Calibration of HVI cotton elongation measurements

[Background] The strength of cotton fiber has been extensively studied and significant improvements in fiber strength have been made, but fiber elongation has largely been ignored, despite it contributing to the energy needed to break fibers, which affects fiber handling and processing. High Volume Instruments (HVI) measure fiber elongation but have not been calibrated for this property, making the measurement unavailable for comparative work among instruments. In prior work, a set of elongation calibration materials had been developed based on Stelometer results. A round trial of ten Australian and U.S. instruments was conducted on six cotton samples representing a range of 4.9% to 8.1% elongation.

[Results] By scaling the HVI elongation values of each instrument to the values of the two calibration samples, the coefficient of variation in instrument measurements was reduced from an average of 34% for the uncalibrated measurements to 5% for the calibrated measurements. The reduction in variance allows for the direct comparison of results among instruments. A single-point elongation calibration was also assessed but found to be less effective than the proposed two-point calibration.

[Conclusion] The use of an effective calibration routine on HVI measurement of cotton significantly reduces the coefficient of variation of the elongation measurement within and between instruments. The implementation of the elongation calibration will allow testing and breeding programs to implement high-speed elongation testing which makes the use of elongation values possible in breeding programs.

[Title] Calibration of HVI cotton elongation measurements

[Authors] DELHOM Christopher D., HEQUET Eric F., KELLY Brendan, ABIDI Noureddine and MARTIN Vikki B.

Journal of Cotton Research 2020, 331

Bt cotton seed purity in Burkina Faso: status and lessons learnt

[BackgroundSince the commercial release of Bt cotton in Burkina Faso in 2009, the issue of seed purity in producers’ fields has rarely been addressed in an unbiased and objective manner. The potential for contamination of conventional seed varieties with Bt traits and the consequent threat to the continuation of organic cotton production has been documented. However, studies are rare on the varietal purity of Bt cotton seeds, despite the implications for the effectiveness and sustainability of their use.

This paper compensates for the lack of research on the varietal purity of cotton seeds in Burkina Faso by reporting the results of Enzyme linked immunosorbent assay tests collected in 2015 on samples of both conventional and Bt varieties from 646 fields.

[Results] According to the conservative criteria used to declare the presence of a Bt gene in a given variety (more than 10% of seeds of conventional variety exhibit Bt traits, and at least 90% of seeds of Bt variety exhibit Bt traits), seed purity was very questionable for both types of variety. For the supposedly conventional variety, the Cry1Ac gene was observed in 63.6% of samples, the Cry2Ab gene was observed in 59.3% of samples, and both genes were detected in 52.2% of the seed samples. Only 29.3% of the seeds that were supposed to be of conventional type contained no Bt genes. Conversely, for the labeled Bt variety, the Cry1Ac gene was found in only 59.6% of samples, the Cry2Ab gene was found in 53.6% of the samples, and both genes were found in 40.4% of the samples. Finally, for the seeds that were supposed to contain both genes (Bollguard 2), both Cry1Ac and Cry2Ab genes were found in only 40.4% of the samples, only one of the genes was found in 32.4% of the samples, and 27.2% of the seeds in the samples contained neither.

Two factors are responsible for the severe lack of seed purity. First, conventional varieties are being contaminated with Bt traits because of a failure to revise the seed production scheme in Burkina Faso to prevent cross-pollination. Second, the original Bt seeds provided to Burkina Faso lacked varietal purity.

The organic sector plays a very minor role in the cotton sector of Burkina Faso (production of organic cotton totaled 453 t in 2018/2019, out of national cotton production of 183 000 t). Nevertheless, the lack of purity in conventional seed varieties is a threat to efforts to expand certified organic cotton production. The poor presence of Bt proteins in supposed Bt varieties undermines their effectiveness in controlling pests and increases the likelihood of the development of resistance among pest populations.

[Conclusion] Our results show the extent of purity loss when inadequate attention is paid to the preservation of seed purity. Pure conventional seeds could vanish in Burkina Faso, while Bt seeds do not carry the combination of the expected Bt traits. Any country wishing to embark on the use of Bt cotton, or to resume its use, as in the case of Burkina Faso, must first adjust its national seed production scheme to ensure that procedures to preserve varietal purity are enforced. The preservation of varietal purity is necessary to enable the launch or the continuation of identity-cotton production. In addition, the preservation of varietal purity is necessary to ensure the sustainable effectiveness of Bt cotton. In order to ensure that procedures to preserve varietal purity are observed, seed purity must be tested regularly, and test results must be published.

[Title] Bt cotton seed purity in Burkina Faso: status and lessons learnt

[Authors] BOURGOU Larbouga, KARGOUGOU Ester, SAWADOGO Mahamadou and FOK Michel

Journal of Cotton Research 2020, 330

Apprehending the potential of BABY BOOM transcription factors to mitigate cotton regeneration and transformation

[Abstract] Since the advent of transgenic technology, the incorporation of gene(s) encoding traits of economic importance in cotton is being practiced worldwide. However, factors like recalcitrant nature of cotton cultivars, in vitro regeneration via tissue culture (especially via somatic embryogenesis), genotype dependency, long and toilsome protocols impede the pace of development of transgenic cotton. Besides that, types and age of explants, media composition, plant growth regulators and other environmental factors affect in vitro cotton regeneration significantly. The studies of genetic control of in vitro regeneration in plants have elucidated the role of certain transcription factor genes that are induced and expressed during somatic embryogenesis. Among these transcription factors, BABY BOOM (BBM) plays a very important role in signal transduction pathway, leading to cell differentiation and somatic embryos formation. The role of BBM has been established in plant cell proliferation, growth and development even without exogenous growth regulators. This review intends to provide an informative summary of regeneration and transformation problems in cotton and the latest developments in utilization of BBM transcription factors in cotton. We believe that the use of BBM will not only ease cotton genetic improvement but will also accelerate cotton breeding programmes.

[Title] Apprehending the potential of BABY BOOM transcription factors to mitigate cotton regeneration and transformation

[Authors] YAVUZ Caner, TILLABOEVA Shakhnozakhan & BAKHSH Allah

Journal of Cotton Research 2020, 329

Cotton N rate could be reduced further under the planting model of late sowing and high-density in the Yangtze River valley

[Background] An optimal N rate is one of the basic determinants for high cotton yield. The purpose of this study was to determine the optimal N rate on a new cotton cropping pattern with late-sowing, high density and one-time fertilization at the first flower period in Yangtze River Valley, China. A 2-year experiment was conducted in 2015 and 2016 with a randomized complete block design. The cotton growth process, yield, and biomass accumulation were examined.

[Result] The results showed that N rates had no effect on cotton growing progress or periods. Cotton yield was increased with N rates increasing from 120 to 180 kg·hm−2, while the yield was not increased when the N rate was beyond 180 kg·hm−2, or even decreased (929%). Cotton had the highest biomass at the N rate of 180 kg·hm−2 is due to its highest accumulation speed during the fast accumulation period.

[Conclusion] The result suggests that the N rate for cotton could be reduced further to be 180 kg·hm− 2 under the new cropping pattern in the Yangtze River Valley, China.

[Title] Cotton N rate could be reduced further under the planting model of late sowing and high-density in the Yangtze River valley

[Authors] SONG Xinghu, HUANG Ying, YUAN Yuan, SHAHBAZ Atta Tung, BIANGKHAM Souliyanonh & YANG Guozheng

Journal of Cotton Research 2020, 328

Phenylpropanoid metabolism and pigmentation show divergent patterns between brown color and green color cottons as revealed by metabolic and gene expression analyses

[Background] Naturally-colored cotton has become increasingly popular because of their natural properties of coloration, UV protection, flame retardant, antibacterial activity and mildew resistance. But poor fiber quality and limited color choices are two key issues that have restricted the cultivation of naturally-colored cotton. To identify the possible pathways participating in fiber pigmentation in naturally-colored cottons, five colored cotton accessions in three different color types (with green, brown and white fiber) were chosen for a comprehensive analysis of phenylpropanoid metabolism during fiber development.

[Result] The expression levels of flavonoid biosynthesis pathway genes in brown cotton fibers were significantly higher than those in white and green cotton fibers. Total flavonoids and proanthocyanidin were higher in brown cotton fibers relative to those in white and green cotton fibers, which suggested that the flavonoid biosynthesis pathway might not participate in the pigmentation of green cotton fibers. Further expression analysis indicated that the genes encoding enzymes for the synthesis of caffeic acid derivatives, lignin and lignan were activated in the developing fibers of the green cotton at 10 and 15 days post-anthesis.

[Conclusion] Our results strengthen the understanding of phenylpropanoid metabolism and pigmentation in green and brown cotton fibers, and may improve the breeding of naturally-colored cottons.

[Title] Phenylpropanoid metabolism and pigmentation show divergent patterns between brown color and green color cottons as revealed by metabolic and gene expression analyses

[Authors] LI Zhonghua, SU Qian, XU Mingqi, YOU Jiaqi, KHAN Anam Qadir, LI Junyi, ZHANG Xianlong, TU Lili & YOU Chunyuan

Journal of Cotton Research 2020, 327

A genome-wide identification of the BLH gene family reveals BLH1 involved in cotton fiber development

[Background] Cotton is the world’s largest and most important source of renewable natural fiber. BEL1-like homeodomain (BLH) genes are ubiquitous in plants and have been reported to contribute to plant development. However, there is no comprehensive characterization of this gene family in cotton. In this study, 32, 16, and 18 BLH genes were identified from the G. hirsutumG. arboreum, and G. raimondii genome, respectively. In addition, we also studied the phylogenetic relationships, chromosomal location, gene structure, and gene expression patterns of the BLH genes.

[Result] The results indicated that these BLH proteins were divided into seven distinct groups by phylogenetic analysis. Among them, 25 members were assigned to 15 chromosomes. Furthermore, gene structure, chromosomal location, conserved motifs, and expression level of BLH genes were investigated in G. hirsutum. Expression profiles analysis showed that four genes (GhBLH1_3GhBLH1_4GhBLH1_5, and GhBLH1_6) from BLH1 subfamily were highly expressed during the fiber cell elongation period. The expression levels of these genes were significantly induced by gibberellic acid and brassinosteroid, but not auxin. Exogenous application of gibberellic acid significantly enhanced GhBLH1_3GhBLH1_4, and GhBLH1_5transcripts. Expression levels of GhBLH1_3 and GhBLH1_4 genes were significantly increased under brassinosteroid treatment.

[Conclusion] The BLH gene family plays a very important role in many biological processes during plant growth and development. This study deepens our understanding of the role of the GhBLH1gene involved in fiber development and will help us in breeding better cotton varieties in the future.

[Title] A genome-wide identification of the BLH gene family reveals BLH1 involved in cotton fiber development

[Authors] LIU Cuixia, LI Zhifang, DOU Lingling, Yi YUAN, ZOU Changsong, SHANG Haihong, CUI Langjun & XIAO  Guanghui

Journal of Cotton Research 2020, 326

Global identification of genes associated with xylan biosynthesis in cotton fiber

[Background] Mature cotton fiber secondary cell wall comprises largely of cellulose (> 90%) and small amounts of xylan and lignin. Little is known about the cotton fiber xylan biosynthesis by far.

[Result] To comprehensively survey xylan biosynthetic genes in cotton fiber, we identified five IRX9, five IRX10, one IRX14, six IRX15, two FRA8, one PARVUS, eight GUX, four GXM, two RWA, two AXY9, 13 TBL genes by using phylogenetic analysis coupled with expression profile analysis and co-expression analyses. In addition, we also identified two GT61 members, two GT47 members, and two DUF579 family members whose homologs in Arabidopsis were not functionally characterized. These 55 genes were regarded as the most probable genes to be involved in fiber xylan biosynthesis. Further complementation analysis indicated that one IRX10 like and two FRA8 related genes were able to partially recover the irregular xylem phenotype conferred by the xylan deficiency in their respective Arabidopsis mutant. We conclude that these genes are functional orthologs of respective genes that are implicated in GX biosynthesis.

[Conclusion] The list of 55 cotton genes presented here provides not only a solid basis to uncover the biosynthesis of xylan in cotton fiber, but also a genetic resource potentially useful for future studies aiming at fiber improvement via biotechnological approaches.

[Title] Global identification of genes associated with xylan biosynthesis in cotton fiber

[Authors] CHEN Feng, GUO Yanjun, CHEN Li, GAN Xinli, LIU Min, LI Juan & XU Wenliang

Journal of Cotton Research 2020, 325

Development and application of perfect SSR markers in cotton

[Background] This study aimed to develop a set of perfect simple sequence repeat (SSR) markers with a single copy in the cotton genome, to construct a DNA fingerprint database suitable for authentication of cotton cultivars. We optimized the polymerase chain reaction (PCR) system for multi-platform compatibility and improving detection efficiency. Based on the reference genome of upland cotton and 10× resequencing data of 48 basic cotton germplasm lines, single-copy polymorphic SSR sites were identified and developed as diploidization SSR markers. The SSR markers were detected by denaturing polyacrylamide gel electrophoresis (PAGE) for initial screening, then fluorescence capillary electrophoresis for secondary screening. The final perfect SSR markers were evaluated and verified using 210 lines from different sources among Chinese cotton regional trials.

[Result] Using bioinformatics techniques, 1 246 SSR markers were designed from 26 626 single-copy SSR loci. Adopting a stepwise (primary and secondary) screening strategy, a set of 60 perfect SSR markers was selected with high amplification efficiency and stability, easy interpretation of peak type, multiple allelic variations, high polymorphism information content (PIC) value, uniform chromosome distribution, and single-copy characteristics. A multiplex PCR system was established with ten SSR markers using capillary electrophoresis detection.

[Conclusion] A set of perfect SSR markers of cotton was developed and a high-throughput SSR marker detection system was established. This study lays a foundation for large-scale and standardized construction of a cotton DNA fingerprint database for authentication of cotton varieties.

[Title] Development and application of perfect SSR markers in cotton

[Authors] WU Yuzhen, HUANG Longyu, ZHOU Dayun, FU Xiaoqiong, LI Chao, WEI Shoujun, PENG Jun & KUANG Meng

Journal of Cotton Research 2020, 321

Toward the efficient use of Beauveria bassiana in integrated cotton insect pest management

[Background] For controlling the resistance to insects, in particular carpophagous and phyllophagous caterpillars, using chemical pesticides has led to contamination of cotton area in Benin. Facing this problem, alternative methods including the use of entomopathogenic fungi as biopesticide could be a sound measure to preserve the environment, biodiversity and ensure good quality of crops. Previous studies have revealed the insecticidal potential of the entomopathogenic Beauveria bassiana on some insect pest species. However, little is known about its effectiveness on cotton Lepidopteran pests. This review is done to learn more about B. bassina for its application in controlling cotton insect pests, especially Lepidopteran species.

[Main body] Different sections of the current review deal with the related description and action modes of B. bassiana against insects, multi-trophic interactions between B. bassiana and plants, arthropods, soil and other microbes, and biological control programs including B. bassiana during last decade. Advantages and constraints in applying B. bassiana and challenges in commercialization of B. bassiana-based biopesticide have been addressed. In this review, emphasis is put on the application methods and targeted insects in various studies with regard to their applicability in cotton

[Conclusion] This review helps us to identify the knowledge gaps related to application of B. bassiana on cotton pest in general and especially in Lepidopteran species in Benin. This work should be supported by complementary laboratory bioassays, station and/or fields experiments for effective management of cotton Lepidopteran pests in Benin.
[Title] Toward the efficient use of Beauveria bassiana in integrated cotton insect pest management

[Authors] DANNON H. Fabrice, DANNON A. Elie, DOURO-KPINDOU O. Kobi, ZINSOU A. Valerien, HOUNDETE A. Thomas, TOFFA-MEHINTO Joëlle, ELEGBEDE I. A. T. Maurille, OLOU B. Dénis & TAMÒ Manuele

Journal of Cotton Research 2020, 324

Heritability and correlation analysis of morphological and yield traits in genetically modified cotton

[Background] Cotton is known for fiber extraction and it is grown in tropical and sub-tropical areas of the world due to having hot weather. Cotton crop has a significant role in GDP of Pakistan. Therefore, the two-years research was conducted to estimate heritability and association among various yield contributing parameters of cotton, i.e., plant height, number of bolls per plant, number of sympodial branches per plant, seed cotton yield, boll weight, seed index, ginning outturn (GOT), fiber length, fiber strength, and fiber fineness.

[Result] Association analysis revealed that seed cotton yield had a significant positive correlation with plant height, number of bolls per plant, number of sympodial branches per plant, GOT, staple length and fiber strength. Staple length and fiber strength were negatively linked with each other. Estimates of heritability were high for all of the traits except the number of sympodial branches per plant and boll weight.

[Conclusion] The parent IUB-222 was found to be the best for plant height, the number of bolls per plant, boll weight, GOT, seed cotton yield, and seed index. The genotypes namely, NIAB-414 and VH-367 were identified as the best parents for fiber length, strength, and fineness. Among the crosses NIAB-414 × IUB-222 was the best for the number of bolls per plant, seed index, seed cotton yield and fiber fineness, whereas, the cross of NIAB-414 × CIM-632 was good for plant height. The combination of A555 × CIM-632 was the best for the number of sympodial branches per plant, boll weight, fiber length, and strength, and VH-367 × CIM-632 proved the best for GOT.
[Title] Heritability and correlation analysis of morphological and yield traits in genetically modified cotton

[Authors] REHMAN Abdul, MUSTAFA Nida, DU Xiongming & AZHAR Muhammad Tehsee

Journal of Cotton Research 2020, 323