Pak. J. Bot., 45(1): 235-240, 2013. ALLELOPATHIC ASSESSMENT OF GENETICALLY MODIFIED AND NON MODIFIED MAIZE (ZEA MAYS L.) ON PHYSIOLOGY OF WHEAT (TRITICUM AESTIVUM L.) MUHAMMAD IBRAHIM 1 , NASEER AHMAD 1 , ZABTA KHAN SHINWARI 2* ASGHARI BANO 1 AND FAIZAN ULLAH 1 1 Department of Plant sciences Quaid-i-Azam university Islamabad Pakistan 2 Department of Biotechnology Quaid-i-Azam university Islamabad Pakistan * Corresponding author, s e-mail: Shinwari@qau.edu.pk Abstract The aim of this work was to study the allelopathic effect of 3 extracts viz 3%,5% and 10% prepared from leaves of GM (insect resistance) and non GM maize on physiology of succeeding crop wheat (Triticum aestivum L.). The extracts prepared from GM maize significantly decreased chlorophyll a content but significantly increased chlorophyll b content as compared with untreated control. Content of chlorophyll a non-significantly decreased but content of chlorophyll b significantly increased with methanolic extract prepared from non GM maize. Significant decrease in carotenoid content was found with aqueous extracts of both GM and non GMmaize.GM maize leaves extracts significantly decreased proline but have no effect on protein and sugar content of wheat plant. Significant increase in protein and sugar content was found with aqueous extract of non GM maize as compared with untreated control. Significant increase in superoxide dismutase (SOD) and non- significant increase in catalase was found with aqueous extracts however activity of peroxidase (POD) decreased in wheat crop with GM maize leaves extracts. Non-significant increase in antioxidant activities were found with treatment of non GM maize leaves extracts as compared with untreated control. Introduction There is increasing emphasis on sustainable agriculture and concerns about the adverse effects of extensive use of synthetic chemicals, such as contamination of the environment, greater plant resistant to herbicides and high costs. As a result, research attention is now focused on decreasing the dependence on the synthetic herbicides and finding alternative strategies for weed management and insect control. In agro-ecosystem allelopathy is one of promising strategy, which can be put into good use in several ways (Khan et al., 2009). Plants have been engineered to have several required characters, such as insecticide resistance to pests, or tolerate to stressful environmental conditions, improved nutritional value. Since the first commercial cultivation of genetically modified plants in 1996, that has been modified to be tolerant to the herbicides glufosinate and glyphosate, to be resistant to virus damage as in ring spot virus resistant. As we know the world population is increasing day by day reached to over 7 billion people and is expected to double in the coming 50 years (Anon., 2011). In the near future guaranteeing a sufficient food supply for this increasing population is going to be a big challenge. In many ways only GM foods guarantee to convene this requirement. Throughout the world during 20th century there has been a great deal of development in the field of biotechnology and rapid development of biotechnology has promoted the research and acceptance of genetically modified (GM) crops in many countries. The significant achievements in transgenic biotechnology has noticeable impact on the world crop manufacture and crop growing forms of agricultural species such as cotton, soybean, canola, and maize (Shinwari et al., 2010). With global cultivation of genetically modified (GM) crops having reached 134 million hectares and covering 25 countries, a new gesture of adoption of biotech crops is causal to a broad based and continuing hectarage growth worldwide (James, 2010).The state with the largest area of GM crops (half of the world’s total acreage) is the United States of America (USA), followed by Argentina, Brazil, Canada, India and China The global acreage of GM crops reached a record 125 million hectares (309 million acres) in 25 countries in 2009 (James, 2010). There are 2 types of genetically modified maize grown all around the world (a) herbicide tolerance e.g. Monsanto’s roundup ready (b) insect resistance e.g. Monsanto’s MON 810, Pioneers 1507 and Syngenta’s Bt11. Through the insertion of a gene from soil bacterium Bacillus thuringiensis (Bt) MON 810, Bt11 and 1507 maize has been genetically modified to create a pesticide, the Bt protein or toxin. Due to agricultural practice and after harvesting of genetically modified crops, in many countries of the world how much amount of Cry1Ab remains in the soil is questionable. It is reported by Einspanier et al., (2004) that high level of toxin is found in the soil close to the roots and remaining plant residues. In Pakistan maize production has been increased from 0.38 million tons during 1947-50 to 3.037 million tons in 2007. The area of cultivation was 935.1 million ha and production was 3261.5 million tons in 2009-1010 (Anon, 2010), grading third after wheat and rice (9131.6 and 2883.1 million ha). Due to its importance, maize was one of the first crops to be genetically engineered and commercially released but due to biosafety issues transgenic maize is not commercially grown in Pakistan. Wheat (Triticum aestivum L.) is important staple food of Pakistan and wheat straw is an essential part of the daily ration of live stocks in majority areas of our country. Various factors lower the productivity of wheat such as delayed sowing, water shortage, disease and drought. Keeping in view the biosafety issues of transgenic maize, the present research work was conducted to evaluate the allelopathic effect of genetically modified and non-modified maize leaves extracts on physiological aspect of wheat crop.