.68 g tex^-1), representing a 13.07% increase in the second year (Table 7). A significant two-way interaction between variety and application timing was also perceived (P<0.05; Table 6). The Sezener variety exhibited the highest fiber strength (31.13 g tex^-1) when MC was applied 8 WAP, while the lowest strength (30.06 g tex^-1) was observed for the same variety when MC was applied at 11 WAP (Figure 8a).

Although differences among MC concentrations were not statistically significant (P>0.05; Table 6), mean comparisons unveiled notable trends. The control treatment (0 cc. ha^-1) resulted in the highest fiber strength (30.98 g tex^-1), followed by 400 + 400 cc. ha^-1 (30.79 g tex^-1), 400 cc. ha^-1 (30.57 g tex^-1), and 800 cc. ha^-1 (30.41 g tex^-1) (Table 7).

3.3.8. Fiber Micronaire

Analysis of variance showed that the year had a significant effect on fiber micronaire (P<0.01; Table 6). In 2023, varieties supplied with Mepiquat chloride exhibited significantly higher micronaire values (4.73 µg inch^-1) than in 2022 (3.21 µg inch^-1) (Table 7). A significant year × application timing interaction was also observed (P<0.05; Table 6). The highest micronaire (4.77 µg inch^-1) was recorded under the 8 WAP treatment in 2023, whereas other timings resulted in comparatively lower values (Figure 8b).

Moreover, a significant three-way interaction among year, variety, and concentration was detected (P<0.01; Table 6). The Sezener variety in 2023 revealed the highest micronaire (4.89 µg inch^-1) when treated with 400 + 400 cc. ha^-1 of MC (Table 5), representing a 45.59% increase compared with the control × Selin treatment (3.08 µg inch^-1) in 2022.

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Figure 8. Illustrates the interaction effects on fiber quality traits, where (a) shows the interaction between variety and application time on fiber strength, and (b) the interaction between year and application time on micronaire with different letters indicating significant differences at P<0.05.

4. Discussion

The present study demonstrates that genotype, environment, and MC application interactively regulate cotton growth dynamics, yield formation, and fiber quality attributes. The significant year × variety interaction for plant height and leaf area underscores the strong genotype × environment (G × E) influence on vegetative development, consistent with earlier studies showing that climatic variability and cultivar-specific growth habits shape cotton responses to growth regulators

[42, 52]

. The reduction in plant height and leaf expansion with 400 cc ha^-1 MC concentration or earlier application aligns with its known anti-gibberellin mode of action, which restricts vegetative vigor and redirects assimilates toward reproductive sinks

[38, 51, 53]

Environmental conditions exerted a significant influence on monopodial branching, with water deficit conditions reducing branch formation and subsequently influencing fiber yield and quality. This aligns with previous observations that abiotic stress limits vegetative branching and reproductive potential

[54, 55]

. Although varietal differences in branch number were not significant across years, the results emphasize that branch development depends on a complex interplay of genotype, environment, growth stage, and growth regulator application. Optimizing these factors is crucial, as monopodial branches contribute substantially to reproductive capacity and yield performance

[37, 56, 57]

Early MC application enhanced monopodial branching and boll formation, demonstrating that precise timing is critical for maximizing sink strength at the onset of reproductive development

[58]

. This physiological advantage was particularly evident in the Selin cultivar, which exhibited a superior source–sink balance and reproductive efficiency compared to Sezener. These findings corroborate previous reports highlighting cultivar-specific yield responses to MC and the necessity of genotype-targeted growth regulator strategies

[51, 59, 60]

MC application variably influenced yield components such as seed index, seed cotton yield, and individual fiber weight. Enhanced yield, seed index and fiber weight in MC-treated plants likely resulted from improved physiological and biochemical activity, including increased carotenoid and chlorophyll content, higher stomatal conductance, and enhanced enzyme activities, all of which support efficient carbon assimilation, carbohydrate metabolism, and protein and sugar biosynthesis

[40, 61]

. Moreover, morphological adjustments—such as reduced canopy size, improved light penetration, increased monopodial branches, and a lower height-to-node ratio— further enhanced photoassimilate partitioning to reproductive structures, improving boll development and yield potential

[29, 37, 62]

Moisture content, which strongly affects fiber quality traits, was affected by variety, seasonal conditions, and MC application timing. A notable reduction in moisture content with split or moderate MC doses applied at later stages advocates that delayed application may enhance secondary wall deposition and promote fiber maturation, consistent with

[25]

. In contrast, the higher moisture content in untreated plants indicates a potential trade-off between growth regulation and fiber quality

[63]

. The consistently lower moisture levels observed in the Sezener variety underscore inherent genotypic differences in fiber physiology, reflecting the role of intrinsic metabolic traits in fiber development

[64, 65]

. Moreover, the profound impact of climatic variability on short fiber content and moisture levels reinforces the complexity of genotype–environment interactions that collectively determine cotton fiber development and quality attributes

[66, 67]

. The detected reduction in short fiber content under optimized MC regimes further confirms that growth regulator management can modulate fiber structural properties beyond yield-related components

[26, 68]

Fiber elongation, crucial for yarn strength and spinning performance, was significantly higher in 2023 and in the Selin variety under MC treatment. Year-to-year variation is likely due to climatic influences on fiber cell wall elongation and secondary wall formation

[59, 69]

. The significant year × application timing × concentration interaction indicates that MC can modulate fiber elongation dynamics, likely by influencing assimilate partitioning during fiber development

[61]

. Notably, the highest elongation was recorded in the untreated conditions, suggesting that suboptimal or excessive MC suppression can hinder fiber extensibility. Fiber length, vital for spinning efficiency, was consistently greater in Sezener, with significant effects of year and treatment interactions. Enhanced fiber length with split or moderate MC application suggests that balanced vegetative control supports optimal fiber elongation, whereas excessive doses or delayed applications may inhibit cell elongation

[61]

Micronaire, a key determinant of fiber fineness and maturity, was higher in 2023, particularly in Sezener treated with moderate MC doses, reflecting thicker and more mature fibers

[24]

. Environmental conditions, especially temperature during boll maturation, likely contributed to these differences

[70]

. The significant three-way interaction among year, variety, and concentration demonstrates genotype-specific sensitivity to MC, where moderate doses promote secondary wall thickening, while excessive levels can dilute assimilate availability and reduce fiber maturity

[60]

Fiber strength, determined by cell wall thickness, fiber length, and cellulose content, was significantly higher in 2023 and influenced by the variety × application timing interaction. Sezener achieved the highest strength when MC was applied at 8 WAP, suggesting that early growth regulation enhances cellulose deposition and fiber structural integrity. However, these results contrast with the findings reported by

[57]

. Although MC concentration effects were not statistically significant, trends indicated that low or split applications promote fiber reinforcement without compromising plant vigor. Finally, fiber uniformity, which affects yarn evenness and quality, was highest in 2023 for Sezener, with significant interactions involving all studied factors (Table 9). Improved uniformity with moderate MC application (400 cc. ha^-1 at 11 WAP) suggests that balanced growth control and synchronized boll development reduce variability in fiber maturity

[57]

. Excessive or poorly timed MC applications, however, may disrupt developmental synchrony, resulting in uneven fiber formation. These findings reinforce the importance of aligning MC management with varietal characteristics and environmental conditions to optimize fiber uniformity and quality

[71]

5. Conclusions

This study demonstrates that genotype, environmental conditions, and Mepiquat chloride (MC) management interact significantly to influence cotton growth dynamics, yield formation, and fiber quality. The results highlight that optimizing MC application particularly through split or moderate-dose treatments (e.g., 400 + 400 cc. ha^-1) can effectively regulate vegetative growth, enhance yield components, and improve key fiber traits such as micronaire, strength, and uniformity. Early-to-mid reproductive stage applications (around 8 weeks after planting) are more effective in enhancing branching and boll development, whereas slightly later applications can improve fiber uniformity and micronaire. Genotypic differences were evident: Selin unveiling superior yield potential, while Sezener exhibited advantages in fiber quality attributes, signifying that cultivar selection should align with production goals to enable targeted management strategies. Seasonal variability further emphasized the importance of aligning MC strategies with environmental conditions to maximize agronomic performance; therefore, application strategies should be tailored to prevailing climatic conditions and soil fertility status. Collectively, these findings provide a scientific basis for integrating growth regulator management with genotype selection to achieve balanced growth, improved yield, and superior fiber quality under Mediterranean production systems. Hence, further studies should focus on integrating physiological, molecular, and agronomic approaches to refine MC use efficiency across diverse genotypes and environments, ultimately facilitating the development of decision-support tools to promote sustainable cotton production and meet fiber industry requirements.

Abbreviations

cc	Cubic Centimeter
g	Gram
MC	Mepiquat Chloride
PH	Plant Height
pH	Potential of Hydrogen
S.O.V	Sources of Variation
SCY	Seed Cotton Yield
TSMS	Turkish State Meteorological Service
WAP	Weeks After Planting
μg	Microgram

Acknowledgments

The authors gratefully acknowledge the support provided by Ondokuz Mayıs University. They also sincerely thank the Center Manager of TARI Hombolo for agreeing to cover the article processing charges (APC). Additional support was provided by the Eastern Mediterranean Agricultural Research Institute Directorate through the provision of experimental farmland and HVI facilities for fiber quality analysis. The authors further express their sincere appreciation to Mr. Mustafa Demir for his valuable assistance during the experimental work.

Author Contributions

Mashenene Malima: Conceptualization, Investigation, Methodology, Resources, Validation, Visualization, Writing – original draft, Writing – review & editing

Orhan Kurt: Conceptualization, Funding Acquisition, Methodology, Project Administration, Resources, Supervision, Validation, Visualization, Writing – Review & Editing

Sikitu Jonathan Kazungu: Data curation, Formal Analysis, Software

Muhammet Safa Hacikamiloglu: Data curation, Formal Analysis, Validation, Visualization

Thereza Fabiani Deus: Formal Analysis, Writing – original draft, Writing – review & editing

Funding

This work was funded by Ondokuz Mayıs University through the Scientific Research Projects (BAP) grant (PYO.ZRT.1904.23.017), while the article processing charge (APC) was supported by the Tanzania Agricultural Research Institute (TARI), Hombolo Centre.

Data Availability Statement

The data is available from the corresponding author upon reasonable request.

Conflicts of Interest

The authors declare no conflicts of interest.

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Malima, M., Kurt, O., Kazungu, S. J., Hacikamiloglu, M. S., Deus, T. F. (2026). Effectiveness of Mepiquat Chloride Application Timing on Physiological, Agronomic, and Fiber Quality Traits of Cotton (Gossypium spp.) Varieties. International Journal of Applied Agricultural Sciences, 12(2), 54-73. https://doi.org/10.11648/j.ijaas.20261202.15

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Malima, M.; Kurt, O.; Kazungu, S. J.; Hacikamiloglu, M. S.; Deus, T. F. Effectiveness of Mepiquat Chloride Application Timing on Physiological, Agronomic, and Fiber Quality Traits of Cotton (Gossypium spp.) Varieties. Int. J. Appl. Agric. Sci. 2026, 12(2), 54-73. doi: 10.11648/j.ijaas.20261202.15

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Malima M, Kurt O, Kazungu SJ, Hacikamiloglu MS, Deus TF. Effectiveness of Mepiquat Chloride Application Timing on Physiological, Agronomic, and Fiber Quality Traits of Cotton (Gossypium spp.) Varieties. Int J Appl Agric Sci. 2026;12(2):54-73. doi: 10.11648/j.ijaas.20261202.15

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@article{10.11648/j.ijaas.20261202.15,
  author = {Mashenene Malima and Orhan Kurt and Sikitu Jonathan Kazungu and Muhammet Safa Hacikamiloglu and Thereza Fabiani Deus},
  title = {Effectiveness of Mepiquat Chloride Application Timing on Physiological, Agronomic, and Fiber Quality Traits of Cotton (Gossypium spp.) Varieties},
  journal = {International Journal of Applied Agricultural Sciences},
  volume = {12},
  number = {2},
  pages = {54-73},
  doi = {10.11648/j.ijaas.20261202.15},
  url = {https://doi.org/10.11648/j.ijaas.20261202.15},
  eprint = {https://article.sciencepublishinggroup.com/pdf/10.11648.j.ijaas.20261202.15},
  abstract = {A two-year field study underscores the importance of integrating genotype selection with optimized Mepiquat Chloride (MC) management to enhance cotton performance under a split–split–plot design. Significant genotype × environment × management interactions were observed in cotton growth, yield, and fiber quality responses MC application. Plant height was significantly affected by year × variety interaction (p -1 enhanced leaf expansion. Monopodial branches were significantly greater in 2023 (9.59 plant-1), with early MC application favoring branch initiation. Seed cotton yield was peak in Selin (3623 kg ha-1), 25% greater than Sezener, with split application (400 + 400 cc. ha-1) yielding best results. Boll number and individual fiber weight were higher in Selin and Sezener, respectively, with the latter showing a 48% increase under 400 cc. ha-1. Seed index was significantly higher in Sezener, and fiber moisture increased in 2023 (8.94%). Fiber quality traits revealed pronounced year, genotype, and application timing effects: fiber length peaked in Sezener (30.33 mm), elongation reached 5.80%, and micronaire increased to 4.89 µg inch-1 under split MC application. Fiber strength increased by 13.07% in 2023, and while uniformity (85.62%) maximized with later application. Short fiber content decreased by 14.81% in 2023. These findings highlight that MC concentration, timing, and genotype interactions significantly modulate morphophysiological traits, yield components, and fiber quality, with split or moderate-dose applications enhancing productivity and fiber properties under Mediterranean conditions.},
 year = {2026}
}

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TY - JOUR
T1 - Effectiveness of Mepiquat Chloride Application Timing on Physiological, Agronomic, and Fiber Quality Traits of Cotton (Gossypium spp.) Varieties
AU - Mashenene Malima
AU - Orhan Kurt
AU - Sikitu Jonathan Kazungu
AU - Muhammet Safa Hacikamiloglu
AU - Thereza Fabiani Deus
Y1 - 2026/04/24
PY - 2026
N1 - https://doi.org/10.11648/j.ijaas.20261202.15
DO - 10.11648/j.ijaas.20261202.15
T2 - International Journal of Applied Agricultural Sciences
JF - International Journal of Applied Agricultural Sciences
JO - International Journal of Applied Agricultural Sciences
SP - 54
EP - 73
PB - Science Publishing Group
SN - 2469-7885
UR - https://doi.org/10.11648/j.ijaas.20261202.15
AB - A two-year field study underscores the importance of integrating genotype selection with optimized Mepiquat Chloride (MC) management to enhance cotton performance under a split–split–plot design. Significant genotype × environment × management interactions were observed in cotton growth, yield, and fiber quality responses MC application. Plant height was significantly affected by year × variety interaction (p -1 enhanced leaf expansion. Monopodial branches were significantly greater in 2023 (9.59 plant-1), with early MC application favoring branch initiation. Seed cotton yield was peak in Selin (3623 kg ha-1), 25% greater than Sezener, with split application (400 + 400 cc. ha-1) yielding best results. Boll number and individual fiber weight were higher in Selin and Sezener, respectively, with the latter showing a 48% increase under 400 cc. ha-1. Seed index was significantly higher in Sezener, and fiber moisture increased in 2023 (8.94%). Fiber quality traits revealed pronounced year, genotype, and application timing effects: fiber length peaked in Sezener (30.33 mm), elongation reached 5.80%, and micronaire increased to 4.89 µg inch-1 under split MC application. Fiber strength increased by 13.07% in 2023, and while uniformity (85.62%) maximized with later application. Short fiber content decreased by 14.81% in 2023. These findings highlight that MC concentration, timing, and genotype interactions significantly modulate morphophysiological traits, yield components, and fiber quality, with split or moderate-dose applications enhancing productivity and fiber properties under Mediterranean conditions.
VL - 12
IS - 2
ER -

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Author Information

Mashenene Malima

Department of Technology Transfer and Partnership, Tanzania Agricultural Research Institute, Dodoma, Tanzania

Biography: Mashenene Malima is an agronomist at the Tanzania Agricultural Research Institute (TARI), working in the Department of Technology Transfer and Partnerships. He obtained his PhD in Field Crops from Ondokuz Mayıs University in 2025 and holds a Master of Science in Crop Science (Agronomy) from Sokoine University of Agriculture (2017). He has received international recognition for his research contributions. In 2018, he was honored by UNESCO–Africa for excellence in abstract writing, ranking among leading research scientists in Africa. In 2015, he received an award for outstanding postgraduate research proposal writing in Eastern and Southern Africa (ESA), supported by SIDA in collaboration with UNESCO. Dr. Malima has participated in several international collaborative research projects, demonstrating strong engagement in global scientific partnerships. Currently, he serves as the Coordinator of Technology Transfer and Partnerships at TARI Hombolo Centre, where he leads initiatives aimed at strengthening research uptake, innovation dissemination, and stakeholder engagement.

Research Fields: Plant Breeding, Plant Tissue Culture, Plant Genetics, Biodiversity, Crop Production, Crop Management, Climate Change and Agriculture, Plant Nutrition, Crop Science, Conservation Agriculture, Agroecology

Contact Email

http://orcid.org/0009-0000-5221-7613
Orhan Kurt

Department of Field Crops, Faculty of Agriculture, Ondokuz Mayıs University, Samsun, Turkey

Research Fields: Plants, Embryo Culture Techniques, Genetic Diversity, Biodiversity, Inbreeding, Population Genetics, Genetics

http://orcid.org/0000-0002-5662-9372
Sikitu Jonathan Kazungu

Department of Research and Innovation, Tanzania Agricultural Research Institute, Dodoma, Tanzania

Research Fields: Plant Bleeding, Crop Production and Management, Climate Smart Agriculture, Agroecology, Biodiversity

http://orcid.org/0009-0004-2025-454X
Muhammet Safa Hacikamiloglu

Department of Field Crops, Faculty of Agriculture, Ondokuz Mayıs University, Samsun, Turkey

Research Fields: Plant Biotechnology, Plant Molecular Biology, Plant Tissue Culture, Plant Breeding, Crop Improvement, Plant Genetics, Plant Biology, Plant Physiology, Agricultural Biotechnology, Plant Genomics

http://orcid.org/0000-0002-2188-2765
Thereza Fabiani Deus

Department of Research and Innovation, Tanzania Agricultural Research Institute, Dodoma, Tanzania

Research Fields: Agroecology, Climate Change, Genetic diversity, Plant Physiology, Breeding, Conservation Agriculture, Plant Pathology

http://orcid.org/0009-0008-7387-1890

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APA Style

Malima, M., Kurt, O., Kazungu, S. J., Hacikamiloglu, M. S., Deus, T. F. (2026). Effectiveness of Mepiquat Chloride Application Timing on Physiological, Agronomic, and Fiber Quality Traits of Cotton (Gossypium spp.) Varieties. International Journal of Applied Agricultural Sciences, 12(2), 54-73. https://doi.org/10.11648/j.ijaas.20261202.15

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ACS Style

Malima, M.; Kurt, O.; Kazungu, S. J.; Hacikamiloglu, M. S.; Deus, T. F. Effectiveness of Mepiquat Chloride Application Timing on Physiological, Agronomic, and Fiber Quality Traits of Cotton (Gossypium spp.) Varieties. Int. J. Appl. Agric. Sci. 2026, 12(2), 54-73. doi: 10.11648/j.ijaas.20261202.15

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AMA Style

Malima M, Kurt O, Kazungu SJ, Hacikamiloglu MS, Deus TF. Effectiveness of Mepiquat Chloride Application Timing on Physiological, Agronomic, and Fiber Quality Traits of Cotton (Gossypium spp.) Varieties. Int J Appl Agric Sci. 2026;12(2):54-73. doi: 10.11648/j.ijaas.20261202.15

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@article{10.11648/j.ijaas.20261202.15,
  author = {Mashenene Malima and Orhan Kurt and Sikitu Jonathan Kazungu and Muhammet Safa Hacikamiloglu and Thereza Fabiani Deus},
  title = {Effectiveness of Mepiquat Chloride Application Timing on Physiological, Agronomic, and Fiber Quality Traits of Cotton (Gossypium spp.) Varieties},
  journal = {International Journal of Applied Agricultural Sciences},
  volume = {12},
  number = {2},
  pages = {54-73},
  doi = {10.11648/j.ijaas.20261202.15},
  url = {https://doi.org/10.11648/j.ijaas.20261202.15},
  eprint = {https://article.sciencepublishinggroup.com/pdf/10.11648.j.ijaas.20261202.15},
  abstract = {A two-year field study underscores the importance of integrating genotype selection with optimized Mepiquat Chloride (MC) management to enhance cotton performance under a split–split–plot design. Significant genotype × environment × management interactions were observed in cotton growth, yield, and fiber quality responses MC application. Plant height was significantly affected by year × variety interaction (p -1 enhanced leaf expansion. Monopodial branches were significantly greater in 2023 (9.59 plant-1), with early MC application favoring branch initiation. Seed cotton yield was peak in Selin (3623 kg ha-1), 25% greater than Sezener, with split application (400 + 400 cc. ha-1) yielding best results. Boll number and individual fiber weight were higher in Selin and Sezener, respectively, with the latter showing a 48% increase under 400 cc. ha-1. Seed index was significantly higher in Sezener, and fiber moisture increased in 2023 (8.94%). Fiber quality traits revealed pronounced year, genotype, and application timing effects: fiber length peaked in Sezener (30.33 mm), elongation reached 5.80%, and micronaire increased to 4.89 µg inch-1 under split MC application. Fiber strength increased by 13.07% in 2023, and while uniformity (85.62%) maximized with later application. Short fiber content decreased by 14.81% in 2023. These findings highlight that MC concentration, timing, and genotype interactions significantly modulate morphophysiological traits, yield components, and fiber quality, with split or moderate-dose applications enhancing productivity and fiber properties under Mediterranean conditions.},
 year = {2026}
}

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