[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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An artificially synthesized Bacillus thuringiensis insecticidal protein gene, co-constructed with the GUS reporter gene (Bt/GUS), was transferred into fertilized ovaries of the elite cotton (Gossypium hirsutum L.) cultivars Simian 3 and Zhongmiansuo 12 by the pollen tube pathway. Transgenic cotton plants were recovered from the seeds in the treated bolls. Histochemical analysis for GUS activity indicated that the gene was expressed in the transgenic R1 plants of the two recipient cultivars. The presence of the Bt gene in the GUS-positive R1 plants was confirmed by PCR and the same results were obtained in the R2 plant populations. This indicated stable integration of the Bt gene into the recipients and its inheritance from R1 to R2 generations. Resistance to the cotton bollworm (Helicoverpa armigera Hübner) was identified in these transgenic plants. In R1, five plants highly toxic to the insect were found: S545, S591, S636, and S1001 from “Simian 3+Bt/GUS”, and Zh1109 from “Zhongmiansuo 12+Bt/GUS”, with larva mortality up to 91.6%, 93.8%, 92.3%, 85.7% and 75.0%, respectively. Insect-resistant R5 strains were derived from the R1 transgenic insect-resistant plants via selfing and breeding, showing the maintenance of the transgene and insect-resistance and the practical potential in cotton production.
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The Republic of Uzbekistan is a large producer and exporter of cotton but must overcome a number of limitations. Soil salinity has rendered about 20 % of the cotton producing area unsuitable for continued production. Increasing susceptibility to pathogens and pests reduces the yield by 10 – 12 %. Defoliants and harvest aid chemicals increase the cost of production and affect the environment adversely. Certain protein molecular markers are correlated with salt tolerance while others are receptors of abscisic acid, a key hormone in dehiscence of cotton. Key enzymes regulate the synthesis of ethylene that regulates boll opening. A fragment of DNA containing a copy of the gene for chitinase synthesis, the main enzyme in resistance to pathogens, has been cloned. New active Bt toxins have been generated from melon seeds. A vector has been constructed to provide for the transfer of foreign genes to cotton cells and a method has been developed for the transformation of single cotton cells.
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