Gossypium Spp Research Articles

Hyperspectral reflectance and machine learning for multi-site monitoring of cotton growth

Hyperspectral measurements can help with rapid decision-making and collecting data across multiple locations. However, there are multiple data processing methods (Savisky-Golay [SG], first derivative [FD], and normalization) and analyses (partial least squares regression [PLS], weighted k-nearest neighbor [KKNN], support vector machine [SVM], and random forest [RF]) that can be used to determine the best relationship between physical measurements and hyperspectral data. In the current study, FD was the best method for data processing and SVM was the best model for predicting average cotton (Gossypium spp. Malvaceae) height and nodes. However, the combination of FD and RF were best at predicting cotton leaf area index, canopy cover, and chlorophyll content across the growing season. Additionally, results from models developed by both SVM and RF were closely related to pseudo-CHIME satellite wavebands, where in-situ hyperspectral data were matched to the spectral resolutions of a future hyperspectral satellite. The information and results presented will aid producers and other members of the cotton industry to make rapid and meaningful decisions that could result in greater yield and sustainable intensification.

Screening of selected cotton genotypes (Gossypium spp) for resistance to fusarium wilt disease in Tanzania.

Cotton is an important commodity in various industries across the globe; however, cotton yield is adversely affected by the existence of pathogenic fungi included Fusarium oxysporum f.sp. vasinfectum (FOV), the causative of Fusarium wilt (FW), which is among the major disease threatening cotton production in Tanzania. In this study the screening of 25 selected varieties resistance to FOV were done under greenhouse conditions by inoculating the emerged cotton seedlings with 1.0 x 108 conidia/ml of F. oxysporum f. sp. vasinfectum using root cut dip method. The fusarium wilt disease was evaluated based on foliar symptoms (disease severity scaling and vascular coloration). Out of 25 evaluated cotton candidates, three candidates F 135, HC-B4-75 and UK 66 were significantly higher resistant with lower disease severity than others, while QUIT122, IL85, PSF2-1-1 and UK91 have significantly low resistance.

Biotechnology and Solutions: Insect-Pest-Resistance Management for Improvement and Development of Bt Cotton (Gossypium hirsutum L.)

Cotton (Gossypium spp. L.) is a major origin of natural fiber, and is projected at 117 million bales worldwide for 2021/22. A variety of biotic and abiotic stresses have considerable negative impacts on cotton. The significantly decreased applications of chemical insecticidal sprays in the agro-ecosystem have greatly affected the biodiversity and dynamics of primary and secondary insects. Various control measures were taken around the globe to increase production costs. Temperature, drought, and salinity, and biotic stresses such as bacteria, viruses, fungi, nematodes, insects, and mites cause substantial losses to cotton crops. Here, we summarize a number of biotic and abiotic stresses upsetting Bt cotton crop with present and future biotechnology solution strategies that include a refuge strategy, multi-gene pyramiding, the release of sterile insects, seed mixing, RNAi, CRISPR/Cas9, biotic signaling, and the use of bioagents. Surveillance of insect resistance, monitoring of grower compliance, and implementation of remedial actions can lead to the sustainable use of cotton across the globe.

Genetic regulation of nitrogen use efficiency in Gossypium spp.

Cotton (Gossypium spp.) is the most important fibre crop, with desirable characteristics preferred for textile production. Cotton fibre output relies heavily on nitrate as the most important source of inorganic nitrogen (N). However, nitrogen dynamics in extreme environments limit plant growth and lead to yield loss and pollution. Therefore, nitrogen use efficiency (NUE), which involves the utilisation of the 'right rate', 'right source', 'right time', and 'right place' (4Rs), is key for efficient N management. Recent omics techniques have genetically improved NUE in crops. We herein highlight the mechanisms of N uptake and assimilation in the vegetative and reproductive branches of the cotton plant while considering the known and unknown regulatory factors. The phylogenetic relationships among N transporters in four Gossypium spp. have been reviewed. Further, the N regulatory genes that participate in xylem transport and phloem loading are also discussed. In addition, the functions of microRNAs and transcription factors in modulating the expression of target N regulatory genes are highlighted. Overall, this review provides a detailed perspective on the complex N regulatory mechanism in cotton, which would accelerate the research toward improving NUE in crops.

Transcriptome Profiling of Gossypium anomalum Seedlings Reveals Key Regulators and Metabolic Pathways in Response to Drought Stress.

Drought stress is a key limiting factor for cotton (Gossypium spp.) growth, production, development, and production worldwide. Some wild diploid cotton species are remarkably tolerant of water deficit and constitute an important reservoir for understanding the molecular mechanisms of Gossypium spp. drought tolerance and improving cultivated upland cotton. Here, we utilized RNA-Seq technology to characterize the leaf transcriptomes of a wild African diploid cotton species, Gossypium anomalum, under drought stress. A total of 12,322 differentially expressed genes (DEGs) were identified after mapping valid clean reads to the reference genome of G. anomalum, of which 1243 were commonly differentially expressed at all stages of drought stress. These genes were significantly enriched for molecular functions Gene Ontology terms related to cytoskeleton, hydrolase activity, cellular redox, and binding. Additionally, a substantial proportion of enriched biological process terms concerned cell or subcellular processes, while most in the cellular components category concerned membrane function and photosynthesis. An enrichment analysis against the Kyoto Encyclopedia of Genes and Genomes showed the top significantly enriched pathways to be photosynthesis-antenna proteins, amino sugar and nucleotide sugar metabolism, starch and sucrose metabolism, MAPK signaling pathway, glutathione metabolism, and plant hormone signal transduction. The DEGs also exhibited interestingly significant enrichments for drought stress-induced tandemly repeated genes involved in iron ion binding, oxidoreductase activity, heme binding, and other biological processes. A large number of genes encoding transcription factors, such as MYB, bHLH, ERF, NAC, WRKY, and bZIP, were identified as playing key roles in acclimatizing to drought stress. These results will provide deeper insights into the molecular mechanisms of drought stress adaptation in Gossypium spp.

Early and Late Season Nutrient Stress Conditions: Impact on Cotton Productivity and Quality

Modern cotton (Gossypium spp. L) cultivars are efficient in nutrient uptake and utilization, and thus, may potentially tolerate nutrient stress. Early- and late-season nutrient stress (E-stress and L-stress, respectively) effects on cotton productivity and quality were assessed under different production conditions in Camilla and Midville, GA, USA. The E-stress received no nutrient application in the early season, but the full rates were split-applied equally at the initiation of squares and the second week of bloom stages. The L-stress received 30–40% of the full nutrient rates only at the initial stage of planting. The effects of nutrient stress on cotton productivity and fiber quality were not consistent across the different production conditions. Compared to the full nutrient rate, the E-stress did not adversely impact cotton yield, but rather it improved the lint and cottonseed yields under one production condition by 17.5% and 19.3%, respectively. Averaged across all production conditions, the L-stress decreased the lint and cottonseed yields by 34.4% and 36.2%, respectively. The minimal effects of E-stress on cotton suggest nutrient rates at the early season could be reduced and more tailored rates, informed by soil and plant tissue analyses, applied shortly before the reproductive phase.

Preferences of Lygus pratensis (Hemiptera: Miridae) for Four Potential Trap Crop Plants

Abstract The mirid, Lygus pratensis (L.) (Hemiptera: Miridae), is a major pest of cotton (Gossypium spp.) in Xinjiang Uyghur Autonomous Region, China. In this study, we aimed to reveal the preferences of L. pratensis toward four potential trap crop plants for use in controlling this pest. The population densities of L. pratensis on five host plants were investigated by visual observation, and the behavioral responses of L. pratensis to the five host plants were determined by Y-type olfactory assays and laboratory selectivity assays. The results showed significant differences in host preferences in the field. The average numbers of adults on the five host plants are in the following order, from high to low: Lepidium latifolium (L.), Kochia prostrata (L.) Schrad, Chenopodium glaucum (L.), Medicago sativa (L.), and Gossypium spp. Laboratory selectivity assays found that K. prostrata had the highest number of adults at 5 min, but L. latifolium had the highest number of adults from 1.5 to 4.5 h. The Y-tube olfactometer assays found no significant evidence for selection of L. pratensis between the volatiles of M. sativa and pure air, but did for the other four plants. In conclusion, the blooming stage of L. latifolium was the most attractive to L. pratensis in the field and is, thus, a potential trap crop plant for L. pratensis.

The oral secretion from Cotton Boll Weevil (Anthonomus grandis) induces defense responses in cotton (Gossypium spp) and Arabidopsis thaliana

Cotton Boll Weevil (CBW, Anthonomus grandis) is a devastating insect-pest affecting cotton (Gossypium spp), using cotton internal floral structures for larval development, making it difficult to control. Little is known about the mechanism underlying CBW-plant interactions leading to infestation or resistance. Here, we investigated the plant molecular responses triggered by CBW extracts from eggs, larvae, and oral secretions (OS) of larvae and adult. The MAPK pathway, one of the early signaling events in plant pattern-triggered immunity (PTI), was activated by CBW extracts in Arabidopsis thaliana. In cotton, CBW OS activated GhMPK3 and GhMPK6. Importantly, CBW OS activated the PTI marker gene FRK1 and the effector-triggered immunity (ETI) marker gene WRKY46 in Arabidopsis reporter lines, suggesting that Herbivore-Associated Molecular Patterns (HAMPs) present in OS from CBW can elicit plant defense responses in cotton and Arabidopsis. Interestingly, CBW OS-induced MAPK activation shows similar patterns in wild-type and Arabidopsis mutants, which bear mutations in already known receptor and co-receptors complex components, suggesting a distinct signaling cascade likely triggered by the putative HAMPs present in CBW OS. The work points to potentials in the identification and development of CBW extract-derived elicitors for effective pest control combating CBW infestation.

Gossypol from Gossypium spp. Inhibits Helicobacter pylori Clinical Strains and Urease Enzyme Activity: Bioactivity and Safety Assessments

This study investigates the inhibitory activities of gossypol, a natural polyphenolic compound from Gossypium spp., against Helicobacter pylori (HP) clinical strains and a urease enzyme that plays a key role in the pathogenesis of HP. Gossypol was detected to exhibit a bacteriostatic action against all the HP strains tested with minimum inhibitory concentration (MIC) values ranging from 3.51 to 4.14 µg/mL. The activity of HP urease (HPU) was efficiently impeded by gossypol with a 50% inhibitory concentration (IC50) value of 3.3 µM using an Electrospray Ionization–Mass Spectrometry (ESI-MS)-based method. The in vitro cytotoxicity assay showed no significant cytotoxic properties of gossypol against human gastric epithelial cells. Additionally, molecular docking studies were performed to assess the binding mode and the molecular interactions of gossypol with HPU with a binding affinity value of −8.1 kcal/mol compared with an HPU–acetohydroxamic acid (a standard urease inhibitor) docking complex (–6.1 kcal/mol). The overall results reveal that gossypol might help fight against HP infection by two mechanisms of action: inhibition of the growth of HP and inhibition of urease.

The Viral Threat in Cotton: How New and Emerging Technologies Accelerate Virus Identification and Virus Resistance Breeding.

Cotton (Gossypium spp. L., Malvaceae) is the world’s largest source of natural fibers. Virus outbreaks are fast and economically devasting regarding cotton. Identifying new viruses is challenging as virus symptoms usually mimic nutrient deficiency, insect damage, and auxin herbicide injury. Traditional viral identification methods are costly and time-consuming. Developing new resistant cotton lines to face viral threats has been slow until the recent use of molecular virology, genomics, new breeding techniques (NBT), remote sensing, and artificial intelligence (AI). This perspective article demonstrates rapid, sensitive, and cheap technologies to identify viral diseases and propose their use for virus resistance breeding.

Breeding Practice Improves the Mycorrhizal Responsiveness of Cotton (Gossypium spp. L.).

Maximizing the function of indigenous arbuscular mycorrhizal (AM) fungi by choosing specific crop genotypes offers one of the few untapped opportunities to improve the sustainability of agriculture. In this study, the differences in mycorrhizal responsiveness (MR) in plant growth and shoot phosphorus (P) content among cotton (Gossypium spp. L.) genotypes from different release dates were compared and then the relationships between MR and P uptake-related traits were determined. The experimental design in a greenhouse included 24 genotypes released from 1950 to present in Xinjiang Province, inoculation with or without AM fungi, and P levels (15 and 150 mg P kg–1 added as KH2PO4). Results showed that the modern cotton genotypes exhibited a higher degree of mycorrhizal colonization, the hyphal length density (HLD), and mycorrhizae-induced changes in shoot growth than the old genotypes when inoculated with indigenous AM fungi at both the P levels. Moreover, MR was highly correlated with the HLD at low P levels and the HLD may provide useful insights for future cotton breeding aimed at delivering crop genotypes that can benefit more from AM fungi.

Phylogenetic Analysis of the Membrane Attack Complex/Perforin Domain-Containing Proteins in Gossypium and the Role of GhMACPF26 in Cotton Under Cold Stress.

The membrane attack complex/perforin (MACPF) domain-containing proteins are involved in the various developmental processes and in responding to diverse abiotic stress. The function and regulatory network of the MACPF genes are rarely reported in Gossypium spp. We study the detailed identification and partial functional verification of the members of the MACPF family. Totally, 100 putative MACPF proteins containing complete MACPF domain were identified from the four cotton species. They were classified into three phylogenetic groups and underwent multifold pressure indicating that selection produced new functional differentiation. Cotton MACPF gene family members expanded mainly through the whole-genome duplication (WGD)/segmental followed by the dispersed. Expression and cis-acting elements analysis revealed that MACPFs play a role in resistance to abiotic stresses, and some selected GhMACPFs were able to respond to the PEG and cold stresses. Co-expression analysis showed that GhMACPFs might interact with valine-glutamine (VQ), WRKY, and Apetala 2 (AP2)/ethylene responsive factor (ERF) domain-containing genes under cold stress. In addition, silencing endogenous GhMACPF26 in cotton by the virus-induced gene silencing (VIGS) method indicated that GhMACPF26 negatively regulates cold tolerance. Our data provided a comprehensive phylogenetic evolutionary view of Gossypium MACPFs. The MACPFs may work together with multiple transcriptional factors and play roles in acclimation to abiotic stress, especially cold stress in cotton.

In vitro Organogenesis in Cotton (Gossypium spp) for Ex-situ Conservation Issue

Background: Monovarietal cultivation of cotton plant allowed the genetic erosion for traditional cotton varieties that proceed essential traits mainly involved in cotton genetic breeding. These varieties need to be preserved for future used. This study aims to evaluate the effect of gibberellic acid on cotton seed germination and the effect of Benzylaminopurin (BAP), Kinetin (KIN), α-naphthalene acetic acid (NAA) and activated charcoal (CA) on cotton seedlings growth obtained from different type of explants.
 Methodology: The seeds of three improved varieties (KET782, ANG956, OKP768) and five local varieties (Q62, Q64, Q85, Q88, Q92) were germinated with different concentration of gibberellic acid (GA3). Different explants were collected from the germinated plantlets and cultivated in different culture media containing plants growth regulators and activated charcoal in different concentration.
 Results: We found that Gibberellic Acid activity on cotton seeds germination significantly varied according to the variety and GA3 concentration in the medium. 63.33% germination rate in OKP768 was obtained on the medium containing 0.5 mg/L of GA3 while the medium with 1 mg/l of GA3 gave the highest seed germination in Q85 (75%), Q64 (69.17%), and ANG956 (40.83%). The plantlets regeneration rate varied within the explants in different varieties used. 100%of axillary nodes were regenerated in Q62; Q85 and Q92 varieties while 60% were regenerated with the zygotic embryos in ANG956, and OKP768. Moreover, the medium supplemented with GA3 (1mg/l) + NAA (1 mg/l) induced the greatest number of roots (2.75 roots/plantlet) in the ANG956 and OKP768 varieties. With activated charcoal (10 g/l), ANG956 and OKP768 varieties achieved better performance with respective roots length average of 3.4 cm/plantlet and 2.1 cm/plantlet. The activated charcoal at 10 g/l highly influenced the length of roots with an average of 7.7cm in ANG956 variety.
 Implication: The protocol established during this study will be useful for in vitro regeneration and conservation for cotton local varieties.

The Cotton Wall-Associated Kinase GhWAK7A Mediates Responses to Fungal Wilt Pathogens by Complexing with the Chitin Sensory Receptors.

Plant receptor-like kinases (RLKs) are important players in response to pathogen infections. Verticillium and Fusarium wilts, caused by Verticillium dahliae (Vd) and Fusarium oxysporum f. sp vasinfectum (Fov), respectively, are among the most devastating diseases in cotton (Gossypium spp). To understand the cotton response to these soil-borne fungal pathogens, we performed a genome-wide in silico characterization and functional screen of diverse RLKs for their involvement in cotton wilt diseases. We identified Gossypium hirsutum GhWAK7A, a wall-associated kinase, that positively regulates cotton response to both Vd and Fov infections. Chitin, the major constituent of the fungal cell wall, is perceived by lysin-motif-containing RLKs (LYKs/CERK1), leading to the activation of plant defense against fungal pathogens. A conserved chitin sensing and signaling system is present in cotton, including chitin-induced GhLYK5-GhCERK1 dimerization and phosphorylation, and contributes to cotton defense against Vd and Fov Importantly, GhWAK7A directly interacts with both GhLYK5 and GhCERK1 and promotes chitin-induced GhLYK5-GhCERK1 dimerization. GhWAK7A phosphorylates GhLYK5, which itself does not have kinase activity, but requires phosphorylation for its function. Consequently, GhWAK7A plays a crucial role in chitin-induced responses. Thus, our data reveal GhWAK7A as an important component in cotton response to fungal wilt pathogens by complexing with the chitin receptors.

Interspecific hybrid confirmation in wide crosses of cotton (Gossypium spp) through morphological, cytological and molecular analysis

Interspecific triploid hybrids were developed between tetraploid cultivated species Gossypium barbadense cv. Suvin and TCB 37 and diploid wild species Gossypium armourianum. The F1 hybridity was confirmed by morphological, cytological and molecular approaches. The ploidy level of interspecific F1 hybrid was triploid and completely male sterile. Female parents Suvin and TCB 37 had erect growth habit, yellow petals, palmate leaves, green stem, thick and prominent leaf veins, but Suvin had dense yellow anthers while TCB 37 was with dense creamy anthers whereas male parent has a spreading growth habit, yellow petals, cordate leaves, reddish green stem, medium dense yellow anthers, thin leaf veins, protruded stigma and glabrous plant body. The growth habit, petal colour, leaf shape and size of interspecific F1 hybrid were intermediate. Plant stem colour, hairyness, leaf pubescence and anther colour of Gossypium armourianum were observed to be dominant as hybrid fully resembled Gossypium armourianum for these characters. Petal spot was observed in both male and female parents but F1 hybrids had different intensity of petal spot in their petals. Variable expression of petal spot, anther colour and filament colour was observed in the F1 hybrids. Gossypium barbadense cv. Suvin and TCB 37 had 52 chromosomes, Gossypium armourianum had 26 chromosomes and the interspecific F1 was with 39 chromosomes. Significant differences were observed between pollen size, pollen fertility of parents and their hybrids. The F1 interspecific hybrid having more than 97% of sterile pollen grains. Out of 6 polymorphic SSR markers between parents, 3 markers unambiguously confirmed the hybrid status of interspecific hybrid. This hybrid may serve as useful genetic resource for the transfer of jassid resistance gene to Gossypium barbadense cultivars.

English

Cotton is the highest source of natural fiber in textile industry worldwide. With the modern spinning technologies, the demand for cotton fiber with higher quality has increased, making the genetic improvement of fiber quality one of the main challenges for cotton breeders. In cotton breeding, wild species are important source of several desirable genes for genetic improvement of the main cultivated cotton Gossypium hirsutum L (Upland cotton). Besides length and strength, fineness is one of the most important criteria associated with cotton fiber quality. In this study, ten wild diploid species of cotton were investigated for their fiber fineness and potential to improve fiber fineness of G. hirsutum L. The method was measuring of ribbon width after caustic swelling. The results showed the potential of four wild species (G. longicalyx Hutch. & Lee, G. anomalum Wawra & Peyr., G. thurberi Todaro and G. stocksii Mast.) to significantly improve the fiber fineness of upland cotton in a hybrid configuration. Among them, G. longicalyx stood out for its exceptional fiber fineness, and its remarkable impact on reducing the fiber fineness of G. hirsutum L. The wild species highlighted in this study constitute an interesting genetic resource for the development of upland cotton varieties with improved fiber fineness. Key words: Cotton, fiber fineness, Gossypium spp, hybrid, plant breeding, tetraploid species, wild diploid species.

Genome-wide identification and analyses of the AHL gene family in cotton (Gossypium)

BackgroundMembers of the AT-HOOK MOTIF CONTAINING NUCLEAR LOCALIZED (AHL) family are involved in various plant biological processes via protein-DNA and protein-protein interaction. However, no the systematic identification and analysis of AHL gene family have been reported in cotton.ResultsTo investigate the potential functions of AHLs in cotton, genome-wide identification, expressions and structure analysis of the AHL gene family were performed in this study. 48, 51 and 99 AHL genes were identified from the G.raimondii, G.arboreum and G.hirsutum genome, respectively. Phylogenetic analysis revealed that the AHLs in cotton evolved into 2 clades, Clade-A with 4–5 introns and Clade-B with intronless (excluding AHL20–2). Based on the composition of the AT-hook motif(s) and PPC/DUF 296 domain, AHL proteins were classified into three types (Type-I/−II/−III), with Type-I AHLs forming Clade-B, and the other two types together diversifying in Clade-A. The detection of synteny and collinearity showed that the AHLs expanded with the specific WGD in cotton, and the sequence structure of AHL20–2 showed the tendency of increasing intron in three different Gossypium spp. The ratios of non-synonymous (Ka) and synonymous (Ks) substitution rates of orthologous gene pairs revealed that the AHL genes of G.hirsutum had undergone through various selection pressures, purifying selection mainly in A-subgenome and positive selection mainly in D-subgenome. Examination of their expression patterns showed most of AHLs of Clade-B expressed predominantly in stem, while those of Clade-A in ovules, suggesting that the AHLs within each clade shared similar expression patterns with each other. qRT-PCR analysis further confirmed that some GhAHLs higher expression in stems and ovules.ConclusionIn this study, 48, 51 and 99 AHL genes were identified from three cotton genomes respectively. AHLs in cotton were classified into two clades by phylogenetic relationship and three types based on the composition of motif and domain. The AHLs expanded with segmental duplication, not tandem duplication. The expression profiles of GhAHLs revealed abundant differences in expression levels in various tissues and at different stages of ovules development. Our study provided significant insights into the potential functions of AHLs in regulating the growth and development in cotton.

The gland localized CGP1 controls gland pigmentation and gossypol accumulation in cotton.

SummaryPigment glands, also known as black glands or gossypol glands, are specific for Gossypium spp. These glands strictly confine large amounts of secondary metabolites to the lysigenous cavity, leading to the glands’ intense colour and providing defence against pests and pathogens. This study performed a comparative transcriptome analysis of glanded versus glandless cotton cultivars. Twenty‐two transcription factors showed expression patterns associated with pigment glands and were characterized. Phenotypic screening of the genes, via virus‐induced gene silencing, showed an apparent disappearance of pigmented glands after the silencing of a pair of homologous MYB‐encoding genes in the A and D genomes (designated as CGP1). Further study showed that CGP1a encodes an active transcription factor, which is specifically expressed in the gland structure, while CGP1d encodes a non‐functional protein due to a fragment deletion, which causes premature termination. RNAi‐mediated silencing and CRISPR knockout of CGP1 in glanded cotton cultivars generated a glandless‐like phenotype, similar to the dominant glandless mutant Gl2e. Microscopic analysis showed that CGP1 knockout did not affect gland structure or density, but affected gland pigmentation. The levels of gossypol and related terpenoids were significantly decreased in cgp1 mutants, and a number of gossypol biosynthetic genes were strongly down‐regulated. CGP1 is located in the nucleus where it interacts with GoPGF, a critical transcription factor for gland development and gossypol synthesis. Our data suggest that CGP1 and GoPGF form heterodimers to control the synthesis of gossypol and other secondary metabolites in cotton.

The Cotton Boll: The Relationship of Species and Genotype with Temporal Development of Boll Wall Thickness

Cotton (Gossypium spp. L.) is a high‐value cash crop worldwide, and numerous pest insects can injure the developing cotton boll, thereby reducing yields and fiber quality. Thickness of the boll wall may be instrumental in deterring these seasonal pests, but the temporal development, or rate at which the boll wall thickens, is not known. The objective of this study was to determine boll wall thickness in four cotton species (G. arboreum L., G. barbadense L., G. herbaceum L., and G. hirsutum L.) and among selected entries within species at selected boll ages. Temporal boll wall thickness differed significantly between cotton species, as well as among entries within species. Overall, mean wall thickness was significantly affected by cotton species and boll age. When boll ages were pooled, G. barbadense possessed significantly higher mean wall thickness than G. arboreum, G. hirsutum, and G. herbaceum. When cotton species were pooled, maximum wall thickness was observed at 14 d after flowering, followed by 21 d after flowering, and these were significantly greater than at 3, 7, and 28 d after flowering. Within all species, temporal differences in wall thickness were observed between and among entries evaluated. These findings improve our understanding of boll wall development and provide a foundation for screening cotton germplasm to potentially select for increased wall thickness as a source of pest resistance.

English

English