Development Of Cotton Plants Research Articles

Effect of cotton seed size and seeding density on cotton growth, development, and yield

AbstractInterest in cotton seed size and seeding density exists due to increased seeding cost and overall decreased seed size of cotton varieties. An experiment was conducted in 2019 and 2020 in Jackson, TN, Starkville, MS, and Brooksville, MS, to determine the impact of seed size, seeding density, and variety on cotton plant development and yield. Early‐season seedling vigor was impacted by seeding density and seed size. Larger seeds and higher seeding densities produced the greatest seedling vigor. Fresh weight biomass was also impacted by seed size, as larger seed produced greater fresh and dry cotton plant biomass when pooled over seeding density and variety. The greatest seed cotton yields were obtained from planting larger seed, higher seeding densities, and from ‘DP 1646 B2XF’. Cotton variety and seeding density influenced financial returns and fiber quality. ‘NexGen 3406 B2XF’ planted at 148,200 seeds ha−1 resulted in the lowest micronaire. Net returns were not influenced by seed size or seeding density; therefore, depending on seed costs, increasing seeding densities may not be beneficial.

Transcriptomic profiling reveals salt-responsive long non-coding RNAs and their putative target genes for improving salt tolerance in upland cotton (Gossypium hirsutum)

Salt stress continues to exert notable impacts on the growth and development of cotton plants. In various biological processes of plants and in response to abiotic stress, long noncoding RNAs (lncRNAs) play a crucial regulatory role. In this study, we conducted transcriptome sequencing of cotton plants grown under salt stress and normal water conditions. A total of 519 lncRNAs and 75,376 messenger RNAs (mRNAs) were identified. Compared with mRNAs, lncRNAs have shorter transcript lengths and open reading frames, fewer exons, and lower expression levels. By comparing and analyzing the differentially expressed lncRNAs (DELs) and differentially expressed coding genes (DEGs) after salt treatment, we identified a total of 60 DELs and 217 DEGs. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses revealed that these target genes are enriched primarily in intracellular organelles and participate in metabolic regulation pathways. Ultimately, lncRNA XLOC_043671, along with its target gene Gohir.D02G125200, and the lncRNA XLOC_034831, along with its target gene Gohir.A12G114800 was identified as a participant in salt tolerance regulation in cotton. RNA-seq and RTqPCR revealed that both these lncRNAs and their target genes exhibited significantly enhanced expression under salt stress. Subsequently, utilizing virus-induced gene silencing (VIGS) technology, we successfully silenced the two lncRNAs in cotton plants, which resulted in reduced expression levels of the corresponding target genes, rendering the plants less salt tolerant than did the control plants. Similarly, we successfully silenced these two target genes in cotton seedlings, and the silenced plants demonstrated a pronounced salt-sensitive phenotype. In summary, our transcriptome analysis revealed a significant number of differentially expressed lncRNAs and their corresponding coding genes. These findings lay the foundation for further investigating the mechanisms of lncRNAs and their target genes in the salt stress response of cotton.

Zinc Oxide Nanoparticles and Zinc Sulfate Alleviate Boron Toxicity in Cotton (Gossypium hirsutum L.).

Boron toxicity significantly hinders the growth and development of cotton plants, therefore affecting the yield and quality of this important cash crop worldwide. Limited studies have explored the efficacy of ZnSO4 (zinc sulfate) and ZnO nanoparticles (NPs) in alleviating boron toxicity. Nanoparticles have emerged as a novel strategy to reduce abiotic stress directly. The precise mechanism underlying the alleviation of boron toxicity by ZnO NPs in cotton remains unclear. In this study, ZnO NPs demonstrated superior potential for alleviating boron toxicity compared to ZnSO4 in hydroponically cultivated cotton seedlings. Under boron stress, plants supplemented with ZnO NPs exhibited significant increases in total fresh weight (75.97%), root fresh weight (39.64%), and leaf fresh weight (69.91%). ZnO NPs positively affected photosynthetic parameters and SPAD values. ZnO NPs substantially reduced H2O2 (hydrogen peroxide) by 27.87% and 32.26%, MDA (malondialdehyde) by 27.01% and 34.26%, and O2- (superoxide anion) by 41.64% and 48.70% after 24 and 72 h, respectively. The application of ZnO NPs increased the antioxidant activities of SOD (superoxide dismutase) by 82.09% and 76.52%, CAT (catalase) by 16.79% and 16.33%, and POD (peroxidase) by 23.77% and 21.66% after 24 and 72 h, respectively. ZnO NP and ZnSO4 application demonstrated remarkable efficiency in improving plant biomass, mineral nutrient content, and reducing boron levels in cotton seedlings under boron toxicity. A transcriptome analysis and corresponding verification revealed a significant up-regulation of genes encoding antioxidant enzymes, photosynthesis pathway, and ABC transporter genes with the application of ZnO NPs. These findings provide valuable insights for the mechanism of boron stress tolerance in cotton and provide a theoretical basis for applying ZnO NPs and ZnSO4 to reduce boron toxicity in cotton production.

Impact of Biochar on Fusarium Wilt of Cotton and the Dynamics of Soil Microbial Community

The effects of biochar on leaf and soil-borne diseases of plants can be seen in addition to its ability to sequester carbon, improve soil quality, and enhance plant performance. However, the mechanisms by which soil-borne pathogens are suppressed and plant performance is enhanced are not well understood. The present work aims to comprehensively establish the links between biochar-induced changes in the richness of the rhizosphere microbial population, in association with the reduction of soil-borne Fusarium wilt disease (Fusarium oxysporum f. sp. vasinfectum), in cotton (Gossypium hirsutum), with improved plant performance. Biochar made from organic waste significantly decreased the colonization and survival of Fusarium in soil, raised the culture-able counts of numerous microbes with biocontrol potential (microorganisms that boost plant growth and development), and inhibited Fusarium wilt of cotton. The biochar amendment significantly enhanced the cotton plant development and physiological parameters such as chlorophyll content, etc. Overall, 9% organic waste biochar had shown a significant impact on cotton growth as compared to other treatments with or without biochar. Compared to the soil-only control, the disease index was considerably reduced in all biochar-amended treatments. In terms of the plant’s resistance to Fusarium wilt, biochar-induced increases in the level of overall chlorophyll content and biochemicals such as phenolics, flavonoids, etc. Additionally, cotton plants grown with a 9% biochar composition had considerably greater NPK levels than other treatments with or without biochar. The biochar addition resulted in increased counts of Pseudomonas spp., Actinomycetes spp., and Trichoderma spp., while Acidobacteriales, Rhodospirillales, and Frankiales were less when compared with an un-amended (without biochar) soil control. Thus, the composition of rhizosphere bacteria in the treatments with and without modified biochar was found to differ significantly.

Genome-wide identification and expression analysis of terpene synthases in Gossypium species in response to gossypol biosynthesis.

Cottonseed is an invaluable resource, providing protein, oil, and abundant minerals that significantly contribute to the well-being and nutritional needs of both humans and livestock. However, cottonseed also contains a toxic substance called gossypol, a secondary metabolite in Gossypium species that plays an important role in cotton plant development and self-protection. Herein, genome-wide analysis and characterization of the terpene synthase (TPS) gene family identified 304 TPS genes in Gossypium. Bioinformatics analysis revealed that the gene family was grouped into six subgroups TPS-a, TPS-b, TPS-c, TPS-e, TPS-f, and TPS-g. Whole-genome, segmental, and tandem duplication contributed to the evolution of TPS genes. According to the analysis of selection pressure, it was predicted that TPS genes experience predominantly negative selection, with positive selection occurring subsequently. RT-qPCR analysis in TM-1 and CRI-12 lines revealed GhTPS48 gene as the candidate gene for silencing experiments. To summarize, comprehensive genome-wide studies, RT-qPCR, and gene silencing experiments have collectively demonstrated the involvement of the TPS gene family in the biosynthesis of gossypol in cotton.

Analysis of the Effects of Climate Change on Cotton Production in Maharashtra State of India Using Statistical Model and GIS Mapping

Cotton is a prominent cash crop cultivated for fiber, edible oil and oil cake. A global environmental issue, like climate change, alters weather parameters necessary for the healthy growth and development of cotton plants, affecting fiber quality and economic yield. The study aims to illustrate the evidence of climate change in Maharashtra and assess its impact on the production of cotton in this region. The study was conducted in the state of Maharashtra, India. Geographic information system (GIS)-based models were created based on the vector data (geopolitical boundaries of the state of Maharashtra and its districts) and the corresponding raster attributes (meteorological data) to examine the changes in the patterns of distribution of temperature, rainfall and severity of drought (Standardized Precipitation Index-SPI) over the study period (1990 to 2015). Further, a statistical multiple linear regression model was developed using district-wise data on yield and climatic parameters obtained from International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) to estimate the relationship between the dependent variable (yield of cotton) and the independent variables (annual rainfall and annual mean temperature). GIS modeling and mapping provide evidence of changes in the spatial distribution of rainfall and temperature. Although the regression analysis seems weak, it is acceptable for natural systems because natural systems are complex and often highly variable, making it difficult to create a perfect model. The multiple linear regression model shows that such changes in climatic parameters have a significant negative impact on the economic yield of cotton.

THE BEHAVIOR OF SOME COTTON (GOSSYPIUM HIRSUTUM) GENOTYPES UNDER SANDY SOIL CONDITIONS IN SOUTHERN OLTENIA

This study follows the behaviour of seven genotypes of cotton (Gossypium hirsutum), cultivated on the sandy soils of Dăbuleni, with the aim of diversifying the range of plants tolerant to climatic factors in southern Oltenia. Observation of vegetative characteristics such as plant height, number of sympodia, number of flowers in the first decade of flowering and quantitative characteristics such as boll weight, fibre weight, seed weight and number of seeds / plant were the object of the study. Research on cotton plant development was correlated with climatic data recorded by the weather station of Dăbuleni RDSPCS, during the growing season from plant sowing in the field to boll formation. Following the study and showing positive results, The Beli-Lom genotype stood out in terms of flowering yield and fibre percentage, and the Cirpan-539 and Beli-Iskar genotypes had positive vegetative growth yield.

Lignin and cellulose content differences in roots of different cotton cultivars associated with different levels of Fusarium wilt race 4 (FOV4) resistance-response

Fusarium wilt disease is caused by fungal pathogen Fusarium oxysporum f. sp. v asinfectum (FOV) race 4 (FOV4), which enters the plant through the root system for its successful colonization of xylem. Plant cell wall forms the primary barrier against pathogen infection in addition to providing the mechanical support. However, the role of cell walls for developing FOV4 resistance has not been explored. The present study focused on examining the variation in lignin and cellulose contents in root tissue of Pima ( Gossypium barbadense L.) and Upland ( G. hirsutum L.) cotton with different levels of FOV4 wilt resistance-response. Traditional cultivar-checks susceptible Pima S-7, resistant Pima S-6, susceptible Upland Stoneville 474, and resistant Upland PSSJ-FRU14 (U77B) were used in the present study. Biochemical differences in root cell walls were investigated first by a rapid visual staining method for both lignin (phloroglucinol-HCL) and cellulose (Congo red) contents of root cross sections at three stages of cotton plant development followed by biochemical estimation of root lignin and cellulose contents. These studies revealed differences between susceptible and resistant cultivars at specific stages visually by rapid staining as well as biochemically in their cellulose and lignin contents within Pima and Upland cultivars. This is the first report in lignin and cellulose content estimation of Pima and Upland resistant and susceptible FOV4 cotton cultivars and paves the way for developing cell wall mediated FOV resistance. • FOV4 causes cotton wilt disease and causes enormous yield losses. • Cell wall acts as a physical and biochemical barrier against pathogen infection. • We hypothesize that cell wall plays a major role in in FOV4 resistance. • Histochemical analysis showed higher root cellulose and lignin in resistant lines. • Resistant lines showed higher root cellulose and lignin contents.

Use of Lentinan and Fluopimomide to Control Cotton Seedling Damping-Off Disease Caused by Rhizoctonia solani

Lentinan (LNT) is a natural and functional polysaccharide isolated from Lentinus edodes fruiting bodies, which functions in stimulating the plant immune response, improving plant disease resistance and regulating plant growth. This study explores the use of LNT as a plant growth regulator and attractant in cotton production. After treatment with LNT, the content of malondialdehyde (MDA) in cotton seeds decreased, whereas the activities of polyphenol oxidase (PPO), superoxide dismutase (SOD) and peroxidase (POD) in leaves increased significantly. LNT also promoted the growth and development of cotton plants and significantly reduced the incidence of cotton damping-off disease. The relative expression of salicylic acid pathway-related genes in cotton also increased significantly. The prevention mechanism of fluopimomide was also evaluated, and the result showed lower EC50 values and was effective in controlling cotton seedling disease caused by Rhizoctonia solani in both greenhouse experiments and field trials. The use of LNT and fluopimomide in controlling cotton seedling damping-off disease showed a synergistic effect in field trials. These results will provide a new insight into the agricultural application of LNT as a biological fungicide in the field of biological controls.

Comparative transcriptome analysis of leaves during early stages of chilling stress in two different chilling-tolerant brown-fiber cotton cultivars.

Chilling stress generates significant inhibition of normal growth and development of cotton plants and lead to severe reduction of fiber quality and yield. Currently, little is known for the molecular mechanism of brown-fiber cotton (BFC) to respond to chilling stress. Herein, RNA-sequencing (RNA-seq)-based comparative analysis of leaves under 4°C treatment in two different-tolerant BFC cultivars, chilling-sensitive (CS) XC20 and chilling-tolerant (CT) Z1612, was performed to investigate the response mechanism. A total of 72650 unigenes were identified with eight commonly used databases. Venn diagram analysis identified 1194 differentially expressed genes (DEGs) with significant up-regulation in all comparison groups. Furthermore, enrichment analyses of COG and KEGG, as well as qRT-PCR validation, indicated that 279 genes were discovered as up-regulated DEGs (UDEGs) with constant significant increased expression in CT cultivar Z1612 groups at the dimensions of both each comparison group and treatment time, locating in the enriched pathways of signal transduction, protein and carbohydrate metabolism, and cell component. Moreover, the comprehensive analyses of gene expression, physiological index and intracellular metabolite detections, and ascorbate antioxidative metabolism measurement validated the functional contributions of these identified candidate genes and pathways to chilling stress. Together, this study for the first time report the candidate key genes and metabolic pathways responding to chilling stress in BFC, and provide the effective reference for understanding the regulatory mechanism of low temperature adaptation in cotton.

Functional characterization of a receptor for activated C kinase 1 (RACK1) gene from upland cotton (Gossypium hirsutum L.)

Receptor for activated C kinase 1 (RACK1) is a conserved scaffold protein interacting with multiple proteins and participates in diverse cellular activities. Previous high-throughput transcriptome and proteome studies both identified RACK1 gene/protein was differentially expressed in cotton, however, the detailed function of RACK1 in this important fiber-producing plant is still unclear. In the current study, we found that GhRACK1 was preferentially expressed in fast growing tissues, such as cotton fibers and ovules. Down-regulation of GhRACK1 expression in cotton plants through virus-induced gene silencing (VIGS) and ectopic expression of GhRACK1 in Arabidopsis both revealed a positive correlation between GhRACK1 expression level and plant growth rate. Physiological index (protein and soluble sugar content) further indicated that down-regulation of GhRACK1 expression could inhibit protein synthesis and photoassimilate accumulation in cotton, whereas ectopic expression of GhRACK1 exhibited opposite effects in Arabidopsis. These data collectively suggested that GhRACK1 might play an important role in regulating the growth and development of cotton plants.

Performance Evaluation of Three Egyptian Cotton Genotypes under Different Thermal Units Related to Different Planting Dates

FARMERS are often unable to determine the effect of different environmental stress on growth and development of cotton plants. So, the experiment conducted through a wide range of thermal changes by planting cotton at different dates. This work aimed to performance evaluation of some Egyptian cotton genotypes i.e., Giza 90, Giza 90 x Aust. and Giza 95 under different thermal units related to different planting dates i.e., 1st April, 16th April and 1st May.The results demonstrated that late planting led to decreasing plant height, number of leaves/plant and leaf area/plant. Number of fruiting/plant increased in early planting due to lowered of node of the first sympodium and inducing early balance between vegetative and fruiting. Low temperatures at the beginning of the season and the decrease the number of thermal units in early planting led to increase concentration of chlorophyll a, b and carotenoids in leaves and increase earliness index. Late planting produced the first flower and first open boll in shorter period as compared to early planting, but it consumed more number of heat units. Yield and its quality have increased in early planting where utilized the heat units in producing the highest number of open bolls and enhance cotton fiber properties conversely late planting which used most of the heat units in increasing the vegetative growth. Giza 95 surpassed in all studied characters compared to other genotypes. The efficiency of Egyptian cotton genotypes particularly Giza 95 for use of air thermal units increased in early planting. From the results above, it could be concluded that early planting maximized of the use of heat units by increasing the efficiency use of air thermal units through the growing season which lowered the amount of heat units for necessary production one boll.

Uncovering the Host Range for Maize Pathogen Magnaporthiopsis maydis.

The fungus Magnaporthiopsis maydis is a soil-borne, seed-borne vascular wilt pathogen that causes severe damage to sensitive Zea mays L. (maize) hybrids throughout Egypt, Israel, India, Spain, and other countries. It can undergo virulence variations and survive as spores, sclerotia, or mycelia on plant residues. Maize, Lupinus termis L. (lupine) and Gossypium hirsutum L. (cotton) are the only known hosts of M. maydis. Identification of new plant hosts that can assist in the survival of the pathogen is an essential step in restricting disease outbreak and spread. Here, by field survey and growth chamber pathogenicity test, accompanied by real-time PCR analysis, the presence of the fungal DNA inside the roots of cotton (Pima cv.) plants was confirmed in infested soil. Moreover, we identified M. maydis in Setaria viridis (green foxtail) and Citrullus lanatus (watermelon, Malali cv.). Infected watermelon sprouts had delayed emergence and development, were shorter, and had reduced root and shoot biomass. M. maydis infection also affected root biomass and phenological development of cotton plants but caused only mild symptoms in green foxtail. No M. maydis DNA was detected in Hordeum vulgare (barley, Noga cv.) and the plants showed no disease symptoms except for reduced shoot weight. These findings are an important step towards uncovering the host range and endophytic behavior of M. maydis, encouraging expanding this evaluation to other plant species.

English

The root lesion nematode (Pratylenchus brachyurus) is one of the main phytosanitary problems of cotton plants in Brazil. Searching for alternatives that minimize the damages in the crop, several methods are performed aiming to manage these damages. Among them, is the use of vegetal extracts. In this sense, the aim of this study was to evaluate the potential of black angico extract (Anadenanthera macrocarpa) in the management of P. brachyurus in cotton crop. The experiment was conducted in a greenhouse at the Phytopathology Laboratory of the Federal University of Piauí in Bom Jesus-PI. The experimental design was completely randomized, in a factorial scheme (2×6), composed of two sources of extracts (leaf and bark) of black angico under six concentrations (0, 20, 40, 60, 80 and 100 g L-1), with five replications per treatment. The plants were inoculated with 1900 specimen/juveniles and eggs, 96 h after the transplanting. Sixty days after the application of extracts, some agronomic variables of the cotton and P. brachyurus were evaluated. The volume and fresh root mass showed considerable gains for all concentrations with the leaf extract. The plant height was negatively influenced by concentrations above 60.83 g L-1 for both extracts. Regarding the parasitism, all the extract concentrations, regardless of the source (leaf or bark), showed suppressiveness to P. brachyurus. Therefore, the aqueous extracts of black angico present nematicidal action and favor the development of cotton plants.   Key words: Gossypium hirsutum, root lesion nematode, alternative management. &nbsp

Genome-wide identification and characterization of phospholipase C gene family in cotton (Gossypium spp.).

Phospholipase C (PLC) are important regulatory enzymes involved in several lipid and Ca2+-dependent signaling pathways. Previous studies have elucidated the versatile roles of PLC genes in growth, development and stress responses of many plants, however, the systematic analyses of PLC genes in the important fiber-producing plant, cotton, are still deficient. In this study, through genome-wide survey, we identified twelve phosphatidylinositol-specific PLC (PI-PLC) and nine non-specific PLC (NPC) genes in the allotetraploid upland cotton Gossypium hirsutum and nine PI-PLC and six NPC genes in two diploid cotton G. arboretum and G.raimondii, respectively. The PI-PLC and NPC genes of G. hirsutum showed close phylogenetic relationship with their homologous genes in the diploid cottons and Arabidopsis. Segmental and tandem duplication contributed greatly to the formation of the gene family. Expression profiling indicated that few of the PLC genes are constitutely expressed, whereas most of the PLC genes are preferentially expressed in specific tissues and abiotic stress conditions. Promoter analyses further implied that the expression of these PLC genes might be regulated by MYB transcription factors and different phytohormones. These results not only suggest an important role of phospholipase C members in cotton plant development and abiotic stress response but also provide good candidate targets for future molecular breeding of superior cotton cultivars.

Effect of sowing dates on cotton yield, fiber quality, and uptake and utilization of nutrients in Inner Mongolia west desert area, China

Field experiments were conducted in 2014 and 2015 at the "Inner Mongolia cotton comprehensive test station" (39°27' N, 105°39' E) in Alxa Left Banner of Alxa League in Inner Mongolia. By using cotton cultivar CCRI-50 as material and the "6 cotton rows with 3 dripping pipes under a plastic film mulching" plantation pattern, different sowing dates (20-Apr, 30-Apr and 10-May) were set to study the effect of sowing dates on cotton yield, fiber quality and nutrient uptake and utilization. The results showed that as the sowing date delayed, the development of cotton plant was delayed, the yield forming stage shortened, and the mean daily temperature of boll deve-lopment reduced, but the harvesting density increased. Sowing date influenced the biomass accumulation, fiber yield and fiber quality, it also influenced the absorption and distribution of N, P and K. Among the three sowing dates, the biomass distribution proportion to reproductive organ, nutrition (N, P and K) accumulation, lint production efficiency of nutrient and yield were higher in the cotton plant that was sowing at 30-Apr, the seed cotton and lint yield were the highest which could reach up to 6505.9 kg·hm-2 and 2660.9 kg·hm-2, respectively, and the fiber quality was better than that of 10-Mar. For the plant which was sowed at 20-Apr, harvesting density, biomass and nutrient accumulation were the lowest, although economic coefficients of biomass and nutrient were the highest, and the seed cotton and lint yield were respectively 10.9%-14.0% and 11.1%-14.2% lower than that of 30-Apr. When sowing at 10-May, cotton could avoid the low temperature during seed germination, but mean daily temperature during boll development were the lowest, although biomass and nutrient accumulation were the highest. The economic index, lint production efficiency of nutrient were the lowest, which leading to the poorest fiber quality, lowest seed cotton and lowest lint yield which were respectively 32.5%-34.7% and 35.9%-36.2% lower than that of 30-Apr. These results suggested that the optimum sowing date for cotton planting was about 30-Apr in Inner Mongolia west desert area.

Effect of irrigation with saline water on some physiological and biochemical processes of cotton plants

It was found that irrigation with water with salinity of 5–6 g/L increases the concentration of soil solution and the osmotic pressure of cell fluid in plants. An increase in these parameters does not harm the growth and development of cotton plants, since the concentration of cell fluid is five times higher than that of soil solution; i.e., water and nutrient intake from the soil is not affected. The transpiration rate in plants irrigated with water with salinity of 5–6 g/L is lower by 11% than that in plants irrigated with fresh water. This results from the elevation of cell fluid concentration in plants irrigated with saline water and increased mass of leaves in plants irrigated with fresh water. However, the amount of water transpirated by cotton plants irrigated with saline water during the vegetation period is lower by 18% than that in plants irrigated with fresh water. It was found that the transpiration rate, regardless of water salinity and the mass of leaves, increases until the flowering period and then decreases by the end of vegetation period.

Physiological response of cotton seeds treated with thiamethoxam under heat stress

Abstract: This study aimed to verify the effect of seeds treated with thiamethoxam on the emergence, growth and chlorophyll content of seedlings of two cotton cultivars subjected to abiotic stress. The seeds used were from the DeltaOpal and NuOpal cultivars, each one represented by three lots, previously subjected to determination of moisture content, germination and vigor (low temperature germination). Then, the seeds from each lot, treated with thiamethoxam at a dose of 600 mL of product per 100 kg-1 seed or not, were exposed to temperature (18, 25 and 35 °C) and water availability (40, 60 and 80%) stress conditions. The emergence percentage, the root and shoot length, and the chlorophyll content were evaluated. The growth of cotton seedlings from the DeltaOpal and NuOpal cultivars, subjected to low temperature conditions and water availability of 40 to 60%, is favored by seed treatment with thiamethoxam. Seed treatment with thiamethoxam increases chlorophyll content during the development of cotton plants.

English

This paper aimed to evaluate the transmission of Fusarium oxysporum f. sp. vasinfectum (FOV) and the effects of this pathogen on the initial development of cotton plants following inoculation of seeds. Two cultivars (susceptible and resistant) and two strains (most and least aggressive) of the pathogen were used in this study. The inoculation method was based on the contact between seeds and fungal colonies on substrates containing mannitol. Percentage of FOV in seeds and the percentage of seed germination were evaluated by blother test and germination test, after inoculation. Emergence of seedlings and speed index, initial and final stands, size and dry weight of the plants were verified in trays containing soil substrate. Disease severity, pathogen transmission and plant infection, from seed to plant, were determined in separate trial on plants. Occurrence of the pathogen was higher when inoculum potential was increased for all variables analyzed. The number of normal seedlings, determined by seed germination test, decreased when the incidence of the pathogen in the seed was increased. The same occurred to other variables, in which there was difference between cultivars where IAC 20-233 presented the best performance. No significant differences were found between strains for emergence speed index, initial and final stands variables. Transmission and infection rates were increased according to the inoculum potentials increasing and the maximum pathogen transmission rate, from seed to plant was around 50%. Key words: Transmissibility, pathogenicity, fusarium wilt disease, cotton.

Dissecting Functions of KATANIN and WRINKLED1 in Cotton Fiber Development by Virus-Induced Gene Silencing

Most of the world's natural fiber comes from cotton (Gossypium spp.), which is an important crop worldwide. Characterizing genes that regulate cotton yield and fiber quality is expected to benefit the sustainable production of natural fiber. Although a huge number of expressed sequence tag sequences are now available in the public database, large-scale gene function analysis has been hampered by the low-efficiency process of generating transgenic cotton plants. Tobacco rattle virus (TRV) has recently been reported to trigger virus-induced gene silencing (VIGS) in cotton leaves. Here, we extended the utility of this method by showing that TRV-VIGS can operate in reproductive organs as well. We used this method to investigate the function of KATANIN and WRINKLED1 in cotton plant development. Cotton plants with suppressed KATANIN expression produced shorter fibers and elevated weight ratio of seed oil to endosperm. By contrast, silencing of WRINKLED1 expression resulted in increased fiber length but reduced oil seed content, suggesting the possibility to increase fiber length by repartitioning carbon flow. Our results provide evidence that the TRV-VIGS system can be used for rapid functional analysis of genes involved in cotton fiber development.