[Background] Meta-analysis of quantitative trait locus (QTL) is a computational technique to identify consensus QTL and refine QTL positions on the consensus map from multiple mapping studies. The combination of meta-QTL intervals, significant SNPs and transcriptome analysis has been widely used to identify candidate genes in various plants.
[Results] In our study, 884 QTLs associated with cotton fiber quality traits from 12 studies were used for meta-QTL analysis based on reference genome TM-1, as a result, 74 meta-QTLs were identified, including 19 meta-QTLs for fiber length; 18 meta-QTLs for fiber strength; 11 meta-QTLs for fiber uniformity; 11 meta-QTLs for fiber elongation; and 15 meta-QTLs for micronaire. Combined with 8 589 significant single nucleotide polymorphisms associated with fiber quality traits collected from 15 studies, 297 candidate genes were identified in the meta-QTL intervals, 20 of which showed high expression levels specifically in the developing fibers. According to the function annotations, some of the 20 key candidate genes are associated with the fiber development.
[Conclusion] This study provides not only stable QTLs used for marker-assisted selection, but also candidate genes to uncover the molecular mechanisms for cotton fiber development.
[Title] Identification of candidate genes controlling fiber quality traits in upland cotton through integration of meta-QTL, significant SNP and transcriptomic data
[Authors] XU Shudi, PAN Zhenyuan, YIN Feifan, YANG Qingyong, LIN Zhongxu, WEN Tianwang, ZHU Longfu, ZHANG Dawei and NIE Xinhui
Journal of Cotton Research 2020, 3: 34
[Abstract] The introduction of Bacillus thuringiensis (Bt) cotton has reduced the burden of pests without harming the environment and human health. However, the efficacy of Bt cotton has decreased due to field-evolved resistance in insect pests over time. In this review, we have discussed various factors that facilitate the evolution of resistance in cotton pests. Currently, different strategies like pyramided cotton expressing two or more distinct Bt toxin genes, refuge strategy, releasing of sterile insects, and gene silencing by RNAi are being used to control insect pests. Pyramided cotton has shown resistance against different cotton pests. The multiple genes pyramiding and silencing (MGPS) approach has been proposed for the management of cotton pests. The genome information of cotton pests is necessary for the development of MGPS-based cotton. The expression cassettes against various essential genes involved in defense, detoxification, digestion, and development of cotton pests will successfully obtain favorable agronomic characters for crop protection and production. The MGPS involves the construction of transformable artificial chromosomes, that can express multiple distinct Bt toxins and RNAi to knockdown various essential target genes to control pests. The evolution of resistance in cotton pests will be delayed or blocked by the synergistic action of high dose of Bt toxins and RNAi as well as compliance of refuge requirement.
[Title]Insect resistance management in Bacillus thuringiensis cotton by MGPS (multiple genes pyramiding and silencing)
[Authors] ZAFAR Muhammad Mubashar, RAZZAQ Abdul, FAROOQ Muhammad Awais, REHMAN Abdul, FIRDOUS Hina, SHAKEEL Amir, MO Huijuan and REN Maozhi
Journal of Cotton Research 2020, 3: 33
[Background] Gossypium hirsutum is highly susceptible to Verticillium wilt, and once infected Verticillium wilt, its yield is greatly reduced. But G. barbadense is highly resistant to Verticillium wilt. It is possible that transferring some disease-resistant genes from G. barbadense to G. hirsutummay contribute to G. hirsutum resistance to Verticillium wilt.
[Results] Here, we described a new gene in G. barbadense encoding AXMN Toxin Induced Protein-11, GbAt11, which is specifically induced by Verticillium dahliae in G. barbadense and enhances Verticillium wilt resistance in G. hirsutum. Overexpression in G. hirsutum not only significantly improves resistance to Verticillium wilt, but also increases the boll number per plant. Transcriptome analysis and real-time polymerase chain reaction showed that GbAt11overexpression can simultaneously activate FLS2, BAK1 and other genes, which are involved in ETI and PTI pathways in G. hirsutum.
[Conclusions] These data suggest that GbAt11 plays a very important role in resistance to Verticillium wilt in cotton. And it is significant for improving resistance to Verticillium wilt and breeding high-yield cotton cultivars.
[Title] GbAt11 gene cloned from Gossypium barbadense mediates resistance to Verticillium wilt in Gossypium hirsutum
[Authors] QIU Tingting, WANG Yanjun, JIANG Juan, ZHAO Jia, WANG Yanqing & QI Junsheng
Transgenic technologies have emerged as a powerful tool for crop improvement in terms of yield, quality, and quantity in many countries of the world. However, concerns also exist about the possible risks involved in transgenic crop cultivation. In this review, literature is analyzed to gauge the real intensity of the issues caused by environmental stresses in Pakistan. In addition, the research work on genetically modified organisms (GMOs) development and their performance is analyzed to serve as a guide for the scientists to help them select useful genes for crop transformation in Pakistan. The funding of GMOs research in Pakistan shows that it does not follow the global trend. We also present socio-economic impact of GM crops and political dimensions in the seed sector and the policies of the government. We envisage that this review provides guidelines for public and private sectors as well as the policy makers in Pakistan and in other countries that face similar environmental threats posed by the changing climate.
Recent advancements in biotechnology resulted in rapid adoption of genetically modified (GM) crops in the agriculture systems. At the same time, transgene escape has also been reported and examples reveal global dimension of the problem. Pollen mediated gene flow (PMGF) is the major pathway for transgene escape. Almost all transgenes have been escaped into their Non-GM counterpart and wild relatives. Although gene flow varies between species, crops, and ecological zones/environments but intraspecific gene flow (> 10%) is not uncommon in adjacent populations. Whereas in outcrossing species, 1% gene flow at thousand meters’ isolation is not unusual, and magnitude is even higher than the mutation rate. It is well documented that transgene flow is deteriorating different production systems in agriculture and famers choice to cultivate GM, conventional and organic crops. If comprehensive policy is not implemented, then in future it will be difficult to detect and remove transgenes from the environment; if unexpected problems arise.
A single nucleotide polymorphism is the simplest form of genetic variation among individuals and can induce
minor changes in phenotypic, physiological and biochemical characteristics. This polymorphism induces various
mutations that alter the sequence of a gene which can lead to observed changes in amino acids. Several assays
have been developed for identification and validation of these markers. Each method has its own advantages and
disadvantages but genotyping by sequencing is the most common and most widely used assay. These markers are
also associated with several desirable traits like yield, fibre quality, boll size and genes respond to biotic and abiotic
stresses in cotton. Changes in yield related traits are of interest to plant breeders. Numerous quantitative trait loci
with novel functions have been identified in cotton by using these markers. This information can be used for crop
improvement through molecular breeding approaches. In this review, we discuss the identification of these markers
and their effects on gene function of economically important traits in cotton
[Background] Verticillium wilt, caused by Verticillium dahliae, is called a “cancer” disease of cotton. The discovery and identification of defense-related genes is essential for the breeding of Verticillium wilt-resistant varieties. In previous research we identified some possible broad-spectrum resistance genes. Here, we report a tryptophan synthesis-related gene GbTRP1 and its functional analysis in relation to the resistance of cotton to V. dahliae.
[Results] Expression analysis shows that GbTRP1 is suppressed at 1 h and 6 h post V. dahliae infection, but activated at 12 h and 24 h, and the expression of GbTRP1 is highly induced by treatment with salicylic acid and jasmonic acid. Sub-cellular localization studies show that GbTRP1 is localized in the chloroplast. Suppression of GbTRP1 expression leads to lesion-mimic phenotypes and activates the immune response in cotton by showing enhanced resistance to V. dahliae and B. cinerea. Metabolomic analysis shows that anthranilic compounds significantly accumulated in GbTRP1-silenced plants, and these metabolites can inhibit the growth of V. dahliae and B. cinerea in vitro.
[Conclusions] Our results show that suppression of GbTRP1 expression dramatically activates the immune response and increases resistance of cotton to V. dahliae and B. cinerea, possibly due to the accumulation of anthranilate compounds. This study not only provides genetic resources for disease resistance breeding, but also may provide a basis for new chemical control methods for combatting of fungal disease in cotton.
[Title] Down regulation of cotton GbTRP1 leads to accumulation of anthranilates and confers resistance to Verticillium dahliae
[Authors] MIAO Yuhuan, ZHU Longfu and ZHANG Xianlong
Journal of Cotton Research. 2019; 2:19
[Background] Cotton is a significant economic crop that plays an indispensable role in many domains. Gossypium hirsutum L. is the most important fiber crop worldwide and contributes to more than 95% of global cotton production. Identifying stable quantitative trait locus (QTLs) controlling fiber quality and yield related traits are necessary prerequisites for marker-assisted selection (MAS).
[Results] A genetic linkage map was constructed with 312 simple sequence repeat (SSR) loci and 35 linkage groups using JoinMap 4.0; the map spanned 1 929.9 cM, with an average interval between two markers of 6.19 cM, and covered approximately 43.37% of the cotton genome. A total of 74 QTLs controlling fiber quality and 41 QTLs controlling yield-related traits were identified in 4 segregating generations. These QTLs were distributed across 20 chromosomes and collectively explained 1.01%~27.80% of the observed phenotypic variations. In particular, 35 stable QTLs could be identified in multiple generations, 25 common QTLs were consistent with those in previous studies, and 15 QTL clusters were found in 11 chromosome segments.
[Conclusion] These studies provide a theoretical basis for improving cotton yield and fiber quality for molecular marker-assisted selection.
[Title] QTL mapping for fiber quality and yield-related traits across multiple generations in segregating population of CCRI 70
[Authors] DENG Xiaoying, GONG Juwu, LIU Aiying, SHI Yuzhen, GONG Wankui, GE Qun, LI Junwen, SHANG Haihong, WU Yuxiang & YUAN Youlu
Journal of Cotton Research. 2019, 2:13
[Background] Low insecticidal protein expression at reproductive organs affect insect resistance in Bt transgenic cotton. In order to enhance flower insecticidal protein expression, the conventional cultivar Sikang1 (S1) and the hybrid cultivar Sikang3 (S3) were used as experimental materials; the applications of selected 5 types of amino acids and 21 types of amino acids were sprayed on the flowers in 2016 and 2017 cotton growing seasons.
[Results] The flower Bt protein contents increased significantly under the two amino acid treatments in both cultivars, the Bt protein concentration increased by 15.2 to 25.8% compared with the control. However, no significant differences were detected between the two treatments of amino acid application. Increased amino acid and soluble protein contents, enhanced GPT, GOT, protease,and peptidase activities were observed under the amino acid application at the flowering stage.
[Conclusions] These results suggest that exterior application of the amino acids treatments could bolster the flower insecticidal protein expression.
[Authors] TAMBEL Leila. I. M., ZHOU Mingyuan, CHEN Yuan, ZHANG Xiang, CHEN Yuan and CHEN Dehua
Journal of Cotton Research. 2019; 2:7
The in vitro culture response of immature zygotic embryos (IZE), from six Gossypium hirsutum and one G. barbadense variety, was studied. Explants were collected from plants grown in the field and the greenhouse. Bolls were collected 12, 14 and 16 days after pollination (DAP) from the field and 10, 12 and 14 DAP from the greenhouse. The young embryos were cultured in vitro in SH and BT supplemented with 2,4-D and kinetin. All genotypes responded well to callogenesis in spite of the environmental conditions where they were grown. Callus formation (%) was higher when the bolls were collected 16 DAP for embryos collected from the field and 14 DAP for embryos collected from the greenhouse. The callus developed was tested for its embryogenic and organogenic potential in several media without positive results. During the callus induction period, it was observed that in some explants the epidermal cells from the upper cotyledon and the hypocotyl were diversified into globular or heart shape embryoids. For their further development, they were transferred to a modified MS medium. Some of the young embryoids formed roots and leaves but they never developed into regular plantlets.
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