Square Insecticidal Protein Concentration Relate to its Biomass in Bt Cotton

Abstract

Core Ideas Cultivar with high square biomass for individual and whole plant had higher insecticidal protein content. The increased square biomass by mepiquat chloride application enhaced Bt protein concentration. The decreased square biomass by nitrogen deficit reduced square Bt protein concentration. The square insecticidal protein concentration relates to its biomass. Bt transgenic cotton has been cultivated in China and many other cotton production areas in the world. However, the insecticidal efficacy is often low for the reproductive organs, especially for the cultivars with a big boll in China. The objective of the study focused on the effect of square biomass on the Bt protein concentration during the squaring period for Bt cotton. In the variety effect study in 2015 and 2016, two hybrid Bt cultivars (Sikang3 and Sumian29) and two conventional Bt cultivars (Sikang1 and Nucotn33B) were compared for square biomass and Bt toxin content from 15 to 25 d after square appearance (DASP) during the cotton growing seasons. Cultivars with high square biomass for individual and whole plant had higher insecticidal protein content. In the cultural practice effect study in 2017, the experiment of mepiquat chloride (MC) dose and different nitrogen deficit extents were designed to further investigate the relationship between square biomass and square Bt protein concentration. The MC application significantly increased square mass and square Bt protein content. In contrast, the nitrogen deficit decreased square mass together with square insecticidal protein concentration. The positive correlation between square biomass (the individual square biomass and the square biomass per plant) and square insecticidal protein content was highly significant in variety study and cultural practice study. The results indicated that increment of square development by variety selection and cultural practice could increase insect resistance during squaring period of Bt cotton.

Effect of Urea Spray on Boll Shell Insecticidal Protein Content in Bt Cotton

“…Previous studies have shown that nitrogen fertilizer could affect the expression of Bt cotton insecticidal protein, and the expression of Bt protein is closely related to nitrogen metabolism ( Chen et al, 2005 , 2013 , 2017 ; Dong and Li, 2007 ). Some studies have shown that increasing nitrogen fertilizer or spraying amino acid can increase the expression of insecticidal protein in reproductive organs such as squares, flowers, and bolls ( Pettigrew and Adamczyk, 2006 ; Abidallha et al, 2017a , b ; Chen et al, 2018 ; Zhou et al, 2019 ). The results of our study further showed that spraying urea could significantly increase the expression of insecticidal protein in boll shell, and as urea concentration enhanced, the expression of insecticidal protein increased first and then decreased, with the highest level recorded under 36 kg·ha −1 urea.…”

“…Bacillus thuringiensis transgenic cotton (Bt cotton) is the cotton cultivar with insect resistance, which is obtained by transferring Bt toxin gene from B. thuringiensis into cotton (Ma et al, 2020). In the whole process of growth and development of Bt cotton, all tissues and organs can express insecticidal protein, which can effectively reduce the harm of cotton bollworm and other related pests (Chen et al, 2005(Chen et al, , 2018Zhang et al, 2019;Zhou et al, 2019). In addition, the application of Bt cotton effectively reduced the use of pesticides (Fang et al, 2011;Qiao et al, 2017b) and thus decreased input and environmental pollution (Sun et al, 2016).…”

The effects of mepiquat chloride (DPC) on the soluble protein content and the activities of protective enzymes in cotton in response to aphid feeding and on the activities of detoxifying enzymes in aphids

“…By increasing leaf wax deposition and chlorophyll content, the photosynthetic rate of cotton leaves was effectively improved [ 27 ]. In addition, DPC induces the production of phenolic secondary metabolites in cotton leaves, and the increase in lignin, total phenols, tannins, flavonoids, and related compounds can enhance stress resistance in cotton [ 28 ].…”

Increasing plant density increases Bt toxin concentration of boll wall in cotton by decreasing boll setting speed

“…Along with temporal and spatial variations of Bt protein expression, abiotic stress, such as extreme temperature, moisture, and salt, all influenced the expression of Bt toxin (Chen et al 2005(Chen et al , 2012b(Chen et al , 2013(Chen et al , 2019Jiang et al 2006;Zhang et al 2017). The square size and biomass, boll number and boll size also impacted Bt protein concentration (Wang et al 2009;Chen et al 2017;Zhou et al 2019). Agronomic practices, including plant density, fertilizer, growth regulators, also affect the Bt protein content of cotton plants (Pettigrew and Adamczyk 2006;Chen et al 2017Chen et al , 2018Chen et al , 2019.…”