139 Pishbin et al. Int. J. Biosci. 2014 RESEARCH PAPER OPEN ACCESS The effect of plant growth regulators and different types of explants on in vitro regeneration of sweet pepper (Capsicum annuum L.) Neda Pishbin 1 , Amir Mousavi 2* , Sepideh Kalatejari 1 , Mehran Shariatpanahi 3 , Behnam Behrooznam Jahromi 4 1 Department of Horticultural Sciences, Science and Research Branch, Islamic Azad University, Tehran, Iran 2 National Institute of Genetic Engineering and Biotechnology (NIGEB), Tehran, Iran 3 Agricultural Biotechnology Research Institute of Iran (ABRII), Karaj, Iran 4 Department of Horticultural Sciences, Jahrom Branch, Islamic Azad University, Jahrom, Iran Key words: Sweet pepper, Regeneration, Hypocotyl, Cotyledon, Cotyledonary petiole. http://dx.doi.org/10.12692/ijb/5.5.139-146 Article published on September 10, 2014 Abstract Present study was conducted to standardize a protocol for in vitro plant regeneration in Capsicum annuum L. cv California Wonder. Three different types of explants (Hypocotyl, Cotyledon and Cotyledonary petiole) from 8- day-old seedling were used. Various concentrations of BA (2, 3 mgL -1 ), IBA (0.1, 0.2 mgL -1 ) and NAA (0.1, 0.2 mgL -1 ) were used for shoot regeneration. The highest number of shoot per explant was obtained from cotyledonary petiole on a MS medium supplemented with 3 mgL -1 BA and 0.2 mgL -1 IBA. Effective in vitro shoot elongation was achieved on half strength MS medium containing 0.1 mgL -1 BA in combination with 0.5 mgL -1 GA3. As well as adding activated charcoal (3 gL -1 ) and citric acid along with ascorbic acid caused eliminate phenolic material and prevent shoot necrosis in sweet pepper. Elongated shoots were rooted on half strength MS medium supplemented with 1 mgL -1 IBA. * Corresponding Author: Amir Mousavi  m-amir@nigeb.ac.ir International Journal of Biosciences | IJB | ISSN: 2220-6655 (Print) 2222-5234 (Online) http://www.innspub.net Vol. 5, No. 5, p. 139-146, 2014