A Temporal Expression of Cry1Ac Protein in Cotton Plant and its Impact on Soil Health
Mirza Muhammad Sajjad
Mehboob ur Rahman
International Journal of Agriculture and Biology, 2015, 17(2): 280-288.
Like many other cotton growing countries, area under the cultivation of genetically modified cotton containing Cry1Ac gene has been increased tremendously in Pakistan because of its added advantage towards conferring resistance to bollworms especially Helicoverpa armigera. It has been reported that this gene derived from Bacillus thuringiensis has no negative impact on the soil ecosystem. Studies covering biosafety aspect of transgene involving Bt gene are non-existent in our ecological system. Every country has different microbiota which is the compelling factor to design studies for estimating the negative impact, if any, in our indigenous environment. In the present study, the concentration of Cry 1Ac protein in leaf tissues have shown increasing trend from 60 DAS to 90 DAS, and decreased at 120 DAS. Similar results were observed during each cropping season. Variation in protein concentration was found non-significant over different cropping years but it was significant at different sampling stages. We also observed that the Cry 1Ac toxin in the soil was stumpy low (78 times) when we compare it to leaf. Experiments related to the colony farming units (CFUs) of culturable bacteria, actinomycetes and fungi were undertaken in the rhizosphere of Bt- and non-Bt-cotton plants at various growth stages at 30 days interval from sowing till maturity for three consecutive years (2006-2008). A cotton variety IR-NIBGE-901 (containing Cry1Ac gene, bred at NIBGE) and its non-Bt isogenic variety (FH-901) were sown in NIBGE cotton field, Faisalabad Pakistan. The concentration of Cry 1Ac protein released in the soil through root exudates, and in the terminal leaves was measured 60, 90 and 120 DAS. Results showed no significant impact (P < 0.05) on CFUs of bacteria, actinomycetes and fungus between the Bt and non-Bt cotton rhizosphere during cropping season at one particular stage. However, the temporal and spatial variations for microbes were observed significant among the different time interval (30, 60, 90, 120, 150 and 180 DAS) and the year of cultivation. Thus, our studies have demonstrated that the repeated cultivation of Bt cotton had no significant impact on soil health of Pakistan.