Cotton Germplasm Research Articles

Development of an eco-friendly pink cotton germplasm by engineering betalain biosynthesis pathway.

Development of an eco-friendly pink cotton germplasm by engineering betalain biosynthesis pathway.

Registration of Arkot 0902 cotton germplasm line

AbstractArkot 0902 (Reg. no. GP‐1130, PI 700940) is a conventional cotton (Gossypium hirsutum L.) germplasm line released by the Arkansas Agricultural Experiment Station in May 2022. Arkot 0902 was derived from a cross of ‘GA 230’ (PVP 201500309) and Arkot 0012. Over 5 yr and four test sites in Arkansas, Arkot 0902 produced 10 and 20% higher lint yields than ‘UA222’ and ‘UA48’, respectively. The high lint yield of Arkot 0902 was attributed to producing more (and smaller) seed per area than UA222 or UA48. Arkot 0902 possesses leaf and stem pubescence similar to UA48 (smooth leaf) but has higher density of marginal bract trichomes. Arkot 0902 displayed high resistance to bacterial blight and was similar to UA222 and UA48 in their response to other diseases. Arkot 0902 was more resistant to tarnished plant bug than UA48 and equal to UA222. Most fiber quality traits of Arkot 0902 approached those of UA48, a high fiber–quality cultivar.

Registration of Arkot 1005, Arkot 1015, and Arkot 1019 cotton germplasm lines

AbstractArkot 1005 (Reg. no. GP‐1127, PI 700852), Arkot 1015 (Reg. no. GP‐1128, PI 700853), and Arkot 1019 (Reg. no. GP‐1129, PI 700854) are conventional cotton (Gossypium hirsutum L.) germplasm lines released by the Arkansas Agricultural Experiment Station in April 2022. The lines were compared with UA48 and UA222 (check cultivars) in replicated field tests at four Arkansas sites over 5 yr. Over these tests, lint yields of the three lines did not differ from each other and were greater than UA48. Lint yield of Arkot 1015 was greater than UA222, while lint yields of Arkot 1005 and Arkot 1019 were equal to UA222. Performance in regional tests indicates that the lines have wide adaptation. The lint yields of Arkot 1015 and Arkot 1019 were attributed to producing more (and smaller) seed per area and less lint per seed (lint index) than UA222. Arkot 1005 produced higher lint index than the other two lines and the two check cultivars. Seed per area for Arkot 1005 was higher than UA48, equal to UA222, and lower than Arkot 1015 and Arkot 1019. Leaf pubescence, stem pubescence, and bract trichome density of the three lines were intermediate between UA222 and UA48. All three lines displayed high resistance to bacterial blight and were similar to UA222 and UA48 in their response to other diseases. Arkot 1015 was more resistant to tarnished plant bug (TPB) than Arkot 1005, Arkot 1019, and UA48, but all were more susceptible to TPB than UA222. Compared with the other lines and check cultivars, Arkot 1005 and Arkot 1019 displayed higher and lower, respectively, resistance to seed deterioration. Fiber quality of Arkot 1019 was superior to UA48, UA222, and the other lines. Fiber quality of Arkot 1005 and Arkot 1015 was superior to UA222.

Registration of 17 upland cotton germplasm lines with improved resistance to Fusarium wilt race 4 and good fiber quality

AbstractWith Fusarium wilt (Fusarium oxysporum f. sp. vasinfectum W.C. Snyder & H.N. Hansen) race 4 (FOV4) formally identified in proximity to the High Plains of west Texas—the largest upland cotton (Gossypium hirsutum L.) producing region in the United States—the need to develop cultivars resistant to FOV4 has become urgent. Currently, there are no commercial upland cultivars available claiming FOV4 resistance. Fusarium wilt race 4, a soil‐borne fungus, has affected the cotton crop in the San Joaquin Valley of California for two decades. The primary purpose for the release of the upland PSSJ‐FRU01–PSSJ‐FRU17 (Reg. no. GP‐110–GP‐1126, PI 699966–PI 699982) germplasm lines is to provide cotton breeders with urgently needed sources for FOV4 resistance in upland cotton. The lines were derived from six different cross‐combinations using 10 parental lines with different genetic backgrounds (e.g., ‘DES 920’ [PI 536522], ‘NM12Y1004’ [NuMex COT 15 GLS, PI 678371], ‘MARS ROSE CLUSTER’ [PI 528483], ‘AUBURN M’ [PI 529214], and ‘SA‐3208’ [LIAO MIAN 7 HAO]). Several cycles of selection were applied to these developed lines based on an asymptomatic single plant selection after greenhouse FOV4 inoculations or infested field evaluations from F1 to F4. In 2019–2021 evaluations, germplasm lines showed enhanced resistance to FOV4 with significantly lower percentage mortality and vascular root staining as compared to resistant controls (‘Pima‐S6’ and ‘PHY 881 RF’) and improved fiber strength and some long fibers. These released lines will help to reduce the vulnerability of upland cotton to this fungal pathogen and advance efforts to broaden the resistance genetic base which is critical for the upland cotton industry.

Evaluation of Genetic Potential of Cotton Lines against Whitefly Tolerance

Cotton (Gossypium hirsutism L.) is a primary source of natural fiber, fuel, wood, and oil worldwide and an essential raw material source for the textile industry. Whitefly (Bemisia tabaci) is one of the major pests distributed worldwide and has broad genetic diversity. In this research, the genetic diversity in the cotton germplasm was explored against the whitefly infestation. Broad sense heritability is a common approach used to detect the association and inheritance of the target trait. Maximum (PIC 0.96) and minimum (PIC 0.36) polymorphism was explored by the SSR primer NAU 988 and NAU 5121, respectively, with an average value of 0.73. Pair-wise genetic estimation ranged from 0.500 to 1.00. Neighbor-joining (NJ) tree, based on UPGMA (Unweighted pair group method with arithmetic), grouped the genotypes into six main clusters, i.e., A, B, C, D, E, and F. Maximum accessions fall into a single cluster showing low genetic diversity among them. The upland cotton accessions FH 326, SLH 07, FH18, and Cris 541, showed divergence from the rest of the genotypes and might have resistance against the whitefly attack. Our results also explain the utilization of the SSR markers to explore genetic diversity and its utilization in a cotton breeding program.

Biochemical Evaluation of Cotton Genotypes using Soluble Protein, Esterase (EST), Peroxidase (POX) And Polyphenol Oxidase (PPO) and their Role in Plant Disease Resistance

Isozyme analysis is a powerful biochemical technique that has numerous applications in plant biology. It has long been used by geneticists to study the population genetics. The isozyme esterase, peroxidase and polyphenol oxidase were standardized for upland cotton (Gossypium hirsutum L.) germplasm lines collected from all over the country. The knowledge of nature and magnitude of genetic diversity present in the germplasm is most important pre-requisite for the success of any breeding program. The thirty-four cotton germplasm lines were screened for prime three isozymes based on quantification assay and qualitative PAGE profiling. Among the material, the genotype AKH – 24 (190.60 mg ml-1), AKH – 053 (189.42 mg ml-1) and VIKAS (184.53 mg ml-1) recorded high protein content, whereas the enzymatic activities of esterase, peroxidase and polyphenol oxidase exhibited remarkable differences along with the protein content. The genotype LRA–5166 exhibited high esterase (462.68 mM mg protein-1 min-1) and peroxidase activity (250.97mM mg protein-1 min-1), while AKH – 24 recorded the maximum polyphenol oxidase activity (131.45 mM mg protein-1min-1). The banding pattern of biochemical markers revealed that the maximum number of bands were recorded in esterase analysis (fifteen) followed by protein (twelve) whereas, only five bands each were detected in peroxidase and polyphenol oxidase analysis indicating limited polymorphism. The Relative Mobility (Rm) values were ranged from 0.083 to 0.883 (protein), 0.100 to 0.971 (esterase), 0.033 to 0.283 (peroxidase) and 0.048 to 0.206 (polyphenol oxidase). The present study demonstrated that cotton genotypes could be differentiated by their quantity and quality through electrophoretic banding profiles. These results could be of practical value for cultivar identification, purity testing along with associated prediction of pest and disease resistance. However, the major constraint is that these biochemical markers do not able to reproduce the similar kind of variation pattern, but can provide strong distinguishing polymorphism each time.

Structure and character analysis of cotton response regulator genes family reveals that GhRR7 responses to draught stress

BackgroundCytokinin signal transduction is mediated by a two-component system (TCS). Two-component systems are utilized in plant responses to hormones as well as to biotic and abiotic environmental stimuli. In plants, response regulatory genes (RRs) are one of the main members of the two-component system (TCS).MethodFrom the aspects of gene structure, evolution mode, expression type, regulatory network and gene function, the evolution process and role of RR genes in the evolution of the cotton genome were analyzed.ResultA total of 284 RR genes in four cotton species were identified. Including 1049 orthologous/paralogous gene pairs were identified, most of which were whole genome duplication (WGD). The RR genes promoter elements contain phytohormone responses and abiotic or biotic stress-related cis-elements. Expression analysis showed that RR genes family may be negatively regulate and involved in salt stress and drought stress in plants. Protein regulatory network analysis showed that RR family proteins are involved in regulating the DNA-binding transcription factor activity (COG5641) pathway and HP kinase pathways. VIGS analysis showed that the GhRR7 gene may be in the same regulatory pathway as GhAHP5 and GhPHYB, ultimately negatively regulating cotton drought stress by regulating POD, SOD, CAT, H2O2 and other reactive oxygen removal systems.ConclusionThis study is the first to gain insight into RR gene members in cotton. Our research lays the foundation for discovering the genes related to drought and salt tolerance and creating new cotton germplasm materials for drought and salt tolerance.

Genetic variability, correlation and path analysis of upland cotton (Gossypium hirsutum L.) germplasm for seed cotton yield

One hundred upland cotton germplasm accessions were evaluated for eight traits to evaluate the per se performance, genetic variability, heritability, genetic advance as a per cent of mean, correlation and path analysis. The estimation of variability indicated that the number of monopodia per plant had high GCV and PCV. High heritability along with high GAM was  found in plant height, internode length, the number of monopodia per plant, the number of sympodia per plant, the number of bolls per plant and seed cotton yield per plant which suggested that additive gene activity had a significant influence in the inheritance of these traits. Correlation analysis showed that the number of sympodia per plant, the number of bolls per plant and boll weight have a significant high positive correlation on the seed cotton yield. Path analysis showed that the number of bolls per plant and boll weight had the highest positive direct effect on seed cotton yield per plant. Keywords: Cotton, phenotypic coefficient of variation (PCV), genotypic coefficient of variation (GCV), heritability, genetic advance, correlation, path analysis.

Transcriptomics for Drought Stress Mediated by Biological Processes in-relation to Key Regulated Pathways in Gossypium darwinii.

Wild cotton Gossypium darwinii, an allotetraploid harbours important traits useful for tolerating abiotic stress, i.e., drought, salt and good genetic stability, hence these characteristics can be transferred to cultivated cotton for genetic improvement. In this study, we analyzed the RNA-seq transcriptomes from leaves of G. darwinii seedlings with and without drought stress. A total of 86.7 million valid reads with an average length of 95.79bp were generated from the two samples and 58,960 transcripts with a length of more than 500bp were assembled. We searched the known proteins on the strength of sequence similarity; these transcripts were annotated with COG, KEGG and GO functional categories. According to gene expression abundance RPKM value, we carried out RT-qPCR analysis to determine the expression pattern of the obtained transcription factors. A total of 58,960 genes was differentially expressed (DEG), with 32,693 and 25,919 genes found to be upregulated and downregulated, respectively. Through gene ontology and KEGG pathways, the upregulated genes were found to associate with all the GO terms, molecular functions (MF), biological process (BP) and cellular components (CC), which are highly linked to enhancing drought stress tolerance. The study provides an in-depth knowledge of regulation of pathways and genes involved in photosynthesis during drought stress in G. darwinii. These pathways and genes were found to be significantly downregulated and this information could be further utilized by cotton breeders in developing a more drought tolerant cotton germplasm.

Assessment of genetic variability in cotton (Gossypium hirsutum L.) genotypes

The selection of high-yielding cotton lines is critical for the evaluation of phenotypic characteristics. For Cotton Breeders, it is always in preference to select desirable genotypes, based on the diversified characters from the available germplasm. The selected phenotypic diversity can be useful for aiding information in parental selection, adherence to this, a set of 12 advanced cotton lines were evaluated for genetic diversity at Cotton Research Institute, Tandojam during Kharif season in the year of 2020. The experiment was laid out in Randomized Complete Block Design (RCBD) with three replications while seven agronomical traits, were included in the experiment. The mean square of genotypes, was differed significantly (P<0.05) for all studied traits, representing that genetic diversity exists in these cotton germplasms and can be used in further utilization. Considering the agronomic performance, the genotype of B-2 was on the top in average values including plant height (174.40 cm), bolls plant-1 (42.067), seed cotton yield plant-1(139.34 g), GOT% (37.800%), and staple length (28.00 mm), hence indicating its valuable breeding resources for future cotton breeding. A Genetic Distance of 92.683 was found between B5 and B2 genotypes, which is high enough, and revealing that this pair may be used in a hybridization program for vigorous hybrid production and better selection in subsequent generations. The Variance Percentages for the first, second, and third principal components were 42.70, 23.10, and 17.20, respectively. The first three components contributed 83.00 percent of the variation for genotypes, which is high enough for the cotton crop improvements. The cotton genotypes, were divided into three categories, based on phenotypic data. The number of groups obtained, might be beneficial in generating cotton genotypes with a variety of characteristics and diversifying the Cotton Gene Pool. Keywords: cotton, genetic variations, morphological traits, seed yield.

Perennial Cotton Ratoon Cultivation: A Sustainable Method for Cotton Production and Breeding.

Cotton production is challenged by high costs with multiple management and material inputs including seed, pesticide, and fertilizer application. The production costs can be decreased and profits can be increased by developing efficient crop management strategies, including perennial cotton ratoon cultivation. This review focuses on the role of ratoon cultivation in cotton productivity and breeding. In areas that are frost-free throughout the year, when the soil temperature is suitable for cotton growth in spring, the buds of survived plants begin to sprout, and so their flowering and fruiting periods are approximately 4–6 weeks earlier than those of sown cotton. Due to the absence of frost damage, the ratoon cotton continues to grow, and the renewed plants can offer a higher yield than cotton sown in the following season. Moreover, ratoon cultivation from the last crop without sowing can help conserve seeds, reduce labor inputs, and reduce soil and water loss. In this review, the preservation of perennial cotton germplasm resources, the classification and genome assignment of perennial species in the cotton gene pools, and effective strategies for the collection, preservation, identification, and utilization of perennial cotton germplasms are discussed. Ratoon cultivation is the main driver of cotton production and breeding, especially to maintain male sterility for the utilization and fixation of heterosis. Ratoon cultivation of cotton is worth adopting because it has succeeded in Brazil, China, and India. Therefore, taking advantages of the warm environment to exploit the indeterminant growth habit of perennial cotton for breeding would be an efficiency-increasing, cost-saving, and eco-friendly approach in frost-free regions. In the future, more attention should be given to ratooning perennial cotton for breeding male-sterile lines.

Overexpression of AmCBF1 enhances drought and cold stress tolerance, and improves photosynthesis in transgenic cotton.

China’s main cotton production area is located in the northwest where abiotic stresses, particularly cold and drought, have serious effects on cotton production. In this study, Ammopiptanthus mongolicus C-repeat-binding factor (AmCBF1) isolated from the shrub Ammopiptanthus mongolicus was inserted into upland cotton (Gossypium hirsutum L.) cultivar R15 to evaluate the potential benefits of this gene. Two transgenic lines were selected, and the transgene insertion site was identified using whole-genome sequencing. The results showed that AmCBF1 was incorporated into the cotton genome as a single copy. Transgenic plants had distinctly higher relative water content (RWC), chlorophyll content, soluble sugar content, and lower ion leakage than R15 after drought and cold stress. Some characteristics, such as the area of lower epidermal cells, stomatal density, and root to shoot ratio, varied significantly between transgenic cotton lines and R15. Although the photosynthetic ability of transgenic plants was inhibited after stress, the net photosynthetic rate, stomatal conductance, and transpiration rate in transgenic plants were significantly higher than in R15. This suggested that an enhanced stress tolerance and photosynthesis of transgenic cotton was achieved by overexpressing AmCBF1. All together, our results demonstrate that the new transgenic cotton germplasm has great application value against abiotic stresses, especially in the northwest inland area of China.

Overexpression of LT, an Oncoprotein Derived from the Polyomavirus SV40, Promotes Somatic Embryogenesis in Cotton.

Although genetic transformation has opened up a new era for cotton molecular breeding, it still suffers from the limitation problem of long transformation periods, which slows down the generation of new cotton germplasms. In this study, LT gene (SV40 large T antigen), which promotes the transformation efficiency of animal cells, was codon-optimized. Its overexpression vector was transformed into cotton. It was observed that EC (embryogenic callus) formation period was 33% shorter and transformation efficiency was slightly higher in the LT T0 generation than that of control. RNA-seq data of NEC (non-embryonic callus) and EC from LT and control revealed that more DEGs (differential expression genes) in NEC were identified than that of EC, indicating LT mainly functioned in NEC. Further KEGG, GO, and transcription factor analyses showed that DEGs were significantly enriched in brassinosteroid biosynthesis pathways and that bHLH, MYB, and AP2/ERF were the top three gene families, which are involved in EC formation. In addition, the key genes related to the auxin pathway were differentially expressed only in LT overexpression NEC, which caused early response, biosynthesis, and transportation of the hormone, resulting in EC earlier formation. In summary, the results demonstrated that LT can promote somatic embryogenesis in cotton, which provides a new strategy for improving cotton transformation and shortening EC formation time.

Core Collections: Is There Any Value for Cotton Breeding?

Global plant breeding activities are reliant on the available genetic variation held in extant varieties and germplasm collections. Throughout the mid- to late 1900s, germplasm collecting efforts were prioritized for breeding programs to archive precious material before it disappeared and led to the development of the numerous large germplasm resources now available in different countries. In recent decades, however, the maintenance and particularly the expansion of these germplasm resources have come under threat, and there has been a significant decline in investment in further collecting expeditions, an increase in global biosecurity restrictions, and restrictions placed on the open exchange of some commercial germplasm between breeders. The large size of most genebank collections, as well as constraints surrounding the availability and reliability of accurate germplasm passport data and physical or genetic characterization of the accessions in collections, limits germplasm utilization by plant breeders. To overcome these constraints, core collections, defined as a representative subset of the total germplasm collection, have gained popularity. Core collections aim to increase germplasm utilization by containing highly characterized germplasm that attempts to capture the majority of the variation in a whole collection. With the recent availability of many new genetic tools, the potential to unlock the value of these resources can now be realized. The Commonwealth Scientific and Industrial Research Organisation (CSIRO) cotton breeding program supplies 100% of the cotton cultivars grown in Australia. The program is reliant on the use of plant genetic resources for the development of improved cotton varieties to address emerging challenges in pest and disease resistance as well as the global changes occurring in the climate. Currently, the CSIRO germplasm collection is actively maintained but underutilized by plant breeders. This review presents an overview of the Australian cotton germplasm resources and discusses the appropriateness of a core collection for cotton breeding programs.

Leveraging National Germplasm Collections to Determine Significantly Associated Categorical Traits in Crops: Upland and Pima Cotton as a Case Study.

Observable qualitative traits are relatively stable across environments and are commonly used to evaluate crop genetic diversity. Recently, molecular markers have largely superseded describing phenotypes in diversity surveys. However, qualitative descriptors are useful in cataloging germplasm collections and for describing new germplasm in patents, publications, and/or the Plant Variety Protection (PVP) system. This research focused on the comparative analysis of standardized cotton traits as represented within the National Cotton Germplasm Collection (NCGC). The cotton traits are named by ‘descriptors’ that have non-numerical sub-categories (descriptor states) reflecting the details of how each trait manifests or is absent in the plant. We statistically assessed selected accessions from three major groups of Gossypium as defined by the NCGC curator: (1) “Stoneville accessions (SA),” containing mainly Upland cotton (Gossypium hirsutum) cultivars; (2) “Texas accessions (TEX),” containing mainly G. hirsutum landraces; and (3) Gossypium barbadense (Gb), containing cultivars or landraces of Pima cotton (Gossypium barbadense). For 33 cotton descriptors we: (a) revealed distributions of character states for each descriptor within each group; (b) analyzed bivariate associations between paired descriptors; and (c) clustered accessions based on their descriptors. The fewest significant associations between descriptors occurred in the SA dataset, likely reflecting extensive breeding for cultivar development. In contrast, the TEX and Gb datasets showed a higher number of significant associations between descriptors, likely correlating with less impact from breeding efforts. Three significant bivariate associations were identified for all three groups, bract nectaries:boll nectaries, leaf hair:stem hair, and lint color:seed fuzz color. Unsupervised clustering analysis recapitulated the species labels for about 97% of the accessions. Unexpected clustering results indicated accessions that may benefit from potential further investigation. In the future, the significant associations between standardized descriptors can be used by curators to determine whether new exotic/unusual accessions most closely resemble Upland or Pima cotton. In addition, the study shows how existing descriptors for large germplasm datasets can be useful to inform downstream goals in breeding and research, such as identifying rare individuals with specific trait combinations and targeting breakdown of remaining trait associations through breeding, thus demonstrating the utility of the analytical methods employed in categorizing germplasm diversity within the collection.

Improved Upland Cotton Germplasm for Multiple Fiber Traits Mediated by Transferring and Pyramiding Novel Alleles From Ethyl Methanesulfonate-Generated Mutant Lines Into Elite Genotypes.

Ethyl methanesulfonate (EMS) mutagenesis offers important advantages for improving crops, such as cotton, with limited diversity in elite gene pools. EMS-induced point mutations are less frequently associated with deleterious traits than alleles from wild or exotic germplasm. From 157 mutant lines that have significantly improved fiber properties, we focused on nine mutant lines here. A total of eight populations were developed by crossing mutant lines in different combinations into GA230 (GA2004230) background. Multiple lines in each population were significantly improved for the fiber trait that distinguished the donor parent(s), demonstrating that an elite breeding line (GA230) could be improved for fiber qualities using the mutant lines. Genotypes improved for multiple fiber traits of interest suggesting that allele pyramiding is possible. Compared to midparent values, individual progeny in the population conferred fiber quality improvements of as much as 31.7% (in population O) for micronaire (MIC), 16.1% (in population P) for length, 22.4% (in population K) for strength, 4.1% (in population Q) for uniformity, 45.8% (in population N) for elongation, and 13.9% (in population O) for lint percentage (lint%). While further testing for stability of the phenotype and estimation of yield potential is necessary, mutation breeding shows promise as an approach to reduce the problem of the genetic bottleneck of upland cotton. The populations developed here may also contribute to identifying candidate genes and causal mutations for fiber quality improvement.

Genome –wide Allelic Variations and Population Structure Analysis of Cotton Genotypes using SSR Markers

The limited genetic base of modern cotton genotypes makes it difficult to improve cotton fibre yield and quality, emphasizing the necessity to study existing cotton germplasm resources. Therefore, this study was conducted to assess the genetic diversity and population structure of different cotton genotypes at DNA level. A total of 105 cotton genotypes were analyzed using 208 polymorphic SSR markers which were distributed on both A and D genomes. The total number of alleles in all genomes are 1382 Out of which 665 and 717 alleles were recorded in A and D genomes, respectively. In A genome, the maximum PIC values; 0.89 was observed for markers M92, M82 and M76 with the 10-total number of alleles exhibiting 100% polymorphism. These markers (M92, M82 and M76) located at the chromosomes 12A, 11A and 10A respectively with the estimation of 0.84 gene diversity. The highest PIC value 0.89 of D genome was detected for M191, M128 and M117 markers on 24D, 16D and 15D chromosomes with the 10 total numbers of alleles having the 0.84 values of gene diversity with 100% polymorphism. The UPGMA cluster DARWIN tree and Model-based Bayesian analysis clustered the studied cotton germplasm into four subpopulations, and the highest molecular variation revealed among subpopulations. Phylogenetic tree constructed for the whole germplasm population identified four major groups including; Group 1, Group 2, Group 3 and Group 4 consisting of 12, 21, 39 and 69 genotypes, respectively. Genetic distances among clusters clearly showed the variations among one another. SSR markers appear to be useful and reliable assets for future genetic and genomic analyses of cotton, such as genetic map construction, comparative genomic analyses, genetic diversity, and molecular marker-assisted breeding to select promising cotton genotypes, according to the current experiment.

Analysis of a tetraploid cotton line Mac7 transcriptome reveals mechanisms underlying resistance against the whitefly Bemisia tabaci.

Whitefly inflicts both direct and indirect losses to cotton crop. Whitefly resistant cotton germplasm is a high priority and considered among the best possible solutions to mitigate this issue. In this study, we evaluated cotton leaf curl disease (CLCuD) resistant cotton line Mac7 under whitefly stress. Furthermore, we utilized the already available transcriptome data of Mac7 concerning whitefly stress to elucidate associated mechanisms and identify functionally important genes in cotton. In transcriptomic data analysis, differentially expressed genes (DEGs) were found involved in complex relay pathways, activated on whitefly exposure. The response implicates signalling through resistance genes (R-genes), MAPK, ROS, VQs or RLKs, transcription factors, which leads to the activation of defence responses including, Ca2+messengers, phytohormonal cross-talk, gossypol, flavonoids, PhasiRNA and susceptibility genes (S-genes). The qRT-PCR assay of 10 functionally important genes also showed their involvement in differential responses at 24 and 48h post whitefly infestation. Briefly, our study helps in understanding the resistant nature of Mac7 under whitefly stress.

Screening of cotton germplasm for their reaction against leafhopper, Amrasca biguttula biguttula Ishida (Homoptera: Cicadellidae)

Preliminary screening of twenty-nine cotton genotypes (Gossypium hirsutum) against the leafhopper Amrasca biguttula biguttula Ishida undertaken, during August 2019 to February 2020, revealed fifteen genotypes viz., TCH 357, TCH 1809, TCH 1828, TCH 1895, TCH 1897, TCH 1941, TSH 383, TVH 002, TVH 003, TKH 0762, TKH 1225, SVPR 6, CO 15, KC3 and Suraj, as moderately resistant. Selected preliminary screening entries subjected to advanced screening revealed TCH 357, TCH 1809, TCH 1895, TCH 1897, TCH 1941, TCH 1828, TSH 383, TVH 002, TVH 003, TKH 0762, SVPR 6 and CO 15 as moderately resistant with population range of 2.75 to 4.42 numbers per three leaves and KC3 resistant. In the artificial screening, the resistant cultivar KC3 had least leafhoppers (2.67 per plant) and it had 56 trichomes per 300 mm2, which was higher than resistant check NDLH 1938. The resistant genotype KC3 had the maximum phenol (4.3 mg g-1), amino acid (136 mg g-1) and tannin (167 mg g-1), while the susceptible genotype DCH 32 had the lowest amount of total phenol (1.2 mg g-1), amino acids (18 mg g-1) and tannin (40 mg g-1).

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.