مجله پژوهش های پنبه ایران
سال یازدهم شماره 2 (پیاپی 22، پاییز و زمستان 1402)

Cotton is a critical crop in Golestan Province, yet there is a notable discrepancy between actual and attainable yields, largely due to suboptimal agricultural management practices. In each region, specific factors contribute more significantly to the yield gap, influenced by local resources and farmer experience. Identifying these factors and their contributions can guide targeted improvements in agricultural management. This study aims to identify the yield-limiting factors for cotton and estimate the yield gap in Kordkuy County. 

This study assessed 57 cotton farms in Kordkuy County during 2020. Data on agricultural management practices—including seedbed preparation, cultivar choice, seed source, planting timing, weed control, pesticide application, and seed consumption—were collected through field visits and farmer interviews. Actual yields were recorded. The Comparative Performance Analysis (CPA) method was employed to determine the contribution of each factor to the yield gap. Data were analyzed using SAS software, with quantitative variables examined through linear regression and qualitative variables assessed via a completely randomized design. Mean comparisons were performed using the Least Significant Difference (LSD) test at the 5% significance level. 

The study revealed a substantial yield gap of 56.7% in Kordkuy cotton farms. Key factors affecting yield were identified as pest issues (49%), seed disinfection (31%), pre-planting irrigation (10.2%), weed presence (6.7%), and planting method (2.9%). Addressing these issues—by controlling pests, performing seed disinfection and pre-planting irrigation, mechanizing planting, and managing weeds—could potentially increase yields from 2,192 kg/ha to 5,061 kg/ha. Without optimal management, the yield gap remains at 2,869 kg/ha.

The findings highlight that optimizing management practices related to plant density, intra-row spacing, planting dates, mechanized planting, seed disinfection, pre-planting irrigation, pest control, and weed management can significantly boost cotton yields. These insights are valuable for the Agricultural Jihad Organization and extension workers aiming to enhance cotton production.

Ethylene is a plant hormone with specific gaseous form that plays key role in many growth and development processes. Biosynthesis and signaling pathway of ethylene has been well undertaken by a wide number of studies. In addition to its function as a plant growth regulator, ethylene is involved in phenomena such as pathogenesis and defense responses in plants. Also, ethylene exhibits antagonistic and synergistic effects on other defense hormones like salicylic acid, jasmonic acid and abscisic acid, regulating various defense responses through activating different transcription factors in its complicated signaling pathway. Dual function of ethylene in two completely different processes, pathogenesis and resistance, clearly shows this complexity. Investigation of spatial patterns of ethylene shows its local and systemic activity in the induction of plant defense genes. The cotton plant (Gossypium hirsutum L.) as an economically important crop, is attacked by a number of pests and plant pathogens that significantly reduce the quantity and quality of the cotton product. One of the most important pathogens is the soil fungus Verticillium dahliae, which causes verticillium wilt disease in cotton and is highly destructive pathogen. This pathogen causes symptoms such as wilting, chlorosis and necrosis in the cotton plants. In this paper, we attempted to review the results of previous studies on the interaction between ethylene and cotton diseases for illustrating a clearer picture of ethylene role in both pathogenesis and resistance processes against cotton pathogens. 

Ethylene plays a role in signaling during cotton-fungus V. dahliae interaction, and some components involved in ethylene signaling positively regulate cotton resistance to V. dahliae. On the other hand, in the cotton plants with defoliation symptoms induced by the fungus V. dahliae, the ethylene production is directly related to the severity of verticillium wilt in cotton. As a result, it seems that ethylene plays multiple and complex roles in regulating the immunity of cotton plant against V. dahliae fungus, which is involved in increasing the resistance and sensitivity of the cotton plants. Knowing more about the role of ethylene in cotton plants and identifying the positive and negative regulators of ethylene could be a promising option in order to generate disease resistance against plant pathogens.

Cotton is one of the valuable agricultural plants, which is known as white gold due to its economic, agricultural and commercial importance. This plant is very sensitive to environmental conditions, and factors such as variety, plant density, planting time, nutrition, water management methods and planting methods are effective on its performance; Therefore, it is possible to increase the yield with a proper combination of different methods of crop management, compliance with the appropriate planting date and method to achieve the potential of a variety. This research was conducted to determine the optimal planting date of new cotton cultivars and evaluate its effects on yield and yield components of cotton. 

This research was conducted in the two years of 2018 and 2019 at the Research and Training Station of Agriculture and Natural Resources of Kashmar as a split plot experiment in the form of a randomized complete block design with three replications. The main factor included planting date in three levels (10 May, 31 May, and 20 June) and the second factor included commercial cotton cultivars in four levels (Armaghan, Shayan, Khorshid, and Khordad). At the time of harvest, traits of boll weight, plant height, crown diameter, number of monopodial and sympodial branches, number of open and closed bolls, earliness and crop yield were measured and recorded. The yield was measured at the end of the season, after removing half a meter from the beginning and end of each plot by removing all plants from the two middle lines. Earliness was calculated from the ratio of the yield of the first harvest to the total yield multiplied by the number of hundred. Analysis of variance and mean comparison were performed using SAS software. 

The results showed that the highest number of closed bolls and the lowest boll weight, yield, plant height, number of monopodial and sympodial branches, and the number of open bolls were belonged to the last planting date (20 June). The delay in planting reduced the average yield of cotton by 24%. In 20 June, due to the non-opening of the bolls and exposure to the autumn cold, no yield was harvested and a 100% yield reduction was observed. The highest and lowest yield was related to Khorshid variety in 10 May and Shayan variety in 31 May, respectively. Khordad cultivar had the lowest yield reduction due to the delay in planting compared to the other cultivars, and Khorshid cultivar was ranked next. 

The results of the current study showed that the optimal planting date of the studied cultivars in Kashmir region is up to June 10, and further delay in the planting time causes a severe decrease in yield. However, the response of cultivars to the delay in planting was different, and Khordad and Khorshid cultivars, having the highest yield, showed a lower yield reduction than the other two cultivars.

Cotton is a vital industrial crop worldwide, recognized as a strategic commodity in many countries and particularly well-suited for cultivation in arid and semi-arid regions. Its significance stems from its potential to generate employment, its diverse applications—including fiber production, animal feed, and vegetable oil—and its compatibility with sustainable agricultural practices compared to other crops, such as corn. 

To evaluate key traits and identify the most suitable cotton cultivars for the Sistan region, a study was conducted involving 14 cotton cultivars. The experiment was designed as a randomized complete block design with three replications, carried out at the Zahak Agriculture and Natural Resources Research Station over two crop years (2021-2022 and 2022-2023). 

Analysis of the composite data revealed significant differences in several traits. Traits such as earliness, number of bolls per plant, boll weight, yield from the third row, and yield per hectare showed significant differences at the 1% probability level. Additionally, the number of sympodial branches, yield from the first row, and yield from the second row were significant at the 5% probability level. The cultivars exhibited distinct characteristics, with Latif (6,932 kg/ha), Khordad (6,880 kg/ha), Golestan (6,766 kg/ha), Khorshid (6,664 kg/ha), and Sepid (6,394 kg/ha) demonstrating the highest yields per hectare. In contrast, the Armaghan variety yielded the lowest at 3,408 kg/ha. Among the cultivars, Khorshid and Khordad had the shortest growth periods, while the white cultivars had the longest growth and ripening times. 

The Latif and Golestan cultivars showed more stable production compared to others, particularly under changing climate conditions in the second year of cultivation. Considering the impacts of climate change and environmental challenges such as increasing water and soil salinity, these cultivars offer better production sustainability. Additionally, Khorshid and Khordad cultivars, with their earlier maturation, are well-suited to the Sistan region's climatic conditions, including its 120-day winds. These cultivars not only have shorter growth periods but also rank among the highest in yield.

Diverse plant genetic materials are potential treasures that are considered valuable support for plant breeding programs, because the plant breeding research is based on wide genetic diversity, and basically, without diversity, breeding and selection will have no meaning. This study was conducted to evaluate the diversity of different cotton landraces and identify the traits affecting their yield. 

In this study, 44 landraces of cotton were cultivated in the agricultural research station of Kashmir during the two years of 2018 and 2019. The traits of the number of open and closed bolls, crown diameter, crop yield, boll weight, number of monopodial and sympodial branches, plant height, and crop maturity were measured. Descriptive statistics, trait × genotype (GT) biplot analysis, factor analysis, and cluster analysis were used to investigate the objectives of this research. Statistical analyzes were performed based on the average of two-year data. In analyzing of descriptive statistics, JUMP software was used, SPSS 21 software was used for factor analysis and cluster analysis, and GEA-R software was used for GT biplot analysis. 

Based on the average of two-year data, the range of boll weight and the number of closed bolls were high, which indicates the diversity of the investigated genotypes for the mentioned traits. Comparison between genotypes based on multiple traits made it possible to distinguish different genotypic groups. Cluster analysis of studied traits classified the genotypes into four main groups. The first group obtained from cluster analysis was earlier, but had the lowest average plant height, the number of monopodial and sympodial branches, the number of open bolls, and crown diameter. On the other hand, the second and third groups had the lowest amount of earliness. The genotypes of the second group had the lowest boll weight, the number of shoot branches, and the crown diameter, and the third group had the highest plant height, the number of branches, and the number of open bolls. The genotypes of the forth group had the highest earliness and the number of closed bolls. In order to increase earliness and reduced the plant height, the selection of genotypes from the first group for breeding programs can be helpful in obtaining cultivars with greater tolerance to environmental stresses, including drought. It is also possible to use the genotypes of the third group with the highest number of open bolls to cross with the genotypes of the first group in order to create quality and early cultivars. 

 There was considerable genetic diversity among the studied landraces in terms of most of the evaluated traits, indicating high potential for improving these traits through targeted selection in the breeding programs. The boll weight was the most important factor affecting the yield of cotton, and the fiber component had a greater effect on the boll weight of some studied genotypes than the seed component.

Cotton plant yield is influenced by numerous factors throughout its growth period. Notably, critical growth stages, including the onset of budding, flowering, and boll formation, are particularly vulnerable to adverse environmental conditions such as drought, poor soil and air quality (low relative humidity), and extreme temperatures. Effective agricultural management strategies, including the selection of appropriate cultivars, optimal planting dates, and plant density, are essential for mitigating the impact of heat stress on the loss of fruiting structures and enhancing crop yield. This study aims to investigate the effects of various cultivars, planting dates, and plant densities on yield and its components.

To evaluate yield and its components in novel cotton cultivars, a split factorial experiment was conducted using a randomised complete block design with four replications at the Hashemabad Cotton Research Station over a two-year period commencing in 2018. The primary factor examined was planting date: (1) early season planting in May and (2) post-wheat planting. The secondary factor, structured factorially, comprised four cultivars: Hikmat, Latif, Shayan, and the SNK847 genotype, alongside three inter-plant distances of 10, 20, and 30 cm. Cultivation was conducted with an 80 cm row spacing and a seed rate of 40 kg per hectare. Thinning was performed one week after emergence in accordance with the specified inter-plant spacing treatments.

The interaction between planting date, cultivar, and inter-plant spacing significantly influenced both mean and total yield. The SNK847 genotype exhibited superior yield performance on both planting dates, achieving 2601 kg/ha and 1734 kg/ha for the first and second planting dates, respectively, thereby outperforming other treatments. Higher plant density per unit area was found to offset the slower growth observed in the early season, enabling the plant canopy to reach optimal levels. This facilitated maximum solar radiation absorption, enhanced assimilate production, and improved reproductive organ development, resulting in a significantly higher yield of 2011 kg/ha with a 10 cm inter-plant spacing compared to other treatments.

The SNK847 genotype and a 10 cm inter-plant spacing are recommended for both planting dates based on these findings.

Understanding inheritance patterns, gene action types, and effective breeding strategies is crucial for improving agricultural traits. Generation mean analysis is a powerful method for assessing genetic parameters and heritability of traits. This study was designed to investigate the genetic parameters involved in the inheritance of morphological traits and yield components in four cotton cultivars through generation mean analysis. 

To analyse the genetic inheritance of traits, P1, P2, F1, F2, BC1, and BC2 generations were produced in 2020-2021. These generations were evaluated in 2022 using a randomized complete block design with three replications across three regions. After performing analysis of variance and identifying significant differences among generations, genetic analysis was conducted using the Method of Jinks and Hayman with three- and six-parameter models. The means and standard errors for each trait were calculated across the different generations. 

The variance analysis revealed significant differences among regions and cultivars. At Hashemabad, the Armaghan variety yielded the highest, whereas at Karkandeh and Darab, the Golestan variety was superior. No significant differences were found among generations in terms of plant height, number and length of reproductive branches, and number of bolls. However, significant variations were observed for boll weight, lint percentage, yield, and earliness. The lowest boll weight, lint percentage, and yield were associated with the green seed parent (P1). The F2 progeny exhibited the highest yield, averaging 2899 g/plot, which may be attributed to its genetic diversity. Additionally, performance differences between the green seed parent and the white seed parent were evident. 

The superior performance of progenies relative to their parents suggests the presence of a dominance effect in controlling these traits. For boll weight and number of reproductive branches, both additive and dominance × additive effects are significant. The prominence of the additive effect indicates that selection and self-pollination are effective breeding methods for these traits. In contrast, traits such as lint percentage were more influenced by dominance × dominance interactions, indicating potential double epistasis effects. The dominance variance exceeded the additive variance, and the degree of dominance was greater than one, suggesting that selection alone may be inadequate. Therefore, hybridisation may be a more effective approach for achieving breeding objectives for these traits.

Hormesis refers to the beneficial response to exposure to low levels of chemicals under otherwise adverse conditions. Certain herbicides can stimulate growth at reduced concentrations, making them promising agents for inducing hormesis. However, research on herbicide-induced stimulatory effects on germination indices is limited. This study aims to evaluate the impact of different glyphosate concentrations on the germination and seedling characteristics of cotton. 

To assess the effect of glyphosate on cotton germination and seedling development, two experiments were conducted in 2024. These experiments explored the hormetic effects of glyphosate by incorporating it into the growth medium and by seed priming with various glyphosate concentrations. Both experiments were designed as randomised complete block designs with three replications. Glyphosate was applied at six concentrations: 10, 20, 40, 80, 160, and 320 ppm, alongside a control. The traits measured included seedling length, fresh and dry weight, germination percentage, seed germination index, phytotoxicity percentage, tolerance index, and germination speed. 

The results indicated that the 10 ppm glyphosate treatment elicited hormetic effects on several traits. In the growth medium experiment, this treatment increased seedling length by 83% compared to the control. Similarly, in the seed priming experiment, seedling length was enhanced by 164% with the same concentration. The 10 ppm treatment also resulted in a 60% increase in fresh weight and a 120% increase in dry weight in the growth medium experiment, while in the seed priming experiment, fresh weight increased by 250% and dry weight by 315% compared to the control. Additionally, the 10 ppm treatment improved seed germination by 77% in the growth medium test and by approximately 89% in the seed priming test. Conversely, the 40 and 320 ppm treatments were associated with the most pronounced inhibitory effects on seedling length, fresh weight, dry weight, and germination in both experiments. 

The 10 ppm glyphosate treatment demonstrated the most favourable impact on the studied traits. These findings suggest that non-toxic concentrations of glyphosate can enhance seedling establishment and improve competitive ability against weeds through hormesis.