Gossypol Glands Research Articles

Studies on Morphophysiological and Biochemical Parameters for Sucking Pest Tolerance in Organic Cotton

The demand for organic cotton is primarily driven by manufacturers and brands with a corporate focus on environmental and social responsibility. These entities strive to be responsible stewards by seeking organic cotton, which not only offers environmental benefits but also provides softer, more durable, and longer-lasting clothing. Unlike conventional cotton, organic cotton is processed without the use of harsh chemicals, making it more comfortable for individuals with sensitive skin. A study was conducted at the Center of Organic Agriculture Research and Training Center, Department of Agronomy, Dr. PDKV, Akola, Maharashtra, India to evaluate 22 cotton genotypes, including control samples, using a randomized block design with three replications during the kharif (June–October) season in the years 2019–2020 and 2020–2021, under complete organic conditions. During the initial year of the study (2019–2020), visual observations were made to assess the incidence of sucking pests on the cotton genotypes’ leaves, including the top, middle, and bottom portions. The observations indicated promising results, leading to a more detailed study in the subsequent year (2020–2021). This extended study identified several tolerant genotypes to sucking pests, such as AV-G11, PA-255, GA-8004, AV-C14, and AV-G13 from the arboreum species, as well as AKH-09-5, a hirsutum cultivar. Among the recorded data, it was found that the lowest mean aphid population occurred at 90 days after sowing (DAS), with only 1.53 aphids per leaf. Similarly, the lowest mean populations of Cicadellidae, thrips, and whitefly were recorded at 0.75, 0.97, and 0.63 per leaf, respectively, all at 30 DAS. Microscopic analysis of trichome density and gossypol glands revealed a negative and significant correlation with Aphis gossypi (aphids), Cicadellidae sp. (Cicadellidae), and Thrips tabaci (thrips). However, a positive and significant correlation was found with Bemesia tabaci (whitefly). Furthermore, the estimation of total soluble sugar using the Anthrone method, total nitrogen, and crude protein showed positive and significant correlations with aphids, Cicadellidae, and thrips, but negative, significant correlations with whitefly. The findings indicate that higher trichome density provides greater resistance to sucking pest infestation. It was concluded that G. arboreum genotypes exhibit greater tolerance to sucking pests compared to G. hirsutum varieties. This implies that G. arboreum varieties may require less intensive pest management, aligning with organic farming principles. The discovery of these genotypes opens up possibilities for utilizing them as sustainable and pest-resistant options in cotton cultivation, promoting environmentally friendly and organic farming practices in cotton fiber production.

An Overview of Cotton Gland Development and Its Transcriptional Regulation

Cotton refers to species in the genus Gossypium that bear spinnable seed coat fibers. A total of 50 species in the genus Gossypium have been described to date. Of these, only four species, viz. Gossypium, hirsutum, G. barbadense, G. arboretum, and G. herbaceum are cultivated; the rest are wild. The black dot-like structures on the surfaces of cotton organs or tissues, such as the leaves, stem, calyx, bracts, and boll surface, are called gossypol glands or pigment glands, which store terpenoid aldehydes, including gossypol. The cotton (Gossypium hirsutum) pigment gland is a distinctive structure that stores gossypol and its derivatives. It provides an ideal system for studying cell differentiation and organogenesis. However, only a few genes involved in the process of gland formation have been identified to date, and the molecular mechanisms underlying gland initiation remain unclear. The terpenoid aldehydes in the lysigenous glands of Gossypium species are important secondary phytoalexins (with gossypol being the most important) and one of the main defenses of plants against pests and diseases. Here, we review recent research on the development of gossypol glands in Gossypium species, the regulation of the terpenoid aldehyde biosynthesis pathway, discoveries from genetic engineering studies, and future research directions.

Genome-wide identification and characterization of terpene synthase genes in Gossypium hirsutum

Terpenoids are widely distributed in plants and play important roles in the regulation of plant growth and development and in the interactions between plants and both the environment and other organisms. However, terpene synthase (TPS) genes have not been systematically investigated in the tetraploid Gossypium hirsutum. In this study, whole genome identification and characterization of the TPS family from G. hirsutum were carried out. Eighty-five TPS genes, including 47 previously unidentified genes, were identified in the G. hirsutum genome and classified into 5 subfamilies according to protein sequence similarities, as follows: 43 GhTPS-a, 29 GhTPS-b, 4 GhTPS-c, 7 GhTPS-e/f, and 2 GhTPS-g members. These 85 TPS genes were mapped onto 19 chromosomes of the G. hirsutum genome. Segmental duplications and tandem duplications contributed greatly to the expansion of TPS genes in G. hirsutum and were followed by intense purifying selection during evolution. Indentification of cis-acting regulatory elements suggest that the expression of TPS genes is regulated by a variety of hormones. RNA sequencing (RNA-seq) expression profile analysis revealed that the TPS genes had distinct spatiotemporal expression patterns, and several genes were highly and preferentially expressed in the leaves of cotton with gossypol glands (glanded cotton) versus a glandless strain. Virus-induced gene silencing (VIGS) of three TPS genes yielded plants characterized by fewer, smaller, and lighter gossypol glands, which indicated that these three genes were responsible for gland activity. Taken together, our results provide a solid basis for further elucidation of the biological functions of TPS genes in relation to gland activity and gossypol biosynthesis to develop cotton cultivars with low cottonseed gossypol contents.

GhCDNC and GhCYP706B1 genes mediate gossypol biosynthesis in upland cotton.

In cotton the identification and characterization of natural defense is a cost-effective, sustainable, and environment-friendly strategy to combat cotton pests. The secondary metabolites traits in cotton plant i.e., toxic gossypol glands play significant role for development and self-defense mechanism. To utilize gossypol in breeding implements, the understanding of gossypol initiation biosynthesis genes has vital importance at reproductive organ development stages. Cotton germplasm of 100 genotypes screened visually based on gossypol glandedness and a core set of ten genotypes was developed. Further three genotypes FH-330 (high glanding), F-280 (low glanding) and IRMA-197 (glandless) were used for determining the transcript abundance of twelve gossypol biosynthesis genes. Out of 100, germplasm categorized as (76) high glanding, (22) medium glanding), one genotype for each (low glanding) and (glandless) category. Real-time qPCR analysis revealed varied expression patterns among selected three genotypes. Out of twelve, three genes CYP706B1, CDNC and 2ODD-1 had strong expression levels in all tested tissues in high glanded genotype, while, slight or no expression of these genes was recorded in low glanding and glandless genotype, respectively. The shell of developing boll (10, 20, 30 DPA), and developing embryo (20, 30 DPA) showed substantially medium to maximum expression, respectively while high to medium expression was recorded in sepals and leaf tissue. Our study demonstrated that CYP706B1, CDNC and 2ODD-1 are the most promising genes involved in gossypol biosynthesis. Developing boll shell, developing embryo, leaf and sepal also have significant ability to synthesize gossypol. This will provide scientists a way to manipulate gossypol contents in economically important organs of cotton plant for targeted breeding.

Chemical Composition and Thermogravimetric Behaviors of Glanded and Glandless Cottonseed Kernels.

Common “glanded” (Gd) cottonseeds contain the toxic compound gossypol that restricts human consumption of the derived products. The “glandless” (Gl) cottonseeds of a new cotton variety, in contrast, show a trace gossypol content, indicating the great potential of cottonseed for agro-food applications. This work comparatively evaluated the chemical composition and thermogravimetric behaviors of the two types of cottonseed kernels. In contrast to the high gossypol content (3.75 g kg−1) observed in Gd kernels, the gossypol level detected in Gl kernels was only 0.06 g kg−1, meeting the FDA’s criteria as human food. While the gossypol gland dots in Gd kernels were visually observed, scanning electron microcopy was not able to distinguish the microstructural difference between ground Gd and Gl samples. Chemical analysis and Fourier transform infrared (FTIR) spectroscopy showed that Gl kernels and Gd kernels had similar chemical components and mineral contents, but the former was slightly higher in protein, starch, and phosphorus contents. Thermogravimetric (TG) processes of both kernels and their residues after hexane and ethanol extraction were based on three stages of drying, de-volatilization, and char formation. TG-FTIR analysis revealed apparent spectral differences between Gd and Gl samples, as well as between raw and extracted cottonseed kernel samples, indicating that some components in Gd kernels were more susceptible to thermal decomposition than Gl kernels. The TG and TG-FTIR observations suggested that the Gl kernels could be heat treated (e.g., frying and roasting) at an optimal temperature of 140–150 °C for food applications. On the other hand, optimal pyrolysis temperatures would be much higher (350–500 °C) for Gd cottonseed and its defatted residues for non-food bio-oil and biochar production. The findings from this research enhance the potential utilization of Gd and Gl cottonseed kernels for food applications.

Quantitative comparison of the storage protein distribution in glandless and glanded cottonseeds

AbstractGlanded (Gd) cottonseed (Gossypium hirsutum L.) contains scattered gossypol glands. Glandless (Gl) cottonseed is a new type of seed containing only trace levels of gossypol. This work quantitatively compared the content and migration pattern of Gd and Gl protein isolates. Both protein samples were subjected to sodium dodecyl sulfate (SDS)‐gel electrophoresis, and the protein gel bands were separated into seven partitions for peptide mass spectroscopic analysis. While multiple peptide fragments (isoformers) of vicilin and legumin proteins were present in both samples, the percentage of vicilins in total seed protein was higher in Gd (74.9%) than in Gl (63.4%). In contrast, legumin proteins were more abundant in Gl (30.4%) than Gd (23.6%). Minor protein components such as lipid‐related oleosins and vicilin‐like antimicrobial peptides 2‐2 were also observed at a relatively higher incidence in Gl compared with Gd, potentially reflecting a need for increased protein‐related defense capability in the absence of gossypol against natural predators or adverse growth environment.

Antixenosis in cotton genotypes (Gossypium hirsutum var. marie galante) to Spodoptera frugiperda (Lepidoptera: Noctuidae) mediated by trichome and gossypol densities

Cotton (Gossypium hirsutum L.) is one of the most important crops in Brazil and pest incidence limits its yields. The fall armyworm, Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae), native to tropical and subtropical America, spread and rapidly became an invasive pest worldwide. It is a polyphagous pest that feeds on up to 353 plant species including cotton. The objective of this study was to evaluate the antixenosis to S. frugiperda in 27 cotton genotypes, comparing varieties with non- commercial genotypes. The attractiveness was estimated in no-choice and free-choice tests, offering leaf discs of the 27 cotton genotypes to S. frugiperda, and counting the number of caterpillars feeding at 3, 5, 10, 15, and 30 minutes and 1, 2, 6, 12, and 24 hours after their release. The numbers of trichomes and gossypol glands per cm2 were measured on abaxial and adaxial surface. The free-choice test was performed in a randomized block design with the 27 genotypes (treatments) and 20 arenas (replicates). The no-choice assay was conducted as a completely randomized design with 18 genotypes and 20 replicates. The non-commercial genotypes PI0440, CE0467, PI0416, BA0512 and MA0425 presented antixenosis against S. frugiperda. In the free-choice test the cultivar BRS Buriti and the genotype PI0429 were the most attractive to S. frugiperda, while in no-choice test, the genotype PI0429 was the most attractive. High trichome density and gossypol glands did not influence the attractiveness of S. frugiperda in cotton genotypes, while the absence of trichomes was repellent to the caterpillars. There is polymorphism among cotton genotypes to attractiveness to the pest, and the genotypes with antixenosis can be used in future study in plant breeding program as donor source of resistance to S. frugiperda

Evaluation of cotton germplasm for morphological and biochemical host plant resistance traits against sucking insect pests complex

BackgroundSucking insect pests cause severe damage to cotton crop production. The development of insect resistant cotton cultivars is one of the most effective measures in curtailing the yield losses. Considering the role of morphological and biochemical host plant resistance (HPR) traits in plant defense, 12 cotton genotypes/varieties were evaluated for leaf area, leaf glanding, total soluble sugars, total soluble proteins, total phenolics, tannin and total flavonoids against fluctuating populations of whitefly, thrips and jassid under field conditions.ResultsThe population of these insects fluctuated during the growing season and remained above threshold level (whitefly > 5, thrips > (8–10), or jassid > 1 per leaf) during late June and early July. Strong and negative association of whitefly (r = − 0.825) and jassid (r = − 0.929) with seed cotton yield was observed. Mean population of insects were the highest in Glandless-1 followed by NIA-82 and NIA-M30. NIAB-Kiran followed by NIAB-878 and Sadori were the most resistant, with the mean population of 1.41, 1.60, 1.66 (whitefly); 2.24, 2.32, 2.53 (thrips) and 0.37, 0.31, 0.36 (jassid), respectively. The resistant variety NIAB-Kiran showed less soluble sugars (8.54 mg·g− 1), soluble proteins (27.11 mg·g− 1) and more phenolic (36.56 mg·g− 1) and flavonoids (13.10 mg·g− 1) as compared with the susceptible check Glandless-1. Moreover, all insect populations were positively correlated with total soluble sugars and proteins. Whitefly populations exhibited negative response to leaf gossypol glands, total phenolics, tannins and flavonoids. The thrips and jassid populations had a significant and negative correlation with these four biochemical HPR traits.ConclusionThe identified resistant resources and HPR traits can be deployed against sucking insect pests’ complex in future breeding programs of developing insect resistant cotton varieties.

Seed morphology and cytogenetic characterization of an endangered wild cotton, Gossypium turneri Fryxell, from Mexico

Cotton (genus Gossypium) is an important agricultural crop around the world because of its fiber. Gossypium turneri Fryxell is a wild cotton species endemic to the state of Sonora (northwestern Mexico), whose status has been recently raised to endangered in the IUCN Red List. This species has invaluable characteristics that could be useful in the cultivated cotton gene pool. Despite its importance, G. turneri has been studied very little. To the best of our knowledge, no previous study has characterized its seed morphology and cytogenetics. Therefore, in the present study the seed morphology and karyotype of G. turneri were analyzed. Seeds of G. turneri have nonuniform oval shape and brown-gray color. This species produces short fibers attached to its seed surface that are not long enough for commercial use. Our seed sizes were greater than those previously described for G. turneri and other diploid cottons. The length and width of seeds were 8.80 mm and 4.83 mm, respectively. Traits such as embryo and seed coat were measured and carefully observed, and gossypol glands were observed only in the embryo during the evaluation of internal features of seeds. Cytogenetic analysis revealed 26 chromosomes (2n = 2x = 26) in mitotic cells of G. turneri. The karyotype analysis showed mainly metacentric (m), submetacentric (sm) and subtelocentric (st) chromosomes. Our results reveal important biological traits of G. turneri that could be considered in future studies to improve cultivated cotton.

Effects of soil salinity on the expression of direct and indirect defences in wild cotton Gossypium hirsutum

Abstract Previous studies have frequently reported effects of abiotic factors on herbivore‐induced plant defences based on effects on single plant traits. However, plants commonly express multiple defences simultaneously and these traits are often correlated. Thus, a fuller understanding of abiotic‐context dependency in plant defence requires measuring multiple traits and addressing their patterns of correlated expression. We evaluated the effects of soil salinity on the expression of direct (phenolic compounds, gossypol gland density) and indirect (volatile organic compounds, extrafloral nectar) defensive traits in wild cotton Gossypium hirsutum. Specifically, we asked whether soil salinity affects the induction of these traits, and whether it shapes trait correlations potentially underlying altered patterns of trait induction. We conducted a factorial experiment with 16 cotton genotypes where we manipulated soil salinity and defence induction by applying artificial leaf damage (25% mechanical damage and caterpillar oral secretions) and measured defence levels at different time points post damage. Leaf damage induced most traits except gossypol gland density, whereas salinity did not have a mean effect (across constitutive and induced levels) on any of the measured traits. Nonetheless, salinity prevented the induction of phenolic compounds (condensed and hydrolysable tannins), and also affected trait correlations. Specifically, phenolic compounds were negatively associated with nectar production only under salinized conditions, an apparent trade‐off that could affect the induction of phenolic compounds. In addition, positive correlations between phenolic compounds and gland density and root biomass observed under control conditions were lost under salinized conditions. Synthesis. By investigating the effects of soil salinity on the expression of multiple direct and indirect defensive traits and their underlying correlations, these findings build towards a better understanding of how abiotic context dependency shapes plant allocation to and expression of multiple defensive traits.

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.

Physiological traits and anatomic structures of the seed for two short cotton season genotypes (Gossypium hirsutum L.) under water stress

Cotton (Gossypium hirsutum L.) is utilized commercially in the production of textile, clothing, and household goods. Its growth is affected by various environmental conditions such as soil, climate, and water supply. Irrigation is one of the most important factors for crop management. This research was designed with the aim of studying the biochemical and anatomical features of two genotypes of cottonseed (Latif and Golestan) in order to determine optimum irrigation. Protein, starch, gossypol gland, total soluble protein, starch content, and the anatomical structure of the cotton seeds were investigated. The data were analyzed using the SAS Software. The results showed that when rainfed, Golestan genotype seeds had a larger number of secretory cavities, soluble protein, and starch compared to Latif seeds. There was also a noticeable difference in the size of the seeds. Cellulosic cell walls and protein particles were also observed in the seed structure under induced water stress conditions. It can therefore be concluded that in response to water shortage, there was a noticeable change in the morphometric, anatomic, and biochemical features of the cottonseeds. It can be concluded that when rainfed, the Golestan genotype of cottonseed has more compatibility than the Latif genotype. In general, the application of different levels of irrigation showed that at moderate levels of irrigation, anatomical features appeared more normal. The observations indicate that at high levels of irrigation, some cells begin to dehisce due to osmotic stress, which results in a lack of accurate formation of tissue structures. The Golestan genotype is therefore the best suited for dryland farming.

Bottom-up control of geographic variation in insect herbivory on wild cotton (Gossypium hirsutum) by plant defenses and climate.

The occurrence and amount of herbivory are shaped by bottom-up forces, primarily plant traits (e.g., defenses), and by abiotic factors. Addressing these concurrent effects in a spatial context has been useful in efforts to understand the mechanisms governing variation in plant-herbivore interactions. Still, few studies have evaluated the simultaneous influence of multiple sources of bottom-up variation on spatial variation in herbivory. We tested to what extent chemical (phenolics, production of terpenoid glands) and physical (pubescence) defensive plant traits and climatic factors are associated with variation in herbivory by leaf-chewing insects across populations of wild cotton (Gossypium hirsutum). We found substantial population variation in cotton leaf defenses and insect leaf herbivory. Leaf pubescence, but not gossypol gland density or phenolic content, was significantly negatively associated with herbivory by leaf-chewing insects. In addition, there were direct effects of climate on defenses and herbivory, with leaf pubescence increasing toward drier conditions and leaf damage increasing toward wetter and cooler conditions. There was no evidence, however, of indirect effects (via plant defenses) of climate on herbivory. These results suggest thatspatial variation in insect herbivory on wild G. hirsutum is predominantly driven by concurrent and independent influences of population variation in leaf pubescence and climatic factors.

Isolation of Cottonseed Extracts That Affect Human Cancer Cell Growth

Cottonseeds are classified as glanded or glandless seeds depending on the presence or absence of gossypol glands. Glanded cottonseed has anticancer property and glandless cottonseed was reported to cause cancer in one animal study. It is important to investigate the effect of bioactive components from cottonseeds. Our objectives were to isolate ethanol extracts from cottonseeds and investigate their effects on human cancer cells. A protocol was developed for isolating bioactive extracts from seed coat and kernel of glanded and glandless cottonseeds. HPLC-MS analyzed the four ethanol extracts but only quercetin was identified in the glandless seed coat extract. Residual gossypol was detected in the glanded and glandless seed kernel extracts and but only in the glanded seed coat extract. Ethanol extracts were used to treat human cancer cells derived from breast and pancreas followed by MTT assay for cell viability. Ethanol extracts from glanded and glandless cottonseed kernels and gossypol significantly decreased breast cancer cell mitochondrial activity. Ethanol extract from glanded cottonseed kernel and gossypol also significantly decreased pancreas cancer cell mitochondrial activity. These results suggest that ethanol extracts from cottonseeds, like gossypol, contain anticancer activities.

Cladistic analysis of some taxa in Malvaceae s.l. “Core Malvales” based on anatomical characteristics

Malvaceae s.l. “Core Malvales” which in their broad circumscription include members of four traditional families; Malvaceae s.s., Bombacaceae, Sterculiaceae and Tiliaceae. The aim of the present study is to evaluate the use of stem, petiole and lamina anatomical characters in analyzing the phylogenetic relationships among 39 studied taxa from Malvaceae s.l. in addition to one representative of Elaeocarpaceae as outgroup through the parsimony analysis using upgraded WinClada and TNT cladistics programs. The anatomy in cross section of stem, petiole and lamina of the 40 studied taxa of Core Malvales were examined by light microscope and photos were taken. The different anatomical characters are discussed and revealed that certain synapomorphic diagnostic characters has great taxonomic values which in turn used for analyzing the phylogenetic relationships between the studied taxa. These characters viz. (petiole outline and vascular system, cuticle thickness, diverse shapes of secondary phloem fibers, presence and types of crystals and trichomes, gossypol gland, resin ducts, tanniferous cells, star-shaped idioblasts, vessels size and distribution, anomalous xylem structure, extrafloral nectaries, ...). Our results of the phylogenetic analysis conducted from the cladogram (rooted tree) based on 44 anatomical characters and 111 character states strongly support the monophyly of family Malvaceae s.s. while, the other three families are para- or polyphyletic. It shows, also the graduation of the taxa under study in relation to the outgroup; from Tiliaceae and Sterculiaceae directly attached to the tree (ancestor) while taxa from Bombacaceae and Malvaceae are far away from the root of the tree with little deviation. This indicates that Tiliaceae is the most primitive family followed by Sterculiaceae, Bombacaceae ending recently by the most advanced family Malvaceae. Our results agree to some extent with APG IV classification in transferring Elaeocarpaceae to order Oxalidales instead of Malvales also agree with other worker in transferring Gossypium and Lagunaria in family Sterculiaceae while transferring Dombeya to family Tiliaceae. For more accurate assignment of Malvaceae s.l. still more studies on a large number of taxa are needed.

Effects of plant morphology on the incidence of sucking insect pests complex in few genotypes of cotton

The study was conducted to find the role of physico-morphic plant factors viz., number of gossypol glands, hair density, length of hair, plant height and thickness of leaf lamina per plant in fluctuating the population of thrips (Thrips tabaci Lind.), jassid (Amrasca bigutella Dist.) and whitefly (Bemisia tabaci Genn.) on six genotypes of cotton viz., BT-703, CIM-557, CIM-608, CIM-573, BT-3701 and FH-113. All the genotypes showed significant differences against sucking insect pest population. Whitefly adult population exhibited negative response with gossypol glands on leaf lamina, midrib and vein and also with plant height. Whitefly adult and nymphal population correlated positively with hair density on leaf lamina and vein and length of hair on leaf midrib. The nymphal and adult population of jassid showed positive correlation with gossypol glands on leaf lamina, vein and length of hair on leaf lamina, midrib and vein. Adult and nymph population of jassid revealed negative response with hair density on leaf lamina and midrib and also with plant height and leaf lamina thickness. Thrips population showed negative correlation with gossypol glands on leaf midrib, vein, length of hair on leaf lamina and vein. Thrips population correlated positively with hair density on leaf midrib, thickness of leaf lamina and plant height. The genotypes CIM-608 (3.70/leaf), CIM-608 (5.67 /leaf), BT-703(0.86/leaf), BT-703 (1.14/leaf) and FH-113 (0.34/leaf) were found to be susceptible, whereas FH-113 (2.85/leaf), CIM-557 (3.46/leaf), CIM-573 (0.40/leaf), CIM-557 (0.48/leaf) and BT-703 (0.08/leaf) were resistant to whitefly adult, whitefly nymph, jassid adult, jassid nymph and thrips population respectively.

Microscopic Methods to Evaluate Gland Initiation and Development in Cotton Ovules

Gossypol is a terpenoid aldehyde found in cotton (Gossypium hirsutum L.) glands that are located throughout the plant and seed, where it serves a protective function against pests and pathogens. Cottonseed use is limited mainly to cattle feed because gossypol is toxic to most animals except ruminants. Lowering gossypol content in the seed would increase the possible uses for cottonseed. Developing new strategies to modify gossypol in cottonseed requires a better understanding of the development of gossypol containing glands. The first step is to determine when gossypol glands are initiated and filled with gossypol. Gland development was investigated using microscopic images of developing seeds from 10 glanded and two glandless cotton lines. A digital microscope with a VH-Z20R (20X to 200X) lens was used to capture developing ovule (seed) images at 14 to 22 d after flowering (DAF). One boll per plot was imaged for each DAF time point and five different sets of time intervals were collected in each of two years. Imaging revealed empty glands forming as early as 14 DAF and as late as 20 DAF. For most of the entries, some glands were filling by 18 DAF and as early as 16 DAF for ultra early lines (< 110 d to maturity).

Biological aspects of Aphis gossypii Glöver, 1877 (Hemiptera: Aphididae) on colored lint cotton cultivars

This paper outlines the results of a study into the biological aspects of Aphis gossypii Glöver on colored cotton cultivars through the construction of life tables. In addition, we evaluate the influence of density of gossypol glands and trichomes of leaves on the biology of the aphid. Tests were conducted in a climate chamber at 25 ± 2°C, with relative humidity (RH) at 70 ± 10%, and a photophase of 12 hours, using the cultivars BRS Rubi, BRS Safira, and BRS Verde. Newly hatched nymphs were individually isolated in petri dishes containing leaf discs of cotton cultivars on a layer of water-agar (1%) of approximately 5 mm thick. An evaluation of the trichomes and gossypol gland densities of the cotton leaf plants was performed under a stereomicroscope, delimited to an area of 1 cm², and a count and identification of those on the surface was made. The feed substrates that were evaluated influenced the nymphal stage of A. gossypii. BRS Verde provided the shortest duration and BRS Safira was the longest during this phase. The cultivar BRS Verde, with the lowest density of trichomes, provided a large number of nymphs and led to a higher net reproductive rate (R0). Given these results, conclusions can be drawn that the colored cotton cultivars influence the duration of nymphal and adult stages of A. gossypii. The cultivar with a high density of trichomes on leaves (BRS Safira) adversely affects the fertility parameters of A. gossypii.

Morphological basis of resistance to spotted bollworm, Earias vittella (Fabricius) in Asiatic cotton

Ten genotypes of Asiatic cotton, Gossypium arboreum, viz. C-353, G 17, G 33, AC-3545, LD 491, LD 575, B 11 A, SAG-BLY (Red), Sargosi and LD 694, were screened under epiphytotic conditions against spotted bollworm, Earias vittella, at the cotton farm of the Department of Plant Breeding and Genetics, Punjab Agricultural University, Ludhiana, India, and their morphological basis of resistance to spotted bollworm was studied. The plant characters examined were plant color, leaf shape, size and shape of bract, density of gossypol glands, nectaries, hair density and hair length. Hair density was positive (r = 0.81, P = 0.005) and significantly correlated with the number of eggs laid by E. vittella, whereas a significantly negative (r = –0.66, P = 0.038) correlation was obtained with gossypol glands. Similarly, correlation of larval population with hair density was significantly positive (r = 0.68, P = 0.030) and gossypol glands were negative (r = –0.63, P = 0.050) and significantly correlated with larval population. The R2 values, computed together for multiple regression analysis, indicated that the morphological plant traits, viz., gossypol glands and hair density, cumulatively contributed 67% and 50% variability in the egg and larval population, respectively. Genotype B 11 A, with the lowest egg and larval population, had a high number of gossypol glands, low hair density and smaller bracts and proved to be the best, followed by LD 491. Genotypes with low hair density, smaller bracts and a greater number of gossypol glands are desirable for low oviposition and larval population of E. vittella. These characteristics should be taken into consideration when planning a resistance breeding program against spotted bollworm in arboreum cotton.

Friend or Foe?: A Plant's Induced Response to an Omnivore

Omnivorous natural enemies of herbivores consume plant-based resources and may elicit induced resistance in their host plant. A greater induction threshold for damage produced by omnivorous predators than for strict herbivores might be expected if omnivore performance is enhanced on noninduced plants, allowing them to reduce future levels of herbivory. Currently, it is not known if a plant responds to feeding by omnivorous predators and by herbivores similarly. To examine this question, we chose herbivore and omnivore species that produce the same kind of quantifiable damage to cotton leaves, enabling us to control statistically for the intensity of plant damage, and ask whether plant responses differed depending on the identity of the damaging species. We first compared changes in plant peroxidase activity, gossypol gland number and density, and leaf area in response to feeding by the spider mite Tetranychus turkestani (Ugarov and Nikolski) (an herbivore) and by one of the mite’s principal natural enemies, the western flower thrips Frankliniella occidentalis (Pergande) (an omnivore). Both species increased the activity of peroxidase, but when we controlled for the amount of damage, the peroxidase activity of mite-damaged plants was higher than that of thrips-damaged plants. We also found that thrips, but not spider mites, increased the density of gossypol glands in the second true leaf. In a second experiment we included an additional herbivore, the bean thrips Caliothrips fasciatus (Pergande), to see if the different responses of cotton to thrips and mite herbivory we first observed were attributable to differences in trophic function (herbivore versus omnivore) or to other differences in feeding generated by thrips versus mites. Cotton plants exhibited the same pattern of induced responses (elevated peroxidase, increased number of glands, reduced leaf area) to herbivory generated by the bean thrips (an herbivore) and western flower thrips (an omnivore), suggesting that trophic function was not a key determinant of plant response. Thrips-damaged plants again showed a significantly higher density of gossypol glands than did mite-damaged plants. Overall, our results suggest that (1) an omnivorous predator systemically induces resistance traits in cotton and (2) whereas there is evidence of taxonomic specificity (thrips versus mites), there is little support for trophic specificity (herbivorous thrips versus omnivorous thrips) in the elicitation of induced responses.