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Journal of Integrative Agriculture  2021, Vol. 20 Issue (7): 1796-1806    DOI: 10.1016/S2095-3119(20)63232-4
Special Issue: 棉花合辑Cotton
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High plant density increases seed Bt endotoxin content in Bt transgenic cotton
CHEN Yuan1, LIU Zhen-yu1, HENG Li1, Leila I. M. TAMBEL2, CHEN De-hua1
1 Jiangsu Key Laboratory of Crops Genetics and Physiology/Jiangsu Key Laboratory of Crop Cultivation and Physiology/ Agricultural College, Yangzhou University/Jiangsu Co-Innovation Center for Modern Production Technology of Grain Crops, Yangzhou 225009, P.R.China
2 Agricultural Research Cooperation, Biotechnology and Biosafety Research Center, Khartoum 999129, Sudan
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Plant density is the cultivation practice usually employed to manipulate boll distribution, boll setting and yield in cotton production.  In order to determine the effect of plant density on the insecticidal protein content of Bacillus thuringiensis (Bt) cotton plants, a study was conducted in Yangzhou University of China in 2015 and 2016.  Five plant densities (PD1–PD5, representing 15 000, 30 000, 45 000, 60 000, and 75 000 plants ha–1) were imposed on two Bt cotton cultivars, Sikang 1 (the conventional cultivar, SK-1) and Sikang 3 (the hybrid cultivar, SK-3).  The boll number per plant, boll weight and boll volume all decreased as plant density increased.  As plant density increased from 15 000 to 75 000 plants ha–1, seed Bt protein content increased, with increases of 66.5% in SK-1 and 53.4% in SK-3 at 40 days after flowering (DAF) in 2015, and 36.8% in SK-1 and 38.6% in SK-3 in 2016.  Nitrogen (N) metabolism was investigated to uncover the potential mechanism.  The analysis of N metabolism showed enhanced soluble protein content, glutamic-pyruvic transaminase (GPT) and glutamate oxaloacetate transaminase (GOT) activities, but reduced free amino acid content, and protease and peptidase activities with increasing plant density.  At 20 DAF, the seed Bt toxin amount was positively correlated with soluble protein level, with correlation coefficients of 0.825** in SK-1 and 0.926** in SK-3 in 2015, and 0.955** in SK-1 and 0.965** in SK-3 in 2016.  In contrast, the seed Bt protein level was negatively correlated with free amino acid content, with correlation coefficients of –0.983** in SK-1 and –0.974** in SK-3 in 2015, and –0.996** in SK-1 and –0.986** in SK-3 in 2016.  To further confirm the relationship of Bt protein content and N metabolism, the Bt protein content was found to be positively correlated with the activities of GPT and GOT, but negatively correlated with the activities of protease and peptidase.  In conclusion, our present study indicated that high plant density elevated the amount of seed Bt protein, and this increase was associated with decreased boll number per plant, boll weight and boll volume.  In addition, altered N metabolism also contributed to the increased Bt protein content under high plant density.
Keywords:   Bt cotton        plant density        Bt insecticidal protein        nitrogen metabolism  
Received: 31 December 2019   Accepted:
Fund: This study was supported by the National Natural Science Foundation of China (31901462 and 31671613), the National Key Research and Development Program of China (2018YFD0100406 and 2018YFD1000907), the Natural Science Foundation of the Jiangsu Higher Education Institutions, China (18KJB210013 and 17KJA210003), and the Natural Science Foundation of Jiangsu Province, China (BK20191439).

Cite this article: 

CHEN Yuan, LIU Zhen-yu, HENG Li, Leila I. M. TAMBEL, CHEN De-hua. 2021. High plant density increases seed Bt endotoxin content in Bt transgenic cotton. Journal of Integrative Agriculture, 20(7): 1796-1806.

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