Abstract
An efficient plant regeneration system from embryogenic callus of two elite indica rice (Oryza sativa spp. indica) varieties of Northeast India, Ketokijoha and Monoharsali is established. The effect of auxin, 2,4-dicholorophenoxy acetic acid (2,4-D) on callus induction was optimized. Friable, nodular and creamish-white embryogenic calli were induced from mature seeds on NB medium supplemented with 2.5 mg/l 2,4-D. Plants were regenerated from 40-50 days old embryogenic callus on NB medium containing 0.5 mg/l BAP (6-benzylaminopurine) and 0.25 mg/l ABA (abscisic acid). Regenerated plants with multiple tillers were rooted on half strength MS medium and rooted plants were acclimatized with 94% survival rate. Higher frequency of callus induction as well as plant regeneration was recorded in Ketokijoha as compared to Monoharsali. The calli of both the varieties were found amenable to Agrobacterium-mediated transformation as evident from strong GUS (β-glucuronidase) expression. The results may find wide application for genetic improvement for valuable traits these elite indica rice varieties of Northeast India. Int J Appl Sci Biotechnol, Vol 3(4): 680-686
Highlights
Rice (Oryza sativa L.) is the main staple food for more than half of the world
There are several reports of successful regeneration of transgenic indica rice from Agrobacterium-mediated transformation of embryogenic calli (Ignacimuthu and Arockiasamy 2006, Mohanty et al.,2002), many indica varieties are still recalcitrant to cultural manipulations due to poor callus induction, proliferation and regeneration abilities (Islam et al.,2004, Khaleda and Al-Forkan 2006, Zuraida et al, 2011)
Efficient transformation of rice using Agrobacterium mediated approach and subsequent plant regeneration are dependent on crucial factors such as the choice of explant, hormonal composition of the medium used and nutritional supplements for effective induction of callus and regeneration (Ratnayake and Hettiarachchi 2010)
Summary
Rice (Oryza sativa L.) is the main staple food for more than half of the world. In Asia, more than 90% of rice is produced and consumed (Datta 2004). Genetic transformation of rice in general and indica subspecies in particular is considered to be difficult due to their recalcitrance to in vitro manipulations. These constraints have been overcome in part by regenerating transgenic rice plants from transformed embryogenic calli (Hiei et al, 1994) as these tissues are known for their amenability to both gene delivery and plant regeneration. There are several reports of successful regeneration of transgenic indica rice from Agrobacterium-mediated transformation of embryogenic calli (Ignacimuthu and Arockiasamy 2006, Mohanty et al.,2002), many indica varieties are still recalcitrant to cultural manipulations due to poor callus induction, proliferation and regeneration abilities (Islam et al.,2004, Khaleda and Al-Forkan 2006, Zuraida et al, 2011). Protocols for high frequency plant regeneration using embryogenic callus cultures have not been reported in these highly popular two local indica rice varieties
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