Mepiquat Chloride Application Research Articles

Managing earliness and yield of cotton by modulating plant population, foliar boron feeding and mepiquat chloride application

ABSTRACT Early maturity and simultaneous increase in yield of cotton are pivotal for increasing the productivity of cropping systems involving cotton. Current two-year study was performed to simultaneously enhance the earliness and yield of cotton by modulating plant population (PP) (5.3 and 8.8 plants m−2), foliar boron (B) (0, 0.6 and 1.2 g/L B) and 0.07 g/L mepiquat chloride (MC) solution (at squaring and flowering stages) application. Internodes length was exalted at high PP (8.8 plants m-2) and B (1.2 g/L B), while declined by MC. Nevertheless, nodes above the white flower and cracked boll were decreased at high PP, and the application of B and MC indicated earlier cutout. Similarly, high PP, and application of 1.2 g/L B and MC at squaring reduced calendar and thermal time needed for flowering and boll opening. The boll maturation period was not affected by the application of B and MC but declined at high PP. Earliness index, production rate index (PRI) and seed cotton yield were increased at high PP, application of 1.2 g/L B and MC at squaring. In crux, increasing PP and B concentration, and MC application at squaring resulted in early maturity and enhanced seed cotton yield by modulating plant structure and time required for various phenophases.

The application potential of mepiquat chloride in soybean: improvement of yield characteristics and drought resistance

BackgroundDrought can result in yield losses, the application of plant growth regulators is an effective measure to improve drought resistance and yield. The objective of the study was to explore the application potential of mepiquat chloride (MC) in regulating soybean yield and drought resistance.MethodsIn this study, a three-year field experiment was designed and combined with drought experiments to measure the yield of popularized varieties during 2021–2022 and drought-resistant and drought-sensitive varieties were selected, and planted in the field in 2023.ResultsMC increased the yield of HN84 and HN87 for two consecutive years from 2021 to 2022 and improved their physiological characteristics under field conditions. Under M200 treatment, the yield of HN84 increased by 6.93% and 9.46%, and HN87 increased by 11.11% and 15.72%. Different concentrations of MC have different effects on soybeans. The maximum increase of SOD, POD and proline in HN84 under M400 treatment reached 71.92%, 63.26% and 71.54%, respectively; the maximum increase of SOD, POD and proline in HN87 under M200 treatment reached 21.96%, 93.49% and 40.45%, respectively. In 2023, the foliar application of MC improved the physiological characteristics of HN44 and HN65 under drought-stress conditions. On the eighth day of drought treatment, compared to the drought treatment, the leaf and root dry weight of HN44 under M100 treatment increased by 17.91% and 32.76%, respectively; the dry weight of leaves and roots of HN65 increased by 20.74% and 29.29% under M200 treatment, respectively. MC also reduced malondialdehyde (MDA) content, decreased antioxidant enzyme activity and proline content. In addition, different concentrations of MC increased the chlorophyll fluorescence parameters (Fs, Fv/Fm, YII, and SPAD). In the field, the plant height of the two varieties decreased significantly, the yield increased, the number of two-grain and three-grain pods increased, and the stem length at the bottom and middle decreased with MC induction.ConclusionsThe application of 100–200 mg/L MC effectively improved drought resistance and increased yield. This study provided support for the rational application of MC in soybean production.

Exogenous application of bio-stimulants and growth retardants improve nutrient absorption and fiber quality in upland cotton

BackgroundNatural and synthetic plant growth regulators are essential for plant health, likewise these regulators also play a role in increasing organic production productivity and improving quality and yield stability. In the present study, we have evaluated the effects of foliar applied plant growth regulators, i.e., moringa leaf extract (MLE) and mepiquat chloride (MC) alone and in combination MC and MLE on the conventional cotton cultivar (CIM 573) and transgenic one (CIM 598). The growth regulators were applied at the start of bloom, 45 and 90 days after blooming.ResultsThe application of MC and MLE at 90 days after blooming significantly improved the relative growth rate, net assimilation rate, the number of bolls per plant, and seed cotton yield. Likewise, the combined application of MLE and MC at 90 days after blooming significantly boosted the nitrogen uptake in locules, as well as the phosphorus and potassium uptake in the leaves of both cotton cultivars. The application of MLE alone has considerably improved the nitrogen uptake in leaves, and phosphorus and potassium contents in locules of Bt and conventional cotton cultivars. Similarly, Bt cotton treated with MLE at 90 days after blooming produced significantly higher ginning out turn and oil contents. Treatment in combination (MLE + MC) at 90 days after blooming produced considerably higher micronaire value, fiber strength, and staple length in conventional cultivar.ConclusionThe natural growth enhancer, MLE is a rich source of minerals and zeatin, improving the nutrient absorption and quality of cotton fiber in both conventional and Bt cotton cultivars.

Effects of Mepiquat Chloride on Physiology of Soybean under Drought Stress

Background: Drought is an important factor restricting the development of agriculture. In recent years, plant growth regulators have achieved more results in improving crop stress resistance. The physiological mechanism of exogenous application of mepiquat chloride on soybean seedlings has undergone significant changes under drought stress. Methods: In order to study the effect of exogenous chlorine on the physiology of soybean under drought stress., ‘Heinong 65’ was used as the experimental material, 15% PEG-6000 was used to simulate drought stress and different concentrations of mepiquat chloride solution (100, 300, 500, 700 mg/L) were sprayed at the three-leaf stage of soybean growth by pot method. The dry matter accumulation, auxin (IAA), zeatin (ZA), gibberellin (GA3), abscisic acid (ABA) content and superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), ascorbate peroxidase (APX) activity of soybean were determined. Result: The results showed that the activities of antioxidant enzymes SOD, POD, CAT and APX in soybean leaves under drought stress were significantly increased by the treatment of appropriate concentration of mepiquat chloride solution. IAA, GA3 and ZA endogenous hormone levels increased, dry matter accumulation increased, root-shoot ratio and ABA endogenous hormone levels decreased significantly. It can be seen that mepiquat chloride treatment can improve the antioxidant capacity, promote the growth of soybean seedlings under drought stress and effectively alleviate the inhibition of drought stress on soybean growth and development.

Productivity and Morpho-phenological Characters of Pigeonpea [Cajanus cajan (L.) Millsp.] as Influenced by Crop Geometry and Nipping Practice

Background: One of the possible agronomic ways for increasing productivity of pigeonpea is adoption of suitable crop geometry with nipping practices for getting suitable crop architecture for optimum utilization of resources. This investigation was planned to study the influence of crop geometry and nipping practices on production potential of pigeonpea. Methods: The field experiment was conducted at experimental farm of the Department of Pulses, TNAU, Coimbatore, during kharif season of 2021 and 2022. The experiment was laid out in split plot design with each four main and sub plot treatments. The main plot treatments comprised of four crop geometries while thesub plot treatments were nipping practices which includes no nipping, mechanical nipping and chemical nipping. Result: Various crop geometries shown remarkable effect on growth and development of pigeonpea. The crop geometry of 90 cm ´ 30 cm and 90 cm ´ 45 cm recorded maximum plant height of pigeonpea as compared to other wider crop geometries. While in case of all the other growth attributes viz. number of functional leaves per plant, leaf area, number of branches per plant and dry matter accumulation per plant crop geometry of 120 cm ´ 45 cm and 120 cm ´ 30 cm were found superior as compared to othertreatments and were at par with each other. The yield per hectare was increased at wider crop geometry 120 cm 45 cm as the higher per plant yield was compensated by lesser plant population. The crop geometry 120 cm ´ 45 cm produced significantly higher seed yield (1187, 1275 and 1231 kg ha-1 during 2021, 2022 and pooled mean respectively) over crop geometry of 90 cm ´ 30 cm and crop geometry 90 cm ´ 45 cm, but it was found at par with crop geometry 120 cm ´ 30 cm. Among the nipping practices, growth characters viz., plant height, number of functional leaves, leaf area, number of branches and dry matter accumulation per plant as well as phenological characters were enhanced with the foliar application of chlormequat chloride @500 ppm during both the years of study. Foliar application of chlormequat chloride @ 500 ppm also recorded significantly highest seed yield (1152, 1237and 1195 kg ha-1 during 2021, 2022 and in pooled data, respectively), while it was at par with foliar application of mepiquat chloride @ 500 ppm.

Effect of Mepiquat Chloride and Nitrogen levels on yield and economics of Bt (Bacillus thuringiensis) cotton

A field experiment was conducted in Bt cotton during the kharif season 2018 at the National Seed Production Area of Choudhary Charan Singh Haryana Agricultural University, Hisar. As cotton has indeterminate growth habit, so to control plant height and encourages the translocation of photosynthesis towards reproductive sinks (growing cotton bolls), which lead to higher yields this experiment was conducted in factorial R.B.D with three replications comprising three levels of Nitrogen (N1: 100% RDF, N2: 125%RDF, N3: 150%RDF) and three different doses of growth retardant (G1: Control, G2: Mepiquat chloride application 20g a.i./ha. at 60 DAS, G3: Mepiquat chloride application 20g a.i./ha at 60 DAS and 75 DAS). The results indicated that several bolls/m2, boll weight (g), and seed cotton yield (kg/ha) was higher at 150% and 125% RDF than 100% RDF. However, seed index is significantly high with 100% RDF. A number of bolls/m2, boll weight (g) and seed cotton yield (kg/ha) was significantly higher with twice the spray of mepiquat chloride at 60 and 75 DAS compared to the control. Similarly highest gross and net return was recorded with 150% RDF level of nitrogen followed by 125% RDF and 100% RDF. Among spraying of mepiquat chloride higher gross returns and net returns was recorded with two sprays of mepiquat chloride (Rs.1,87,138/ha& 95,850/ha) followed by single spray (Rs 1,82,457/ha & Rs 92,473/ha) and control (Rs 1,66,902/ha &Rs 88,364/ha).

Influence of plant growth retardants on morpho-physiological parameters and yield of pigeonpea (Cajanus cajan L. Millsp)

The field experiment was conducted at Agricultural Research Station, Bheemarayanagudi, during Kharif 2021- 22 to know the influence of plant growth retardants on morpho-physiological and yield parameters in pigeonpea. The experiment was laid out in randomized complete block design and replicated three times with eight treatments including control, nipping at 60 DAS, mepiquat chloride @ 1000 ppm, thiourea @ 1000 ppm, chlormequat chloride @ 1000 ppm, daminozide @ 1250 ppm, ancymidol @ 1000 ppm and paclobutrazol @ 150 ppm were applied through foliar application at 60 DAS. Results revealed that nipping and all growth retardant treatments significantly reduced the plant height (cm) and increased total number of branches, total dry matter production, total leaf area, leaf area index and seed yield compared to control. Among the treatments, foliar application of mepiquat chloride @ 1000 ppm was recorded significantly lower plant height (153.72 cm) and higher total number of branches (37.85 plant-1), total dry matter production (149.12 g plant-1), total leaf area (85.83 dm2 plant-1), leaf area index (2.384) and seed yield (1970 kg ha-1) as compared to all other treatments. The treatment T5 (chlormequat chloride @ 1000 ppm) was recorded second best morpho-physiological parameters and yield in pigeonpea. The results concluded that foliar application of mepiquat chloride @ 1000 ppm at 60 DAS was found best in recording better growth parameters and higher yield in pigeonpea.

High dosage of mepiquat chloride delays defoliation of harvest aids in cotton

The plant growth regulator mepiquat chloride (MC) has been widely used to regulate cotton growth and development worldwide. However, little is known about whether MC application during cotton growing season affects defoliation efficiency of the harvest aids (TE), a novel product with the mixture of 10% thidiazuron and 40% ethephon. Here, a 3-year (2018–2020) field experiment was carried out in Hejian, Hebei province, China, involving six treatments as three different MC rates (MC free, farmers’ practice-conventional amount, high MC amount) and two defoliant rates (0 ml ha−1 [CK] and 2250 ml ha−1 [TE]). High MC rate delayed cotton leaf abscission and decreased the defoliation percentage at 7 days after TE treatment, but hardly affected harvest aids efficacy at harvest time. The delay of leaf abscission was due to an increase in auxin and cytokinin concentration of cotton leaves in MC treatment. The MC treatment accelerated the natural maturation of cotton, achieving a higher boll-opening percentage before defoliant spraying, and increased cotton lint yield. Over the 3-year period, compared to CK, the defoliant application TE increased the defoliation percentage by 43.4%, the boll-opening percentage by 10.4%, and the cotton lint yield by 9.1% due to an increase in opened boll number per unit land area. We concluded that the optimal MC dose (about 200 g ha−1) would decrease the risk of reducing defoliation and achieve higher cotton lint yield.

Effect of Seed Fungicide Treatment, Microelement Fertilizer and Mepiquat Chloride Applications on Yield and Yield Components of Peanut

Seed treatment against soil pests and soil-borne pathogenic fungi, foliar application of microelement and mepiquat chloride at flowering and after flowering periods promise to increase peanut (Arachis hypogaea L.) yield. A two-year field study was conducted to test this hypothesis by seed fungicide and insecticide treatment, foliar micronutrient and mepiquat chloride (Pix) applications at different combinations and different growth stages of peanut in the eastern Mediterranean region. The treatments were different combinations of Vitavax (200 g/L Carboxin + 200 g/L Thiram) 400 g/L 100 kg seed, Gaucho (600 g/L Imidacloprid) 800 g/L 100 kg seed, Fertilon Combi (Fe, Zn, B, Mn, Cu, Mn and Mo) 1000 g /ha and Pix (150 cc /ha mepiquat chloride). Peanut seeds were treated with fungicide and insecticide before planting. Microelement fertilizer and Pix combinations were applied at the beginning of flowering, after flowering and at the beginning of flowering + after flowering. The best results for seed kernel ratio, 100 seed weight and pod yield were obtained from Pix + Fertilon Combin treatment after flowering. This treatment was followed by Goucho + Vitavax seed treatment before planting + Pix application after flowering. In this study, it was observed that Goucho + Vitavax seed treatment and Pix, Fertilon Combi and Pix + Fertilon Combi applications at flowering, after flowering and at flowering + after flowering applications generally contributed pod yield increases.

Mechanism of Mepiquat Chloride Regulating Soybean Response to Drought Stress Revealed by Proteomics.

Soybeans are the main sources of oil and protein for most of the global population. As the population grows, so does the demand for soybeans. However, drought is a major factor that limits soybean production. Regulating soybean response to drought stress using mepiquat chloride (MC) is a feasible method; however, its mechanism is still unclear. This study used PEG-6000 to simulate drought stress and quantitative proteomic techniques to reveal changes in Heinong44 (HN44) and Heinong65 (HN65) subjected to drought following the application of 100 mg/L of MC. The results showed that SOD in HN44 did not change significantly but decreased by 22.61% in HN65 after MC pretreatment, and MDA content decreased by 22.75% and 21.54% in HN44 and HN65, respectively. Furthermore, MC improved the GSH-ASA cycle and simultaneously promoted the Calvin cycle process to enable the plant to maintain a certain carbon assimilation rate under osmotic stress. In addition, MC upregulated some proteins during gluconeogenesis and starch metabolism and increased soluble sugar content by 8.41% in HN44. MC also reduced ribosomal protein abundance, affecting translation and amino acid metabolism. In summary, MC improved GSH-ASA cycle and Calvin cycle under stress to alleviate oxidative damage and maintain crop growth. Our study is the first to report the mechanism of MC regulation in soybean under osmotic stress, providing new insights for the rational application of MC in soybean.

Regulation of soybean drought response by mepiquat chloride pretreatment.

Soybean is the world's most important cultivated crop, and drought can affect their growth and, eventually, yields. Foliar application of mepiquat chloride (MC) can potentially alleviate the damage caused by drought stress in plants; however, the mechanism of MC regulation of soybean drought response has not been studied. This study investigated the mechanism of soybean drought response regulation by mepiquat chloride in two varieties of soybean, sensitive Heinong 65 (HN65) and drought-tolerant Heinong44 (HN44), under three treatment scenarios, normal, drought stress, and drought stress + MC conditions. MC promoted dry matter accumulation under drought stress, reduced plant height, decreased antioxidant enzyme activity, and significantly decreased malondialdehyde content. The light capture processes, photosystems I and II, were inhibited; however, accumulation and upregulation of several amino acids and flavonoids by MC was observed. Multi-omics joint analysis indicated 2-oxocarboxylic acid metabolism and isoflavone biosynthetic pathways to be the core pathways by which MC regulated soybean drought response. Candidate genes such as LOC100816177, SOMT-2, LOC100784120, LOC100797504, LOC100794610, and LOC100819853 were identified to be crucial for the drought resistance of soybeans. Finally, a model was constructed to systematically describe the regulatory mechanism of MC application in soybean under drought stress. This study fills the research gap of MC in the field of soybean resistance.

Investigating the rain‐free period of mepiquat chloride as affected by surfactant, rate, and interval between application and simulated rainfall

AbstractSporadic and unpredictable rain events can reduce agrichemical efficacy if a sufficient rain‐free period is not reached following application. Mepiquat chloride (MC) is used to regulate vegetative growth in cotton (Gossypium spp.), and the rain‐free period, according to the label, is 8 h or reduced to 4 h when applied with a surfactant. Experiments were conducted in 2021–2022 to evaluate the effect of MC treatment and dry time between application and a simulated rainfall event on cotton growth following application. The MC treatments were applied during the second week of squaring and were washed from the surface of the leaves 0, 2, 4, and 8 h after application using a center pivot irrigation system that delivered 0.4–0.6 inches of simulated rainfall. All MC treatments, averaged across dry time, slowed cotton growth regardless of surfactant or rate applied. Dry time demonstrated similar results, with dry times ≥2 h slowing growth. However, when cotton growth over time was evaluated, it was determined that in situations where cotton growth is more aggressive, reapplication of MC was necessary sooner where the initial application was removed from the surface of the leaf 0–2 h after application compared to 4–8 h after application. Adding a surfactant to MC applications did not reduce the rain‐free period, and when at least 4 h of dry time was achieved, MC applications were just as effective as an 8 h dry time, even when cotton growth was aggressive.

Mepiquat chloride application combined with high plant population density promotes carbon remobilization in the roots of upland cotton

Carbon reserves in cotton roots can be remobilized to support reproductive growth, thus potentially affecting cotton yield. However, the regulation of carbon remobilization in cotton roots and its relationship with cotton yield are still poorly understood. Plant population density (PPD) and mepiquat chloride (MC) have been hypothesized to affect the dynamics of nonstructural carbohydrate content and the resulting carbon remobilization in cotton roots through the regulation of carbohydrate metabolism enzyme activities. A mid-maturation cotton line 4003–6 was field-grown in 2019 and 2020. Three different levels of PPD (D1: 2.25 plants m−2, D2: 4.5 plants m−2, and D3: 6.75 plants m−2) and two levels of MC dosage (M0: 0 g hm−2, M1: 82.5 g hm−2) were combined to create six populations differing in terms of the source–sink relationship. The changes in the hexose, sucrose, and starch contents and the key carbon metabolic enzyme activities in cotton roots were examined during peak squaring (PS) to late boll opening (LB). The combination of the PPD of 6.75 plants m−2 and MC application (M1D3) exhibited the greatest cotton yield and reproductive biomass–to–leaf area ratio from peak flowering (PF) onwards. M1D3 presented the greatest total nonstructural carbohydrate (TNC) remobilization amount of 2.96 and 3.80 g m−2, the highest efficiency of 39.11% and 48.39%, and the largest gross contribution to seed cotton yield of 0.66% and 0.79% in 2019 and 2020, respectively. The three parameters were positively correlated with the seed cotton yield except for the remobilization rate in 2019. Unlike the other treatments, the greater carbohydrate content per unit ground area in M1D3 prior to the PF stage was attributed to the higher sucrose phosphate synthase (SPS) and ADP-glucose pyrophosphorylase (AGPase) activities during the PS to first flowering (FF) stages. Conversely, the greater α-amylase and β-amylase activities in M1D3 at the PF stage accounted for the lower starch content at the EB stage, and the smaller vacuolar invertase (VIN) and cell wall invertase (CWIN) activities at the EB stage could be responsible for the lower hexose concentration at that time. The TNC remobilization amount had a positive association with the AGPase and SPS activities at the FF stage and with β-amylase activity at the PF stage in cotton tap roots in 2019 and 2020. This study provides a cotton yield-improving alternative through the promotion of carbon remobilization in roots using certain agronomic practices.

Efficacy of growth retardants on physiology and yield of pearl millet under rainfed condition

A field experiment was conducted during kharif 2015-17 to study the efficacy of growth retardants on physiology and yield of pearl millet at Durgapura (Jaipur). Growth retardants, viz. cycocel and mepiquat chloride were sprayed @ 250, 500 and 750 ppm at tillering (40 DAS) and flowering (60 DAS) stages. The experiment was laid out in randomized block design with 4 replications. Results showed that plant height decreased, whereas chlorophyll content and relative water content increased significantly with the foliar application of mepiquat chloride @ 500 ppm over rest of the treatments. A significantly higher specific leaf weight was noted under cycocel @ 750 ppm over control. Foliar application of mepiquat chloride @ 500 ppm produced significantly higher grain yield over control. However, it was statistically at par with cycocel @ 500 ppm and mepiquat chloride @ 750 ppm. On the other hand, significantly higher fodder yield was registered with the foliar spray of cycocel @ 250 ppm over cycocel @ 500 ppm, cycocel @ 750 ppm, mepiquat chloride @ 250 ppm and 750 ppm that was at par with the control and mepiquat chloride @ 500 ppm. Maximum net returns and benefit cost ratio were accrued under mepiquat chloride @ 500 ppm. Thus, foliar application of mepiquat chloride @ 500 ppm at 40 and 60 DAS could be recommended for obtaining higher grain yield and net returns from pearl millet under rainfed condition of Rajasthan.

Cultivar, irrigation management, and mepiquat chloride strategy: Effects on cotton growth, maturity, yield, and fiber quality

Drought negatively affects cotton growth and yield, whereas excessive irrigation can limit yield through excessive vegetative growth and poor fruit retention. Mepiquat chloride (MC) application limits plant height, improves fruit retention and hastens maturity in responsive cultivars. Thus, the objective of this study was to address the effects of cultivar, irrigation, and MC strategy on cotton growth, maturity, yield, and fiber quality. Therefore, a field study was carried out using three cultivars, three different irrigation treatments, and three different MC treatments during the 2020 and 2021 growing seasons. In both years there was an interaction between irrigation and MC management for plant height. In 2020, MC treatments hastened cutout by two to three weeks in irrigated plots but did not affect cutout date in dryland plots. 2020 and 2021 differed substantially in rainfall (347 mm and 735 mm, respectively from planting to harvest). 2020 was a dry year in which yield responded positively to irrigation and 2021 was a wet year in which yield responded negatively to irrigation. There was no effect of MC treatments or interaction between MC and any other effect on lint yield. Fiber length was reduced, whereas strength and micronaire were increased by drought stress in 2020. Increased fiber length, strength, uniformity, and micronaire were observed by MC application in both years. Therefore, we can conclude that aggressive MC management reduces vegetative growth, promotes earlier physiological maturity under well-watered conditions, and affects fiber quality, but does not necessarily interact with irrigation management to affect lint yield. • Growth and maturity responses to mepiquat chloride depend on water availability. • Mepiquat chloride hastens maturity under water replete conditions, but not dryland. • Occasionally, fiber quality was positively impacted by mepiquat chloride application. • Mepiquat chloride did not alter cotton yield response to water excess or drought.

Impact of Growth Retardant and Defoliant on Morpho-physiological Traits and Yield Improvement in Cotton

In cotton, mechanized harvesting has gained popularity in recent years due to labor-intensive process and shortage of labor. Moreover, mechanized harvesting of cotton depends on plant morphological characters like plant height, internodal length and synchronized boll maturity and opening etc. Mechanized harvesting enhancing the harvesting efficiency of cotton which is achieved by the use of some chemicals to attain good lint yield and fibre quality. With this background, the field experiment was conducted to study the impact of growth retardant and defoliant on morpho-physiological traits and yield improvement in cotton (CO 17) during 2021-2022 by following randomized block design with four treatments and five replications. The current study revealed that spraying of 0.015% mepiquat chloride (MC) at square formation and boll development stage significantly reduced the leaf area, plant height, total dry weight and boll number when compared to control. However, chlorophyll content and normalized difference vegetation index (NDVI) were recorded higher in 0.015% mepiquat chloride (MC) applied treatments than control. Moreover, spraying of mepiquat chloride (0.015%) at square formation and boll development stage followed by spraying of 0.9% sodium chlorate (SC) at 60% boll bursting stage significantly increased the seed cotton yield compared to other treatments and recorded maximum seed cotton yield of 25.22% compared to control. Results clearly indicate that application of MC followed by SC could be a better practice for canopy management in cotton, resulting in improved efficiency of mechanical harvesting and good lint yield and fibre quality.

Chemical topping improves the efficiency of spraying harvest aids using unmanned aerial vehicles in high-density cotton

The cotton defoliation strategy is highly appreciated in Xinjiang, where mechanical harvesting is limited by a large proportion of green leaves and unopened bolls at harvest due to an insufficient temperature sum. Because of a high plant density, the application of defoliants (harvest aids) by tractors is less efficient; thus, unmanned aerial vehicles (UAVs) for spraying harvest aids are becoming more and more popular. However, it is unknown if this method affects spraying quality and whether the spray is affected by the cotton plant type that was shaped by chemical topping. This study aims to address if chemical topping could enhance defoliation when harvest aids is sprayed using UAV. Field experiments were carried out in 2019 and 2020 in Alaer, Xinjiang, China. The topping treatments included manual topping (MT) as the control and chemical topping (CT) that inhibit apical growth of the stem by foliar application of mepiquat chloride (MC) at 90 (MC90), 180 (MC180), or 270 (MC270) g ha –1 in mid-July. The harvest aids was sprayed in mid-September using UAVs. The average droplet deposition and deposits of harvest aids within the canopy in CT and MT were not different in 2019. However, the average droplet deposition and deposits of CT were much higher than those of MT in 2020. Both droplet deposition and deposits decreased with canopy height, and the droplet distribution performance of CT was better than that of MT. The droplet deposition and deposits in the upper and middle canopy of CT were significantly higher than those of MT in 2020. At 21 days after harvest aids application, the number of leaves per plant in CT was significantly lower than that in MT, while there was no difference between the amounts of MC. CT did not affect boll opening. Moreover, the yield and quality were not affected by harvest aids application using UAVs and CT. We concluded that spraying harvest aids using UAVs combined with CT improved management efficiency and economic benefits by saving labor, without loss of cotton yield and quality. Our results demonstrate that applying harvest aids using UAVs in cotton with CT could improve the quality of defoliation and provide a reference for optimizing cotton managements globally.

Foliar application of mepiquat chloride and nitrogen improves yield and fiber quality traits of cotton (Gossypium hirsutum L.).

Cotton (Gossypium hirsutum L.) is one of the most important cash crops primarily grown for fiber. It is a perennial crop with indeterminate growth pattern. Nitrogen (N) is extremely important for vegetative growth as balanced N-nutrition improves photosynthesis, resulting in better vegetative growth. Excessive N-supply results in more vegetative growth, which increases the incidence of insect pest and diseases’ infestation, pollute surface and ground water, delays maturity and produces low crop yield with poor quality. The use of plant growth regulators (PGRs) is an emerging option to control excessive vegetative growth. The PGRs help in improving plant architecture, boll retention, boll opening, yield and quality by altering growth and physiological processes such as photosynthesis, assimilate partitioning and nutrients dynamic inside the plant body. Mepiquat chloride (1,1-dimethylpiperidinum chloride) is globally used PGR for canopy development and control of excessive vegetative growth in cotton. This study investigated the effect of mepiquat chloride (MC) and N application on yield and yield components of transgenic cotton variety ‘BT-FSH-326’. Two N rates (0, 198 kg ha-1) and five MC rates (0, 30,60, 90 and 120 g ha-1) were included in the study. Results revealed that MC and N application improved boll weight, number of bolls per plant, and seed cotton and lint yields. The highest seed cotton and lint yields (3595 kg ha-1 and 1701 kg ha-1, respectively) were observed under foliar application of 198 kg ha-1 N and 120 g ha-1 MC. Fiber length, fiber strength, micronaire and uniformity were significantly improved with foliar application of MC and N. In conclusion, foliar application of MC and N could be helpful in improving yield and fiber quality of cotton.

Effect of Mepiquat Chloride on Phenology, Yield and Quality of Cotton as a Function of Application Time Using Different Sowing Techniques

Mepiquat chloride (MC) is a plant growth regulator used to manage the rampant vegetative growth of cotton. A two-year field experiment was conducted at the Postgraduate Agricultural Research Station, University of Agriculture, Faisalabad, Pakistan, during 2017 and 2018 to investigate the influence of MC applied at different times on phenology, morphology, lint yield and quality of cotton cultivated using different sowing techniques. MC was applied 50 days after sowing (DAS), 60 DAS and 70 DAS to cotton planted in flat fields (flat sowing), ridges (ridge sowing) and beds (bed sowing). The interactive effect of MC application time and sowing technique did not influence crop phenology, morphology, and lint yield and quality. It was revealed that the crop planted on beds took fewer days to flower (10%) as compared to that on the flat field, and the bed-sown crop produced a higher number of opened bolls (60%) and was characterized by a higher boll weight (32%) and seed cotton yield (50%) in comparison to the flat-sown crop. A late application of MC (at 70 DAS) caused a significant reduction in the time to flowering (8%), with a simultaneous increase in the number of opened bolls (60%), boll weight (32%), ginning out turn (8%) and lint yield (27%) as compared to MC application at 50 DAS. In terms of lint quality, cotton planted on beds had better fiber uniformity (8%) compared to that on the flat field, while MC applied at 70 DAS produced better fiber fineness by 27% in comparison to MC applied earlier. Overall, cotton planting on beds and MC application at 70 DAS may help improve cotton yield and fiber quality and may help in the mechanical picking of cotton.

Transcriptome Profiling Provides New Insights into the Molecular Mechanism Underlying the Sensitivity of Cotton Varieties to Mepiquat Chloride.

Mepiquat chloride (MC) is a plant growth regulator widely used in cotton production to control vegetative overgrowth of cotton plants to achieve ideal plant architecture required for high yielding. Cotton varieties respond differently to MC application, but there is little information about the molecular mechanisms underlying the varietal difference. In this study, comparative transcriptome analysis was conducted by using two Upland cotton varieties with different sensitivity (XLZ74, insensitive; SD1068, sensitive) to MC treatment, aiming to understand the molecular mechanisms responsible for varietal difference of MC sensitivity. RNA-seq data were generated from the two varieties treated with MC or water at three time points, 1, 3 and 6 days post-spray (dps). Genes differentially expressed between the MC and mock treatments of XLZ74 (6252) and SD1068 (6163) were subjected to Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses to compare the enriched GO terms and KEGG pathways between the two varieties. Signal transduction of phytohormones, biosynthesis of gibberellins (GAs) and brassinosteroids (BRs) and profiles of transcription factors (TFs) seemed to be differentially affected by MC in the two varieties. The transcriptomic results were further consolidated with the content changes of phytohormones in young stem. Several GA catabolic genes, GA2ox, were highly induced by MC in both varieties especially in SD1068, consistent with a more significant decrease in GA4 in SD1068. Several AUX/IAA and SAUR genes and CKX genes were induced by MC in both varieties, but with a more profound effect observed in SD1068 that showed a significant reduction in indole-3-acetic acid (IAA) and a significant increase in cytokinin (CTK) at 6 days post-spray (dps). BR biosynthesis-related genes were downregulated in SD1068, but not in XLZ74. Additionally, more downregulated TFs were observed in MC-treated SD1068 than in MC-treated XLZ74, and the two varieties had very different profiles of genes involved in starch and sucrose metabolism, with those of SD1068 and XLZ74 being downregulated and upregulated by MC treatment, respectively. Together, these results indicate that although the same or similar biological pathways are affected by MC treatment in cotton varieties showing different MC sensitivity, the extent of effect is variable, leading to their different phenotypic outcomes. How the quantitative effect of MC on the biological processes associated with growth retardation is regulated is still an open question.