Mendelian segregation pattern and expression studies of insecticidal gene (cry1Ac) in insect resistant cotton progeny

Abstract

The progenies of transgenic lines Bt-14 and Bt-17 developed as an independent transformation event from a local cotton variety CIM-482 harboring two insecticidal genes (cry1Ac & cry2a) were evaluated to determine resistance against lepidopterans, mainly Helicoverpa armigera L. under field conditions. The standard molecular techniques, i.e. polymerase chain reaction (PCR), enzyme-linked immunosorbent assay (ELISA) and western dot blot were used to confirm gene presence and expression level of transformed Bt gene, and its transfer pattern to further progeny. PCR confirmed integration of insecticidal gene in most of the plants in transgenic progeny, while expression of Bt gene quantified by ELISA and western dot blot showed variation in cry1Ac expression levels but interestingly, it conferred full protection against targeted insect pests. The leaf bioassays were conducted to determine the effectiveness of Bt genes against Helicoverpa armigera by calculating the mortality percentage of larvae. Most of the transgenic lines showed 70-100% mortality % age of Helicoverpa armigera. The agronomic characteristics of the transgenic lines were also recorded along with non transgenic control variety CIM-482. Morphological, agronomic and fibre data of these transgenic lines was recorded and analyzed statistically. Our results show that these transgenic lines (especially Bt-17 line) are promising cotton germplasm to be used in an efficient breeding programme.

Towards better insect management strategy: restriction of insecticidal gene expression to biting sites in transgenic cotton

“…Hence not all the primary transformants were positive at this stage; escapes were recorded that probably avoided selection pressure (McCormick et al 1986). Our results are in line with several research workers who confirmed the integration of foreign DNA in cotton genome through PCR and ELISA (Schrammeijer et al 1990;Cousins et al 1991;Tohidfar et al 2008;Khan et al 2011;Bakhsh et al 2012;Hussain et al 2014).…”

Study of Expression of Indigenous Bt cry2AX1 Gene in T3 Progeny of Cotton and its Efficacy Against Helicoverpa armigera (Hubner)

“…An explanation for these results would be the total protein production goes down towards the latter part of plant growth. These results are in concurrence with the earlier studies in Bt cotton [28][29][30][31][32][33][34][35][36][37][38][39] which reported a decline in expression of other Bt protein(s) during the crop growth period. Besides, decrease in expression of Bt protein gene at later developmental stages was also correlated with changes in the methylation state of CaMV35S promoter region [28,40].…”

Transgene behavior in Zea mays L. crosses across different genetic backgrounds: Segregation patterns, cry1Ab transgene expression, insecticidal protein concentration and bioactivity against insect pests

“…Many studies report that the mode of transgene inheritance follows directly a Mendelian segregation pattern [ 54 – 57 ] In maize, Duncan et al [ 58 ] reported that after GM traits were introgressed into landrace maize varieties the transgene segregated like other endogenous genes, following Mendelian principles,. In contrast, non-Mendelian segregation of transgenes has been reported in studies on rice [ 59 ], soybean [ 60 ], tobacco [ 61 ], wheat [ 62 ] and cotton [ 63 , 64 ]. In a study with white clover, non-Mendelian segregation was found in F2 populations and the distortion was influenced by genetic background [ 65 ].…”